Make new overhang slowdonw(PrusaSlicer's slowdown) default again.

And tweak it

src/libslic3r/GCode.cpp

@@ -23,6 +23,8 @@
 #include <cstdlib>
 #include <chrono>
 #include <math.h>
+#include <stdlib.h>
+#include <string>
 #include <utility>
 #include <string_view>
 
@@ -4354,6 +4356,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
 
         for (size_t i = 1; i < new_points.size(); i++) {
             const ProcessedPoint &processed_point = new_points[i];
+            const ProcessedPoint &pre_processed_point = new_points[i-1];
             Vec2d p = this->point_to_gcode_quantized(processed_point.p);
             if (m_enable_cooling_markers) {
                 if (enable_overhang_bridge_fan) {
@@ -4387,7 +4390,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             }
 
             const double line_length = (p - prev).norm();
-            double new_speed = std::max((float)EXTRUDER_CONFIG(slow_down_min_speed), processed_point.speed) * 60.0;
+            double new_speed = std::max((float)EXTRUDER_CONFIG(slow_down_min_speed), pre_processed_point.speed) * 60.0;
             if (last_set_speed != new_speed) {
                 gcode += m_writer.set_speed(new_speed, "", comment);
                 last_set_speed = new_speed;

src/libslic3r/GCode/ExtrusionProcessor.hpp

@@ -1,6 +1,8 @@
 #ifndef slic3r_ExtrusionProcessor_hpp_
 #define slic3r_ExtrusionProcessor_hpp_
 
+// This algorithm is copied from PrusaSlicer, original author is Pavel Mikus(pavel.mikus.mail@seznam.cz)
+
 #include "../AABBTreeLines.hpp"
 //#include "../SupportSpotsGenerator.hpp"
 #include "../libslic3r.h"
@@ -68,7 +70,7 @@ public:
 class CurvatureEstimator
 {
     static const size_t               sliders_count          = 3;
-    SlidingWindowCurvatureAccumulator sliders[sliders_count] = {{1.0},{4.0}, {10.0}};
+    SlidingWindowCurvatureAccumulator sliders[sliders_count] = {{3.0},{9.0}, {16.0}};
 
 public:
     void add_point(float distance, float angle)

src/libslic3r/PerimeterGenerator.cpp

@@ -609,7 +609,7 @@ static ExtrusionEntityCollection traverse_extrusions(const PerimeterGenerator& p
             extrusion_paths_append(temp_paths, clip_extrusion(extrusion_path, lower_slices_paths, ClipperLib_Z::ctIntersection), role,
                                    is_external ? perimeter_generator.ext_perimeter_flow : perimeter_generator.perimeter_flow);
 
-            if (perimeter_generator.config->enable_overhang_speed && perimeter_generator.config->fuzzy_skin == FuzzySkinType::None) {
+            if (perimeter_generator.config->overhang_speed_classic && perimeter_generator.config->enable_overhang_speed && perimeter_generator.config->fuzzy_skin == FuzzySkinType::None) {
 
                 Flow flow = is_external ? perimeter_generator.ext_perimeter_flow : perimeter_generator.perimeter_flow;
                 std::map<double, std::vector<Polygons>> clipper_serise;

src/libslic3r/PrintConfig.cpp

@@ -783,7 +783,7 @@ void PrintConfigDef::init_fff_params()
     def->category = L("Speed");
     def->tooltip = L("Enable this option to use classic mode");
     def->mode = comAdvanced;
-    def->set_default_value(new ConfigOptionBool{ true });
+    def->set_default_value(new ConfigOptionBool{ false });
 
     def = this->add("enable_overhang_speed", coBool);
     def->label = L("Slow down for overhang");
@@ -4607,7 +4607,7 @@ 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"/*, "overhang_speed_classic"*/
+        "z_hop_type", "z_lift_type"
     };
 
     if (ignore.find(opt_key) != ignore.end()) {

src/slic3r/GUI/ConfigManipulation.cpp

@@ -321,37 +321,6 @@ void ConfigManipulation::update_print_fff_config(DynamicPrintConfig* config, con
         is_msg_dlg_already_exist = false;
     }
 
-    //BBS
-    /*
-    if (config->opt_enum<PerimeterGeneratorType>("wall_generator") == PerimeterGeneratorType::Arachne &&
-        config->opt_bool("overhang_speed_classic"))
-    {
-        wxString msg_text = _(L("Arachne engine doesn't work with classic overhang speed mode.\n")) + "\n";
-        if (is_global_config)
-            msg_text += "\n" + _(L("Turn off classic mode automatically? \n"
-                "Yes - Enable arachne with classic mode off\n"
-                "No  - Give up using arachne this time"));
-        MessageDialog dialog(m_msg_dlg_parent, msg_text, "",
-            wxICON_WARNING | (is_global_config ? wxYES | wxNO : wxOK));
-        DynamicPrintConfig new_conf = *config;
-        is_msg_dlg_already_exist = true;
-        auto answer = dialog.ShowModal();
-        bool enable_overhang_slow_down_legacy = false;
-        if (!is_global_config || answer == wxID_YES) {
-            new_conf.set_key_value("overhang_speed_classic", new ConfigOptionBool(false));
-            enable_overhang_slow_down_legacy = true;
-        }
-        else {
-            new_conf.set_key_value("wall_generator", new ConfigOptionEnum<PerimeterGeneratorType>(PerimeterGeneratorType::Classic));
-        }
-        apply(config, &new_conf);
-        if (cb_value_change) {
-            if (!enable_overhang_slow_down_legacy)
-                cb_value_change("overhang_speed_classic", false);
-        }
-        is_msg_dlg_already_exist = false;
-    }
-    */
     // BBS
     int filament_cnt = wxGetApp().preset_bundle->filament_presets.size();
 #if 0