perf: speed up G-code export by up to 8% via cheaper G-code text building (#16108)

src/libslic3r/GCode.cpp

@@ -5204,7 +5204,8 @@ namespace Skirt {
 // Orca: Klipper can't parse object names with spaces and other spetical characters
 std::string sanitize_instance_name(const std::string& name) {
     // Replace sequences of non-word characters with an underscore
-    std::string result = std::regex_replace(name, std::regex("[ !@#$%^&*()=+\\[\\]{};:\",']+"), "_");
+    static const std::regex non_word_characters("[ !@#$%^&*()=+\\[\\]{};:\",']+");
+    std::string result = std::regex_replace(name, non_word_characters, "_");
     // Remove leading and trailing underscores
     if (!result.empty() && result.front() == '_') {
         result.erase(result.begin());
@@ -5218,12 +5219,16 @@ std::string sanitize_instance_name(const std::string& name) {
 
 inline std::string get_instance_name(const PrintObject *object, size_t inst_id) {
     auto obj_name = sanitize_instance_name(object->model_object()->name);
-    auto name = (boost::format("%1%_id_%2%_copy_%3%") % obj_name % object->get_id() % inst_id).str();
+    auto name = obj_name + "_id_" + std::to_string(object->get_id()) + "_copy_" + std::to_string(inst_id);
     return sanitize_instance_name(name);
 }
 
-inline std::string get_instance_name(const PrintObject *object, const PrintInstance &inst) {
-    return get_instance_name(object, inst.id);
+const std::string& GCode::instance_name(const PrintInstance &instance)
+{
+    auto [it, inserted] = m_instance_names.try_emplace(&instance);
+    if (inserted)
+        it->second = get_instance_name(instance.print_object, instance.id);
+    return it->second;
 }
 
 std::string GCode::generate_skirt(const Print &print,
@@ -6642,7 +6647,7 @@ LayerResult GCode::process_layer(
                         const auto gflavor = print.config().gcode_flavor.value;
                         if (gflavor == gcfKlipper) {
                             m_writer.set_object_start_str(std::string("EXCLUDE_OBJECT_START NAME=") +
-                                                          get_instance_name(&instance_to_print.print_object, inst.id) + "\n");
+                                                          instance_name(inst) + "\n");
                         }
                         else if (gflavor == gcfMarlinLegacy || gflavor == gcfMarlinFirmware || gflavor == gcfRepRapFirmware) {
                             std::string str = std::string("M486 S") + std::to_string(inst.unique_id) + "\n";
@@ -6791,7 +6796,7 @@ LayerResult GCode::process_layer(
                         const auto gflavor = print.config().gcode_flavor.value;
                         if (gflavor == gcfKlipper) {
                             m_writer.set_object_end_str(std::string("EXCLUDE_OBJECT_END NAME=") +
-                                                        get_instance_name(&instance_to_print.print_object, inst.id) + "\n");
+                                                        instance_name(inst) + "\n");
                         } else if (gflavor == gcfMarlinLegacy || gflavor == gcfMarlinFirmware || gflavor == gcfRepRapFirmware) {
                             m_writer.set_object_end_str(std::string("M486 S-1\n"));
                         }
@@ -6866,7 +6871,7 @@ LayerResult GCode::process_layer(
                         const auto gflavor = print.config().gcode_flavor.value;
                         if (gflavor == gcfKlipper) {
                             m_writer.set_object_start_str(std::string("EXCLUDE_OBJECT_START NAME=") +
-                                                          get_instance_name(&instance_to_print.print_object, inst.id) + "\n");
+                                                          instance_name(inst) + "\n");
                         } else if (gflavor == gcfMarlinLegacy || gflavor == gcfMarlinFirmware || gflavor == gcfRepRapFirmware) {
                             m_writer.set_object_start_str(std::string("M486 S") + std::to_string(inst.unique_id) + "\n");
                         }
@@ -7092,7 +7097,7 @@ LayerResult GCode::process_layer(
                         const auto gflavor = print.config().gcode_flavor.value;
                         if (gflavor == gcfKlipper) {
                             m_writer.set_object_end_str(std::string("EXCLUDE_OBJECT_END NAME=") +
-                                                        get_instance_name(&instance_to_print.print_object, inst.id) + "\n");
+                                                        instance_name(inst) + "\n");
                         } else if (gflavor == gcfMarlinLegacy || gflavor == gcfMarlinFirmware || gflavor == gcfRepRapFirmware) {
                             m_writer.set_object_end_str(std::string("M486 S-1\n"));
                         }
@@ -8084,12 +8089,12 @@ static float overhang_fan_overlap_threshold(int overhang_fan_threshold)
     }
 }
 
