Follow-up to beee18f22991e369b1722a43bbcb692fa0d68af0

WIP to G-code export parallelization through pipelining:
Decoupled CoolingBuffer from GCode / GCodeWriter, ready to be
pipelined on a different thread.

7 files changed, 96 insertions, 85 deletions

diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index efea240e5..7e1afb5a8 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -1219,7 +1219,7 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
 
     // Disable fan.
     if (! print.config().cooling.get_at(initial_extruder_id) || print.config().disable_fan_first_layers.get_at(initial_extruder_id))
-        file.write(m_writer.set_fan(0, true));
+        file.write(m_writer.set_fan(0));
 
     // Let the start-up script prime the 1st printing tool.
     m_placeholder_parser.set("initial_tool", initial_extruder_id);
@@ -1334,7 +1334,7 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
                 file.writeln(between_objects_gcode);
             }
             // Reset the cooling buffer internal state (the current position, feed rate, accelerations).
-            m_cooling_buffer->reset();
+            m_cooling_buffer->reset(this->writer().get_position());
             m_cooling_buffer->set_current_extruder(initial_extruder_id);
             // Pair the object layers with the support layers by z, extrude them.
             std::vector<LayerToPrint> layers_to_print = collect_layers_to_print(object);
@@ -1420,7 +1420,7 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
 
     // Write end commands to file.
     file.write(this->retract());
-    file.write(m_writer.set_fan(false));
+    file.write(m_writer.set_fan(0));
 
     // adds tag for processor
     file.write_format(";%s%s\n", GCodeProcessor::reserved_tag(GCodeProcessor::ETags::Role).c_str(), ExtrusionEntity::role_to_string(erCustom).c_str());
diff --git a/src/libslic3r/GCode/CoolingBuffer.cpp b/src/libslic3r/GCode/CoolingBuffer.cpp
index 17f3e0b73..9ca85c728 100644
--- a/src/libslic3r/GCode/CoolingBuffer.cpp
+++ b/src/libslic3r/GCode/CoolingBuffer.cpp
@@ -16,19 +16,25 @@
 
 namespace Slic3r {
 
-CoolingBuffer::CoolingBuffer(GCode &gcodegen) : m_gcodegen(gcodegen), m_current_extruder(0)
+CoolingBuffer::CoolingBuffer(GCode &gcodegen) : m_config(gcodegen.config()), m_toolchange_prefix(gcodegen.writer().toolchange_prefix()), m_current_extruder(0)
 {
-    this->reset();
+    this->reset(gcodegen.writer().get_position());
+
+    const std::vector<Extruder> &extruders = gcodegen.writer().extruders();
+    m_extruder_ids.reserve(extruders.size());
+    for (const Extruder &ex : extruders) {
+        m_num_extruders = std::max(ex.id() + 1, m_num_extruders);
+        m_extruder_ids.emplace_back(ex.id());
+    }
 }
 
-void CoolingBuffer::reset()
+void CoolingBuffer::reset(const Vec3d &position)
 {
     m_current_pos.assign(5, 0.f);
-    Vec3d pos = m_gcodegen.writer().get_position();
-    m_current_pos[0] = float(pos(0));
-    m_current_pos[1] = float(pos(1));
-    m_current_pos[2] = float(pos(2));
-    m_current_pos[4] = float(m_gcodegen.config().travel_speed.value);
+    m_current_pos[0] = float(position.x());
+    m_current_pos[1] = float(position.y());
+    m_current_pos[2] = float(position.z());
+    m_current_pos[4] = float(m_config.travel_speed.value);
 }
 
