support_material_synchronize_layers configuration value

for synchronization of object layers with print layers.

lib/Slic3r/GUI/Tab.pm

@@ -532,7 +532,7 @@ sub build {
         brim_width
         support_material support_material_threshold support_material_enforce_layers
         raft_layers
-        support_material_pattern support_material_with_sheath support_material_spacing support_material_angle
+        support_material_pattern support_material_with_sheath support_material_spacing support_material_synchronize_layers support_material_angle
         support_material_interface_layers support_material_interface_spacing
         support_material_contact_distance support_material_buildplate_only dont_support_bridges
         notes
@@ -648,6 +648,7 @@ sub build {
             $optgroup->append_single_option_line('support_material_interface_spacing');
             $optgroup->append_single_option_line('support_material_buildplate_only');
             $optgroup->append_single_option_line('dont_support_bridges');
+            $optgroup->append_single_option_line('support_material_synchronize_layers');
         }
     }
     
@@ -910,7 +911,7 @@ sub _update {
     my $have_support_interface = $config->support_material_interface_layers > 0;
     $self->get_field($_)->toggle($have_support_material)
         for qw(support_material_threshold support_material_pattern support_material_with_sheath
-            support_material_spacing support_material_angle
+            support_material_spacing support_material_synchronize_layers support_material_angle
             support_material_interface_layers dont_support_bridges
             support_material_extrusion_width support_material_contact_distance);
     $self->get_field($_)->toggle($have_support_material && $have_support_interface)

xs/src/libslic3r/PrintConfig.cpp

@@ -1247,6 +1247,13 @@ PrintConfigDef::PrintConfigDef()
     def->min = 0;
     def->default_value = new ConfigOptionFloat(60);
 
+    def = this->add("support_material_synchronize_layers", coBool);
+    def->label = "Synchronize with object layers";
+    def->category = "Support material";
+    def->tooltip = "Synchronize support layers with the object print layers. This is useful with multi-material printers, where the extruder switch is expensive.";
+    def->cli = "support-material-synchronize-layers!";
+    def->default_value = new ConfigOptionBool(true);
+
     def = this->add("support_material_threshold", coInt);
     def->label = "Overhang threshold";
     def->category = "Support material";

xs/src/libslic3r/PrintConfig.hpp

@@ -160,6 +160,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
     ConfigOptionEnum<SupportMaterialPattern> support_material_pattern;
     ConfigOptionFloat               support_material_spacing;
     ConfigOptionFloat               support_material_speed;
+    ConfigOptionBool                support_material_synchronize_layers;
     ConfigOptionInt                 support_material_threshold;
     ConfigOptionBool                support_material_with_sheath;
     ConfigOptionFloat               xy_size_compensation;
@@ -194,6 +195,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
         OPT_PTR(support_material_pattern);
         OPT_PTR(support_material_spacing);
         OPT_PTR(support_material_speed);
+        OPT_PTR(support_material_synchronize_layers);
         OPT_PTR(support_material_threshold);
         OPT_PTR(support_material_with_sheath);
         OPT_PTR(xy_size_compensation);

xs/src/libslic3r/PrintObject.cpp

@@ -203,6 +203,7 @@ PrintObject::invalidate_state_by_config_options(const std::vector<t_config_optio
             || *opt_key == "support_material_buildplate_only"
             || *opt_key == "support_material_pattern"
             || *opt_key == "support_material_spacing"
+            || *opt_key == "support_material_synchronize_layers"
             || *opt_key == "support_material_threshold"
             || *opt_key == "support_material_with_sheath"
             || *opt_key == "dont_support_bridges"