SuperSlicer/src/libslic3r/Print.cpp

#include "clipper/clipper_z.hpp"

#include "Exception.hpp"
#include "Print.hpp"
#include "BoundingBox.hpp"
#include "ClipperUtils.hpp"
#include "Extruder.hpp"
#include "Flow.hpp"
#include "Fill/FillBase.hpp"
#include "Geometry.hpp"
#include "I18N.hpp"
#include "ShortestPath.hpp"
#include "SupportMaterial.hpp"
#include "Thread.hpp"
#include "GCode.hpp"
#include "GCode/WipeTower.hpp"
#include "Utils.hpp"

//#include "PrintExport.hpp"

#include <float.h>

#include <algorithm>
#include <limits>
#include <unordered_set>
#include <boost/filesystem/path.hpp>
#include <boost/format.hpp>
#include <boost/log/trivial.hpp>

// Mark string for localization and translate.
#define L(s) Slic3r::I18N::translate(s)

namespace Slic3r {

template class PrintState<PrintStep, psCount>;
template class PrintState<PrintObjectStep, posCount>;

void Print::clear() 
{
	tbb::mutex::scoped_lock lock(this->state_mutex());
    // The following call should stop background processing if it is running.
    this->invalidate_all_steps();
	for (PrintObject *object : m_objects)
		delete object;
	m_objects.clear();
    for (PrintRegion *region : m_regions)
        delete region;
    m_regions.clear();
    m_model.clear_objects();
}

//PrintRegion* Print::add_region()
//{
//    m_regions.emplace_back(new PrintRegion(this));
//    return m_regions.back();
//}

PrintRegion* Print::add_region(const PrintRegionConfig &config)
{
    m_regions.emplace_back(new PrintRegion(this, config));
    return m_regions.back();
}

// Called by Print::apply().
// This method only accepts PrintConfig option keys.
bool Print::invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys)
{
    if (opt_keys.empty())
        return false;

    // Cache the plenty of parameters, which influence the G-code generator only,
    // or they are only notes not influencing the generated G-code.
    static std::unordered_set<std::string> steps_gcode = {
        "avoid_crossing_perimeters",
        "avoid_crossing_perimeters_max_detour",
        "avoid_crossing_not_first_layer",
        "bed_shape",
        "bed_temperature",
        "chamber_temperature",
        "before_layer_gcode",
        "between_objects_gcode",
        "bridge_acceleration",
        "bridge_internal_acceleration",
        "bridge_fan_speed",
        "bridge_internal_fan_speed",
        "colorprint_heights",
        "complete_objects_sort",
        "cooling",
        "default_acceleration",
        "deretract_speed",
        "disable_fan_first_layers",
        "duplicate_distance",
        "end_gcode",
        "end_filament_gcode",
        "external_perimeter_acceleration",
        "external_perimeter_cut_corners",
        "external_perimeter_fan_speed",
        "extrusion_axis",
        "extruder_clearance_height",
        "extruder_clearance_radius",
        "extruder_colour",
        "extruder_offset",
        "extruder_fan_offset"
        "extruder_temperature_offset",
        "extrusion_multiplier",
        "fan_always_on",
        "fan_below_layer_time",
        "fan_kickstart",
        "fan_speedup_overhangs",
        "fan_speedup_time",
        "fan_percentage",
        "filament_colour",
        "filament_custom_variables",
        "filament_diameter",
        "filament_density",
        "filament_notes",
        "filament_cost",
        "filament_spool_weight",
        "first_layer_acceleration",
        "first_layer_bed_temperature",
        "first_layer_flow_ratio",
        "first_layer_speed",
        "first_layer_infill_speed",
        "first_layer_min_speed",
        "full_fan_speed_layer",
        "gap_fill_acceleration",
        "gap_fill_speed",
        "gcode_comments",
        "gcode_filename_illegal_char",
        "gcode_label_objects",
        "gcode_precision_xyz",
        "gcode_precision_e",
        "infill_acceleration",
        "ironing_acceleration",
        "layer_gcode",
        "max_fan_speed",
        "max_gcode_per_second",
        "max_print_height",
        "max_print_speed",
        "max_volumetric_speed",
        "min_fan_speed",
        "min_length",
        "min_print_speed",
        "milling_toolchange_end_gcode",
        "milling_toolchange_start_gcode",
        "milling_offset",
        "milling_z_offset",
        "milling_z_lift",
#ifdef HAS_PRESSURE_EQUALIZER
        "max_volumetric_extrusion_rate_slope_positive",
        "max_volumetric_extrusion_rate_slope_negative",
#endif /* HAS_PRESSURE_EQUALIZER */
        "notes",
        "only_retract_when_crossing_perimeters",
        "output_filename_format",
        "overhangs_acceleration",
        "perimeter_acceleration",
        "post_process",
        "printer_notes",
        "retract_before_travel",
        "retract_before_wipe",
        "retract_layer_change",
        "retract_length",
        "retract_length_toolchange",
        "retract_lift",
        "retract_lift_above",
        "retract_lift_below",
        "retract_lift_first_layer",
        "retract_lift_top",
        "retract_restart_extra",
        "retract_restart_extra_toolchange",
        "retract_speed",
        "single_extruder_multi_material_priming",
        "slowdown_below_layer_time",
        "solid_infill_acceleration",
        "support_material_acceleration",
        "support_material_interface_acceleration",
        "standby_temperature_delta",
        "start_gcode",
        "start_gcode_manual",
        "start_filament_gcode",
        "thin_walls_acceleration",
        "thin_walls_speed",
        "time_estimation_compensation",
        "tool_name",
        "toolchange_gcode",
        "top_fan_speed",
        "top_solid_infill_acceleration",
        "threads",
        "travel_acceleration",
        "travel_deceleration_use_target",
        "travel_speed",
        "travel_speed_z",
        "use_firmware_retraction",
        "use_relative_e_distances",
        "use_volumetric_e",
        "variable_layer_height",
        "wipe",
        "wipe_speed",
        "wipe_extra_perimeter"
    };

    static std::unordered_set<std::string> steps_ignore;

    std::vector<PrintStep> steps;
    std::vector<PrintObjectStep> osteps;
    bool invalidated = false;

    for (const t_config_option_key &opt_key : opt_keys) {
        if (steps_gcode.find(opt_key) != steps_gcode.end()) {
            // These options only affect G-code export or they are just notes without influence on the generated G-code,
            // so there is nothing to invalidate.
            steps.emplace_back(psGCodeExport);
        } else if (steps_ignore.find(opt_key) != steps_ignore.end()) {
            // These steps have no influence on the G-code whatsoever. Just ignore them.
        } else if (
               opt_key == "skirts"
            || opt_key == "skirt_height"
            || opt_key == "draft_shield"
            || opt_key == "skirt_brim"
            || opt_key == "skirt_distance"
            || opt_key == "skirt_distance_from_brim"
            || opt_key == "min_skirt_length"
            || opt_key == "complete_objects_one_skirt"
            || opt_key == "complete_objects_one_brim"
            || opt_key == "ooze_prevention"
            || opt_key == "wipe_tower_x"
            || opt_key == "wipe_tower_y"
            || opt_key == "wipe_tower_rotation_angle") {
            steps.emplace_back(psSkirt);
        } else if (
            opt_key == "complete_objects") {
            steps.emplace_back(psBrim);
            steps.emplace_back(psSkirt);
            steps.emplace_back(psWipeTower);
        } else if (
            opt_key == "brim_inside_holes"
            || opt_key == "brim_width"
            || opt_key == "brim_width_interior"
            || opt_key == "brim_offset"
            || opt_key == "brim_ears"
            || opt_key == "brim_ears_detection_length"
            || opt_key == "brim_ears_max_angle"
            || opt_key == "brim_ears_pattern") {
            steps.emplace_back(psBrim);
            steps.emplace_back(psSkirt);
        } else if (
               opt_key == "filament_shrink"
            || opt_key == "nozzle_diameter"
            || opt_key == "model_precision"
            || opt_key == "resolution"
            || opt_key == "resolution_internal"
            || opt_key == "slice_closing_radius"
            // Spiral Vase forces different kind of slicing than the normal model:
            // In Spiral Vase mode, holes are closed and only the largest area contour is kept at each layer.
            // Therefore toggling the Spiral Vase on / off requires complete reslicing.
            || opt_key == "spiral_vase"
            || opt_key == "z_step") {
            osteps.emplace_back(posSlice);
        } else if (
               opt_key == "filament_type"
            || opt_key == "filament_soluble"
            || opt_key == "first_layer_temperature"
            || opt_key == "filament_loading_speed"
            || opt_key == "filament_loading_speed_start"
            || opt_key == "filament_unloading_speed"
            || opt_key == "filament_unloading_speed_start"
            || opt_key == "filament_toolchange_delay"
            || opt_key == "filament_cooling_moves"
            || opt_key == "filament_minimal_purge_on_wipe_tower"
            || opt_key == "filament_cooling_initial_speed"
            || opt_key == "filament_cooling_final_speed"
            || opt_key == "filament_ramming_parameters"
            || opt_key == "filament_max_speed"
            || opt_key == "filament_max_volumetric_speed"
            || opt_key == "filament_use_skinnydip"        // skinnydip params start
            || opt_key == "filament_use_fast_skinnydip"
            || opt_key == "filament_skinnydip_distance"
            || opt_key == "filament_melt_zone_pause"
            || opt_key == "filament_cooling_zone_pause"
            || opt_key == "filament_toolchange_temp"
            || opt_key == "filament_enable_toolchange_temp"
            || opt_key == "filament_enable_toolchange_part_fan"
            || opt_key == "filament_toolchange_part_fan_speed"
            || opt_key == "filament_dip_insertion_speed"
            || opt_key == "filament_dip_extraction_speed"    //skinnydip params end	
            || opt_key == "gcode_flavor"
            || opt_key == "high_current_on_filament_swap"
            || opt_key == "infill_first"
            || opt_key == "single_extruder_multi_material"
            || opt_key == "temperature"
            || opt_key == "wipe_tower"
            || opt_key == "wipe_tower_width"
            || opt_key == "wipe_tower_bridging"
            || opt_key == "wipe_tower_no_sparse_layers"
            || opt_key == "wiping_volumes_matrix"
            || opt_key == "parking_pos_retraction"
            || opt_key == "cooling_tube_retraction"
            || opt_key == "cooling_tube_length"
            || opt_key == "extra_loading_move"
            || opt_key == "z_offset"
            || opt_key == "wipe_tower_brim") {
            steps.emplace_back(psWipeTower);
            steps.emplace_back(psSkirt);
        }
        else if (
            opt_key == "first_layer_extrusion_width"
            || opt_key == "min_layer_height"
            || opt_key == "max_layer_height"
            || opt_key == "filament_max_overlap") {
            osteps.emplace_back(posPerimeters);
            osteps.emplace_back(posInfill);
            osteps.emplace_back(posSupportMaterial);
            steps.emplace_back(psSkirt);
            steps.emplace_back(psBrim);
        }
        else if (opt_key == "posSlice")
            osteps.emplace_back(posSlice);
        else if (opt_key == "posPerimeters")
            osteps.emplace_back(posPerimeters);
        else if (opt_key == "posPrepareInfill")
            osteps.emplace_back(posPrepareInfill);
        else if (opt_key == "posInfill")
            osteps.emplace_back(posInfill);
        else if (opt_key == "posSupportMaterial")
            osteps.emplace_back(posSupportMaterial);
        else if (opt_key == "posCount")
            osteps.emplace_back(posCount);
        else {
            // for legacy, if we can't handle this option let's invalidate all steps
            //FIXME invalidate all steps of all objects as well?
            invalidated |= this->invalidate_all_steps();
            // Continue with the other opt_keys to possibly invalidate any object specific steps.
        }
    }

    sort_remove_duplicates(steps);
    for (PrintStep step : steps)
        invalidated |= this->invalidate_step(step);
    sort_remove_duplicates(osteps);
    for (PrintObjectStep ostep : osteps)
        for (PrintObject *object : m_objects)
            invalidated |= object->invalidate_step(ostep);
    return invalidated;
}

bool Print::invalidate_step(PrintStep step)
{
	bool invalidated = Inherited::invalidate_step(step);
    // Propagate to dependent steps.
    if (step == psSkirt)
        invalidated |= Inherited::invalidate_step(psBrim);
    if (step == psBrim) // this one only if skirt_distance_from_brim
        invalidated |= Inherited::invalidate_step(psSkirt);
    if (step != psGCodeExport)
        invalidated |= Inherited::invalidate_step(psGCodeExport);
    return invalidated;
}

// returns true if an object step is done on all objects
// and there's at least one object
bool Print::is_step_done(PrintObjectStep step) const
{
    if (m_objects.empty())
        return false;
    tbb::mutex::scoped_lock lock(this->state_mutex());
    for (const PrintObject *object : m_objects)
        if (! object->is_step_done_unguarded(step))
            return false;
    return true;
}

// returns 0-based indices of used extruders
std::set<uint16_t> Print::object_extruders(const PrintObjectPtrs &objects) const
{
    std::set<uint16_t> extruders;
    std::vector<unsigned char> region_used(m_regions.size(), false);
    for (const PrintObject *object : objects)
		for (const std::vector<std::pair<t_layer_height_range, int>> &volumes_per_region : object->region_volumes)
        	if (! volumes_per_region.empty())
        		region_used[&volumes_per_region - &object->region_volumes.front()] = true;
    for (size_t idx_region = 0; idx_region < m_regions.size(); ++ idx_region)
    	if (region_used[idx_region])
        	m_regions[idx_region]->collect_object_printing_extruders(extruders);
    return extruders;
}

// returns 0-based indices of used extruders
std::set<uint16_t> Print::support_material_extruders() const
{
    std::set<uint16_t> extruders;
    bool support_uses_current_extruder = false;
    auto num_extruders = (uint16_t)m_config.nozzle_diameter.size();

    for (PrintObject *object : m_objects) {
        if (object->has_support_material()) {
        	assert(object->config().support_material_extruder >= 0);
            if (object->config().support_material_extruder == 0)
                support_uses_current_extruder = true;
            else {
                uint16_t i = (uint16_t)object->config().support_material_extruder - 1;
                extruders.insert((i >= num_extruders) ? 0 : i);
            }
            if (object->config().support_material_interface_layers > 0) {
                assert(object->config().support_material_interface_extruder >= 0);
                if (object->config().support_material_interface_extruder == 0)
                    support_uses_current_extruder = true;
                else {
                    uint16_t i = (uint16_t)object->config().support_material_interface_extruder - 1;
                    extruders.insert((i >= num_extruders) ? 0 : i);
                }
            }
        }
    }

    if (support_uses_current_extruder)
        // Add all object extruders to the support extruders as it is not know which one will be used to print supports.
        append(extruders, this->object_extruders(m_objects));
    
    return extruders;
}

// returns 0-based indices of used extruders
std::set<uint16_t> Print::extruders() const
{
    std::set<uint16_t> extruders = this->object_extruders(m_objects);
    append(extruders, this->support_material_extruders());
    return extruders;
}

uint16_t Print::num_object_instances() const
{
    uint16_t instances = 0;
    for (const PrintObject *print_object : m_objects)
        instances += (uint16_t)print_object->instances().size();
    return instances;
}

double Print::max_allowed_layer_height() const
{
    double nozzle_diameter_max = 0.;
    for (unsigned int extruder_id : this->extruders())
        nozzle_diameter_max = std::max(nozzle_diameter_max, m_config.nozzle_diameter.get_at(extruder_id));
    return nozzle_diameter_max;
}