-std::string GCode::_extrude(const ExtrusionPath &path, std::string description, double speed)
+std::string GCode::_extrude(const ExtrusionPath &path, const std::string &path_description, double speed)
 {
     std::string gcode;
 
-    if (is_bridge(path.role()))
-        description += " (bridge)";
+    const std::string  bridge_description = is_bridge(path.role()) ? path_description + " (bridge)" : std::string();
+    const std::string &description        = bridge_description.empty() ? path_description : bridge_description;
 
     const ExtrusionPathSloped* sloped = dynamic_cast<const ExtrusionPathSloped*>(&path);
 
@@ -8760,7 +8765,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             // ORCA: End of adaptive PA code segment
         }
         
-        gcode += m_writer.set_speed(F, "", comment);
+        m_writer.set_speed(gcode, F, "", comment);
         {
             if (m_enable_cooling_markers) {
                 if (enable_overhang_bridge_fan) {
@@ -8784,7 +8789,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                 double saved_z      = m_writer.get_position().z();
 
                 for (const Line3& line : path.polyline.lines()) {
-                    std::string tempDescription = description;
+                    std::string flow_description;
                     const double line_length = line.length() * SCALING_FACTOR;
                     if (line_length < EPSILON)
                         continue;
@@ -8795,7 +8800,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                         dE = m_small_area_infill_flow_compensator->modify_flow(line_length, dE, path.role());
 
                         if (m_config.gcode_comments && oldE > 0 && oldE != dE) {
-                            tempDescription += Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
+                            flow_description = description + Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
                         }
                     }
                     if (path.z_contoured) {
@@ -8814,24 +8819,24 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                         if (z < 0.1) {
                             throw RuntimeError("GCode: very low z");
                         }
-                        gcode += m_writer.extrude_to_xyz(Vec3d(dest2d.x(), dest2d.y(), z), e,
-                                                         GCodeWriter::full_gcode_comment ? tempDescription : "");
+                        m_writer.extrude_to_xyz(gcode, Vec3d(dest2d.x(), dest2d.y(), z), e,
+                                                flow_description.empty() ? description : flow_description);
 
                     } else if (sloped == nullptr) {
                         // Normal extrusion
-                        gcode += m_writer.extrude_to_xy(
+                        m_writer.extrude_to_xy(gcode,
                             this->point_to_gcode(line.b.to_point()),
                             dE,
-                            GCodeWriter::full_gcode_comment ? tempDescription : "", path.is_force_no_extrusion());
+                            flow_description.empty() ? description : flow_description, path.is_force_no_extrusion());
                     } else {
                         // Sloped extrusion
                         const auto [z_ratio, e_ratio] = sloped->interpolate(path_length / total_length);
                         Vec2d dest2d = this->point_to_gcode(line.b.to_point());
                         Vec3d dest3d(dest2d(0), dest2d(1), get_sloped_z(z_ratio));
-                        gcode += m_writer.extrude_to_xyz(
+                        m_writer.extrude_to_xyz(gcode,
                             dest3d,
                             dE * e_ratio,
-                            GCodeWriter::full_gcode_comment ? tempDescription : "", path.is_force_no_extrusion());
+                            flow_description.empty() ? description : flow_description, path.is_force_no_extrusion());
                     }
                     check_and_insert_timelapse(line.b.to_point()); // Inline farthest-point snapshot
                 }
@@ -8839,13 +8844,13 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                 // BBS: start to generate gcode from arc fitting data which includes line and arc
                 const std::vector<PathFittingData>& fitting_result = path.polyline.fitting_result;
                 for (size_t fitting_index = 0; fitting_index < fitting_result.size(); fitting_index++) {
-                    std::string tempDescription = description;
+                    std::string flow_description;
                     switch (fitting_result[fitting_index].path_type) {
                     case EMovePathType::Linear_move: {
                         size_t start_index = fitting_result[fitting_index].start_point_index;
                         size_t end_index = fitting_result[fitting_index].end_point_index;
                         for (size_t point_index = start_index + 1; point_index < end_index + 1; point_index++) {
-                            tempDescription = description;
+                            flow_description.clear();
                             const Line line = Line(path.polyline.points[point_index - 1].to_point(), path.polyline.points[point_index].to_point());
                             const double line_length = line.length() * SCALING_FACTOR;
                             if (line_length < EPSILON)
@@ -8856,13 +8861,13 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                                 dE = m_small_area_infill_flow_compensator->modify_flow(line_length, dE, path.role());
 