 struct CoolingLine
@@ -303,30 +309,23 @@ std::string CoolingBuffer::process_layer(std::string &&gcode, size_t layer_id, b
 // Return the list of parsed lines, bucketed by an extruder.
 std::vector<PerExtruderAdjustments> CoolingBuffer::parse_layer_gcode(const std::string &gcode, std::vector<float> &current_pos) const
 {
-    const FullPrintConfig       &config        = m_gcodegen.config();
-    const std::vector<Extruder> &extruders     = m_gcodegen.writer().extruders();
-    unsigned int                 num_extruders = 0;
-    for (const Extruder &ex : extruders)
-        num_extruders = std::max(ex.id() + 1, num_extruders);
-    
-    std::vector<PerExtruderAdjustments> per_extruder_adjustments(extruders.size());
-    std::vector<size_t>                 map_extruder_to_per_extruder_adjustment(num_extruders, 0);
-    for (size_t i = 0; i < extruders.size(); ++ i) {
+    std::vector<PerExtruderAdjustments> per_extruder_adjustments(m_extruder_ids.size());
+    std::vector<size_t>                 map_extruder_to_per_extruder_adjustment(m_num_extruders, 0);
+    for (size_t i = 0; i < m_extruder_ids.size(); ++ i) {
         PerExtruderAdjustments &adj         = per_extruder_adjustments[i];
-        unsigned int            extruder_id = extruders[i].id();
+        unsigned int            extruder_id = m_extruder_ids[i];
         adj.extruder_id               = extruder_id;
-        adj.cooling_slow_down_enabled = config.cooling.get_at(extruder_id);
-        adj.slowdown_below_layer_time = float(config.slowdown_below_layer_time.get_at(extruder_id));
-        adj.min_print_speed           = float(config.min_print_speed.get_at(extruder_id));
+        adj.cooling_slow_down_enabled = m_config.cooling.get_at(extruder_id);
+        adj.slowdown_below_layer_time = float(m_config.slowdown_below_layer_time.get_at(extruder_id));
+        adj.min_print_speed           = float(m_config.min_print_speed.get_at(extruder_id));
         map_extruder_to_per_extruder_adjustment[extruder_id] = i;
     }
 
-    const std::string toolchange_prefix = m_gcodegen.writer().toolchange_prefix();
     unsigned int      current_extruder  = m_current_extruder;
     PerExtruderAdjustments *adjustment  = &per_extruder_adjustments[map_extruder_to_per_extruder_adjustment[current_extruder]];
     const char       *line_start = gcode.c_str();
     const char       *line_end   = line_start;
-    const char        extrusion_axis = get_extrusion_axis(config)[0];
+    const char        extrusion_axis = get_extrusion_axis(m_config)[0];
     // Index of an existing CoolingLine of the current adjustment, which holds the feedrate setting command
     // for a sequence of extrusion moves.
     size_t            active_speed_modifier = size_t(-1);
@@ -387,7 +386,7 @@ std::vector<PerExtruderAdjustments> CoolingBuffer::parse_layer_gcode(const std::
             }
             if ((line.type & CoolingLine::TYPE_G92) == 0) {
                 // G0 or G1. Calculate the duration.
-                if (config.use_relative_e_distances.value)
+                if (m_config.use_relative_e_distances.value)
                     // Reset extruder accumulator.
                     current_pos[3] = 0.f;
                 float dif[4];
@@ -430,8 +429,8 @@ std::vector<PerExtruderAdjustments> CoolingBuffer::parse_layer_gcode(const std::
         } else if (boost::starts_with(sline, ";_EXTRUDE_END")) {
             line.type = CoolingLine::TYPE_EXTRUDE_END;
             active_speed_modifier = size_t(-1);
-        } else if (boost::starts_with(sline, toolchange_prefix)) {
-            unsigned int new_extruder = (unsigned int)atoi(sline.c_str() + toolchange_prefix.size());
+        } else if (boost::starts_with(sline, m_toolchange_prefix)) {
+            unsigned int new_extruder = (unsigned int)atoi(sline.c_str() + m_toolchange_prefix.size());
             // Only change extruder in case the number is meaningful. User could provide an out-of-range index through custom gcodes - those shall be ignored.
             if (new_extruder < map_extruder_to_per_extruder_adjustment.size()) {
                 if (new_extruder != current_extruder) {
@@ -641,7 +640,7 @@ float CoolingBuffer::calculate_layer_slowdown(std::vector<PerExtruderAdjustments
         if (total > slowdown_below_layer_time) {
             // The current total time is above the minimum threshold of the rest of the extruders, don't adjust anything.
         } else {
-            // Adjust this and all the following (higher config.slowdown_below_layer_time) extruders.
+            // Adjust this and all the following (higher m_config.slowdown_below_layer_time) extruders.
             // Sum maximum slow down time as if everything was slowed down including the external perimeters.
             float max_time = elapsed_time_total0;
             for (auto it = cur_begin; it != by_slowdown_time.end(); ++ it)
@@ -694,8 +693,7 @@ std::string CoolingBuffer::apply_layer_cooldown(
     bool bridge_fan_control = false;
     int  bridge_fan_speed   = 0;
     auto change_extruder_set_fan = [ this, layer_id, layer_time, &new_gcode, &fan_speed, &bridge_fan_control, &bridge_fan_speed ]() {
-        const FullPrintConfig &config = m_gcodegen.config();
-#define EXTRUDER_CONFIG(OPT) config.OPT.get_at(m_current_extruder)
+#define EXTRUDER_CONFIG(OPT) m_config.OPT.get_at(m_current_extruder)
         int min_fan_speed = EXTRUDER_CONFIG(min_fan_speed);
         int fan_speed_new = EXTRUDER_CONFIG(fan_always_on) ? min_fan_speed : 0;
         int disable_fan_first_layers = EXTRUDER_CONFIG(disable_fan_first_layers);
@@ -737,13 +735,12 @@ std::string CoolingBuffer::apply_layer_cooldown(
         }
         if (fan_speed_new != fan_speed) {
             fan_speed = fan_speed_new;
-            new_gcode += m_gcodegen.writer().set_fan(fan_speed);
+            new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_config.gcode_comments, fan_speed);
         }
     };
 