// Add or remove support modifier ModelVolumes from model_object_dst to match the ModelVolumes of model_object_new
// in the exact order and with the same IDs.
// It is expected, that the model_object_dst already contains the non-support volumes of model_object_new in the correct order.
void Print::model_volume_list_update_supports_seams(ModelObject &model_object_dst, const ModelObject &model_object_new)
{
	typedef std::pair<const ModelVolume*, bool> ModelVolumeWithStatus;
	std::vector<ModelVolumeWithStatus> old_volumes;
    old_volumes.reserve(model_object_dst.volumes.size());
	for (const ModelVolume *model_volume : model_object_dst.volumes)
		old_volumes.emplace_back(ModelVolumeWithStatus(model_volume, false));
	auto model_volume_lower = [](const ModelVolumeWithStatus &mv1, const ModelVolumeWithStatus &mv2){ return mv1.first->id() <  mv2.first->id(); };
	auto model_volume_equal = [](const ModelVolumeWithStatus &mv1, const ModelVolumeWithStatus &mv2){ return mv1.first->id() == mv2.first->id(); };
    std::sort(old_volumes.begin(), old_volumes.end(), model_volume_lower);
    model_object_dst.volumes.clear();
    model_object_dst.volumes.reserve(model_object_new.volumes.size());
    for (const ModelVolume *model_volume_src : model_object_new.volumes) {
		ModelVolumeWithStatus key(model_volume_src, false);
		auto it = std::lower_bound(old_volumes.begin(), old_volumes.end(), key, model_volume_lower);
		if (it != old_volumes.end() && model_volume_equal(*it, key)) {
            // The volume was found in the old list. Just copy it.
            assert(! it->second); // not consumed yet
            it->second = true;
            ModelVolume *model_volume_dst = const_cast<ModelVolume*>(it->first);
			// For support modifiers, the type may have been switched from blocker to enforcer and vice versa.
			assert((model_volume_dst->is_support_modifier() && model_volume_src->is_support_modifier()) || model_volume_dst->type() == model_volume_src->type());
            model_object_dst.volumes.emplace_back(model_volume_dst);
			if (model_volume_dst->is_support_modifier() || model_volume_dst->is_seam_position()) {
				// For support modifiers, the type may have been switched from blocker to enforcer and vice versa.
				model_volume_dst->set_type(model_volume_src->type());
				model_volume_dst->set_transformation(model_volume_src->get_transformation());
			}
            assert(model_volume_dst->get_matrix().isApprox(model_volume_src->get_matrix()));
        } else {
            // The volume was not found in the old list. Create a new copy.
            assert(model_volume_src->is_support_modifier() || model_volume_src->is_seam_position());
            model_object_dst.volumes.emplace_back(new ModelVolume(*model_volume_src));
            model_object_dst.volumes.back()->set_model_object(&model_object_dst);
        }
    }
    // Release the non-consumed old volumes (those were deleted from the new list).
	for (ModelVolumeWithStatus &mv_with_status : old_volumes)
        if (! mv_with_status.second)
            delete mv_with_status.first;
}

static inline void model_volume_list_copy_configs(ModelObject &model_object_dst, const ModelObject &model_object_src, const ModelVolumeType type)
{
    size_t i_src, i_dst;
    for (i_src = 0, i_dst = 0; i_src < model_object_src.volumes.size() && i_dst < model_object_dst.volumes.size();) {
        const ModelVolume &mv_src = *model_object_src.volumes[i_src];
        ModelVolume       &mv_dst = *model_object_dst.volumes[i_dst];
        if (mv_src.type() != type) {
            ++ i_src;
            continue;
        }
        if (mv_dst.type() != type) {
            ++ i_dst;
            continue;
        }
        assert(mv_src.id() == mv_dst.id());
        // Copy the ModelVolume data.
        mv_dst.name   = mv_src.name;
        mv_dst.config.assign_config(mv_src.config);
        assert(mv_dst.supported_facets.id() == mv_src.supported_facets.id());
        mv_dst.supported_facets.assign(mv_src.supported_facets);
        assert(mv_dst.seam_facets.id() == mv_src.seam_facets.id());
        mv_dst.seam_facets.assign(mv_src.seam_facets);
        //FIXME what to do with the materials?
        // mv_dst.m_material_id = mv_src.m_material_id;
        ++ i_src;
        ++ i_dst;
    }
}

static inline void layer_height_ranges_copy_configs(t_layer_config_ranges &lr_dst, const t_layer_config_ranges &lr_src)
{
    assert(lr_dst.size() == lr_src.size());
    auto it_src = lr_src.cbegin();
    for (auto &kvp_dst : lr_dst) {
        const auto &kvp_src = *it_src ++;
        assert(std::abs(kvp_dst.first.first  - kvp_src.first.first ) <= EPSILON);
        assert(std::abs(kvp_dst.first.second - kvp_src.first.second) <= EPSILON);
        // Layer heights are allowed do differ in case the layer height table is being overriden by the smooth profile.
        // assert(std::abs(kvp_dst.second.option("layer_height")->getFloat() - kvp_src.second.option("layer_height")->getFloat()) <= EPSILON);
        kvp_dst.second = kvp_src.second;
    }
}

static inline bool transform3d_lower(const Transform3d &lhs, const Transform3d &rhs) 
{
    typedef Transform3d::Scalar T;
    const T *lv = lhs.data();
    const T *rv = rhs.data();
    for (size_t i = 0; i < 16; ++ i, ++ lv, ++ rv) {
        if (*lv < *rv)
            return true;
        else if (*lv > *rv)
            return false;
    }
    return false;
}

static inline bool transform3d_equal(const Transform3d &lhs, const Transform3d &rhs) 
{
    typedef Transform3d::Scalar T;
    const T *lv = lhs.data();
    const T *rv = rhs.data();
    for (size_t i = 0; i < 16; ++ i, ++ lv, ++ rv)
        if (*lv != *rv)
            return false;
    return true;
}

struct PrintObjectTrafoAndInstances
{
    Transform3d    	trafo;
    PrintInstances	instances;
    bool operator<(const PrintObjectTrafoAndInstances &rhs) const { return transform3d_lower(this->trafo, rhs.trafo); }
};

// Generate a list of trafos and XY offsets for instances of a ModelObject
static std::vector<PrintObjectTrafoAndInstances> print_objects_from_model_object(const ModelObject &model_object)
{
    std::set<PrintObjectTrafoAndInstances> trafos;
    PrintObjectTrafoAndInstances           trafo;
    for (ModelInstance *model_instance : model_object.instances)
        if (model_instance->is_printable()) {
            trafo.trafo = model_instance->get_matrix();
            auto shift = Point::new_scale(trafo.trafo.data()[12], trafo.trafo.data()[13]);
            // Reset the XY axes of the transformation.
            trafo.trafo.data()[12] = 0;
            trafo.trafo.data()[13] = 0;
            // Search or insert a trafo.
            auto it = trafos.emplace(trafo).first;
            const_cast<PrintObjectTrafoAndInstances&>(*it).instances.emplace_back(PrintInstance{ nullptr, model_instance, shift });
        }
    return std::vector<PrintObjectTrafoAndInstances>(trafos.begin(), trafos.end());
}

// Compare just the layer ranges and their layer heights, not the associated configs.
// Ignore the layer heights if check_layer_heights is false.
static bool layer_height_ranges_equal(const t_layer_config_ranges &lr1, const t_layer_config_ranges &lr2, bool check_layer_height)
{
    if (lr1.size() != lr2.size())
        return false;
    auto it2 = lr2.begin();
    for (const auto &kvp1 : lr1) {
        const auto &kvp2 = *it2 ++;
        if (std::abs(kvp1.first.first  - kvp2.first.first ) > EPSILON ||
            std::abs(kvp1.first.second - kvp2.first.second) > EPSILON ||
            (check_layer_height && std::abs(kvp1.second.option("layer_height")->getFloat() - kvp2.second.option("layer_height")->getFloat()) > EPSILON))
            return false;
    }
    return true;
}

// Returns true if va == vb when all CustomGCode items that are not ToolChangeCode are ignored.
static bool custom_per_printz_gcodes_tool_changes_differ(const std::vector<CustomGCode::Item> &va, const std::vector<CustomGCode::Item> &vb)
{
	auto it_a = va.begin();
	auto it_b = vb.begin();
	while (it_a != va.end() || it_b != vb.end()) {
		if (it_a != va.end() && it_a->type != CustomGCode::ToolChange) {
			// Skip any CustomGCode items, which are not tool changes.
			++ it_a;
			continue;
		}
		if (it_b != vb.end() && it_b->type != CustomGCode::ToolChange) {
			// Skip any CustomGCode items, which are not tool changes.
			++ it_b;
			continue;
		}
		if (it_a == va.end() || it_b == vb.end())
			// va or vb contains more Tool Changes than the other.
			return true;
		assert(it_a->type == CustomGCode::ToolChange);
		assert(it_b->type == CustomGCode::ToolChange);
		if (*it_a != *it_b)
			// The two Tool Changes differ.
			return true;
		++ it_a;
		++ it_b;
	}
	// There is no change in custom Tool Changes.
	return false;
}

// Collect diffs of configuration values at various containers,
// resolve the filament rectract overrides of extruder retract values.
void Print::config_diffs(
	const DynamicPrintConfig &new_full_config, 
	t_config_option_keys &print_diff, t_config_option_keys &object_diff, t_config_option_keys &region_diff, 
	t_config_option_keys &full_config_diff, 
	DynamicPrintConfig &filament_overrides) const
{
    // Collect changes to print config, account for overrides of extruder retract values by filament presets.
    {
	    const std::vector<std::string> &extruder_retract_keys = print_config_def.extruder_retract_keys();
	    const std::string               filament_prefix       = "filament_";
	    for (const t_config_option_key &opt_key : m_config.keys()) {
	        const ConfigOption *opt_old = m_config.option(opt_key);
	        assert(opt_old != nullptr);
	        const ConfigOption *opt_new = new_full_config.option(opt_key);
			// assert(opt_new != nullptr);
			if (opt_new == nullptr)
				//FIXME This may happen when executing some test cases.
				continue;
	        const ConfigOption *opt_new_filament = std::binary_search(extruder_retract_keys.begin(), extruder_retract_keys.end(), opt_key) ? new_full_config.option(filament_prefix + opt_key) : nullptr;
	        if (opt_new_filament != nullptr && ! opt_new_filament->is_nil()) {
	        	// An extruder retract override is available at some of the filament presets.
	        	if (*opt_old != *opt_new || opt_new->overriden_by(opt_new_filament)) {
	        		auto opt_copy = opt_new->clone();
	        		opt_copy->apply_override(opt_new_filament);
	        		if (*opt_old == *opt_copy)
	        			delete opt_copy;
	        		else {
	        			filament_overrides.set_key_value(opt_key, opt_copy);
	        			print_diff.emplace_back(opt_key);
	        		}
	        	}
	        } else if (*opt_new != *opt_old)
	            print_diff.emplace_back(opt_key);
	    }
	}
	// Collect changes to object and region configs.
    object_diff = m_default_object_config.diff(new_full_config);
    region_diff = m_default_region_config.diff(new_full_config);
    // Prepare for storing of the full print config into new_full_config to be exported into the G-code and to be used by the PlaceholderParser.
    for (const t_config_option_key &opt_key : new_full_config.keys()) {
        const ConfigOption *opt_old = m_full_print_config.option(opt_key);
        const ConfigOption *opt_new = new_full_config.option(opt_key);
        if (opt_old == nullptr || *opt_new != *opt_old)
            full_config_diff.emplace_back(opt_key);
    }
}

std::vector<ObjectID> Print::print_object_ids() const 
{ 
    std::vector<ObjectID> out; 
    // Reserve one more for the caller to append the ID of the Print itself.
    out.reserve(m_objects.size() + 1);
    for (const PrintObject *print_object : m_objects)
        out.emplace_back(print_object->id());
    return out;
}

Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_config)
{
#ifdef _DEBUG
    check_model_ids_validity(model);
#endif /* _DEBUG */

    // Normalize the config.
	new_full_config.option("print_settings_id",    true);
	new_full_config.option("filament_settings_id", true);
	new_full_config.option("printer_settings_id",  true);
    new_full_config.option("physical_printer_settings_id", true);
    new_full_config.normalize_fdm();

    // Find modified keys of the various configs. Resolve overrides extruder retract values by filament profiles.
	t_config_option_keys print_diff, object_diff, region_diff, full_config_diff;
	DynamicPrintConfig filament_overrides;
	this->config_diffs(new_full_config, print_diff, object_diff, region_diff, full_config_diff, filament_overrides);

    // Do not use the ApplyStatus as we will use the max function when updating apply_status.
    unsigned int apply_status = APPLY_STATUS_UNCHANGED;
    auto update_apply_status = [&apply_status](bool invalidated)
        { apply_status = std::max<unsigned int>(apply_status, invalidated ? APPLY_STATUS_INVALIDATED : APPLY_STATUS_CHANGED); };
    if (! (print_diff.empty() && object_diff.empty() && region_diff.empty()))
        update_apply_status(false);

    // Grab the lock for the Print / PrintObject milestones.
	tbb::mutex::scoped_lock lock(this->state_mutex());

    // The following call may stop the background processing.
    if (! print_diff.empty())
        update_apply_status(this->invalidate_state_by_config_options(print_diff));

    // Apply variables to placeholder parser. The placeholder parser is used by G-code export,
    // which should be stopped if print_diff is not empty.
    size_t num_extruders = m_config.nozzle_diameter.size();
    bool   num_extruders_changed = false;
    if (! full_config_diff.empty()) {
        update_apply_status(this->invalidate_step(psGCodeExport));
        // Set the profile aliases for the PrintBase::output_filename()
		m_placeholder_parser.set("print_preset",    new_full_config.option("print_settings_id")->clone());
		m_placeholder_parser.set("filament_preset", new_full_config.option("filament_settings_id")->clone());
		m_placeholder_parser.set("printer_preset",  new_full_config.option("printer_settings_id")->clone());
        m_placeholder_parser.set("physical_printer_preset",   new_full_config.option("physical_printer_settings_id")->clone());
		// We want the filament overrides to be applied over their respective extruder parameters by the PlaceholderParser.
		// see "Placeholders do not respect filament overrides." GH issue #3649
		m_placeholder_parser.apply_config(filament_overrides);
	    // It is also safe to change m_config now after this->invalidate_state_by_config_options() call.
	    m_config.apply_only(new_full_config, print_diff, true);
	    //FIXME use move semantics once ConfigBase supports it.
	    m_config.apply(filament_overrides);
	    // Handle changes to object config defaults
	    m_default_object_config.apply_only(new_full_config, object_diff, true);
	    // Handle changes to regions config defaults
	    m_default_region_config.apply_only(new_full_config, region_diff, true);
        m_full_print_config = std::move(new_full_config);
        if (num_extruders != m_config.nozzle_diameter.size()) {
        	num_extruders = m_config.nozzle_diameter.size();
        	num_extruders_changed = true;
    }
    }
    
    class LayerRanges
    {
    public:
        LayerRanges() {}
        // Convert input config ranges into continuous non-overlapping sorted vector of intervals and their configs.
        void assign(const t_layer_config_ranges &in) {
            m_ranges.clear();
            m_ranges.reserve(in.size());
            // Input ranges are sorted lexicographically. First range trims the other ranges.
            coordf_t last_z = 0;
            for (const std::pair<const t_layer_height_range, ModelConfig> &range : in)
				if (range.first.second > last_z) {
                    coordf_t min_z = std::max(range.first.first, 0.);
                    if (min_z > last_z + EPSILON) {
                        m_ranges.emplace_back(t_layer_height_range(last_z, min_z), nullptr);
                        last_z = min_z;
                    }
                    if (range.first.second > last_z + EPSILON) {
						const DynamicPrintConfig *cfg = &range.second.get();
                        m_ranges.emplace_back(t_layer_height_range(last_z, range.first.second), cfg);
                        last_z = range.first.second;
                    }
                }
            if (m_ranges.empty())
                m_ranges.emplace_back(t_layer_height_range(0, DBL_MAX), nullptr);
            else if (m_ranges.back().second == nullptr)
                m_ranges.back().first.second = DBL_MAX;
            else
                m_ranges.emplace_back(t_layer_height_range(m_ranges.back().first.second, DBL_MAX), nullptr);
        }

        const DynamicPrintConfig* config(const t_layer_height_range &range) const {
            auto it = std::lower_bound(m_ranges.begin(), m_ranges.end(), std::make_pair< t_layer_height_range, const DynamicPrintConfig*>(t_layer_height_range(range.first - EPSILON, range.second - EPSILON), nullptr));
            // #ys_FIXME_COLOR
            // assert(it != m_ranges.end());
            // assert(it == m_ranges.end() || std::abs(it->first.first  - range.first ) < EPSILON);
            // assert(it == m_ranges.end() || std::abs(it->first.second - range.second) < EPSILON);
            if (it == m_ranges.end() ||
                std::abs(it->first.first - range.first) > EPSILON ||
                std::abs(it->first.second - range.second) > EPSILON )
                return nullptr; // desired range doesn't found
            return (it == m_ranges.end()) ? nullptr : it->second;
        }
        std::vector<std::pair<t_layer_height_range, const DynamicPrintConfig*>>::const_iterator begin() const { return m_ranges.cbegin(); }
        std::vector<std::pair<t_layer_height_range, const DynamicPrintConfig*>>::const_iterator end() const { return m_ranges.cend(); }
    private:
        std::vector<std::pair<t_layer_height_range, const DynamicPrintConfig*>> m_ranges;
    };
    struct ModelObjectStatus {
        enum Status {
            Unknown,
            Old,
            New,
            Moved,
            Deleted,
        };
        ModelObjectStatus(ObjectID id, Status status = Unknown) : id(id), status(status) {}
		ObjectID     id;
        Status       status;
        LayerRanges  layer_ranges;
        // Search by id.
        bool operator<(const ModelObjectStatus &rhs) const { return id < rhs.id; }
    };
    std::set<ModelObjectStatus> model_object_status;

    // 1) Synchronize model objects.
    if (model.id() != m_model.id()) {
        // Kill everything, initialize from scratch.
        // Stop background processing.
        this->call_cancel_callback();
        update_apply_status(this->invalidate_all_steps());
        for (PrintObject *object : m_objects) {
            model_object_status.emplace(object->model_object()->id(), ModelObjectStatus::Deleted);
			update_apply_status(object->invalidate_all_steps());
			delete object;
        }
        m_objects.clear();
        for (PrintRegion *region : m_regions)
            delete region;
        m_regions.clear();
        m_model.assign_copy(model);
		for (const ModelObject *model_object : m_model.objects)
			model_object_status.emplace(model_object->id(), ModelObjectStatus::New);
    } else {
        if (m_model.custom_gcode_per_print_z != model.custom_gcode_per_print_z) {
            update_apply_status(num_extruders_changed || 
            	// Tool change G-codes are applied as color changes for a single extruder printer, no need to invalidate tool ordering.
            	//FIXME The tool ordering may be invalidated unnecessarily if the custom_gcode_per_print_z.mode is not applicable
            	// to the active print / model state, and then it is reset, so it is being applicable, but empty, thus the effect is the same.
            	(num_extruders > 1 && custom_per_printz_gcodes_tool_changes_differ(m_model.custom_gcode_per_print_z.gcodes, model.custom_gcode_per_print_z.gcodes)) ?
            	// The Tool Ordering and the Wipe Tower are no more valid.
            	this->invalidate_steps({ psWipeTower, psGCodeExport }) :
            	// There is no change in Tool Changes stored in custom_gcode_per_print_z, therefore there is no need to update Tool Ordering.
            	this->invalidate_step(psGCodeExport));
            m_model.custom_gcode_per_print_z = model.custom_gcode_per_print_z;
        }
        if (model_object_list_equal(m_model, model)) {
            // The object list did not change.
			for (const ModelObject *model_object : m_model.objects)
				model_object_status.emplace(model_object->id(), ModelObjectStatus::Old);
        } else if (model_object_list_extended(m_model, model)) {
            // Add new objects. Their volumes and configs will be synchronized later.
            update_apply_status(this->invalidate_step(psGCodeExport));
            for (const ModelObject *model_object : m_model.objects)
                model_object_status.emplace(model_object->id(), ModelObjectStatus::Old);
            for (size_t i = m_model.objects.size(); i < model.objects.size(); ++ i) {
                model_object_status.emplace(model.objects[i]->id(), ModelObjectStatus::New);
                m_model.objects.emplace_back(ModelObject::new_copy(*model.objects[i]));
				m_model.objects.back()->set_model(&m_model);
            }
        } else {
            // Reorder the objects, add new objects.
            // First stop background processing before shuffling or deleting the PrintObjects in the object list.
            this->call_cancel_callback();
            update_apply_status(this->invalidate_step(psGCodeExport));
            // Second create a new list of objects.
            std::vector<ModelObject*> model_objects_old(std::move(m_model.objects));
            m_model.objects.clear();
            m_model.objects.reserve(model.objects.size());
            auto by_id_lower = [](const ModelObject *lhs, const ModelObject *rhs){ return lhs->id() < rhs->id(); };
            std::sort(model_objects_old.begin(), model_objects_old.end(), by_id_lower);
            for (const ModelObject *mobj : model.objects) {
                auto it = std::lower_bound(model_objects_old.begin(), model_objects_old.end(), mobj, by_id_lower);
                if (it == model_objects_old.end() || (*it)->id() != mobj->id()) {
                    // New ModelObject added.
					m_model.objects.emplace_back(ModelObject::new_copy(*mobj));
					m_model.objects.back()->set_model(&m_model);
                    model_object_status.emplace(mobj->id(), ModelObjectStatus::New);
                } else {
                    // Existing ModelObject re-added (possibly moved in the list).
                    m_model.objects.emplace_back(*it);
                    model_object_status.emplace(mobj->id(), ModelObjectStatus::Moved);
                }
            }
            bool deleted_any = false;
			for (ModelObject *&model_object : model_objects_old) {
                if (model_object_status.find(ModelObjectStatus(model_object->id())) == model_object_status.end()) {
                    model_object_status.emplace(model_object->id(), ModelObjectStatus::Deleted);
                    deleted_any = true;
                } else
                    // Do not delete this ModelObject instance.
                    model_object = nullptr;
            }
            if (deleted_any) {
                // Delete PrintObjects of the deleted ModelObjects.
                std::vector<PrintObject*> print_objects_old = std::move(m_objects);
                m_objects.clear();
                m_objects.reserve(print_objects_old.size());
                for (PrintObject *print_object : print_objects_old) {
                    auto it_status = model_object_status.find(ModelObjectStatus(print_object->model_object()->id()));
                    assert(it_status != model_object_status.end());
                    if (it_status->status == ModelObjectStatus::Deleted) {
                        update_apply_status(print_object->invalidate_all_steps());
                        delete print_object;
                    } else
                        m_objects.emplace_back(print_object);
                }
                for (ModelObject *model_object : model_objects_old)
                    delete model_object;
            }
        }
    }