                                 if (m_config.gcode_comments && oldE > 0 && oldE != dE) {
-                                    tempDescription += Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
+                                    flow_description = description + Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
                                 }
                             }
-                            gcode += m_writer.extrude_to_xy(
+                            m_writer.extrude_to_xy(gcode,
                                 this->point_to_gcode(line.b),
                                 dE,
-                                GCodeWriter::full_gcode_comment ? tempDescription : "", path.is_force_no_extrusion());
+                                flow_description.empty() ? description : flow_description, path.is_force_no_extrusion());
                             check_and_insert_timelapse(line.b); // Inline farthest-point snapshot
                         }
                         break;
@@ -8880,15 +8885,15 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                             dE = m_small_area_infill_flow_compensator->modify_flow(arc_length, dE, path.role());
 
                             if (m_config.gcode_comments && oldE > 0 && oldE != dE) {
-                                tempDescription += Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, arc_length);
+                                flow_description = description + Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, arc_length);
                             }
                         }
-                        gcode += m_writer.extrude_arc_to_xy(
+                        m_writer.extrude_arc_to_xy(gcode,
                             this->point_to_gcode(arc.end_point),
                             center_offset,
                             dE,
                             arc.direction == ArcDirection::Arc_Dir_CCW,
-                            GCodeWriter::full_gcode_comment ? tempDescription : "", path.is_force_no_extrusion());
+                            flow_description.empty() ? description : flow_description, path.is_force_no_extrusion());
                         check_and_insert_timelapse(arc.end_point); // Inline farthest-point snapshot
                         break;
                     }
@@ -8912,7 +8917,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             Polyline3 l(p);
             total_length = l.length() * SCALING_FACTOR;
         }
-        gcode += m_writer.set_speed(last_set_speed, "", comment);
+        m_writer.set_speed(gcode, last_set_speed, "", comment);
         Vec3d prev            = this->point_to_gcode_quantized(new_points[0].p);
         bool pre_fan_enabled = false;
         bool cur_fan_enabled = false;
@@ -8924,7 +8929,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
 
         double path_length = 0.;
         for (size_t i = 1; i < new_points.size(); i++) {
-            std::string tempDescription = description;
+            std::string flow_description;
             const ProcessedPoint &processed_point = new_points[i];
             const ProcessedPoint &pre_processed_point = new_points[i-1];
             Vec3d                 p                   = this->point_to_gcode_quantized(processed_point.p);
@@ -8991,10 +8996,10 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
             // Ignore small speed variations - emit speed change if the delta between current and new is greater than 60mm/min / 1mm/sec
             // Reset speed to F if delta to F is less than 1mm/sec
             if ((std::abs(last_set_speed - new_speed) > 60)) {
-                gcode += m_writer.set_speed(new_speed, "", comment);
+                m_writer.set_speed(gcode, new_speed, "", comment);
                 last_set_speed = new_speed;
             } else if ((std::abs(F - new_speed) <= 60)) {
-                gcode += m_writer.set_speed(F, "", comment);
+                m_writer.set_speed(gcode, F, "", comment);
                 last_set_speed = F;
             }
             auto dE = e_per_mm * line_length;
@@ -9003,7 +9008,7 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                 dE = m_small_area_infill_flow_compensator->modify_flow(line_length, dE, path.role());
 