     const char         *pos               = gcode.c_str();
     int                 current_feedrate  = 0;
-    const std::string   toolchange_prefix = m_gcodegen.writer().toolchange_prefix();
     change_extruder_set_fan();
     for (const CoolingLine *line : lines) {
         const char *line_start  = gcode.c_str() + line->line_start;
@@ -751,7 +748,7 @@ std::string CoolingBuffer::apply_layer_cooldown(
         if (line_start > pos)
             new_gcode.append(pos, line_start - pos);
         if (line->type & CoolingLine::TYPE_SET_TOOL) {
-            unsigned int new_extruder = (unsigned int)atoi(line_start + toolchange_prefix.size());
+            unsigned int new_extruder = (unsigned int)atoi(line_start + m_toolchange_prefix.size());
             if (new_extruder != m_current_extruder) {
                 m_current_extruder = new_extruder;
                 change_extruder_set_fan();
@@ -759,10 +756,10 @@ std::string CoolingBuffer::apply_layer_cooldown(
             new_gcode.append(line_start, line_end - line_start);
         } else if (line->type & CoolingLine::TYPE_BRIDGE_FAN_START) {
             if (bridge_fan_control)
-                new_gcode += m_gcodegen.writer().set_fan(bridge_fan_speed, true);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_config.gcode_comments, bridge_fan_speed);
         } else if (line->type & CoolingLine::TYPE_BRIDGE_FAN_END) {
             if (bridge_fan_control)
-                new_gcode += m_gcodegen.writer().set_fan(fan_speed, true);
+                new_gcode += GCodeWriter::set_fan(m_config.gcode_flavor, m_config.gcode_comments, fan_speed);
         } else if (line->type & CoolingLine::TYPE_EXTRUDE_END) {
             // Just remove this comment.
         } else if (line->type & (CoolingLine::TYPE_ADJUSTABLE | CoolingLine::TYPE_EXTERNAL_PERIMETER | CoolingLine::TYPE_WIPE | CoolingLine::TYPE_HAS_F)) {
diff --git a/src/libslic3r/GCode/CoolingBuffer.hpp b/src/libslic3r/GCode/CoolingBuffer.hpp
index 0932d62d3..5f49ef455 100644
--- a/src/libslic3r/GCode/CoolingBuffer.hpp
+++ b/src/libslic3r/GCode/CoolingBuffer.hpp
@@ -23,10 +23,9 @@ struct PerExtruderAdjustments;
 class CoolingBuffer {
 public:
     CoolingBuffer(GCode &gcodegen);
-    void        reset();
+    void        reset(const Vec3d &position);
     void        set_current_extruder(unsigned int extruder_id) { m_current_extruder = extruder_id; }
     std::string process_layer(std::string &&gcode, size_t layer_id, bool flush);
-    GCode* 	    gcodegen() { return &m_gcodegen; }
 