    // 2) Map print objects including their transformation matrices.
    struct PrintObjectStatus {
        enum Status {
            Unknown,
            Deleted,
            Reused,
            New
        };
        PrintObjectStatus(PrintObject *print_object, Status status = Unknown) : 
            id(print_object->model_object()->id()),
            print_object(print_object),
            trafo(print_object->trafo()),
            status(status) {}
        PrintObjectStatus(ObjectID id) : id(id), print_object(nullptr), trafo(Transform3d::Identity()), status(Unknown) {}
        // ID of the ModelObject & PrintObject
        ObjectID          id;
        // Pointer to the old PrintObject
        PrintObject     *print_object;
        // Trafo generated with model_object->world_matrix(true) 
        Transform3d      trafo;
        Status           status;
        // Search by id.
        bool operator<(const PrintObjectStatus &rhs) const { return id < rhs.id; }
    };
    std::multiset<PrintObjectStatus> print_object_status;
    for (PrintObject *print_object : m_objects)
        print_object_status.emplace(PrintObjectStatus(print_object));

    // 3) Synchronize ModelObjects & PrintObjects.
    for (size_t idx_model_object = 0; idx_model_object < model.objects.size(); ++ idx_model_object) {
        ModelObject &model_object = *m_model.objects[idx_model_object];
        auto it_status = model_object_status.find(ModelObjectStatus(model_object.id()));
        assert(it_status != model_object_status.end());
        assert(it_status->status != ModelObjectStatus::Deleted);
		const ModelObject& model_object_new = *model.objects[idx_model_object];
		const_cast<ModelObjectStatus&>(*it_status).layer_ranges.assign(model_object_new.layer_config_ranges);
        if (it_status->status == ModelObjectStatus::New)
            // PrintObject instances will be added in the next loop.
            continue;
        // Update the ModelObject instance, possibly invalidate the linked PrintObjects.
        assert(it_status->status == ModelObjectStatus::Old || it_status->status == ModelObjectStatus::Moved);
        // Check whether a model part volume was added or removed, their transformations or order changed.
        // Only volume IDs, volume types, transformation matrices and their order are checked, configuration and other parameters are NOT checked.
        bool model_parts_differ         = model_volume_list_changed(model_object, model_object_new, ModelVolumeType::MODEL_PART);
        bool modifiers_differ           = model_volume_list_changed(model_object, model_object_new, ModelVolumeType::PARAMETER_MODIFIER);
        bool supports_differ            = model_volume_list_changed(model_object, model_object_new, ModelVolumeType::SUPPORT_BLOCKER) ||
                                          model_volume_list_changed(model_object, model_object_new, ModelVolumeType::SUPPORT_ENFORCER);
        bool seam_position_differ       = model_volume_list_changed(model_object, model_object_new, ModelVolumeType::SEAM_POSITION);
        if (model_parts_differ || modifiers_differ ||
            model_object.origin_translation         != model_object_new.origin_translation   ||
            ! model_object.layer_height_profile.timestamp_matches(model_object_new.layer_height_profile) ||
            ! layer_height_ranges_equal(model_object.layer_config_ranges, model_object_new.layer_config_ranges, model_object_new.layer_height_profile.empty())) {
            // The very first step (the slicing step) is invalidated. One may freely remove all associated PrintObjects.
            auto range = print_object_status.equal_range(PrintObjectStatus(model_object.id()));
            for (auto it = range.first; it != range.second; ++ it) {
                update_apply_status(it->print_object->invalidate_all_steps());
                const_cast<PrintObjectStatus&>(*it).status = PrintObjectStatus::Deleted;
            }
            // Copy content of the ModelObject including its ID, do not change the parent.
            model_object.assign_copy(model_object_new);
        } else if (supports_differ || seam_position_differ || model_custom_supports_data_changed(model_object, model_object_new)) {
            // First stop background processing before shuffling or deleting the ModelVolumes in the ModelObject's list.
            if (supports_differ) {
                this->call_cancel_callback();
                update_apply_status(false);
            }
            // Invalidate just the supports step.
            auto range = print_object_status.equal_range(PrintObjectStatus(model_object.id()));
            for (auto it = range.first; it != range.second; ++ it)
                update_apply_status(it->print_object->invalidate_step(posSupportMaterial));
            if (supports_differ) {
                // Copy just the support volumes.
                model_volume_list_update_supports_seams(model_object, model_object_new);
            }else if (seam_position_differ) {
                // First stop background processing before shuffling or deleting the ModelVolumes in the ModelObject's list.
                this->call_cancel_callback();
                update_apply_status(false);
                // Invalidate just the gcode step.
                invalidate_step(psGCodeExport);
                // Copy just the seam volumes.
                model_volume_list_update_supports_seams(model_object, model_object_new);
            }
        } else if (model_custom_seam_data_changed(model_object, model_object_new)) {
            update_apply_status(this->invalidate_step(psGCodeExport));
        }
        if (! model_parts_differ && ! modifiers_differ) {
            // Synchronize Object's config.
            bool object_config_changed = ! model_object.config.timestamp_matches(model_object_new.config);
			if (object_config_changed)
				model_object.config.assign_config(model_object_new.config);
            if (! object_diff.empty() || object_config_changed || num_extruders_changed) {
                PrintObjectConfig new_config = PrintObject::object_config_from_model_object(m_default_object_config, model_object, num_extruders);
                auto range = print_object_status.equal_range(PrintObjectStatus(model_object.id()));
                for (auto it = range.first; it != range.second; ++ it) {
                    t_config_option_keys diff = it->print_object->config().diff(new_config);
                    if (! diff.empty()) {
                        update_apply_status(it->print_object->invalidate_state_by_config_options(diff));
                        it->print_object->config_apply_only(new_config, diff, true);
                    }
                }
            }
            // Synchronize (just copy) the remaining data of ModelVolumes (name, config, custom supports data).
            //FIXME What to do with m_material_id?
			model_volume_list_copy_configs(model_object /* dst */, model_object_new /* src */, ModelVolumeType::MODEL_PART);
			model_volume_list_copy_configs(model_object /* dst */, model_object_new /* src */, ModelVolumeType::PARAMETER_MODIFIER);
            layer_height_ranges_copy_configs(model_object.layer_config_ranges /* dst */, model_object_new.layer_config_ranges /* src */);
            // Copy the ModelObject name, input_file and instances. The instances will be compared against PrintObject instances in the next step.
            model_object.name       = model_object_new.name;
            model_object.input_file = model_object_new.input_file;
            // Only refresh ModelInstances if there is any change.
            if (model_object.instances.size() != model_object_new.instances.size() || 
            	! std::equal(model_object.instances.begin(), model_object.instances.end(), model_object_new.instances.begin(), [](auto l, auto r){ return l->id() == r->id(); })) {
            	// G-code generator accesses model_object.instances to generate sequential print ordering matching the Plater object list.
            	update_apply_status(this->invalidate_step(psGCodeExport));
	            model_object.clear_instances();
	            model_object.instances.reserve(model_object_new.instances.size());
	            for (const ModelInstance *model_instance : model_object_new.instances) {
	                model_object.instances.emplace_back(new ModelInstance(*model_instance));
	                model_object.instances.back()->set_model_object(&model_object);
	            }
	        } else if (! std::equal(model_object.instances.begin(), model_object.instances.end(), model_object_new.instances.begin(), 
	        		[](auto l, auto r){ return l->print_volume_state == r->print_volume_state && l->printable == r->printable && 
	        						           l->get_transformation().get_matrix().isApprox(r->get_transformation().get_matrix()); })) {
	        	// If some of the instances changed, the bounding box of the updated ModelObject is likely no more valid.
	        	// This is safe as the ModelObject's bounding box is only accessed from this function, which is called from the main thread only.
	 			model_object.invalidate_bounding_box();
	        	// Synchronize the content of instances.
	        	auto new_instance = model_object_new.instances.begin();
				for (auto old_instance = model_object.instances.begin(); old_instance != model_object.instances.end(); ++ old_instance, ++ new_instance) {
					(*old_instance)->set_transformation((*new_instance)->get_transformation());
                    (*old_instance)->print_volume_state = (*new_instance)->print_volume_state;
                    (*old_instance)->printable 		    = (*new_instance)->printable;
  				}
	        }
        }
    }

    // 4) Generate PrintObjects from ModelObjects and their instances.
    {
        std::vector<PrintObject*> print_objects_new;
        print_objects_new.reserve(std::max(m_objects.size(), m_model.objects.size()));
        bool new_objects = false;
        // Walk over all new model objects and check, whether there are matching PrintObjects.
        for (ModelObject *model_object : m_model.objects) {
            auto range = print_object_status.equal_range(PrintObjectStatus(model_object->id()));
            std::vector<const PrintObjectStatus*> old;
            if (range.first != range.second) {
                old.reserve(print_object_status.count(PrintObjectStatus(model_object->id())));
                for (auto it = range.first; it != range.second; ++ it)
                    if (it->status != PrintObjectStatus::Deleted)
                        old.emplace_back(&(*it));
            }
            // Generate a list of trafos and XY offsets for instances of a ModelObject
            // Producing the config for PrintObject on demand, caching it at print_object_last.
            const PrintObject *print_object_last = nullptr;
            auto print_object_apply_config = [this, &print_object_last, model_object, num_extruders](PrintObject* print_object) {
                print_object->config_apply(print_object_last ?
                    print_object_last->config() :
                    PrintObject::object_config_from_model_object(m_default_object_config, *model_object, num_extruders));
                print_object_last = print_object;
            };
            std::vector<PrintObjectTrafoAndInstances> new_print_instances = print_objects_from_model_object(*model_object);
            if (old.empty()) {
                // Simple case, just generate new instances.
                for (PrintObjectTrafoAndInstances &print_instances : new_print_instances) {
                    PrintObject *print_object = new PrintObject(this, model_object, print_instances.trafo, std::move(print_instances.instances));
                    print_object_apply_config(print_object);
                    print_objects_new.emplace_back(print_object);
                    // print_object_status.emplace(PrintObjectStatus(print_object, PrintObjectStatus::New));
                    new_objects = true;
                }
                continue;
            }
            // Complex case, try to merge the two lists.
            // Sort the old lexicographically by their trafos.
            std::sort(old.begin(), old.end(), [](const PrintObjectStatus *lhs, const PrintObjectStatus *rhs){ return transform3d_lower(lhs->trafo, rhs->trafo); });
            // Merge the old / new lists.
            auto it_old = old.begin();
            for (PrintObjectTrafoAndInstances &new_instances : new_print_instances) {
				for (; it_old != old.end() && transform3d_lower((*it_old)->trafo, new_instances.trafo); ++ it_old);
				if (it_old == old.end() || ! transform3d_equal((*it_old)->trafo, new_instances.trafo)) {
                    // This is a new instance (or a set of instances with the same trafo). Just add it.
                    PrintObject *print_object = new PrintObject(this, model_object, new_instances.trafo, std::move(new_instances.instances));
                    print_object_apply_config(print_object);
                    print_objects_new.emplace_back(print_object);
                    // print_object_status.emplace(PrintObjectStatus(print_object, PrintObjectStatus::New));
                    new_objects = true;
                    if (it_old != old.end())
                        const_cast<PrintObjectStatus*>(*it_old)->status = PrintObjectStatus::Deleted;
                } else {
                    // The PrintObject already exists and the copies differ.
					PrintBase::ApplyStatus status = (*it_old)->print_object->set_instances(std::move(new_instances.instances));
                    if (status != PrintBase::APPLY_STATUS_UNCHANGED)
						update_apply_status(status == PrintBase::APPLY_STATUS_INVALIDATED);
					print_objects_new.emplace_back((*it_old)->print_object);
					const_cast<PrintObjectStatus*>(*it_old)->status = PrintObjectStatus::Reused;
				}
            }
        }
        if (m_objects != print_objects_new) {
            this->call_cancel_callback();
			update_apply_status(this->invalidate_all_steps());
            m_objects = print_objects_new;
            // Delete the PrintObjects marked as Unknown or Deleted.
            bool deleted_objects = false;
            for (auto &pos : print_object_status)
                if (pos.status == PrintObjectStatus::Unknown || pos.status == PrintObjectStatus::Deleted) {
                    update_apply_status(pos.print_object->invalidate_all_steps());
                    delete pos.print_object;
					deleted_objects = true;
                }
			if (new_objects || deleted_objects)
				update_apply_status(this->invalidate_steps({ psSkirt, psBrim, psWipeTower, psGCodeExport }));
			if (new_objects)
	            update_apply_status(false);
        }
        print_object_status.clear();
    }

    // 5) Synchronize configs of ModelVolumes, synchronize AMF / 3MF materials (and their configs), refresh PrintRegions.
    // Update reference counts of regions from the remaining PrintObjects and their volumes.
    // Regions with zero references could and should be reused.
    for (PrintRegion *region : m_regions)
        region->m_refcnt = 0;
    for (PrintObject *print_object : m_objects) {
        for (int idx_region = 0; idx_region < print_object->region_volumes.size(); ++idx_region) {
            if (!print_object->region_volumes[idx_region].empty())
                ++ m_regions[idx_region]->m_refcnt;
        }
    }

    // All regions now have distinct settings.
    // Check whether applying the new region config defaults we'd get different regions.
    for (size_t region_id = 0; region_id < m_regions.size(); ++ region_id) {
        PrintRegion       &region = *m_regions[region_id];
        PrintRegionConfig  this_region_config;
        bool               this_region_config_set = false;
        for (PrintObject *print_object : m_objects) {
            const LayerRanges *layer_ranges;
            {
                auto it_status = model_object_status.find(ModelObjectStatus(print_object->model_object()->id()));
                assert(it_status != model_object_status.end());
                assert(it_status->status != ModelObjectStatus::Deleted);
                layer_ranges = &it_status->layer_ranges;
            }
            if (region_id < print_object->region_volumes.size()) {
                for (const std::pair<t_layer_height_range, int> &volume_and_range : print_object->region_volumes[region_id]) {
                    const ModelVolume        &volume             = *print_object->model_object()->volumes[volume_and_range.second];
                    const DynamicPrintConfig *layer_range_config = layer_ranges->config(volume_and_range.first);
                    if (this_region_config_set) {
                        // If the new config for this volume differs from the other
                        // volume configs currently associated to this region, it means
                        // the region subdivision does not make sense anymore.
                        if (! this_region_config.equals(PrintObject::region_config_from_model_volume(m_default_region_config, layer_range_config, volume, num_extruders)))
                            // Regions were split. Reset this print_object.
                            goto print_object_end;
                    } else {
                        this_region_config = PrintObject::region_config_from_model_volume(m_default_region_config, layer_range_config, volume, num_extruders);
						for (size_t i = 0; i < region_id; ++ i) {
							const PrintRegion &region_other = *m_regions[i];
							if (region_other.m_refcnt != 0 && region_other.config().equals(this_region_config))
								// Regions were merged. Reset this print_object.
								goto print_object_end;
						}
                        this_region_config_set = true;
                    }
                }
            }
            continue;
        print_object_end:
            update_apply_status(print_object->invalidate_all_steps());
            // Decrease the references to regions from this volume.
            int ireg = 0;
            for (const std::vector<std::pair<t_layer_height_range, int>> &volumes : print_object->region_volumes) {
                if (! volumes.empty())
                    -- m_regions[ireg]->m_refcnt;
                ++ ireg;
            }
            print_object->region_volumes.clear();
        }
        if (this_region_config_set) {
            t_config_option_keys diff = region.config().diff(this_region_config);
            if (! diff.empty()) {
                region.config_apply_only(this_region_config, diff, false);
                for (PrintObject *print_object : m_objects)
                    if (region_id < print_object->region_volumes.size() && ! print_object->region_volumes[region_id].empty())
                        update_apply_status(print_object->invalidate_state_by_config_options(diff));
            }
        }
    }