                 if (m_config.gcode_comments && oldE > 0 && oldE != dE) {
-                    tempDescription += Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
+                    flow_description = description + Slic3r::format(" | Old Flow Value: %0.5f Length: %0.5f",oldE, line_length);
                 }
             }
             if (path.z_contoured) {
@@ -9021,16 +9026,16 @@ std::string GCode::_extrude(const ExtrusionPath &path, std::string description,
                 if (z < 0.1) {
                     throw RuntimeError("GCode: very low z");
                 }
-                gcode += m_writer.extrude_to_xyz(Vec3d(dest2d.x(), dest2d.y(), z), e,
-                                                 GCodeWriter::full_gcode_comment ? tempDescription : "");
+                m_writer.extrude_to_xyz(gcode, Vec3d(dest2d.x(), dest2d.y(), z), e,
+                                        flow_description.empty() ? description : flow_description);
             } else if (sloped == nullptr) {
                 // Normal extrusion
-                gcode += m_writer.extrude_to_xy(p.head<2>(), dE, GCodeWriter::full_gcode_comment ? tempDescription : "");
+                m_writer.extrude_to_xy(gcode, p.head<2>(), dE, flow_description.empty() ? description : flow_description);
             } else {
                 // Sloped extrusion
                 const auto [z_ratio, e_ratio] = sloped->interpolate(path_length / total_length);
                 Vec3d dest3d(p(0), p(1), get_sloped_z(z_ratio));
-                gcode += m_writer.extrude_to_xyz(dest3d, dE * e_ratio, GCodeWriter::full_gcode_comment ? tempDescription : "");
+                m_writer.extrude_to_xyz(gcode, dest3d, dE * e_ratio, flow_description.empty() ? description : flow_description);
             }
 
             // Inline farthest-point snapshot on the variable-speed emission path. Inert unless the
@@ -10074,6 +10079,7 @@ std::string GCode::set_object_info(Print *print) {
         // PA_Line has only one object, no EXCLUDE_OBJECT_DEFINE needed
     } else {
         size_t unique_id = 0;
+        m_instance_names.clear();
         for (PrintObject* object : print->objects()) {
             object->set_id(object_id++);
             size_t inst_id = 0;
@@ -10082,7 +10088,7 @@ std::string GCode::set_object_info(Print *print) {
                 inst.id        = inst_id++;
                 auto bbox      = inst.get_bounding_box();
                 auto center    = print->translate_to_print_space(Vec2d(bbox.center().x(), bbox.center().y()));
-                auto inst_name = get_instance_name(object, inst);
+                const std::string &inst_name = instance_name(inst);
                 if (gflavor == gcfKlipper) {
                     gcode << "EXCLUDE_OBJECT_DEFINE NAME=" << inst_name << " CENTER=" << center.x() << "," << center.y()
                           << " POLYGON=" << polygon_to_string(inst.get_convex_hull_2d(), print) << "\n";

src/libslic3r/GCode.hpp

@@ -42,6 +42,7 @@
 #include <cstdlib>
 #include <memory>
 #include <map>
+#include <unordered_map>
 #include <set>
 #include <string>
 #include <cfloat>
@@ -715,6 +716,9 @@ private:
     
     bool m_enable_exclude_object;
     std::vector<size_t> m_label_objects_ids;
+    // Object label names by instance, built on first use from the ids set_object_info() assigns.
+    std::unordered_map<const PrintInstance*, std::string> m_instance_names;
+    const std::string& instance_name(const PrintInstance &instance);
     std::string _encode_label_ids_to_base64(std::vector<size_t> ids);
     // ORCA: Add support for role based fan speed control
     std::array<bool, ExtrusionRole::erCount> m_is_role_based_fan_on;
@@ -827,7 +831,7 @@ private:
     void update_layer_related_config(int layer_id);
 
