Apply support expansion to platform adhesion and shields

Platform adhesion and shields all go around the support, the expanded support. Support expansion is almost like an expansion of the mesh itself, except that infill wipe distance and such don't apply to it.

Contributes to issue CURA-2407.

cura/BuildVolume.py

@@ -553,6 +553,10 @@ class BuildVolume(SceneNode):
         else:
             raise Exception("Unknown bed adhesion type. Did you forget to update the build volume calculations for your new bed adhesion type?")
 
+        support_expansion = 0
+        if self._getSettingFromSupportInfillExtruder("support_offset"):
+            support_expansion += self._getSettingFromSupportInfillExtruder("support_offset")
+
         farthest_shield_distance = 0
         if container_stack.getProperty("draft_shield_enabled", "value"):
             farthest_shield_distance = max(farthest_shield_distance, container_stack.getProperty("draft_shield_dist", "value"))
@@ -564,11 +568,11 @@ class BuildVolume(SceneNode):
             move_from_wall_radius = max(move_from_wall_radius, self._getSettingFromAdhesionExtruder("infill_wipe_dist"))
         if self._getSettingFromAdhesionExtruder("travel_avoid_distance"):
             move_from_wall_radius = max(move_from_wall_radius, self._getSettingFromAdhesionExtruder("travel_avoid_distance"))
-        if self._getSettingFromSupportInfillExtruder("support_offset"):
-            move_from_wall_radius = max(move_from_wall_radius, self._getSettingFromSupportInfillExtruder("support_offset"))
 
         #Now combine our different pieces of data to get the final border size.
-        border_size = max(farthest_shield_distance, move_from_wall_radius, bed_adhesion_size)
+        #Support expansion is added to the bed adhesion, since the bed adhesion goes around support.
+        #Support expansion is added to farthest shield distance, since the shields go around support.
+        border_size = max(move_from_wall_radius, support_expansion + farthest_shield_distance, support_expansion + bed_adhesion_size)
         return border_size
 
     def _clamp(self, value, min_value, max_value):