    // Possibly add new regions for the newly added or resetted PrintObjects.
    for (size_t idx_print_object = 0; idx_print_object < m_objects.size(); ++ idx_print_object) {
        PrintObject        &print_object0 = *m_objects[idx_print_object];
        const ModelObject  &model_object  = *print_object0.model_object();
        const LayerRanges *layer_ranges;
        {
            auto it_status = model_object_status.find(ModelObjectStatus(model_object.id()));
            assert(it_status != model_object_status.end());
            assert(it_status->status != ModelObjectStatus::Deleted);
            layer_ranges = &it_status->layer_ranges;
        }
        std::vector<int>   regions_in_object;
        regions_in_object.reserve(64);
        for (size_t i = idx_print_object; i < m_objects.size() && m_objects[i]->model_object() == &model_object; ++ i) {
            PrintObject &print_object = *m_objects[i];
			bool         fresh = print_object.region_volumes.empty();
            unsigned int volume_id = 0;
            unsigned int idx_region_in_object = 0;
            for (const ModelVolume *volume : model_object.volumes) {
                if (! volume->is_model_part() && ! volume->is_modifier()) {
					++ volume_id;
					continue;
				}
                // Filter the layer ranges, so they do not overlap and they contain at least a single layer.
                // Now insert a volume with a layer range to its own region.
                for (auto it_range = layer_ranges->begin(); it_range != layer_ranges->end(); ++ it_range) {
                    int region_id = -1;
                    if (&print_object == &print_object0) {
                        // Get the config applied to this volume.
                        PrintRegionConfig config = PrintObject::region_config_from_model_volume(m_default_region_config, it_range->second, *volume, num_extruders);
                        // Find an existing print region with the same config.
    					int idx_empty_slot = -1;
    					for (int i = 0; i < (int)m_regions.size(); ++ i) {
    						if (m_regions[i]->m_refcnt == 0) {
                                if (idx_empty_slot == -1)
                                    idx_empty_slot = i;
                            } else if (config.equals(m_regions[i]->config())) {
                                region_id = i;
                                break;
                            }
    					}
                        // If no region exists with the same config, create a new one.
    					if (region_id == -1) {
    						if (idx_empty_slot == -1) {
    							region_id = (int)m_regions.size();
    							this->add_region(config);
    						} else {
    							region_id = idx_empty_slot;
                                m_regions[region_id]->set_config(std::move(config));
    						}
                        }
                        regions_in_object.emplace_back(region_id);
                    } else
                        region_id = regions_in_object[idx_region_in_object ++];
                    // Assign volume to a region.
    				if (fresh) {
    					if ((size_t)region_id >= print_object.region_volumes.size() || print_object.region_volumes[region_id].empty())
    						++ m_regions[region_id]->m_refcnt;
    					print_object.add_region_volume(region_id, volume_id, it_range->first);
    				}
                }
				++ volume_id;
			}
        }
    }

    // Update SlicingParameters for each object where the SlicingParameters is not valid.
    // If it is not valid, then it is ensured that PrintObject.m_slicing_params is not in use
    // (posSlicing and posSupportMaterial was invalidated).
    for (PrintObject *object : m_objects)
        object->update_slicing_parameters();

#ifdef _DEBUG
    check_model_ids_equal(m_model, model);
#endif /* _DEBUG */

	return static_cast<ApplyStatus>(apply_status);
}

bool Print::has_infinite_skirt() const
{
    return (m_config.draft_shield && m_config.skirts > 0) || (m_config.ooze_prevention && this->extruders().size() > 1);
}

bool Print::has_skirt() const
{
    return (m_config.skirt_height > 0 && m_config.skirts > 0) || this->has_infinite_skirt();
}

static inline bool sequential_print_horizontal_clearance_valid(const Print &print)
{
    if (print.config().extruder_clearance_radius == 0)
        return true;
	Polygons convex_hulls_other;
	std::map<ObjectID, Polygon> map_model_object_to_convex_hull;
    const double dist_grow = PrintConfig::min_object_distance(&print.default_region_config()) * 2;
	for (const PrintObject *print_object : print.objects()) {
        const double object_grow = print.config().complete_objects_one_brim ? dist_grow : std::max(dist_grow, print_object->config().brim_width.value);
	    assert(! print_object->model_object()->instances.empty());
	    assert(! print_object->instances().empty());
	    ObjectID model_object_id = print_object->model_object()->id();
	    auto it_convex_hull = map_model_object_to_convex_hull.find(model_object_id);
        // Get convex hull of all printable volumes assigned to this print object.
        ModelInstance *model_instance0 = print_object->model_object()->instances.front();
	    if (it_convex_hull == map_model_object_to_convex_hull.end()) {
	        // Calculate the convex hull of a printable object. 
	        // Grow convex hull with the clearance margin.
	        // FIXME: Arrangement has different parameters for offsetting (jtMiter, limit 2)
	        // which causes that the warning will be showed after arrangement with the
	        // appropriate object distance. Even if I set this to jtMiter the warning still shows up.
	        it_convex_hull = map_model_object_to_convex_hull.emplace_hint(it_convex_hull, model_object_id, 
                offset(print_object->model_object()->convex_hull_2d(
	                        Geometry::assemble_transform(Vec3d::Zero(), model_instance0->get_rotation(), model_instance0->get_scaling_factor(), model_instance0->get_mirror())),
                	// Shrink the extruder_clearance_radius a tiny bit, so that if the object arrangement algorithm placed the objects
	                // exactly by satisfying the extruder_clearance_radius, this test will not trigger collision.
	                float(scale_(0.5 * object_grow - EPSILON)),
	                jtRound, float(scale_(0.1))).front());
	    }
	    // Make a copy, so it may be rotated for instances.
        //FIXME seems like the rotation isn't taken into account
	    Polygon convex_hull0 = it_convex_hull->second;
        //this can create bugs in macos, for reasons.
		double z_diff = Geometry::rotation_diff_z(model_instance0->get_rotation(), print_object->instances().front().model_instance->get_rotation());
		if (std::abs(z_diff) > EPSILON)
			convex_hull0.rotate(z_diff);
        // Now we check that no instance of convex_hull intersects any of the previously checked object instances.
        for (const PrintInstance& instance : print_object->instances()) {
            Polygon convex_hull = convex_hull0;
            // instance.shift is a position of a centered object, while model object may not be centered.
            // Conver the shift from the PrintObject's coordinates into ModelObject's coordinates by removing the centering offset.
            convex_hull.translate(instance.shift - print_object->center_offset());
	        if (! intersection(convex_hulls_other, (Polygons)convex_hull).empty())
                return false;
	        convex_hulls_other.emplace_back(std::move(convex_hull));
        }

        /*
        'old' superslicer sequential_print_horizontal_clearance_valid, that is better at skirts, but need some works, as the arrange has changed.
	    // Now we check that no instance of convex_hull intersects any of the previously checked object instances.
	    for (const PrintInstance &instance : print_object->instances()) {
            Polygons convex_hull = print_object->model_object()->convex_hull_2d(
                Geometry::assemble_transform(Vec3d::Zero(),
                    instance.model_instance->get_rotation(), instance.model_instance->get_scaling_factor(), instance.model_instance->get_mirror()));
                // Shrink the extruder_clearance_radius a tiny bit, so that if the object arrangement algorithm placed the objects
                // exactly by satisfying the extruder_clearance_radius, this test will not trigger collision.
                //float(scale_(0.5 * print.config().extruder_clearance_radius.value - EPSILON)),
                //jtRound, float(scale_(0.1)));
            if (convex_hull.empty())
                continue;
	        // instance.shift is a position of a centered object, while model object may not be centered.
	        // Conver the shift from the PrintObject's coordinates into ModelObject's coordinates by removing the centering offset.
            for(Polygon &poly : convex_hull)
	            poly.translate(instance.shift - print_object->center_offset());
	        if (! intersection(
                    convex_hulls_other, 
                    offset(convex_hull[0], double(scale_(PrintConfig::min_object_distance(&instance.print_object->config(),0.)) - SCALED_EPSILON), jtRound, scale_(0.1))).empty())
	            return false;
            double extra_grow = PrintConfig::min_object_distance(&instance.print_object->config(), 1.);
            if (extra_grow > 0)
                convex_hull = offset(convex_hull, scale_(extra_grow));
	        polygons_append(convex_hulls_other, convex_hull);
	    }
        */
	}
	return true;
}

static inline bool sequential_print_vertical_clearance_valid(const Print &print)
{
	std::vector<const PrintInstance*> print_instances_ordered = sort_object_instances_by_model_order(print);
	// Ignore the last instance printed.
	print_instances_ordered.pop_back();
	// Find the other highest instance.
	auto it = std::max_element(print_instances_ordered.begin(), print_instances_ordered.end(), [](auto l, auto r) {
		return l->print_object->height() < r->print_object->height();
	});
    return it == print_instances_ordered.end() || (*it)->print_object->height() <= scale_(print.config().extruder_clearance_height.value);
}


double Print::get_object_first_layer_height(const PrintObject& object) const {
    //get object first layer height
    double object_first_layer_height = object.config().first_layer_height.value;
    if (object.config().first_layer_height.percent) {
        std::set<uint16_t> object_extruders;
        for (size_t region_id = 0; region_id < object.region_volumes.size(); ++region_id) {
            if (object.region_volumes[region_id].empty()) continue;
            const PrintRegion* region = this->regions()[region_id];
            PrintRegion::collect_object_printing_extruders(config(), object.config(), region->config(), object_extruders);
        }
        object_first_layer_height = 1000000000;
        for (uint16_t extruder_id : object_extruders) {
            double nozzle_diameter = config().nozzle_diameter.values[extruder_id];
            object_first_layer_height = std::min(object_first_layer_height, object.config().first_layer_height.get_abs_value(nozzle_diameter));
        }
    }
    return object_first_layer_height;
}

double Print::get_first_layer_height() const
{
    if (m_objects.empty())
        throw Slic3r::InvalidArgument("first_layer_height() can't be called without PrintObjects");

    double min_layer_height = 10000000000.;
    for(PrintObject* obj : m_objects)
        min_layer_height = std::fmin(min_layer_height, get_object_first_layer_height(*obj));

    if(min_layer_height == 10000000000.)
        throw Slic3r::InvalidArgument("first_layer_height() can't be computed");

    return min_layer_height;
}

// Precondition: Print::validate() requires the Print::apply() to be called its invocation.
std::pair<PrintBase::PrintValidationError, std::string> Print::validate() const
{
    if (m_objects.empty())
        return { PrintBase::PrintValidationError::pveWrongPosition, L("All objects are outside of the print volume.") };

    if (extruders().empty())
        return { PrintBase::PrintValidationError::pveNoPrint, L("The supplied settings will cause an empty print.") };

    if (m_config.complete_objects) {
    	if (! sequential_print_horizontal_clearance_valid(*this))
            return { PrintBase::PrintValidationError::pveWrongPosition, L("Some objects are too close; your extruder will collide with them.") };
        if (! sequential_print_vertical_clearance_valid(*this))
            return { PrintBase::PrintValidationError::pveWrongPosition,L("Some objects are too tall and cannot be printed without extruder collisions.") };
    }

    if (m_config.spiral_vase) {
        size_t total_copies_count = 0;
        for (const PrintObject *object : m_objects)
            total_copies_count += object->instances().size();
        // #4043
        if (total_copies_count > 1 && ! m_config.complete_objects.value)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("Only a single object may be printed at a time in Spiral Vase mode. "
                     "Either remove all but the last object, or enable sequential mode by \"complete_objects\".") };
        assert(m_objects.size() == 1 || config().complete_objects.value);
        size_t num_regions = 0;
        for (const std::vector<std::pair<t_layer_height_range, int>> &volumes_per_region : m_objects.front()->region_volumes)
        	if (! volumes_per_region.empty())
        		++ num_regions;
        if (num_regions > 1)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Spiral Vase option can only be used when printing single material objects.") };
    }

    if (this->has_wipe_tower() && ! m_objects.empty()) {
        // Make sure all extruders use same diameter filament and have the same nozzle diameter
        // EPSILON comparison is used for nozzles and 10 % tolerance is used for filaments
        double first_nozzle_diam = m_config.nozzle_diameter.get_at(*extruders().begin());
        double first_filament_diam = m_config.filament_diameter.get_at(*extruders().begin());
        for (const auto& extruder_idx : extruders()) {
            double nozzle_diam = m_config.nozzle_diameter.get_at(extruder_idx);
            double filament_diam = m_config.filament_diameter.get_at(extruder_idx);
            if (nozzle_diam - EPSILON > first_nozzle_diam || nozzle_diam + EPSILON < first_nozzle_diam
             || std::abs((filament_diam-first_filament_diam)/first_filament_diam) > 0.1)
                return { PrintBase::PrintValidationError::pveWrongSettings,L("The wipe tower is only supported if all extruders have the same nozzle diameter "
                         "and use filaments of the same diameter.") };
        }

        if (m_config.gcode_flavor != gcfRepRap && m_config.gcode_flavor != gcfSprinter && m_config.gcode_flavor != gcfRepetier && m_config.gcode_flavor != gcfMarlin
            && m_config.gcode_flavor != gcfKlipper)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is currently only supported for the Marlin, RepRap/Sprinter and Repetier G-code flavors.") };
        if (! m_config.use_relative_e_distances)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is currently only supported with the relative extruder addressing (use_relative_e_distances=1).") };
        if (m_config.ooze_prevention)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("Ooze prevention is currently not supported with the wipe tower enabled.") };
        if (m_config.use_volumetric_e)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower currently does not support volumetric E (use_volumetric_e=0).") };
        if (m_config.complete_objects && extruders().size() > 1)
            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is currently not supported for multimaterial sequential prints.") };
        
        if (m_objects.size() > 1) {
            bool                                has_custom_layering = false;
            std::vector<std::vector<coordf_t>>  layer_height_profiles;
            for (const PrintObject *object : m_objects) {
                has_custom_layering = ! object->model_object()->layer_config_ranges.empty() || ! object->model_object()->layer_height_profile.empty();
                if (has_custom_layering) {
                    layer_height_profiles.assign(m_objects.size(), std::vector<coordf_t>());
                    break;
                }
            }
            const SlicingParameters &slicing_params0 = m_objects.front()->slicing_parameters();
            size_t            tallest_object_idx = 0;
            if (has_custom_layering)
                PrintObject::update_layer_height_profile(*m_objects.front()->model_object(), slicing_params0, layer_height_profiles.front());
            for (size_t i = 1; i < m_objects.size(); ++ i) {
                const PrintObject       *object         = m_objects[i];
                const SlicingParameters &slicing_params = object->slicing_parameters();
                if (std::abs(slicing_params.first_print_layer_height - slicing_params0.first_print_layer_height) > EPSILON ||
                    std::abs(slicing_params.layer_height             - slicing_params0.layer_height            ) > EPSILON)
                    return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is only supported for multiple objects if they have equal layer heights") };
                if (slicing_params.raft_layers() != slicing_params0.raft_layers())
                    return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is only supported for multiple objects if they are printed over an equal number of raft layers") };
                if (object->config().support_material_contact_distance_type != m_objects.front()->config().support_material_contact_distance_type
                    || object->config().support_material_contact_distance_top != m_objects.front()->config().support_material_contact_distance_top
                    || object->config().support_material_contact_distance_bottom != m_objects.front()->config().support_material_contact_distance_bottom)
                    return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is only supported for multiple objects if they are printed with the same support_material_contact_distance") };
                if (! equal_layering(slicing_params, slicing_params0))
                    return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower is only supported for multiple objects if they are sliced equally.") };
                if (has_custom_layering) {
                    PrintObject::update_layer_height_profile(*object->model_object(), slicing_params, layer_height_profiles[i]);
                    if (*(layer_height_profiles[i].end()-2) > *(layer_height_profiles[tallest_object_idx].end()-2))
                        tallest_object_idx = i;
                }
            }

            if (has_custom_layering) {
                const std::vector<coordf_t> &layer_height_profile_tallest = layer_height_profiles[tallest_object_idx];
                for (size_t idx_object = 0; idx_object < m_objects.size(); ++ idx_object) {
                    if (idx_object == tallest_object_idx)
                        continue;
                    const std::vector<coordf_t> &layer_height_profile = layer_height_profiles[idx_object];

                    // The comparison of the profiles is not just about element-wise equality, some layers may not be
                    // explicitely included. Always remember z and height of last reference layer that in the vector
                    // and compare to that. In case some layers are in the vectors multiple times, only the last entry is
                    // taken into account and compared.
                    size_t i = 0; // index into tested profile
                    size_t j = 0; // index into reference profile
                    coordf_t ref_z = -1.;
                    coordf_t next_ref_z = layer_height_profile_tallest[0];
                    coordf_t ref_height = -1.;
                    while (i < layer_height_profile.size()) {
                        coordf_t this_z = layer_height_profile[i];
                        // find the last entry with this z
                        while (i+2 < layer_height_profile.size() && layer_height_profile[i+2] == this_z)
                            i += 2;

                        coordf_t this_height = layer_height_profile[i+1];
                        if (ref_height < -1. || next_ref_z < this_z + EPSILON) {
                            ref_z = next_ref_z;
                            do { // one layer can be in the vector several times
                                ref_height = layer_height_profile_tallest[j+1];
                                if (j+2 >= layer_height_profile_tallest.size())
                                    break;
                                j += 2;
                                next_ref_z = layer_height_profile_tallest[j];
                            } while (ref_z == next_ref_z);
                        }
                        if (std::abs(this_height - ref_height) > EPSILON)
                            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe tower is only supported if all objects have the same variable layer height") };
                        i += 2;
                    }
                }
            }
    }
    }
    
	{
		std::set<uint16_t> extruders = this->extruders();

		// Find the smallest used nozzle diameter and the number of unique nozzle diameters.
		double min_nozzle_diameter = std::numeric_limits<double>::max();
		double max_nozzle_diameter = 0;
		for (uint16_t extruder_id : extruders) {
			double dmr = m_config.nozzle_diameter.get_at(extruder_id);
			min_nozzle_diameter = std::min(min_nozzle_diameter, dmr);
			max_nozzle_diameter = std::max(max_nozzle_diameter, dmr);
		}