     double      calc_max_volumetric_speed(const double layer_height, const double line_width, const std::string co_str);
-    std::string _extrude(const ExtrusionPath &path, std::string description = "", double speed = -1);
+    std::string _extrude(const ExtrusionPath &path, const std::string &path_description = "", double speed = -1);
     bool _needSAFC(const ExtrusionPath &path);
     void print_machine_envelope(GCodeOutputStream& file, Print& print);
     void _print_first_layer_bed_temperature(GCodeOutputStream &file, Print &print, const std::string &gcode, unsigned int first_printing_extruder_id, bool wait);

src/libslic3r/GCodeReader.cpp

@@ -21,6 +21,7 @@
 
 #include <Shiny/Shiny.h>
 #include <fast_float/fast_float.h>
+#include <memory>
 #include <utility>
 #include <vector>
 #include <string_view>
@@ -28,14 +29,24 @@
 
 namespace Slic3r {
 
+const GCodeConfig& GCodeReader::default_config()
+{
+    static const GCodeConfig config;
+    return config;
+}
+
 void GCodeReader::apply_config(const GCodeConfig &config)
 {
-    m_config = config;
+    m_config                   = std::make_shared<const GCodeConfig>(config);
+    m_use_relative_e_distances = config.use_relative_e_distances.value;
 }
 
 void GCodeReader::apply_config(const DynamicPrintConfig &config)
 {
-    m_config.apply(config, true);
+    auto applied = std::make_shared<GCodeConfig>(m_config ? *m_config : default_config());
+    applied->apply(config, true);
+    m_use_relative_e_distances = applied->use_relative_e_distances.value;
+    m_config                   = std::move(applied);
 }
 
 const char* GCodeReader::parse_line_internal(const char *ptr, const char *end, GCodeLine &gline, std::pair<const char*, const char*> &command)
@@ -95,7 +106,7 @@ const char* GCodeReader::parse_line_internal(const char *ptr, const char *end, G
         }
     }
     
-    if (gline.has(E) && m_config.use_relative_e_distances)
+    if (gline.has(E) && m_use_relative_e_distances)
         m_position[E] = 0;
 
     // Skip the rest of the line.

src/libslic3r/GCodeReader.hpp

@@ -7,6 +7,7 @@
 #include <cstdlib>
 #include <cstring>
 #include <functional>
+#include <memory>
 #include <string>
 #include <string_view>
 #include <utility>
@@ -111,7 +112,7 @@ public:
     void reset() { memset(m_position, 0, sizeof(m_position)); }
     void apply_config(const GCodeConfig &config);
     void apply_config(const DynamicPrintConfig &config);
-    const GCodeConfig& config() { return m_config; };
+    const GCodeConfig& config() { return m_config ? *m_config : default_config(); };
 
     template<typename Callback>
     void parse_buffer(const std::string &buffer, Callback callback)
@@ -172,7 +173,7 @@ public:
 
     GCodeConfig get_config() const
     { 
-        return m_config;
+        return m_config ? *m_config : default_config();
     }
 
 private:
@@ -199,8 +200,11 @@ private:
         return c;
     }
     static const char*  axis_pos(const char *raw_str, char axis);
+    static const GCodeConfig& default_config();
 
-    GCodeConfig m_config;
+    // Set by apply_config() and shared by copies, so a reader without a config builds none.
+    std::shared_ptr<const GCodeConfig> m_config;
+    bool        m_use_relative_e_distances{ default_config().use_relative_e_distances.value };
     float       m_position[NUM_AXES];
     bool        m_verbose;
     // To be set by the callback to stop parsing.

src/libslic3r/GCodeWriter.cpp

@@ -9,6 +9,7 @@
 #include "ClipperUtils.hpp"
 #include "Geometry/ArcWelder.hpp"
 #include "Line.hpp"
+#include "LocalesUtils.hpp"
 #include "libslic3r.h"
 #include <algorithm>
 #include <cmath>
@@ -380,26 +381,35 @@ std::string GCodeWriter::set_acceleration_internal(Acceleration type, unsigned i
 
     last_value = acceleration;
 
