Overhang tweaks:

1. Revert back to classic overhang
2. Support percent for overhang speed

src/libslic3r/GCode.cpp

@@ -2959,11 +2959,13 @@ GCode::LayerResult GCode::process_layer(
         Skirt::make_skirt_loops_per_extruder_1st_layer(print, layer_tools, m_skirt_done) :
         Skirt::make_skirt_loops_per_extruder_other_layers(print, layer_tools, m_skirt_done);
 
-    for (const auto& layer_to_print : layers) {
-      m_extrusion_quality_estimator.prepare_for_new_layer(layer_to_print.original_object, layer_to_print.object_layer);
+    if (m_config.enable_overhang_speed && !m_config.overhang_speed_classic) {
+        for (const auto &layer_to_print : layers) {
+            m_extrusion_quality_estimator.prepare_for_new_layer(layer_to_print.original_object,
+                                                                layer_to_print.object_layer);
+        }
     }
 
-
     // Group extrusions by an extruder, then by an object, an island and a region.
     std::map<unsigned int, std::vector<ObjectByExtruder>> by_extruder;
     bool is_anything_overridden = const_cast<LayerTools&>(layer_tools).wiping_extrusions().is_anything_overridden();
@@ -3275,7 +3277,9 @@ GCode::LayerResult GCode::process_layer(
                 // ref to: https://github.com/SoftFever/OrcaSlicer/pull/205/commits/7f1fe0bd544077626080aa1a9a0576aa735da1a4#r1083470162
                 if (reset_e && !m_config.use_relative_e_distances)
                     gcode += m_writer.reset_e(true);
-                m_extrusion_quality_estimator.set_current_object(&instance_to_print.print_object);
+                
+                if (m_config.enable_overhang_speed && !m_config.overhang_speed_classic)
+                    m_extrusion_quality_estimator.set_current_object(&instance_to_print.print_object);
 
                 // When starting a new object, use the external motion planner for the first travel move.
                 const Point &offset = inst.shift;

src/libslic3r/PrintConfig.cpp

@@ -759,8 +759,8 @@ void PrintConfigDef::init_fff_params()
     def->label = L("Classic mode");
     def->category = L("Speed");
     def->tooltip = L("Enable this option to use classic mode");
-    def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionBool{ false });
+    def->mode = comDevelop;
+    def->set_default_value(new ConfigOptionBool{ true });
 
     def = this->add("enable_overhang_speed", coBool);
     def->label = L("Slow down for overhang");
@@ -769,47 +769,51 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionBool{ true });
 
-    def = this->add("overhang_1_4_speed", coFloat);
+    def = this->add("overhang_1_4_speed", coFloatOrPercent);
     def->label = "(10%, 25%)";
     def->category = L("Speed");
     def->full_label = "(10%, 25%)";
     //def->tooltip = L("Speed for line of wall which has degree of overhang between 10% and 25% line width. "
     //                 "0 means using original wall speed");
-    def->sidetext = L("mm/s");
+    def->sidetext = L("mm/s or %");
+    def->ratio_over = "outer_wall_speed";
     def->min = 0;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(0));
+    def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
 
-    def = this->add("overhang_2_4_speed", coFloat);
+    def = this->add("overhang_2_4_speed", coFloatOrPercent);
     def->label = "[25%, 50%)";
     def->category = L("Speed");
     def->full_label = "[25%, 50%)";
     //def->tooltip = L("Speed for line of wall which has degree of overhang between 25% and 50% line width. "
     //                 "0 means using original wall speed");
-    def->sidetext = L("mm/s");
+    def->sidetext = L("mm/s or %");
+    def->ratio_over = "outer_wall_speed";
     def->min = 0;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(0));
+    def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
 
-    def = this->add("overhang_3_4_speed", coFloat);
+    def = this->add("overhang_3_4_speed", coFloatOrPercent);
     def->label = "[50%, 75%)";
     def->category = L("Speed");
     def->full_label = "[50%, 75%)";
     //def->tooltip = L("Speed for line of wall which has degree of overhang between 50% and 75% line width. 0 means using original wall speed");
-    def->sidetext = L("mm/s");
+    def->sidetext = L("mm/s or %");
+    def->ratio_over = "outer_wall_speed";
     def->min = 0;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(0));
+    def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
 
-    def = this->add("overhang_4_4_speed", coFloat);
+    def = this->add("overhang_4_4_speed", coFloatOrPercent);
     def->label = "[75%, 100%)";
     def->category = L("Speed");
     def->full_label = "[75%, 100%)";
     //def->tooltip = L("Speed for line of wall which has degree of overhang between 75% and 100% line width. 0 means using original wall speed");
-    def->sidetext = L("mm/s");
+    def->sidetext = L("mm/s or %");
+    def->ratio_over = "outer_wall_speed";
     def->min = 0;
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionFloat(0));
+    def->set_default_value(new ConfigOptionFloatOrPercent(0, false));
 
     def = this->add("bridge_speed", coFloat);
     def->label = L("Bridge");
@@ -4476,7 +4480,7 @@ void PrintConfigDef::handle_legacy(t_config_option_key &opt_key, std::string &va
         "remove_freq_sweep", "remove_bed_leveling", "remove_extrusion_calibration",
         "support_transition_line_width", "support_transition_speed", "bed_temperature", "bed_temperature_initial_layer",
         "can_switch_nozzle_type", "can_add_auxiliary_fan", "extra_flush_volume", "spaghetti_detector", "adaptive_layer_height",
-        "z_hop_type", "z_lift_type"
+        "z_hop_type", "z_lift_type", "overhang_speed_classic"
     };
 
     if (ignore.find(opt_key) != ignore.end()) {

src/libslic3r/PrintConfig.hpp

@@ -766,10 +766,10 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionFloat, top_surface_speed))
     //BBS
     ((ConfigOptionBool,                 enable_overhang_speed))
-    ((ConfigOptionFloat,                overhang_1_4_speed))
-    ((ConfigOptionFloat,                overhang_2_4_speed))
-    ((ConfigOptionFloat,                overhang_3_4_speed))
-    ((ConfigOptionFloat,                overhang_4_4_speed))
+    ((ConfigOptionFloatOrPercent,       overhang_1_4_speed))
+    ((ConfigOptionFloatOrPercent,       overhang_2_4_speed))
+    ((ConfigOptionFloatOrPercent,       overhang_3_4_speed))
+    ((ConfigOptionFloatOrPercent,       overhang_4_4_speed))
     ((ConfigOptionBool,                 only_one_wall_top))
 
     //SoftFever