#if 0
        // We currently allow one to assign extruders with a higher index than the number
        // of physical extruders the machine is equipped with, as the Printer::apply() clamps them.
        unsigned int total_extruders_count = m_config.nozzle_diameter.size();
        for (const auto& extruder_idx : extruders)
            if ( extruder_idx >= total_extruders_count )
                return L("One or more object were assigned an extruder that the printer does not have.");
#endif

        const double print_first_layer_height = get_first_layer_height();
        for (PrintObject *object : m_objects) {
            if (object->config().raft_layers > 0 || object->config().support_material.value) {
                if ((object->config().support_material_extruder == 0 || object->config().support_material_interface_extruder == 0) && max_nozzle_diameter - min_nozzle_diameter > EPSILON) {
                    // The object has some form of support and either support_material_extruder or support_material_interface_extruder
                    // will be printed with the current tool without a forced tool change. Play safe, assert that all object nozzles
                    // are of the same diameter.
                    return { PrintBase::PrintValidationError::pveWrongSettings,L("Printing with multiple extruders of differing nozzle diameters. "
                           "If support is to be printed with the current extruder (support_material_extruder == 0 or support_material_interface_extruder == 0), "
                           "all nozzles have to be of the same diameter.") };
                }
                if (this->has_wipe_tower()) {
                    if (object->config().support_material_contact_distance_type.value == zdNone) {
                        // Soluble interface
                        if (! object->config().support_material_synchronize_layers)
                            return { PrintBase::PrintValidationError::pveWrongSettings,L("For the Wipe Tower to work with the soluble supports, the support layers need to be synchronized with the object layers.") };
                    } else {
                        // Non-soluble interface
                        if (object->config().support_material_extruder != 0 || object->config().support_material_interface_extruder != 0)
                            return { PrintBase::PrintValidationError::pveWrongSettings,L("The Wipe Tower currently supports the non-soluble supports only if they are printed with the current extruder without triggering a tool change. "
                                     "(both support_material_extruder and support_material_interface_extruder need to be set to 0).") };
                    }
                }
            }
            
            const double object_first_layer_height = get_object_first_layer_height(*object);
            // validate layer_height for each region
            for (size_t region_id = 0; region_id < object->region_volumes.size(); ++region_id) {
                if (object->region_volumes[region_id].empty()) continue;
                const PrintRegion* region = this->regions()[region_id];
                std::set<uint16_t> object_extruders;
                PrintRegion::collect_object_printing_extruders(config(), object->config(), region->config(), object_extruders);
                double layer_height = object->config().layer_height.value;
                for (uint16_t extruder_id : object_extruders) {
                    double nozzle_diameter = config().nozzle_diameter.get_at(extruder_id);
                    double min_layer_height = config().min_layer_height.get_abs_value(extruder_id, nozzle_diameter);
                    double max_layer_height = config().max_layer_height.get_abs_value(extruder_id, nozzle_diameter);
                    if (max_layer_height < EPSILON) max_layer_height = nozzle_diameter * 0.75;
                    if (min_layer_height > max_layer_height) return { PrintBase::PrintValidationError::pveWrongSettings, L("Min layer height can't be greater than Max layer height") };
                    if (max_layer_height > nozzle_diameter) return { PrintBase::PrintValidationError::pveWrongSettings, L("Max layer height can't be greater than nozzle diameter") };
                    double skirt_width = Flow::new_from_config_width(frPerimeter, 
                        *Flow::extrusion_option("skirt_extrusion_width", m_default_region_config), 
                        (float)m_config.nozzle_diameter.get_at(extruder_id), 
                        print_first_layer_height,
                        1,0 //don't care, all i want if width from width
                    ).width;
                    //check first layer
                    if (object->region_volumes[region_id].front().first.first < object_first_layer_height) {
                        if (object_first_layer_height + EPSILON < min_layer_height)
                            return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("First layer height can't be thinner than %s")) % "min layer height").str() };
                        for (auto tuple : std::vector<std::pair<double, const char*>>{
                                {nozzle_diameter, "nozzle diameter"},
                                {max_layer_height, "max layer height"},
                                {skirt_width, "skirt extrusion width"},
                                {object->config().support_material ? region->width(FlowRole::frSupportMaterial, true, *object) : object_first_layer_height, "support material extrusion width"},
                                {region->width(FlowRole::frPerimeter, true, *object), "perimeter extrusion width"},
                                {region->width(FlowRole::frExternalPerimeter, true, *object), "perimeter extrusion width"},
                                {region->width(FlowRole::frInfill, true, *object), "infill extrusion width"},
                                {region->width(FlowRole::frSolidInfill, true, *object), "solid infill extrusion width"},
                                {region->width(FlowRole::frTopSolidInfill, true, *object), "top solid infill extrusion width"},
                            })
                            if (object_first_layer_height > tuple.first + EPSILON)
                                return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("First layer height can't be greater than %s")) % tuple.second).str() };

                    }
                    //check not-first layer
                    if (object->region_volumes[region_id].front().first.second > layer_height) {
                        if (layer_height + EPSILON < min_layer_height)
                            return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("First layer height can't be higher than %s")) % "min layer height").str() };
                        for (auto tuple : std::vector<std::pair<double, const char*>>{
                                {nozzle_diameter, "nozzle diameter"},
                                {max_layer_height, "max layer height"},
                                {skirt_width, "skirt extrusion width"},
                                {object->config().support_material ? region->width(FlowRole::frSupportMaterial, false, *object) : layer_height, "support material extrusion width"},
                                {region->width(FlowRole::frPerimeter, false, *object), "perimeter extrusion width"},
                                {region->width(FlowRole::frExternalPerimeter, false, *object), "perimeter extrusion width"},
                                {region->width(FlowRole::frInfill, false, *object), "infill extrusion width"},
                                {region->width(FlowRole::frSolidInfill, false, *object), "solid infill extrusion width"},
                                {region->width(FlowRole::frTopSolidInfill, false, *object), "top solid infill extrusion width"},
                            })
                            if (layer_height > tuple.first + EPSILON)
                                return { PrintBase::PrintValidationError::pveWrongSettings, (boost::format(L("Layer height can't be greater than %s")) % tuple.second).str() };
                    }
                }
            }

        }
    }

    return { PrintValidationError::pveNone, std::string() };
}

#if 0
// the bounding box of objects placed in copies position
// (without taking skirt/brim/support material into account)
BoundingBox Print::bounding_box() const
{
    BoundingBox bb;
    for (const PrintObject *object : m_objects)
        for (const PrintInstance &instance : object->instances()) {
            BoundingBox bb2(object->bounding_box());
            bb.merge(bb2.min + instance.shift);
            bb.merge(bb2.max + instance.shift);
        }
    return bb;
}

// the total bounding box of extrusions, including skirt/brim/support material
// this methods needs to be called even when no steps were processed, so it should
// only use configuration values
BoundingBox Print::total_bounding_box() const
{
    // get objects bounding box
    BoundingBox bb = this->bounding_box();
    
    // we need to offset the objects bounding box by at least half the perimeters extrusion width
    Flow perimeter_flow = m_objects.front()->get_layer(0)->get_region(0)->flow(frPerimeter);
    double extra = perimeter_flow.width/2;
    
    // consider support material
    if (this->has_support_material()) {
        extra = std::max(extra, SUPPORT_MATERIAL_MARGIN);
    }
    
    // consider brim and skirt
    if (m_config.brim_width.value > 0) {
        Flow brim_flow = this->brim_flow();
        extra = std::max(extra, m_config.brim_width.value + brim_flow.width/2);
    }
    if (this->has_skirt()) {
        int skirts = m_config.skirts.value + m_config.skirt_brim.value;
        if (skirts == 0 && this->has_infinite_skirt()) skirts = 1;
        Flow skirt_flow = this->skirt_flow();
        if (m_config.skirt_distance_from_brim)
            extra += m_config.brim_width.value
                + m_config.skirt_distance.value
                + skirts * skirt_flow.spacing()
                + skirt_flow.width / 2;
        else
            extra = std::max(
                extra,
                m_config.brim_width.value
                    + m_config.skirt_distance.value
                    + skirts * skirt_flow.spacing()
                    + skirt_flow.width/2
            );
    }
    
    if (extra > 0)
        bb.offset(scale_(extra));
    
    return bb;
}
#endif

Flow Print::brim_flow(size_t extruder_id, const PrintObjectConfig& brim_config) const
{
    //use default region, but current object config.
    PrintRegionConfig tempConf = m_default_region_config;
    tempConf.parent = &brim_config;
    return Flow::new_from_config_width(
        frPerimeter,
        *Flow::extrusion_option("brim_extrusion_width", tempConf),
        (float)m_config.nozzle_diameter.get_at(extruder_id),
        (float)get_first_layer_height(),
        (extruder_id < m_config.nozzle_diameter.values.size()) ? brim_config.get_computed_value("filament_max_overlap", extruder_id) : 1,
        0
    );
}

Flow Print::skirt_flow(size_t extruder_id, bool first_layer/*=false*/) const
{
    if (m_objects.empty())
        throw Slic3r::InvalidArgument("skirt_first_layer_height() can't be called without PrintObjects");

    //get extruder used to compute first layer height
    double max_nozzle_diam;
    for (PrintObject* pobject : m_objects) {
        PrintObject& object = *pobject;
        std::set<uint16_t> object_extruders;
        for (size_t region_id = 0; region_id < object.region_volumes.size(); ++region_id) {
            if (object.region_volumes[region_id].empty()) continue;
            const PrintRegion* region = this->regions()[region_id];
            PrintRegion::collect_object_printing_extruders(config(), object.config(), region->config(), object_extruders);
        }
        //get object first layer extruder
        int first_layer_extruder = 0;
        for (uint16_t extruder_id : object_extruders) {
            double nozzle_diameter = config().nozzle_diameter.values[extruder_id];
            max_nozzle_diam = std::max(max_nozzle_diam, nozzle_diameter);
        }
    }

    
    //send m_default_object_config becasue it's the lowest config needed (extrusion_option need config from object & print)
    return Flow::new_from_config_width(
        frPerimeter,
        *Flow::extrusion_option("skirt_extrusion_width", m_default_region_config),
        (float)max_nozzle_diam,
        (float)get_first_layer_height(),
        1, // hard to say what extruder we have here(many) m_default_region_config.get_computed_value("filament_max_overlap", extruder -1),
        0
    );
    
}

bool Print::has_support_material() const
{
    for (const PrintObject *object : m_objects)
        if (object->has_support_material()) 
            return true;
    return false;
}

/*  This method assigns extruders to the volumes having a material
    but not having extruders set in the volume config. */
void Print::auto_assign_extruders(ModelObject* model_object) const
{
    // only assign extruders if object has more than one volume
    if (model_object->volumes.size() < 2)
        return;
    
//    size_t extruders = m_config.nozzle_diameter.values.size();
    for (size_t volume_id = 0; volume_id < model_object->volumes.size(); ++ volume_id) {
        ModelVolume *volume = model_object->volumes[volume_id];
        //FIXME Vojtech: This assigns an extruder ID even to a modifier volume, if it has a material assigned.
        if ((volume->is_model_part() || volume->is_modifier()) && ! volume->material_id().empty() && ! volume->config.has("extruder"))
            volume->config.set("extruder", int(volume_id + 1));
    }
}

// Slicing process, running at a background thread.
void Print::process()
{
    name_tbb_thread_pool_threads();
    bool something_done = !is_step_done_unguarded(psBrim);
    BOOST_LOG_TRIVIAL(info) << "Starting the slicing process." << log_memory_info();
    for (PrintObject *obj : m_objects)
        obj->make_perimeters();
    this->set_status(70, L("Infilling layers"));
    //note: as object seems to be sliced independantly, it's maybe possible to add a tbb parallel_loop with simple partitioner on infill,
    //  as prepare_infill has some function not // 
    for (PrintObject *obj : m_objects)
        obj->infill();
    for (PrintObject *obj : m_objects)
        obj->ironing();
    for (PrintObject *obj : m_objects)
        obj->generate_support_material();
    if (this->set_started(psWipeTower)) {
        m_wipe_tower_data.clear();
        m_tool_ordering.clear();
        if (this->has_wipe_tower()) {
            //this->set_status(95, L("Generating wipe tower"));
            this->_make_wipe_tower();
        } else if (! this->config().complete_objects.value) {
            // Initialize the tool ordering, so it could be used by the G-code preview slider for planning tool changes and filament switches.
            m_tool_ordering = ToolOrdering(*this, -1, false);
            if (m_tool_ordering.empty() || m_tool_ordering.last_extruder() == unsigned(-1))
                throw Slic3r::SlicingError("The print is empty. The model is not printable with current print settings.");
        }
        this->set_done(psWipeTower);
    }
    if (this->set_started(psSkirt)) {
        m_skirt.clear();
        m_skirt_first_layer.reset();

        m_skirt_convex_hull.clear();
        m_first_layer_convex_hull.points.clear();
        for (PrintObject *obj : m_objects) {
            obj->m_skirt.clear();
            obj->m_skirt_first_layer.reset();
        }
        if (this->has_skirt()) {
            this->set_status(88, L("Generating skirt"));
            if (config().complete_objects && !config().complete_objects_one_skirt){
                for (PrintObject *obj : m_objects){
                    //create a skirt "pattern" (one per object)
                    const std::vector<PrintInstance> copies{ obj->instances() };
                    obj->m_instances.clear();
                    obj->m_instances.emplace_back();
                    this->_make_skirt({ obj }, obj->m_skirt, obj->m_skirt_first_layer);
                    obj->m_instances = copies;
                }
            } else {
                this->_make_skirt(m_objects, m_skirt, m_skirt_first_layer);
            }
        }
        this->set_done(psSkirt);
    }
	if (this->set_started(psBrim)) {
        m_brim.clear();
        //group object per brim settings
        m_first_layer_convex_hull.points.clear();
        std::vector<std::vector<PrintObject*>> obj_groups;
        for (PrintObject *obj : m_objects) {
            obj->m_brim.clear();
            bool added = false;
            for (std::vector<PrintObject*> &obj_group : obj_groups) {
                if (obj_group.front()->config().brim_ears.value == obj->config().brim_ears.value
                    && obj_group.front()->config().brim_ears_max_angle.value == obj->config().brim_ears_max_angle.value
                    && obj_group.front()->config().brim_ears_pattern.value == obj->config().brim_ears_pattern.value
                    && obj_group.front()->config().brim_inside_holes.value == obj->config().brim_inside_holes.value
                    && obj_group.front()->config().brim_offset.value == obj->config().brim_offset.value
                    && obj_group.front()->config().brim_width.value == obj->config().brim_width.value
                    && obj_group.front()->config().brim_width_interior.value == obj->config().brim_width_interior.value
                    && obj_group.front()->config().first_layer_extrusion_width.value == obj->config().first_layer_extrusion_width.value) {
                    added = true;
                    obj_group.push_back(obj);
                }
            }
            if (!added) {
                obj_groups.emplace_back();
                obj_groups.back().push_back(obj);
            }
        }
        ExPolygons brim_area;
        if (obj_groups.size() > 1) {
            for (std::vector<PrintObject*> &obj_group : obj_groups)
                for (const PrintObject *object : obj_group)
                    if (!object->m_layers.empty())
                        for (const PrintInstance &pt : object->m_instances) {
                            int first_idx = brim_area.size();
                            brim_area.insert(brim_area.end(), object->m_layers.front()->lslices.begin(), object->m_layers.front()->lslices.end());
                            for (int i = first_idx; i < brim_area.size(); i++) {
                                brim_area[i].translate(pt.shift.x(), pt.shift.y());
                            }
                        }
        }
        for (std::vector<PrintObject*> &obj_group : obj_groups) {
            const PrintObjectConfig &brim_config = obj_group.front()->config();
            if (brim_config.brim_width > 0 || brim_config.brim_width_interior > 0) {
                this->set_status(88, L("Generating brim"));
                if (config().complete_objects && !config().complete_objects_one_brim) {
                    for (PrintObject *obj : obj_group) {
                        //get flow
                        std::set<uint16_t> set_extruders = this->object_extruders({ obj });
                        append(set_extruders, this->support_material_extruders());
                        Flow        flow = this->brim_flow(set_extruders.empty() ? m_regions.front()->config().perimeter_extruder - 1 : *set_extruders.begin(), obj->config());
                        //don't consider other objects/instances. It's not possible because it's duplicated by some code afterward... i think.
                        brim_area.clear();
                        //create a brim "pattern" (one per object)
                        const std::vector<PrintInstance> copies{ obj->instances() };
                        obj->m_instances.clear();
                        obj->m_instances.emplace_back();
                        if (brim_config.brim_width > 0) {
                            if (brim_config.brim_ears)
                                this->_make_brim_ears(flow, { obj }, brim_area, obj->m_brim);
                            else
                                this->_make_brim(flow, { obj }, brim_area, obj->m_brim);
                        }
                        if (brim_config.brim_width_interior > 0) {
                            _make_brim_interior(flow, { obj }, brim_area, obj->m_brim);
                        }
                        obj->m_instances = copies;
                    }
                } else {
                    if (obj_groups.size() > 1)
                        brim_area = union_ex(brim_area);
                    //get the first extruder in the list for these objects... replicating gcode generation
                    std::set<uint16_t> set_extruders = this->object_extruders(m_objects);
                    append(set_extruders, this->support_material_extruders());
                    Flow        flow = this->brim_flow(set_extruders.empty() ? m_regions.front()->config().perimeter_extruder - 1 : *set_extruders.begin(), m_default_object_config);
                    if (brim_config.brim_ears)
                        this->_make_brim_ears(flow, obj_group, brim_area, m_brim);
                    else
                        this->_make_brim(flow, obj_group, brim_area, m_brim);
                    if (brim_config.brim_width_interior > 0)
                        _make_brim_interior(flow, obj_group, brim_area, m_brim);
                }
            }
        }
        // Brim depends on skirt (brim lines are trimmed by the skirt lines), therefore if
        // the skirt gets invalidated, brim gets invalidated as well and the following line is called.
        this->finalize_first_layer_convex_hull();
       this->set_done(psBrim);
    }
    BOOST_LOG_TRIVIAL(info) << "Slicing process finished." << log_memory_info();
    //notify gui that the slicing/preview structs are ready to be drawed
    if (something_done)
        this->set_status(90, L("Slicing done"), SlicingStatus::FlagBits::SLICING_ENDED);
}