-    std::ostringstream gcode;
-    if (FLAVOR_IS(gcfRepetier))
-        gcode << (separate_travel ? "M202 X" : "M201 X") << acceleration << " Y" << acceleration;
-    else if (FLAVOR_IS(gcfRepRapFirmware) || FLAVOR_IS(gcfMarlinFirmware))
-        gcode << (separate_travel ? "M204 T" : "M204 P") << acceleration;
-    else if (FLAVOR_IS(gcfKlipper)) {
-        gcode << "SET_VELOCITY_LIMIT ACCEL=" << acceleration;
+    const std::string value = std::to_string(acceleration);
+    std::string       gcode;
+    if (FLAVOR_IS(gcfRepetier)) {
+        gcode += separate_travel ? "M202 X" : "M201 X";
+        gcode += value;
+        gcode += " Y";
+        gcode += value;
+    } else if (FLAVOR_IS(gcfRepRapFirmware) || FLAVOR_IS(gcfMarlinFirmware)) {
+        gcode += separate_travel ? "M204 T" : "M204 P";
+        gcode += value;
+    } else if (FLAVOR_IS(gcfKlipper)) {
+        gcode.reserve(96);
+        gcode += "SET_VELOCITY_LIMIT ACCEL=";
+        gcode += value;
         if (this->config.accel_to_decel_enable) {
-            gcode << " ACCEL_TO_DECEL=" << acceleration * this->config.accel_to_decel_factor / 100;
+            gcode += " ACCEL_TO_DECEL=";
+            gcode += float_to_string_decimal_point(acceleration * this->config.accel_to_decel_factor / 100);
             if (GCodeWriter::full_gcode_comment)
-                gcode << " ; adjust ACCEL_TO_DECEL";
+                gcode += " ; adjust ACCEL_TO_DECEL";
         }
+    } else {
+        gcode += "M204 S";
+        gcode += value;
     }
-    else
-        gcode << "M204 S" << acceleration;
 
-    if (GCodeWriter::full_gcode_comment) gcode << " ; adjust acceleration";
-    gcode << "\n";
+    if (GCodeWriter::full_gcode_comment) gcode += " ; adjust acceleration";
+    gcode += "\n";
 
-    return gcode.str();
+    return gcode;
 }
 
 std::string GCodeWriter::set_jerk_xy(double jerk)
@@ -476,25 +486,29 @@ std::string GCodeWriter::set_accel_and_jerk(unsigned int acceleration, double je
     if (!set_acceleration && !set_jerk)
         return std::string();
 
-    std::ostringstream gcode;
-    gcode << "SET_VELOCITY_LIMIT";
+    std::string gcode;
+    gcode.reserve(96);
+    gcode += "SET_VELOCITY_LIMIT";
     if (set_acceleration) {
-        gcode << " ACCEL=" << acceleration;
+        gcode += " ACCEL=";
+        gcode += std::to_string(acceleration);
         if (this->config.accel_to_decel_enable) {
-            gcode << " ACCEL_TO_DECEL=" << acceleration * this->config.accel_to_decel_factor / 100;
+            gcode += " ACCEL_TO_DECEL=";
+            gcode += float_to_string_decimal_point(acceleration * this->config.accel_to_decel_factor / 100);
         }
         m_last_acceleration = acceleration;
     }
     if (set_jerk) {
-        gcode << " SQUARE_CORNER_VELOCITY=" << jerk;
+        gcode += " SQUARE_CORNER_VELOCITY=";
+        gcode += float_to_string_decimal_point(jerk);
         m_last_jerk = jerk;
     }
 
     if (GCodeWriter::full_gcode_comment)
-        gcode << " ; adjust VELOCITY_LIMIT(accel/jerk)";
-    gcode << "\n";
+        gcode += " ; adjust VELOCITY_LIMIT(accel/jerk)";
+    gcode += "\n";
 
-    return gcode.str();
+    return gcode;
 
