Implementation of "XY size Compensation for first layer"

https://github.com/prusa3d/Slic3r/issues/190

lib/Slic3r/GUI/Tab.pm

@@ -566,7 +566,7 @@ sub build {
         external_perimeter_extrusion_width infill_extrusion_width solid_infill_extrusion_width 
         top_infill_extrusion_width support_material_extrusion_width
         infill_overlap bridge_flow_ratio
-        clip_multipart_objects xy_size_compensation threads resolution
+        clip_multipart_objects elefant_foot_compensation xy_size_compensation threads resolution
         wipe_tower wipe_tower_x wipe_tower_y wipe_tower_width wipe_tower_per_color_wipe
     ));
     $self->{config}->set('print_settings_id', '');
@@ -770,6 +770,7 @@ sub build {
         {
             my $optgroup = $page->new_optgroup('Other');
             $optgroup->append_single_option_line('clip_multipart_objects');
+            $optgroup->append_single_option_line('elefant_foot_compensation');
             $optgroup->append_single_option_line('xy_size_compensation');
             $optgroup->append_single_option_line('threads') if $Slic3r::have_threads;
             $optgroup->append_single_option_line('resolution');

slic3r.pl

@@ -495,9 +495,13 @@ $j
     --dont-arrange      Don't arrange the objects on the build plate. The model coordinates
                         define the absolute positions on the build plate. 
                         The option --print-center will be ignored.
-    --clip_multipart_objects When printing multi-material objects, this settings will make slic3r to clip the overlapping 
+    --clip_multipart_objects 
+                        When printing multi-material objects, this settings will make slic3r to clip the overlapping 
                         object parts one by the other (2nd part will be clipped by the 1st, 3rd part will be clipped 
                         by the 1st and 2nd etc). (default: $config->{clip_multipart_objects})";
+    --elefant-foot-compensation
+                        Shrink the first layer by the configured value to compensate for the 1st layer squish 
+                        aka an Elefant Foot effect (mm, default: $config->{elefant_foot_compensation})
     --xy-size-compensation
                         Grow/shrink objects by the configured absolute distance (mm, default: $config->{xy_size_compensation})
    

xs/src/libslic3r/PrintConfig.cpp

@@ -163,6 +163,15 @@ PrintConfigDef::PrintConfigDef()
     def->min = 0;
     def->default_value = new ConfigOptionFloat(6);
 
+    def = this->add("elefant_foot_compensation", coFloat);
+    def->label = "Elefant foot compensation";
+    def->category = "Advanced";
+    def->tooltip = "The first layer will be shrunk in the XY plane by the configured value to compensate for the 1st layer squish aka an Elefant Foot effect.";
+    def->sidetext = "mm";
+    def->cli = "elefant-foot-compensation=f";
+    def->min = 0;
+    def->default_value = new ConfigOptionFloat(0);
+
     def = this->add("end_gcode", coString);
     def->label = "End G-code";
     def->tooltip = "This end procedure is inserted at the end of the output file. Note that you can use placeholder variables for all Slic3r settings.";

xs/src/libslic3r/PrintConfig.hpp

@@ -165,6 +165,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
 public:
     ConfigOptionBool                clip_multipart_objects;
     ConfigOptionBool                dont_support_bridges;
+    ConfigOptionFloat               elefant_foot_compensation;
     ConfigOptionFloatOrPercent      extrusion_width;
     ConfigOptionFloatOrPercent      first_layer_height;
     ConfigOptionBool                infill_only_where_needed;
@@ -203,6 +204,7 @@ public:
     virtual ConfigOption* optptr(const t_config_option_key &opt_key, bool create = false) {
         OPT_PTR(clip_multipart_objects);
         OPT_PTR(dont_support_bridges);
+        OPT_PTR(elefant_foot_compensation);
         OPT_PTR(extrusion_width);
         OPT_PTR(first_layer_height);
         OPT_PTR(infill_only_where_needed);

xs/src/libslic3r/PrintObject.cpp

@@ -160,6 +160,7 @@ bool PrintObject::invalidate_state_by_config_options(const std::vector<t_config_
 		}
 		else if (
                opt_key == "clip_multipart_objects"
+            || opt_key == "elefant_foot_compensation"
             || opt_key == "support_material_contact_distance" 
             || opt_key == "xy_size_compensation") {
             steps.emplace_back(posSlice);
@@ -1164,6 +1165,8 @@ end:
                 Layer *layer = this->layers[layer_id];
                 // Apply size compensation and perform clipping of multi-part objects.
                 float delta = float(scale_(this->config.xy_size_compensation.value));
+                if (layer_id == 0)
+                    delta -= float(scale_(this->config.elefant_foot_compensation.value));
                 bool  scale = delta != 0.f;
                 bool  clip  = this->config.clip_multipart_objects.value || delta > 0.f;
                 if (layer->regions.size() == 1) {