// G-code export process, running at a background thread.
// The export_gcode may die for various reasons (fails to process output_filename_format,
// write error into the G-code, cannot execute post-processing scripts).
// It is up to the caller to show an error message.
std::string Print::export_gcode(const std::string& path_template, GCodeProcessor::Result* result, ThumbnailsGeneratorCallback thumbnail_cb)
{
    // output everything to a G-code file
    // The following call may die if the output_filename_format template substitution fails.
    std::string path = this->output_filepath(path_template);
    std::string message;
    if (!path.empty() && result == nullptr) {
        // Only show the path if preview_data is not set -> running from command line.
        message = L("Exporting G-code");
        message += " to ";
        message += path;
    } else
        message = L("Generating G-code");
    this->set_status(90, message);

    // The following line may die for multiple reasons.
    GCode gcode;
    gcode.do_export(this, path.c_str(), result, thumbnail_cb);
    return path.c_str();
}

void Print::_make_skirt(const PrintObjectPtrs &objects, ExtrusionEntityCollection &out, std::optional<ExtrusionEntityCollection>& out_first_layer)
{
    // First off we need to decide how tall the skirt must be.
    // The skirt_height option from config is expressed in layers, but our
    // object might have different layer heights, so we need to find the print_z
    // of the highest layer involved.
    // Note that unless has_infinite_skirt() == true
    // the actual skirt might not reach this $skirt_height_z value since the print
    // order of objects on each layer is not guaranteed and will not generally
    // include the thickest object first. It is just guaranteed that a skirt is
    // prepended to the first 'n' layers (with 'n' = skirt_height).
    // $skirt_height_z in this case is the highest possible skirt height for safety.
    coordf_t skirt_height_z = 0.;
    for (const PrintObject *object : objects) {
        size_t skirt_layers = this->has_infinite_skirt() ?
            object->layer_count() : 
            std::min(size_t(m_config.skirt_height.value), object->layer_count());
        skirt_height_z = std::max(skirt_height_z, object->m_layers[skirt_layers-1]->print_z);
    }
    // Collect points from all layers contained in skirt height.
    Points points;
    for (const PrintObject *object : objects) {
        Points object_points;
        // Get object layers up to skirt_height_z.
        for (const Layer *layer : object->m_layers) {
            if (layer->print_z > skirt_height_z)
                break;
            for (const ExPolygon &expoly : layer->lslices)
                // Collect the outer contour points only, ignore holes for the calculation of the convex hull.
                append(object_points, expoly.contour.points);
        }
        // Get support layers up to skirt_height_z.
        for (const SupportLayer *layer : object->support_layers()) {
            if (layer->print_z > skirt_height_z)
                break;
            for (const ExtrusionEntity *extrusion_entity : layer->support_fills.entities) {
                Polylines poly;
                extrusion_entity->collect_polylines(poly);
                for (const Polyline& polyline : poly)
                    append(object_points, polyline.points);
            }
        }
        // if brim, it superseed object & support for first layer
        if (config().skirt_distance_from_brim) {
            // get first layer support
            if (!object->support_layers().empty() && object->support_layers().front()->print_z == object->m_layers[0]->print_z) {
                Points support_points;
                for (const ExtrusionEntity* extrusion_entity : object->support_layers().front()->support_fills.entities) {
                    Polylines poly;
                    extrusion_entity->collect_polylines(poly);
                    for (const Polyline& polyline : poly)
                        append(support_points, polyline.points);
                }
                Polygon hull_support = Slic3r::Geometry::convex_hull(support_points);
                for (const Polygon& poly : offset(hull_support, scale_(object->config().brim_width)))
                    append(object_points, poly.points);
            }
            // get object
            for (const ExPolygon& expoly : object->m_layers[0]->lslices)
                for (const Polygon& poly : offset(expoly.contour, scale_(object->config().brim_width)))
                    append(object_points, poly.points);
        }
        // Repeat points for each object copy.
        for (const PrintInstance &instance : object->instances()) {
            Points copy_points = object_points;
            for (Point &pt : copy_points)
                pt += instance.shift;
            append(points, copy_points);
        }
    }

    // Include the wipe tower.
    append(points, this->first_layer_wipe_tower_corners());

    if (points.size() < 3)
        // At least three points required for a convex hull.
        return;
    
    this->throw_if_canceled();
    Polygon convex_hull = Slic3r::Geometry::convex_hull(points);
    
    // Skirt may be printed on several layers, having distinct layer heights,
    // but loops must be aligned so can't vary width/spacing
    
    std::vector<size_t> extruders;
    std::vector<double> extruders_e_per_mm;
    {
        std::set<uint16_t> set_extruders = this->object_extruders(objects);
        append(set_extruders, this->support_material_extruders());
        extruders.reserve(set_extruders.size());
        extruders_e_per_mm.reserve(set_extruders.size());
        for (unsigned int extruder_id : set_extruders) {
            Flow   flow = this->skirt_flow(extruder_id);
            double mm3_per_mm = flow.mm3_per_mm();
            extruders.push_back(extruder_id);
            extruders_e_per_mm.push_back(Extruder((unsigned int)extruder_id, &m_config).e_per_mm(mm3_per_mm));
        }
    }

    // Number of skirt loops per skirt layer.
    size_t n_skirts = m_config.skirts.value;
    size_t n_skirts_first_layer = n_skirts + m_config.skirt_brim.value;
    if (this->has_infinite_skirt() && n_skirts == 0)
        n_skirts = 1;
    if (m_config.skirt_brim.value > 0)
        out_first_layer.emplace();
    // Initial offset of the brim inner edge from the object (possible with a support & raft).
    // The skirt will touch the brim if the brim is extruded.
    float distance = float(scale_(m_config.skirt_distance.value) - this->skirt_flow(extruders[extruders.size() - 1]).spacing() / 2.);


    size_t lines_per_extruder = (n_skirts + extruders.size() - 1) / extruders.size();
    size_t current_lines_per_extruder = n_skirts - lines_per_extruder * (extruders.size() - 1);

    // Draw outlines from outside to inside.
    // Loop while we have less skirts than required or any extruder hasn't reached the min length if any.
    std::vector<coordf_t> extruded_length(extruders.size(), 0.);
    for (size_t i = std::max(n_skirts, n_skirts_first_layer), extruder_idx = 0, nb_skirts = 1; i > 0; -- i) {
        bool first_layer_only = i <= (n_skirts_first_layer - n_skirts);
        Flow   flow = this->skirt_flow(extruders[extruders.size() - (1+ extruder_idx)]);
        float  spacing = flow.spacing();
        double mm3_per_mm = flow.mm3_per_mm();
        this->throw_if_canceled();
        // Offset the skirt outside.
        distance += float(scale_(spacing/2));
        // Generate the skirt centerline.
        Polygon loop;
        {
            Polygons loops = offset(convex_hull, distance, ClipperLib::jtRound, float(scale_(0.1)));
            //make sure the skirt is simple enough
            Geometry::simplify_polygons(loops, flow.scaled_width() / 10, &loops);
			if (loops.empty())
				break;
			loop = loops.front();
        }
        distance += float(scale_(spacing / 2));
        // Extrude the skirt loop.
        ExtrusionLoop eloop(elrSkirt);
        eloop.paths.emplace_back(ExtrusionPath(
            ExtrusionPath(
                erSkirt,
                (float)mm3_per_mm,         // this will be overridden at G-code export time
                flow.width,
				(float)get_first_layer_height()  // this will be overridden at G-code export time
            )));
        eloop.paths.back().polyline = loop.split_at_first_point();
        //we make it clowkwise, but as it will be reversed, it will be ccw
        eloop.make_clockwise();
        if(!first_layer_only)
            out.append(eloop);
        if(out_first_layer)
            out_first_layer->append(eloop);
        if (m_config.min_skirt_length.value > 0 && !first_layer_only) {
            // The skirt length is limited. Sum the total amount of filament length extruded, in mm.
            extruded_length[extruder_idx] += unscale<double>(loop.length()) * extruders_e_per_mm[extruder_idx];
            if (extruded_length[extruder_idx] < m_config.min_skirt_length.value) {
                // Not extruded enough yet with the current extruder. Add another loop.
                if (i == 1)
                    ++ i;
            } else {
                assert(extruded_length[extruder_idx] >= m_config.min_skirt_length.value);
                // Enough extruded with the current extruder. Extrude with the next one,
                // until the prescribed number of skirt loops is extruded.
                if (extruder_idx + 1 < extruders.size())
                    if (nb_skirts < current_lines_per_extruder) {
                        nb_skirts++;
                    } else {
                        current_lines_per_extruder = lines_per_extruder;
                        nb_skirts = 1;
                        ++extruder_idx;
                    }
            }
        } else {
            // The skirt lenght is not limited, extrude the skirt with the 1st extruder only.
        }
    }
    // Brims were generated inside out, reverse to print the outmost contour first.
    out.reverse();
    if (out_first_layer)
        out_first_layer->reverse();

    // Remember the outer edge of the last skirt line extruded as m_skirt_convex_hull.
    for (Polygon &poly : offset(convex_hull, distance + 0.5f * float(this->skirt_flow(extruders[extruders.size() - 1]).scaled_spacing()), ClipperLib::jtRound, float(scale_(0.1))))
        append(m_skirt_convex_hull, std::move(poly.points));
}

void Print::_extrude_brim_from_tree(std::vector<std::vector<BrimLoop>>& loops, const Polygons& frontiers, const Flow& flow, ExtrusionEntityCollection& out, bool reversed/*= false*/) {

    // nest contour loops (same as in perimetergenerator)
    for (int d = loops.size() - 1; d >= 1; --d) {
        std::vector<BrimLoop>& contours_d = loops[d];
        // loop through all contours having depth == d
        for (int i = 0; i < (int)contours_d.size(); ++i) {
            const BrimLoop& loop = contours_d[i];
            // find the contour loop that contains it
            for (int t = d - 1; t >= 0; --t) {
                for (size_t j = 0; j < loops[t].size(); ++j) {
                    BrimLoop& candidate_parent = loops[t][j];
                    bool test = reversed
                        ? loop.polygon().contains(candidate_parent.lines.front().first_point())
                        : candidate_parent.polygon().contains(loop.lines.front().first_point());
                    if (test) {
                        candidate_parent.children.push_back(loop);
                        contours_d.erase(contours_d.begin() + i);
                        --i;
                        goto NEXT_CONTOUR;
                    }
                }
            }
            //didn't find a contour: add it as a root loop
            loops[0].push_back(loop);
            contours_d.erase(contours_d.begin() + i);
            --i;
        NEXT_CONTOUR:;
        }
    }
    for (int i = loops.size() - 1; i > 0; --i) {
        if (loops[i].empty()) {
            loops.erase(loops.begin() + i);
        }
    }

    //def
    //cut loops if they go inside a forbidden region
    std::function<void(BrimLoop&)> cut_loop = [&frontiers, &flow, reversed](BrimLoop& to_cut) {
        Polylines result;
        if (to_cut.is_loop) {
            result = intersection_pl(Polygons{ to_cut.polygon() }, frontiers, true);
        } else {
            result = intersection_pl(to_cut.lines, frontiers, true);
        }
        //remove too small segments
        for (int i = 0; i < result.size(); i++) {
            if (result[i].length() < flow.scaled_width() * 2) {
                result.erase(result.begin() + i);
                i--;
            }
        }
        if (result.empty()) {
            to_cut.lines.clear();
        } else {
            if (to_cut.lines != result) {
                to_cut.lines = result;
                if (reversed) {
                    std::reverse(to_cut.lines.begin(), to_cut.lines.end());
                }
                to_cut.is_loop = false;
            }
        }

    };
    //calls, deep-first
    std::list< std::pair<BrimLoop*,int>> cut_child_first;
    for (std::vector<BrimLoop>& loops : loops) {
        for (BrimLoop& loop : loops) {
            cut_child_first.emplace_front(&loop, 0);
            //flat recurtion
            while (!cut_child_first.empty()) {
                if (cut_child_first.front().first->children.size() <= cut_child_first.front().second) {
                    //if no child to cut, cut ourself and pop
                    cut_loop(*cut_child_first.front().first);
                    cut_child_first.pop_front();
                } else {
                    // more child to cut, push the next
                    cut_child_first.front().second++;
                    cut_child_first.emplace_front(&cut_child_first.front().first->children[cut_child_first.front().second - 1], 0);
                }
            }
        }
    }

    this->throw_if_canceled();


    //def: push into extrusions, in the right order
    float mm3_per_mm = float(flow.mm3_per_mm());
    float width = float(flow.width);
    float height = float(get_first_layer_height());
    int nextIdx = 0;
    std::function<void(BrimLoop&, ExtrusionEntityCollection*)>* extrude_ptr;
    std::function<void(BrimLoop&, ExtrusionEntityCollection*) > extrude = [&mm3_per_mm, &width, &height, &extrude_ptr, &nextIdx](BrimLoop& to_cut, ExtrusionEntityCollection* parent) {
        int idx = nextIdx++;
        //bool i_have_line = !to_cut.line.points.empty() && to_cut.line.is_valid();
        bool i_have_line = to_cut.lines.size() > 0 && to_cut.lines.front().size() > 0 && to_cut.lines.front().is_valid();
        if (!i_have_line && to_cut.children.empty()) {
            //nothing
        } else if (i_have_line && to_cut.children.empty()) {
            for(Polyline& line : to_cut.lines)
                if (line.points.back() == line.points.front()) {
                    ExtrusionPath path(erSkirt, mm3_per_mm, width, height);
                    path.polyline.points = line.points;
                    parent->entities.emplace_back(new ExtrusionLoop(std::move(path), elrSkirt));
                } else {
                    ExtrusionPath* extrusion_path = new ExtrusionPath(erSkirt, mm3_per_mm, width, height);
                    parent->entities.push_back(extrusion_path);
                    extrusion_path->polyline = line;
                }
        } else if (!i_have_line && !to_cut.children.empty()) {
            if (to_cut.children.size() == 1) {
                (*extrude_ptr)(to_cut.children[0], parent);
            } else {
                ExtrusionEntityCollection* mycoll = new ExtrusionEntityCollection();
                //mycoll->no_sort = true;
                parent->entities.push_back(mycoll);
                for (BrimLoop& child : to_cut.children)
                    (*extrude_ptr)(child, mycoll);
                //remove un-needed collection if possible
                if (mycoll->entities.size() == 1) {
                    parent->entities.back() = mycoll->entities.front();
                    mycoll->entities.clear();
                    delete mycoll;
                } else if (mycoll->entities.size() == 0) {
                    parent->remove(parent->entities.size() - 1);
                }
            }
        } else {
            ExtrusionEntityCollection* print_me_first = new ExtrusionEntityCollection();
            parent->entities.push_back(print_me_first);
            print_me_first->set_can_sort_reverse(false, false);
            for (Polyline& line : to_cut.lines)
                if (line.points.back() == line.points.front()) {
                    ExtrusionPath path(erSkirt, mm3_per_mm, width, height);
                    path.polyline.points = line.points;
                    print_me_first->entities.emplace_back(new ExtrusionLoop(std::move(path), elrSkirt));
                } else {
                    ExtrusionPath* extrusion_path = new ExtrusionPath(erSkirt, mm3_per_mm, width, height);
                    print_me_first->entities.push_back(extrusion_path);
                    extrusion_path->polyline = line;
                }
            if (to_cut.children.size() == 1) {
                (*extrude_ptr)(to_cut.children[0], print_me_first);
            } else {
                ExtrusionEntityCollection* children = new ExtrusionEntityCollection();
                //children->no_sort = true;
                print_me_first->entities.push_back(children);
                for (BrimLoop& child : to_cut.children)
                    (*extrude_ptr)(child, children);
                //remove un-needed collection if possible
                if (children->entities.size() == 1) {
                    print_me_first->entities.back() = children->entities.front();
                    children->entities.clear();
                    delete children;
                } else if (children->entities.size() == 0) {
                    print_me_first->remove(parent->entities.size() - 1);
                }
            }
        }
    };
    extrude_ptr = &extrude;

    if (loops.empty()) {
        BOOST_LOG_TRIVIAL(error) << "Failed to extrude brim: no loops to extrude, are you sure your settings are ok?";
        return;
    }

    //launch extrude
    for (BrimLoop& loop : loops[0]) {
        extrude(loop, &out);
    }
}

//TODO: test if no regression vs old _make_brim.
// this new one can extrude brim for an object inside an other object.
void Print::_make_brim(const Flow &flow, const PrintObjectPtrs &objects, ExPolygons &unbrimmable, ExtrusionEntityCollection &out) {
    const coord_t scaled_spacing = flow.scaled_spacing();
    const PrintObjectConfig &brim_config = objects.front()->config();
    coord_t brim_offset = scale_(brim_config.brim_offset.value);
    ExPolygons    islands;
    for (PrintObject *object : objects) {
        ExPolygons object_islands;
        for (ExPolygon &expoly : object->m_layers.front()->lslices)
            if(brim_config.brim_inside_holes || brim_config.brim_width_interior > 0)
                object_islands.push_back(brim_offset == 0 ? expoly : offset_ex(expoly, brim_offset)[0]);
            else
                object_islands.emplace_back(brim_offset == 0 ? to_expolygon(expoly.contour) : offset_ex(to_expolygon(expoly.contour), brim_offset)[0]);
        if (!object->support_layers().empty()) {
            Polygons polys = object->support_layers().front()->support_fills.polygons_covered_by_spacing(flow.spacing_ratio, float(SCALED_EPSILON));
            for (Polygon poly : polys) {
                object_islands.emplace_back(brim_offset == 0 ? ExPolygon{ poly } : offset_ex(poly, brim_offset)[0]);
            }
        }
        islands.reserve(islands.size() + object_islands.size() * object->m_instances.size());
        for (const PrintInstance &pt : object->m_instances) {
            for (ExPolygon &poly : object_islands) {
                islands.push_back(poly);
                islands.back().translate(pt.shift.x(), pt.shift.y());
            }
        }
    }

    this->throw_if_canceled();

    //simplify & merge
    ExPolygons unbrimmable_areas;
    for (ExPolygon &expoly : islands)
        for (ExPolygon &expoly : expoly.simplify(SCALED_RESOLUTION))
            unbrimmable_areas.emplace_back(std::move(expoly));
    islands = union_ex(unbrimmable_areas, true);
    unbrimmable_areas = islands;