 }
 
@@ -753,6 +767,13 @@ double GCodeWriter::get_extruder_retracted_length(const int filament_id)
 }
 
 std::string GCodeWriter::set_speed(double F, const std::string &comment, const std::string &cooling_marker)
+{
+    std::string gcode;
+    this->set_speed(gcode, F, comment, cooling_marker);
+    return gcode;
+}
+
+void GCodeWriter::set_speed(std::string &out, double F, const std::string &comment, const std::string &cooling_marker)
 {
     assert(F > 0.);
     assert(F < 100000.);
@@ -763,7 +784,7 @@ std::string GCodeWriter::set_speed(double F, const std::string &comment, const s
     //BBS
     w.emit_comment(GCodeWriter::full_gcode_comment, comment);
     w.emit_string(cooling_marker);
-    return w.string();
+    w.append_to(out);
 }
 
 std::string GCodeWriter::travel_to_xy(const Vec2d &point, const std::string &comment)
@@ -1115,6 +1136,13 @@ bool GCodeWriter::will_move_z(double z) const
 }
 
 std::string GCodeWriter::extrude_to_xy(const Vec2d &point, double dE, const std::string &comment, bool force_no_extrusion)
+{
+    std::string gcode;
+    this->extrude_to_xy(gcode, point, dE, comment, force_no_extrusion);
+    return gcode;
+}
+
+void GCodeWriter::extrude_to_xy(std::string &out, const Vec2d &point, double dE, const std::string &comment, bool force_no_extrusion)
 {
     m_pos(0) = point(0);
     m_pos(1) = point(1);
@@ -1133,13 +1161,20 @@ std::string GCodeWriter::extrude_to_xy(const Vec2d &point, double dE, const std:
         w.emit_e(filament()->E());
     //BBS
     w.emit_comment(GCodeWriter::full_gcode_comment, comment);
-    return w.string();
+    w.append_to(out);
 }
 
 //BBS: generate G2 or G3 extrude which moves by arc
 //point is end point which means X and Y axis
 //center_offset is I and J axis
 std::string GCodeWriter::extrude_arc_to_xy(const Vec2d& point, const Vec2d& center_offset, double dE, const bool is_ccw, const std::string& comment, bool force_no_extrusion)
+{
+    std::string gcode;
+    this->extrude_arc_to_xy(gcode, point, center_offset, dE, is_ccw, comment, force_no_extrusion);
+    return gcode;
+}
+
+void GCodeWriter::extrude_arc_to_xy(std::string &out, const Vec2d& point, const Vec2d& center_offset, double dE, const bool is_ccw, const std::string& comment, bool force_no_extrusion)
 {
     m_pos(0) = point(0);
     m_pos(1) = point(1);
@@ -1155,10 +1190,17 @@ std::string GCodeWriter::extrude_arc_to_xy(const Vec2d& point, const Vec2d& cent
         w.emit_e(filament()->E());
     //BBS
     w.emit_comment(GCodeWriter::full_gcode_comment, comment);
-    return w.string();
+    w.append_to(out);
 }
 
 std::string GCodeWriter::extrude_to_xyz(const Vec3d &point, double dE, const std::string &comment, bool force_no_extrusion)
+{
+    std::string gcode;
+    this->extrude_to_xyz(gcode, point, dE, comment, force_no_extrusion);
+    return gcode;
+}
+
+void GCodeWriter::extrude_to_xyz(std::string &out, const Vec3d &point, double dE, const std::string &comment, bool force_no_extrusion)
 {
     // Check if Z actually changes (at export precision) before emitting it.
     // ZAA sloped extrusions call this for every segment, but many consecutive
@@ -1182,7 +1224,7 @@ std::string GCodeWriter::extrude_to_xyz(const Vec3d &point, double dE, const std
         w.emit_e(filament()->E());
     //BBS
     w.emit_comment(GCodeWriter::full_gcode_comment, comment);
-    return w.string();
+    w.append_to(out);
 }
 
 std::string GCodeWriter::retract(bool before_wipe, double retract_length)

