option for no z-lift on top solid infill.

src/libslic3r/GCode.cpp

@@ -2482,15 +2482,15 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
     {
         if (path.role() != m_last_extrusion_role)
         {
-            m_last_extrusion_role = path.role();
             if (m_enable_extrusion_role_markers)
             {
                 char buf[32];
-                sprintf(buf, ";_EXTRUSION_ROLE:%d\n", int(m_last_extrusion_role));
+                sprintf(buf, ";_EXTRUSION_ROLE:%d\n", int(path.role()));
                 gcode += buf;
             }
         }
     }
+    m_last_extrusion_role = path.role();
 
     // adds analyzer tags and updates analyzer's tracking data
     if (m_enable_analyzer)
@@ -2665,9 +2665,9 @@ std::string GCode::retract(bool toolchange)
         methods even if we performed wipe, since this will ensure the entire retraction
         length is honored in case wipe path was too short.  */
     gcode += toolchange ? m_writer.retract_for_toolchange() : m_writer.retract();
-
-    if (m_writer.extruder()->retract_length() > 0 || m_config.use_firmware_retraction)
-        gcode += m_writer.lift();
+    if (toolchange || !this->m_config.retract_lift_not_last_layer.value || !(this->m_last_extrusion_role == ExtrusionRole::erTopSolidInfill))
+        if (m_writer.extruder()->retract_length() > 0 || m_config.use_firmware_retraction)
+            gcode += m_writer.lift();
 
     return gcode;
 }

src/libslic3r/Print.cpp

@@ -153,6 +153,7 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
         "retract_lift",
         "retract_lift_above",
         "retract_lift_below",
+        "retract_lift_not_last_layer",
         "retract_restart_extra",
         "retract_restart_extra_toolchange",
         "retract_speed",

src/libslic3r/PrintConfig.cpp

@@ -1825,6 +1825,13 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->default_value = new ConfigOptionFloats { 0. };
 
+    def = this->add("retract_lift_not_last_layer", coBool);
+    def->label = L("Not on top");
+    def->category = L("Support material");
+    def->tooltip = L("Select this option to not use the z-lift on a top surface.");
+    def->mode = comAdvanced;
+    def->default_value = new ConfigOptionBool(false);
+
     def = this->add("retract_restart_extra", coFloats);
     def->label = L("Extra length on restart");
     def->tooltip = L("When the retraction is compensated after the travel move, the extruder will push "

src/libslic3r/PrintConfig.hpp

@@ -677,6 +677,7 @@ class GCodeConfig : public StaticPrintConfig
     ConfigOptionFloats              retract_lift;
     ConfigOptionFloats              retract_lift_above;
     ConfigOptionFloats              retract_lift_below;
+    ConfigOptionBool                retract_lift_not_last_layer;
     ConfigOptionFloats              retract_restart_extra;
     ConfigOptionFloats              retract_restart_extra_toolchange;
     ConfigOptionFloats              retract_speed;
@@ -747,6 +748,7 @@ class GCodeConfig : public StaticPrintConfig
         OPT_PTR(retract_lift);
         OPT_PTR(retract_lift_above);
         OPT_PTR(retract_lift_below);
+        OPT_PTR(retract_lift_not_last_layer);
         OPT_PTR(retract_restart_extra);
         OPT_PTR(retract_restart_extra_toolchange);
         OPT_PTR(retract_speed);

src/slic3r/GUI/Preset.cpp

@@ -405,7 +405,9 @@ const std::vector<std::string>& Preset::nozzle_options()
     // ConfigOptionFloats, ConfigOptionPercents, ConfigOptionBools, ConfigOptionStrings
     static std::vector<std::string> s_opts {
         "nozzle_diameter", "min_layer_height", "max_layer_height", "extruder_offset",
-        "retract_length", "retract_lift", "retract_lift_above", "retract_lift_below", "retract_speed", "deretract_speed",
+        "retract_length", "retract_lift", "retract_lift_above", "retract_lift_below",
+        "retract_lift_not_last_layer",
+        "retract_speed", "deretract_speed",
         "retract_before_wipe", "retract_restart_extra", "retract_before_travel", "wipe",
         "retract_layer_change", "retract_length_toolchange", "retract_restart_extra_toolchange", "extruder_colour", 
         "default_filament_profile"

src/slic3r/GUI/PresetHints.cpp

@@ -252,7 +252,7 @@ std::string PresetHints::recommended_thin_wall_thickness(const PresetBundle &pre
 
     std::string out;
 	if (layer_height <= 0.f){
-		out += _CHB(L("Recommended object thin wall thickness: Not available due to invalid layer height."));
+		out += _CHB(L("Recommended object min wall thickness: Not available due to invalid layer height."));
 		return out;
 	}
 
@@ -269,14 +269,14 @@ std::string PresetHints::recommended_thin_wall_thickness(const PresetBundle &pre
     if (num_perimeters > 0) {
         int num_lines = std::min(num_perimeters * 2, 10);
 		char buf[MIN_BUF_LENGTH/*256*/];
-        sprintf(buf, _CHB(L("Recommended object thin wall thickness for layer height %.2f and ")), layer_height);
+        sprintf(buf, _CHB(L("Recommended object min wall thickness for layer height %.2f and ")), layer_height);
         out += buf;
         // Start with the width of two closely spaced 
         double width = external_perimeter_flow.width + external_perimeter_flow.spacing();
         for (int i = 2; i <= num_lines; thin_walls ? ++ i : i += 2) {
             if (i > 2)
                 out += ", ";
-            sprintf(buf, _CHB(L("%d lines: %.2lf mm")), i, width);
+            sprintf(buf, _CHB(L("%d perimeter: %.2lf mm")), i/2, width);
             out += buf;
             width += perimeter_flow.spacing() * (thin_walls ? 1.f : 2.f);
         }

src/slic3r/GUI/Tab.cpp

@@ -2187,8 +2187,9 @@ void TabPrinter::build_extruder_pages()
 			optgroup->append_single_option_line("retract_length", extruder_idx);
 			optgroup->append_single_option_line("retract_lift", extruder_idx);
 				Line line = { _(L("Only lift Z")), "" };
-				line.append_option(optgroup->get_option("retract_lift_above", extruder_idx));
-				line.append_option(optgroup->get_option("retract_lift_below", extruder_idx));
+                line.append_option(optgroup->get_option("retract_lift_above", extruder_idx));
+                line.append_option(optgroup->get_option("retract_lift_below", extruder_idx));
+                line.append_option(optgroup->get_option("retract_lift_not_last_layer", extruder_idx));
 				optgroup->append_line(line);
 
 			optgroup->append_single_option_line("retract_speed", extruder_idx);
@@ -2319,7 +2320,7 @@ void TabPrinter::update_fff()
 
 		// retract lift above / below only applies if using retract lift
 		vec.resize(0);
-		vec = { "retract_lift_above", "retract_lift_below" };
+		vec = { "retract_lift_above", "retract_lift_below", "retract_lift_not_last_layer" };
 		for (auto el : vec)
 			get_field(el, i)->toggle(retraction && m_config->opt_float("retract_lift", i) > 0);