    //get the brimmable area
    const size_t num_loops = size_t(floor(std::max(0.,(brim_config.brim_width.value - brim_config.brim_offset.value)) / flow.spacing()));
    ExPolygons brimmable_areas;
    for (ExPolygon &expoly : islands) {
        for (Polygon poly : offset(expoly.contour, num_loops * scaled_spacing, jtSquare)) {
            brimmable_areas.emplace_back();
            brimmable_areas.back().contour = poly;
            brimmable_areas.back().contour.make_counter_clockwise();
            brimmable_areas.back().holes.push_back(expoly.contour);
            brimmable_areas.back().holes.back().make_clockwise();
        }
    }
    brimmable_areas = union_ex(brimmable_areas);
    this->throw_if_canceled();

    //don't collide with objects
    brimmable_areas = diff_ex(brimmable_areas, unbrimmable_areas, true);
    brimmable_areas = diff_ex(brimmable_areas, unbrimmable, true);

    this->throw_if_canceled();

    //now get all holes, use them to create loops
    std::vector<std::vector<BrimLoop>> loops;
    ExPolygons bigger_islands;
    //grow a half of spacing, to go to the first extrusion polyline.
    Polygons unbrimmable_polygons;
    for (ExPolygon &expoly : islands) {
        unbrimmable_polygons.push_back(expoly.contour);
        //do it separately because we don't want to union them
        for (ExPolygon &big_expoly : offset_ex(expoly, double(scaled_spacing) * 0.5, jtSquare)) {
            bigger_islands.emplace_back(big_expoly);
            unbrimmable_polygons.insert(unbrimmable_polygons.end(), big_expoly.holes.begin(), big_expoly.holes.end());
        }
    }
    islands = bigger_islands;
    for (size_t i = 0; i < num_loops; ++i) {
        loops.emplace_back();
        this->throw_if_canceled();
        // only grow the contour, not holes
        bigger_islands.clear();
        if (i > 0) {
            for (ExPolygon &expoly : islands) {
                for (Polygon &big_contour : offset(expoly.contour, double(scaled_spacing) * i, jtSquare)) {
                    bigger_islands.emplace_back(expoly);
                    bigger_islands.back().contour = big_contour;
                }
            }
        } else bigger_islands = islands;
        bigger_islands = union_ex(bigger_islands);
        for (ExPolygon &expoly : bigger_islands) {
            loops[i].emplace_back(expoly.contour);
            // buggy
            ////also add hole, in case of it's merged with a contour. <= HOW? if there's an island inside a hole! (in the same object)
            //for (Polygon &hole : expoly.holes)
            //    //but remove the points that are inside the holes of islands
            //    for (Polyline& pl : diff_pl(Polygons{ hole }, unbrimmable_polygons, true))
            //        loops[i].emplace_back(pl);
        }
    }

    std::reverse(loops.begin(), loops.end());

    //intersection
    Polygons frontiers;
    //use contour from brimmable_areas (external frontier)
    for (ExPolygon &expoly : brimmable_areas) {
        frontiers.push_back(expoly.contour);
        frontiers.back().make_counter_clockwise();
    }
    // add internal frontier
    frontiers.insert(frontiers.begin(), unbrimmable_polygons.begin(), unbrimmable_polygons.end());

    _extrude_brim_from_tree(loops, frontiers, flow, out);
    
    unbrimmable.insert(unbrimmable.end(), brimmable_areas.begin(), brimmable_areas.end());
}

void Print::_make_brim_ears(const Flow &flow, const PrintObjectPtrs &objects, ExPolygons &unbrimmable, ExtrusionEntityCollection &out) {
    const PrintObjectConfig &brim_config = objects.front()->config();
    Points pt_ears;
    coord_t brim_offset = scale_(brim_config.brim_offset.value);
    ExPolygons islands;
    ExPolygons unbrimmable_with_support = unbrimmable;
    for (PrintObject *object : objects) {
        ExPolygons object_islands;
        ExPolygons support_island;
        for (const ExPolygon &expoly : object->m_layers.front()->lslices)
            if (brim_config.brim_inside_holes || brim_config.brim_width_interior > 0)
                object_islands.push_back(brim_offset==0?expoly:offset_ex(expoly, brim_offset)[0]);
            else
                object_islands.emplace_back(brim_offset == 0 ? to_expolygon(expoly.contour) : offset_ex(to_expolygon(expoly.contour), brim_offset)[0]);

        if (!object->support_layers().empty()) {
            Polygons polys = object->support_layers().front()->support_fills.polygons_covered_by_spacing(flow.spacing_ratio, float(SCALED_EPSILON));
            //put ears over supports unless it's 100% fill
            if (object->config().support_material_solid_first_layer) {
                for (Polygon poly : polys) {
                        object_islands.push_back(brim_offset == 0 ? ExPolygon{ poly } : offset_ex(poly, brim_offset)[0]);
                }
            } else {
                // offset2 to avoid bits of brim inside the raft
                append(support_island, offset2_ex(polys, flow.scaled_width() * 2, -flow.scaled_width() * 2));
            }
        }
        islands.reserve(islands.size() + object_islands.size() * object->m_instances.size());
        coord_t ear_detection_length = scale_t(object->config().brim_ears_detection_length.value);
        // duplicate & translate for each instance
        for (const PrintInstance& copy_pt : object->m_instances) {
            for (const ExPolygon& poly : object_islands) {
                islands.push_back(poly);
                islands.back().translate(copy_pt.shift.x(), copy_pt.shift.y());
                Polygon decimated_polygon = poly.contour;
                // brim_ears_detection_length codepath
                if (ear_detection_length > 0) {
                    //decimate polygon
                    Points points = poly.contour.points;
                    points.push_back(points.front());
                    points = MultiPoint::_douglas_peucker(points, ear_detection_length);
                    if (points.size() > 4) { //don't decimate if it's going to be below 4 points, as it's surely enough to fill everything anyway
                        points.erase(points.end() - 1);
                        decimated_polygon.points = points;
                    }
                }
                for (const Point& p : decimated_polygon.convex_points(brim_config.brim_ears_max_angle.value* PI / 180.0)) {
                    pt_ears.push_back(p);
                    pt_ears.back() += (copy_pt.shift);
                }
            }
            // also for support-fobidden area
            for (const ExPolygon& poly : support_island) {
                unbrimmable_with_support.push_back(poly);
                unbrimmable_with_support.back().translate(copy_pt.shift.x(), copy_pt.shift.y());
            }
        }
    }

    islands = union_ex(islands, true);

    //get the brimmable area (for the return value only)
    const size_t num_loops = size_t(floor((brim_config.brim_width.value - brim_config.brim_offset.value) / flow.spacing()));
    ExPolygons brimmable_areas;
    Polygons contours;
    Polygons holes;
    for (ExPolygon &expoly : islands) {
        for (Polygon poly : offset(expoly.contour, num_loops * flow.scaled_width(), jtSquare)) {
            contours.push_back(poly);
        }
        holes.push_back(expoly.contour);
    }
    brimmable_areas = diff_ex(union_(contours), union_(holes));
    brimmable_areas = diff_ex(brimmable_areas, unbrimmable_with_support, true);

    this->throw_if_canceled();

    if (brim_config.brim_ears_pattern.value == InfillPattern::ipConcentric) {

        //create loops (same as standard brim)
        Polygons loops;
        islands = offset_ex(islands, -0.5f * double(flow.scaled_spacing()));
        for (size_t i = 0; i < num_loops; ++i) {
            this->throw_if_canceled();
            islands = offset_ex(islands, double(flow.scaled_spacing()), jtSquare);
            for (ExPolygon &expoly : islands) {
                Polygon poly = expoly.contour;
                poly.points.push_back(poly.points.front());
                Points p = MultiPoint::_douglas_peucker(poly.points, SCALED_RESOLUTION);
                p.pop_back();
                poly.points = std::move(p);
                loops.push_back(poly);
            }
        }
        //order path with least travel possible
        loops = union_pt_chained_outside_in(loops, false);

        //create ear pattern
        coord_t size_ear = (scale_((brim_config.brim_width.value - brim_config.brim_offset.value)) - flow.scaled_spacing());
        Polygon point_round;
        for (size_t i = 0; i < POLY_SIDES; i++) {
            double angle = (2.0 * PI * i) / POLY_SIDES;
            point_round.points.emplace_back(size_ear * cos(angle), size_ear * sin(angle));
        }

        //create ears
        ExPolygons mouse_ears_ex;
        for (Point pt : pt_ears) {
            mouse_ears_ex.emplace_back();
            mouse_ears_ex.back().contour = point_round;
            mouse_ears_ex.back().contour.translate(pt);
        }

        //intersection
        ExPolygons mouse_ears_area = intersection_ex(mouse_ears_ex, brimmable_areas);
        Polylines lines = intersection_pl(loops, to_polygons(mouse_ears_area));
        this->throw_if_canceled();

        //reorder & extrude them
        Polylines lines_sorted = _reorder_brim_polyline(lines, out, flow);

        //push into extrusions
        extrusion_entities_append_paths(
            out.entities,
            lines_sorted,
            erSkirt,
            float(flow.mm3_per_mm()),
            float(flow.width),
            float(get_first_layer_height())
        );

        unbrimmable = union_ex(unbrimmable, offset_ex(mouse_ears_ex, flow.scaled_spacing()/2));

    } else /* brim_config.brim_ears_pattern.value == InfillPattern::ipRectilinear */{
        
        //create ear pattern
        coord_t size_ear = (scale_((brim_config.brim_width.value - brim_config.brim_offset.value)) - flow.scaled_spacing());
        Polygon point_round;
        for (size_t i = 0; i < POLY_SIDES; i++) {
            double angle = (2.0 * PI * i) / POLY_SIDES;
            point_round.points.emplace_back(size_ear * cos(angle), size_ear * sin(angle));
        }

        //create ears
        ExPolygons mouse_ears_ex;
        for (Point pt : pt_ears) {
            mouse_ears_ex.emplace_back();
            mouse_ears_ex.back().contour = point_round;
            mouse_ears_ex.back().contour.translate(pt);
        }

        ExPolygons new_brim_area = intersection_ex(brimmable_areas, mouse_ears_ex);

        std::unique_ptr<Fill> filler = std::unique_ptr<Fill>(Fill::new_from_type(ipRectiWithPerimeter));
        filler->angle = 0;

        FillParams fill_params;
        fill_params.density = 1.f;
        fill_params.fill_exactly = true;
        fill_params.flow = flow;
        fill_params.role = erSkirt;
        filler->init_spacing(flow.spacing(), fill_params);
        for (const ExPolygon &expoly : new_brim_area) {
            Surface surface(stPosInternal | stDensSparse, expoly);
            filler->fill_surface_extrusion(&surface, fill_params, out.entities);
        }

        unbrimmable.insert(unbrimmable.end(), new_brim_area.begin(), new_brim_area.end());
    }

}

void Print::_make_brim_interior(const Flow &flow, const PrintObjectPtrs &objects, ExPolygons &unbrimmable_areas, ExtrusionEntityCollection &out) {
    // Brim is only printed on first layer and uses perimeter extruder.

    const PrintObjectConfig &brim_config = objects.front()->config();
    coord_t brim_offset = scale_(brim_config.brim_offset.value);
    ExPolygons    islands;
    coordf_t spacing;
    for (PrintObject *object : objects) {
        ExPolygons object_islands;
        for (ExPolygon &expoly : object->m_layers.front()->lslices)
            object_islands.push_back(brim_offset == 0 ? expoly : offset_ex(expoly, brim_offset)[0]);
        if (!object->support_layers().empty()) {
            spacing = scaled(object->config().support_material_interface_spacing.value) + support_material_flow(object, float(get_first_layer_height())).scaled_width() * 1.5;
            Polygons polys = offset2(object->support_layers().front()->support_fills.polygons_covered_by_spacing(flow.spacing_ratio, float(SCALED_EPSILON)), spacing, -spacing);
            for (Polygon poly : polys) {
                object_islands.push_back(brim_offset == 0 ? ExPolygon{ poly } : offset_ex(poly, brim_offset)[0]);
            }
        }
        islands.reserve(islands.size() + object_islands.size() * object->instances().size());
        for (const PrintInstance &instance : object->instances())
            for (ExPolygon &poly : object_islands) {
                islands.push_back(poly);
                islands.back().translate(instance.shift.x(), instance.shift.y());
            }
    }

    islands = union_ex(islands);

    //to have the brimmable areas, get all holes, use them as contour , add smaller hole inside and make a diff with unbrimmable
    const size_t num_loops = size_t(floor((brim_config.brim_width_interior.value - brim_config.brim_offset.value) / flow.spacing()));
    ExPolygons brimmable_areas;
    Polygons islands_to_loops;
    for (const ExPolygon &expoly : islands) {
        for (const Polygon &hole : expoly.holes) {
            brimmable_areas.emplace_back();
            brimmable_areas.back().contour = hole;
            brimmable_areas.back().contour.make_counter_clockwise();
            for (Polygon poly : offset(brimmable_areas.back().contour, -flow.scaled_width() * (double)num_loops, jtSquare)) {
                brimmable_areas.back().holes.push_back(poly);
                brimmable_areas.back().holes.back().make_clockwise();
            }
            islands_to_loops.insert(islands_to_loops.begin(), brimmable_areas.back().contour);
        }
    }

    brimmable_areas = diff_ex(brimmable_areas, islands, true);
    brimmable_areas = diff_ex(brimmable_areas, unbrimmable_areas, true);

    //now get all holes, use them to create loops
    std::vector<std::vector<BrimLoop>> loops;
    for (size_t i = 0; i < num_loops; ++i) {
        this->throw_if_canceled();
        loops.emplace_back();
        Polygons islands_to_loops_offseted;
        for (Polygon& poly : islands_to_loops) {
            Polygons temp = offset(poly, double(-flow.scaled_spacing()), jtSquare);
            for (Polygon& poly : temp) {
                poly.points.push_back(poly.points.front());
                Points p = MultiPoint::_douglas_peucker(poly.points, SCALED_RESOLUTION);
                p.pop_back();
                poly.points = std::move(p);
            }
            for (Polygon& poly : offset(temp, 0.5f * double(flow.scaled_spacing())))
                loops[i].emplace_back(poly);
            islands_to_loops_offseted.insert(islands_to_loops_offseted.end(), temp.begin(), temp.end());
        }
        islands_to_loops = islands_to_loops_offseted;
    }
    //loops = union_pt_chained_outside_in(loops, false);
    std::reverse(loops.begin(), loops.end());

    //intersection
    Polygons frontiers;
    for (ExPolygon &expoly : brimmable_areas) {
        for (Polygon &big_contour : offset(expoly.contour, 0.1f * flow.scaled_width())) {
            frontiers.push_back(big_contour);
            for (Polygon &hole : expoly.holes) {
                frontiers.push_back(hole);
                //don't reverse it! back! or it will be ignored by intersection_pl. 
                //frontiers.back().reverse();
            }
        }
    }

    _extrude_brim_from_tree(loops, frontiers, flow, out, true);

    unbrimmable_areas.insert(unbrimmable_areas.end(), brimmable_areas.begin(), brimmable_areas.end());
}

/// reorder & join polyline if their ending are near enough, then extrude the brim from the polyline into 'out'.
Polylines Print::_reorder_brim_polyline(Polylines lines, ExtrusionEntityCollection &out, const Flow &flow) {
    //reorder them
    std::sort(lines.begin(), lines.end(), [](const Polyline &a, const Polyline &b)->bool { return a.closest_point(Point(0, 0))->y() < b.closest_point(Point(0, 0))->y(); });
    Polylines lines_sorted;
    Polyline* previous = NULL;
    Polyline* best = NULL;
    double best_dist = -1;
    size_t best_idx = 0;
    while (lines.size() > 0) {
        if (previous == NULL) {
            lines_sorted.push_back(lines.back());
            previous = &lines_sorted.back();
            lines.erase(lines.end() - 1);
        } else {
            best = NULL;
            best_dist = -1;
            best_idx = 0;
            for (size_t i = 0; i < lines.size(); ++i) {
                Polyline &viewed_line = lines[i];
                double dist = viewed_line.points.front().distance_to(previous->points.front());
                dist = std::min(dist, viewed_line.points.front().distance_to(previous->points.back()));
                dist = std::min(dist, viewed_line.points.back().distance_to(previous->points.front()));
                dist = std::min(dist, viewed_line.points.back().distance_to(previous->points.back()));
                if (dist < best_dist || best == NULL) {
                    best = &viewed_line;
                    best_dist = dist;
                    best_idx = i;
                }
            }
            if (best != NULL) {
                //copy new line inside the sorted array.
                lines_sorted.push_back(lines[best_idx]);
                lines.erase(lines.begin() + best_idx);

                //connect if near enough
                if (lines_sorted.size() > 1) {
                    size_t idx = lines_sorted.size() - 2;
                    bool connect = false;
                    if (lines_sorted[idx].points.back().distance_to(lines_sorted[idx + 1].points.front()) < flow.scaled_spacing() * 2) {
                        connect = true;
                    } else if (lines_sorted[idx].points.back().distance_to(lines_sorted[idx + 1].points.back()) < flow.scaled_spacing() * 2) {
                        lines_sorted[idx + 1].reverse();
                        connect = true;
                    } else if (lines_sorted[idx].points.front().distance_to(lines_sorted[idx + 1].points.front()) < flow.scaled_spacing() * 2) {
                        lines_sorted[idx].reverse();
                        connect = true;
                    } else if (lines_sorted[idx].points.front().distance_to(lines_sorted[idx + 1].points.back()) < flow.scaled_spacing() * 2) {
                        lines_sorted[idx].reverse();
                        lines_sorted[idx + 1].reverse();
                        connect = true;
                    }

                    if (connect) {
                        //connect them
                        lines_sorted[idx].points.insert(
                            lines_sorted[idx].points.end(),
                            lines_sorted[idx + 1].points.begin(),
                            lines_sorted[idx + 1].points.end());
                        lines_sorted.erase(lines_sorted.begin() + idx + 1);
                        idx--;
                    }
                }