src/libslic3r/GCodeWriter.hpp

@@ -92,6 +92,11 @@ public:
     //BBS: generate G2 or G3 extrude which moves by arc
     std::string extrude_arc_to_xy(const Vec2d &point, const Vec2d &center_offset, double dE, const bool is_ccw, const std::string &comment = std::string(), bool force_no_extrusion = false);
     std::string extrude_to_xyz(const Vec3d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
+    // Each appends its line to `out`.
+    void        set_speed(std::string &out, double F, const std::string &comment = std::string(), const std::string &cooling_marker = std::string());
+    void        extrude_to_xy(std::string &out, const Vec2d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
+    void        extrude_arc_to_xy(std::string &out, const Vec2d &point, const Vec2d &center_offset, double dE, const bool is_ccw, const std::string &comment = std::string(), bool force_no_extrusion = false);
+    void        extrude_to_xyz(std::string &out, const Vec3d &point, double dE, const std::string &comment = std::string(), bool force_no_extrusion = false);
     std::string retract(bool before_wipe = false, double retract_length = 0);
     std::string retract_for_toolchange(bool before_wipe = false, double retract_length = 0);
     // extra_retract adds a small over-extrusion to the deretract move (PETG pre-extrusion).
@@ -299,8 +304,14 @@ public:
     }
 
     std::string string() {
+        std::string out;
+        this->append_to(out);
+        return out;
+    }
+
+    void append_to(std::string &out) {
         *ptr_err.ptr ++ = '\n';
-        return std::string(this->buf, ptr_err.ptr - buf);
+        out.append(this->buf, ptr_err.ptr - buf);
     }
 
 protected:

src/libslic3r/LocalesUtils.cpp

@@ -6,15 +6,22 @@
 #include <string>
 #include <ios>
 
-#ifdef _WIN32
-    #include <charconv>
-#endif
+#include <charconv>
 #include <iomanip>
 #include <sstream>
-#include <stdexcept>
+#include <system_error>
 
 #include <fast_float/fast_float.h>
 
+// Defined where the floating point std::to_chars can be called, which with Apple's libc++ runtime is from macOS 13.3.
+#if defined(_LIBCPP_VERSION)
+    #if defined(_LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT) && _LIBCPP_AVAILABILITY_HAS_TO_CHARS_FLOATING_POINT
+        #define SLIC3R_FLOAT_TO_CHARS
+    #endif
+#elif defined(_WIN32) || defined(__cpp_lib_to_chars)
+    #define SLIC3R_FLOAT_TO_CHARS
+#endif
+
 
 namespace Slic3r {
 
@@ -99,9 +106,9 @@ double atof_decimal_point(std::string_view str)
 
 std::string float_to_string_decimal_point(double value, int precision/* = -1*/)
 {
-    // Our Windows build server fully supports C++17 std::to_chars. Let's use it.
-    // Other platforms are behind, fall back to slow stringstreams for now.
-#ifdef _WIN32
+    // Every branch prints the same digits in the classic locale as the stream at the end, which takes over when a branch
+    // is compiled out or the value is too long for the buffer.
+#if defined(SLIC3R_FLOAT_TO_CHARS)
     constexpr size_t SIZE = 20;
     char out[SIZE] = "";
     std::to_chars_result res;
@@ -109,16 +116,26 @@ std::string float_to_string_decimal_point(double value, int precision/* = -1*/)
         res = std::to_chars(out, out+SIZE, value, std::chars_format::fixed, precision);
     else
         res = std::to_chars(out, out+SIZE, value, std::chars_format::general, 6);
-    if (res.ec == std::errc::value_too_large)
-        throw std::invalid_argument("float_to_string_decimal_point conversion failed.");
-    return std::string(out, res.ptr - out);
-#else
+    if (res.ec == std::errc())
+        return std::string(out, res.ptr - out);
+#elif defined(__APPLE__)
+    // Formats in the C locale, as libc++'s stream does, switching only this thread's locale for the call.
+    static const locale_t c_locale = newlocale(LC_NUMERIC_MASK, "C", (locale_t) 0);
+    if (c_locale != (locale_t) 0) {
+        constexpr size_t SIZE = 20;
+        char           out[SIZE];
+        const locale_t previous = uselocale(c_locale);
+        const int      length   = precision >= 0 ? snprintf(out, SIZE, "%.*f", precision, value) : snprintf(out, SIZE, "%.*g", 6, value);
+        uselocale(previous);
+        if (length >= 0 && size_t(length) < SIZE)
+            return std::string(out, length);
+    }
+#endif
     std::stringstream buf;
     if (precision >= 0)
         buf << std::fixed << std::setprecision(precision);
     buf << value;
     return buf.str();
-#endif
 }