Set label width based on the column width

CURA-4428

- Remove the magic number solution
- Use a fixed width for labels so the right side widgets can be properly
  left-aligned.

plugins/MachineSettingsAction/MachineSettingsAction.qml

@@ -71,6 +71,7 @@ Cura.MachineAction
             anchors.topMargin: UM.Theme.getSize("default_margin").height
 
             property real columnWidth: ((width - 3 * UM.Theme.getSize("default_margin").width) / 2) | 0
+            property real labelColumnWidth: columnWidth * 0.5
 
             Tab
             {
@@ -247,13 +248,13 @@ Cura.MachineAction
 
                                 Row
                                 {
-                                    spacing: UM.Theme.getSize("default_margin").width * 4 / 5
+                                    spacing: UM.Theme.getSize("default_margin").width
 
                                     Label
                                     {
                                         text: catalog.i18nc("@label", "Number of Extruders")
                                         elide: Text.ElideRight
-                                        width: Math.max(0, settingsTabs.columnWidth - 2 * UM.Theme.getSize("default_margin").width - extruderCountComboBox.width)
+                                        width: Math.max(0, settingsTabs.labelColumnWidth)
                                         anchors.verticalCenter: extruderCountComboBox.verticalCenter
                                     }
                                     ComboBox
@@ -562,7 +563,7 @@ Cura.MachineAction
                     text: _label
                     visible: _label != ""
                     elide: Text.ElideRight
-                    width: Math.max(0, settingsTabs.columnWidth - 2 * UM.Theme.getSize("default_margin").width - textFieldWithUnit.width)
+                    width: Math.max(0, settingsTabs.labelColumnWidth)
                     anchors.verticalCenter: textFieldWithUnit.verticalCenter
                 }
 
@@ -648,14 +649,14 @@ Cura.MachineAction
 
             Row
             {
-                spacing: UM.Theme.getSize("default_margin").width * 4 / 5
+                spacing: UM.Theme.getSize("default_margin").width
 
                 Label
                 {
                     text: _label
                     visible: _label != ""
                     elide: Text.ElideRight
-                    width: Math.max(0, settingsTabs.columnWidth - 2 * UM.Theme.getSize("default_margin").width - comboBox.width)
+                    width: Math.max(0, settingsTabs.labelColumnWidth)
                     anchors.verticalCenter: comboBox.verticalCenter
                 }
                 ComboBox
@@ -787,7 +788,7 @@ Cura.MachineAction
                     text: _label
                     visible: _label != ""
                     elide: Text.ElideRight
-                    width: Math.max(0, settingsTabs.columnWidth - 2 * UM.Theme.getSize("default_margin").width - textFieldWithUnit.width)
+                    width: Math.max(0, settingsTabs.labelColumnWidth)
                     anchors.verticalCenter: textFieldWithUnit.verticalCenter
                 }