                //update last position
                previous = &lines_sorted.back();
            }
        }
    }

    return lines_sorted;
}

Polygons Print::first_layer_islands() const
{
    Polygons islands;
    for (PrintObject *object : m_objects) {
        Polygons object_islands;
        for (ExPolygon &expoly : object->m_layers.front()->lslices)
            object_islands.push_back(expoly.contour);
        if (! object->support_layers().empty())
            //was polygons_covered_by_spacing, but is it really important?
            object->support_layers().front()->support_fills.polygons_covered_by_width(object_islands, float(SCALED_EPSILON));
        islands.reserve(islands.size() + object_islands.size() * object->instances().size());
        for (const PrintInstance &instance : object->instances())
            for (Polygon &poly : object_islands) {
                islands.push_back(poly);
                islands.back().translate(instance.shift);
            }
    }
    return islands;
}

std::vector<Point> Print::first_layer_wipe_tower_corners() const
{
    std::vector<Point> corners;
    if (has_wipe_tower() && ! m_wipe_tower_data.tool_changes.empty()) {
        double width = m_config.wipe_tower_width + 2*m_wipe_tower_data.brim_width;
        double depth = m_wipe_tower_data.depth + 2*m_wipe_tower_data.brim_width;
        Vec2d pt0(-m_wipe_tower_data.brim_width, -m_wipe_tower_data.brim_width);
        for (Vec2d pt : {
                pt0,
                Vec2d(pt0.x()+width, pt0.y()      ),
                Vec2d(pt0.x()+width, pt0.y()+depth),
                Vec2d(pt0.x(),       pt0.y()+depth)
            }) {
            pt = Eigen::Rotation2Dd(Geometry::deg2rad(m_config.wipe_tower_rotation_angle.value)) * pt;
            pt += Vec2d(m_config.wipe_tower_x.value, m_config.wipe_tower_y.value);
            corners.emplace_back(Point(scale_(pt.x()), scale_(pt.y())));
        }
    }
    return corners;
}

void Print::finalize_first_layer_convex_hull()
{
    append(m_first_layer_convex_hull.points, m_skirt_convex_hull);
    if (m_first_layer_convex_hull.empty()) {
        // Neither skirt nor brim was extruded. Collect points of printed objects from 1st layer.
        for (Polygon &poly : this->first_layer_islands())
            append(m_first_layer_convex_hull.points, std::move(poly.points));
    }
    append(m_first_layer_convex_hull.points, this->first_layer_wipe_tower_corners());
    m_first_layer_convex_hull = Geometry::convex_hull(m_first_layer_convex_hull.points);
}

// Wipe tower support.
bool Print::has_wipe_tower() const
{
    return 
        ! m_config.spiral_vase.value &&
        m_config.wipe_tower.value && 
        m_config.nozzle_diameter.values.size() > 1;
}

const WipeTowerData& Print::wipe_tower_data(size_t extruders_cnt, double first_layer_height, double nozzle_diameter) const
{
    // If the wipe tower wasn't created yet, make sure the depth and brim_width members are set to default.
    if (! is_step_done(psWipeTower) && extruders_cnt !=0) {

        float width = float(m_config.wipe_tower_width);
		float unscaled_brim_width = m_config.wipe_tower_brim.get_abs_value(nozzle_diameter);

        const_cast<Print*>(this)->m_wipe_tower_data.depth = (900.f/width) * float(extruders_cnt - 1);
        const_cast<Print*>(this)->m_wipe_tower_data.brim_width = unscaled_brim_width;
    }

    return m_wipe_tower_data;
}

void Print::_make_wipe_tower()
{
    m_wipe_tower_data.clear();
    if (! this->has_wipe_tower())
        return;

    // Get wiping matrix to get number of extruders and convert vector<double> to vector<float>:
    std::vector<float> wiping_matrix(cast<float>(m_config.wiping_volumes_matrix.values));
    // Extract purging volumes for each extruder pair:
    std::vector<std::vector<float>> wipe_volumes;
    const unsigned int number_of_extruders = (unsigned int)(sqrt(wiping_matrix.size())+EPSILON);
    for (unsigned int i = 0; i<number_of_extruders; ++i)
        wipe_volumes.push_back(std::vector<float>(wiping_matrix.begin()+i*number_of_extruders, wiping_matrix.begin()+(i+1)*number_of_extruders));

    // Let the ToolOrdering class know there will be initial priming extrusions at the start of the print.
    m_wipe_tower_data.tool_ordering = ToolOrdering(*this, (unsigned int)-1, true);

    if (! m_wipe_tower_data.tool_ordering.has_wipe_tower())
        // Don't generate any wipe tower.
        return;

    // Check whether there are any layers in m_tool_ordering, which are marked with has_wipe_tower,
    // they print neither object, nor support. These layers are above the raft and below the object, and they
    // shall be added to the support layers to be printed.
    // see https://github.com/prusa3d/PrusaSlicer/issues/607
    {
        size_t idx_begin = size_t(-1);
        size_t idx_end   = m_wipe_tower_data.tool_ordering.layer_tools().size();
        // Find the first wipe tower layer, which does not have a counterpart in an object or a support layer.
        for (size_t i = 0; i < idx_end; ++ i) {
            const LayerTools &lt = m_wipe_tower_data.tool_ordering.layer_tools()[i];
            if (lt.has_wipe_tower && ! lt.has_object && ! lt.has_support) {
                idx_begin = i;
                break;
            }
        }
        if (idx_begin != size_t(-1)) {
            // Find the position in m_objects.first()->support_layers to insert these new support layers.
            double wipe_tower_new_layer_print_z_first = m_wipe_tower_data.tool_ordering.layer_tools()[idx_begin].print_z;
            SupportLayerPtrs::const_iterator it_layer = m_objects.front()->support_layers().begin();
            SupportLayerPtrs::const_iterator it_end   = m_objects.front()->support_layers().end();
            for (; it_layer != it_end && (*it_layer)->print_z - EPSILON < wipe_tower_new_layer_print_z_first; ++ it_layer);
            // Find the stopper of the sequence of wipe tower layers, which do not have a counterpart in an object or a support layer.
            for (size_t i = idx_begin; i < idx_end; ++ i) {
                LayerTools &lt = const_cast<LayerTools&>(m_wipe_tower_data.tool_ordering.layer_tools()[i]);
                if (! (lt.has_wipe_tower && ! lt.has_object && ! lt.has_support))
                    break;
                lt.has_support = true;
                // Insert the new support layer.
                double height    = lt.print_z - (i == 0 ? 0. : m_wipe_tower_data.tool_ordering.layer_tools()[i-1].print_z);
                //FIXME the support layer ID is set to -1, as Vojtech hopes it is not being used anyway.
                it_layer = m_objects.front()->insert_support_layer(it_layer, -1, height, lt.print_z, lt.print_z - 0.5 * height);
                ++ it_layer;
            }
        }
    }
    this->throw_if_canceled();

    // Initialize the wipe tower.
    WipeTower wipe_tower(m_config, m_default_object_config, wipe_volumes, m_wipe_tower_data.tool_ordering.first_extruder());
    

    //wipe_tower.set_retract();
    //wipe_tower.set_zhop();

    // Set the extruder & material properties at the wipe tower object.
    for (size_t i = 0; i < number_of_extruders; ++i)
        wipe_tower.set_extruder(i);

    m_wipe_tower_data.priming = Slic3r::make_unique<std::vector<WipeTower::ToolChangeResult>>(
        wipe_tower.prime((float)get_first_layer_height(), m_wipe_tower_data.tool_ordering.all_extruders(), false));

    // Lets go through the wipe tower layers and determine pairs of extruder changes for each
    // to pass to wipe_tower (so that it can use it for planning the layout of the tower)
    {
        unsigned int current_extruder_id = m_wipe_tower_data.tool_ordering.all_extruders().back();
        for (auto &layer_tools : m_wipe_tower_data.tool_ordering.layer_tools()) { // for all layers
            if (!layer_tools.has_wipe_tower) continue;
            bool first_layer = &layer_tools == &m_wipe_tower_data.tool_ordering.front();
            wipe_tower.plan_toolchange((float)layer_tools.print_z, (float)layer_tools.wipe_tower_layer_height, current_extruder_id, current_extruder_id, false);
            for (const auto extruder_id : layer_tools.extruders) {
                if ((first_layer && extruder_id == m_wipe_tower_data.tool_ordering.all_extruders().back()) || extruder_id != current_extruder_id) {
                    double volume_to_wipe = wipe_volumes[current_extruder_id][extruder_id];             // total volume to wipe after this toolchange
                    
                    if (m_config.wipe_advanced) {
                        volume_to_wipe = m_config.wipe_advanced_nozzle_melted_volume;
                        float pigmentBef = m_config.filament_wipe_advanced_pigment.get_at(current_extruder_id);
                        float pigmentAft = m_config.filament_wipe_advanced_pigment.get_at(extruder_id);
                        if (m_config.wipe_advanced_algo.value == waLinear) {
                            volume_to_wipe += m_config.wipe_advanced_multiplier.value * (pigmentBef - pigmentAft);
                            BOOST_LOG_TRIVIAL(info) << "advanced wiping (lin) ";
                            BOOST_LOG_TRIVIAL(info) << current_extruder_id << " -> " << extruder_id << " will use " << volume_to_wipe << " mm3\n";
                            BOOST_LOG_TRIVIAL(info) << " calculus : " << m_config.wipe_advanced_nozzle_melted_volume << " + " << m_config.wipe_advanced_multiplier.value
                                << " * ( " << pigmentBef << " - " << pigmentAft << " )\n";
                            BOOST_LOG_TRIVIAL(info) << "    = " << m_config.wipe_advanced_nozzle_melted_volume << " + " << (m_config.wipe_advanced_multiplier.value* (pigmentBef - pigmentAft)) << "\n";
                        } else if (m_config.wipe_advanced_algo.value == waQuadra) {
                            volume_to_wipe += m_config.wipe_advanced_multiplier.value * (pigmentBef - pigmentAft)
                                + m_config.wipe_advanced_multiplier.value * (pigmentBef - pigmentAft) * (pigmentBef - pigmentAft) * (pigmentBef - pigmentAft);
                            BOOST_LOG_TRIVIAL(info) << "advanced wiping (quadra) ";
                            BOOST_LOG_TRIVIAL(info) << current_extruder_id << " -> " << extruder_id << " will use " << volume_to_wipe << " mm3\n";
                            BOOST_LOG_TRIVIAL(info) << " calculus : " << m_config.wipe_advanced_nozzle_melted_volume << " + " << m_config.wipe_advanced_multiplier.value
                                << " * ( " << pigmentBef << " - " << pigmentAft << " ) + " << m_config.wipe_advanced_multiplier.value
                                << " * ( " << pigmentBef << " - " << pigmentAft << " ) ^3 \n";
                            BOOST_LOG_TRIVIAL(info) << "    = " << m_config.wipe_advanced_nozzle_melted_volume << " + " << (m_config.wipe_advanced_multiplier.value* (pigmentBef - pigmentAft))
                                << " + " << (m_config.wipe_advanced_multiplier.value*(pigmentBef - pigmentAft)*(pigmentBef - pigmentAft)*(pigmentBef - pigmentAft))<<"\n";
                        } else if (m_config.wipe_advanced_algo.value == waHyper) {
                            volume_to_wipe += m_config.wipe_advanced_multiplier.value * (0.5 + pigmentBef) / (0.5 + pigmentAft);
                            BOOST_LOG_TRIVIAL(info) << "advanced wiping (hyper) ";
                            BOOST_LOG_TRIVIAL(info) << current_extruder_id << " -> " << extruder_id << " will use " << volume_to_wipe << " mm3\n";
                            BOOST_LOG_TRIVIAL(info) << " calculus : " << m_config.wipe_advanced_nozzle_melted_volume << " + " << m_config.wipe_advanced_multiplier.value
                                << " * ( 0.5 + " << pigmentBef << " ) / ( 0.5 + " << pigmentAft << " )\n";
                            BOOST_LOG_TRIVIAL(info) << "    = " << m_config.wipe_advanced_nozzle_melted_volume << " + " << (m_config.wipe_advanced_multiplier.value * (0.5 + pigmentBef) / (0.5 + pigmentAft)) << "\n";
                        }
                    }
                    //filament_wipe_advanced_pigment
                    
                    // Not all of that can be used for infill purging:
                    volume_to_wipe -= (float)m_config.filament_minimal_purge_on_wipe_tower.get_at(extruder_id);

                    // try to assign some infills/objects for the wiping:
                    volume_to_wipe = layer_tools.wiping_extrusions().mark_wiping_extrusions(*this, current_extruder_id, extruder_id, volume_to_wipe);

                    // add back the minimal amount toforce on the wipe tower:
                    volume_to_wipe += (float)m_config.filament_minimal_purge_on_wipe_tower.get_at(extruder_id);

                    // request a toolchange at the wipe tower with at least volume_to_wipe purging amount
                    wipe_tower.plan_toolchange((float)layer_tools.print_z, (float)layer_tools.wipe_tower_layer_height, current_extruder_id, extruder_id,
                                               first_layer && extruder_id == m_wipe_tower_data.tool_ordering.all_extruders().back(), volume_to_wipe);
                    current_extruder_id = extruder_id;
                }
            }
            layer_tools.wiping_extrusions().ensure_perimeters_infills_order(*this);
            if (&layer_tools == &m_wipe_tower_data.tool_ordering.back() || (&layer_tools + 1)->wipe_tower_partitions == 0)
                break;
        }
    }

    // Generate the wipe tower layers.
    m_wipe_tower_data.tool_changes.reserve(m_wipe_tower_data.tool_ordering.layer_tools().size());
    wipe_tower.generate(m_wipe_tower_data.tool_changes);
    m_wipe_tower_data.depth = wipe_tower.get_depth();
    m_wipe_tower_data.brim_width = wipe_tower.get_brim_width();

    // Unload the current filament over the purge tower.
    coordf_t layer_height = m_objects.front()->config().layer_height.value;
    if (m_wipe_tower_data.tool_ordering.back().wipe_tower_partitions > 0) {
        // The wipe tower goes up to the last layer of the print.
        if (wipe_tower.layer_finished()) {
            // The wipe tower is printed to the top of the print and it has no space left for the final extruder purge.
            // Lift Z to the next layer.
            wipe_tower.set_layer(float(m_wipe_tower_data.tool_ordering.back().print_z + layer_height), float(layer_height), 0, false, true);
        } else {
            // There is yet enough space at this layer of the wipe tower for the final purge.
        }
    } else {
        // The wipe tower does not reach the last print layer, perform the pruge at the last print layer.
        assert(m_wipe_tower_data.tool_ordering.back().wipe_tower_partitions == 0);
        wipe_tower.set_layer(float(m_wipe_tower_data.tool_ordering.back().print_z), float(layer_height), 0, false, true);
    }
    m_wipe_tower_data.final_purge = Slic3r::make_unique<WipeTower::ToolChangeResult>(
        wipe_tower.tool_change((unsigned int)(-1)));

    m_wipe_tower_data.used_filament = wipe_tower.get_used_filament();
    m_wipe_tower_data.number_of_toolchanges = wipe_tower.get_number_of_toolchanges();
}

// Generate a recommended G-code output file name based on the format template, default extension, and template parameters
// (timestamps, object placeholders derived from the model, current placeholder prameters and print statistics.
// Use the final print statistics if available, or just keep the print statistics placeholders if not available yet (before G-code is finalized).
std::string Print::output_filename(const std::string &filename_base) const 
{ 
    // Set the placeholders for the data know first after the G-code export is finished.
    // These values will be just propagated into the output file name.
    DynamicConfig config = this->finished() ? this->print_statistics().config() : this->print_statistics().placeholders();
    config.set_key_value("num_extruders", new ConfigOptionInt((int)m_config.nozzle_diameter.size()));
    return this->PrintBase::output_filename(m_config.output_filename_format.value, ".gcode", filename_base, &config);
}

DynamicConfig PrintStatistics::config() const
{
    DynamicConfig config;
    std::string normal_print_time = short_time(this->estimated_normal_print_time);
    std::string silent_print_time = short_time(this->estimated_silent_print_time);
    config.set_key_value("print_time",                new ConfigOptionString(normal_print_time));
    config.set_key_value("normal_print_time",         new ConfigOptionString(normal_print_time));
    config.set_key_value("silent_print_time",         new ConfigOptionString(silent_print_time));
    config.set_key_value("used_filament",             new ConfigOptionFloat(this->total_used_filament / 1000.));
    config.set_key_value("extruded_volume",           new ConfigOptionFloat(this->total_extruded_volume));
    config.set_key_value("total_cost",                new ConfigOptionFloat(this->total_cost));
    config.set_key_value("total_toolchanges",         new ConfigOptionInt(this->total_toolchanges));
    config.set_key_value("total_weight",              new ConfigOptionFloat(this->total_weight));
    config.set_key_value("total_wipe_tower_cost",     new ConfigOptionFloat(this->total_wipe_tower_cost));
    config.set_key_value("total_wipe_tower_filament", new ConfigOptionFloat(this->total_wipe_tower_filament));
    return config;
}

DynamicConfig PrintStatistics::placeholders()
{
    DynamicConfig config;
    for (const std::string &key : { 
        "print_time", "normal_print_time", "silent_print_time", 
        "used_filament", "extruded_volume", "total_cost", "total_weight", 
        "total_toolchanges", "total_wipe_tower_cost", "total_wipe_tower_filament"})
        config.set_key_value(key, new ConfigOptionString(std::string("{") + key + "}"));
    return config;
}

std::string PrintStatistics::finalize_output_path(const std::string &path_in) const
{
    std::string final_path;
    try {
        boost::filesystem::path path(path_in);
        DynamicConfig cfg = this->config();
        PlaceholderParser pp;
        std::string new_stem = pp.process(path.stem().string(), 0, &cfg);
        final_path = (path.parent_path() / (new_stem + path.extension().string())).string();
    } catch (const std::exception &ex) {
        BOOST_LOG_TRIVIAL(error) << "Failed to apply the print statistics to the export file name: " << ex.what();
        final_path = path_in;
    }
    return final_path;
}

} // namespace Slic3r