 private:
 	CoolingBuffer& operator=(const CoolingBuffer&) = delete;
@@ -36,17 +35,25 @@ private:
     // Returns the adjusted G-code.
     std::string apply_layer_cooldown(const std::string &gcode, size_t layer_id, float layer_time, std::vector<PerExtruderAdjustments> &per_extruder_adjustments);
 
-    GCode&              m_gcodegen;
     // G-code snippet cached for the support layers preceding an object layer.
-    std::string         m_gcode;
+    std::string                 m_gcode;
     // Internal data.
     // X,Y,Z,E,F
-    std::vector<char>   m_axis;
-    std::vector<float>  m_current_pos;
-    unsigned int        m_current_extruder;
+    std::vector<char>           m_axis;
+    std::vector<float>          m_current_pos;
+    // Cached from GCodeWriter.
+    // Printing extruder IDs, zero based.
+    std::vector<unsigned int>   m_extruder_ids;
+    // Highest of m_extruder_ids plus 1.
+    unsigned int                m_num_extruders { 0 };
+    const std::string           m_toolchange_prefix;
+    // Referencs GCode::m_config, which is FullPrintConfig. While the PrintObjectConfig slice of FullPrintConfig is being modified,
+    // the PrintConfig slice of FullPrintConfig is constant, thus no thread synchronization is required.
+    const PrintConfig          &m_config;
+    unsigned int                m_current_extruder;
 
     // Old logic: proportional.
-    bool                m_cooling_logic_proportional = false;
+    bool                        m_cooling_logic_proportional = false;
 };
 
 }
diff --git a/src/libslic3r/GCodeWriter.cpp b/src/libslic3r/GCodeWriter.cpp
index c97180982..793a66675 100644
--- a/src/libslic3r/GCodeWriter.cpp
+++ b/src/libslic3r/GCodeWriter.cpp
@@ -156,41 +156,6 @@ std::string GCodeWriter::set_bed_temperature(unsigned int temperature, bool wait
     return gcode.str();
 }
 
-std::string GCodeWriter::set_fan(unsigned int speed, bool dont_save)
-{
-    std::ostringstream gcode;
-    if (m_last_fan_speed != speed || dont_save) {
-        if (!dont_save) m_last_fan_speed = speed;
-        
-        if (speed == 0) {
-            if (FLAVOR_IS(gcfTeacup)) {
-                gcode << "M106 S0";
-            } else if (FLAVOR_IS(gcfMakerWare) || FLAVOR_IS(gcfSailfish)) {
-                gcode << "M127";
-            } else {
-                gcode << "M107";
-            }
-            if (this->config.gcode_comments) gcode << " ; disable fan";
-            gcode << "\n";
-        } else {
-            if (FLAVOR_IS(gcfMakerWare) || FLAVOR_IS(gcfSailfish)) {
-                gcode << "M126";
-            } else {
-                gcode << "M106 ";
-                if (FLAVOR_IS(gcfMach3) || FLAVOR_IS(gcfMachinekit)) {
-                    gcode << "P";
-                } else {
-                    gcode << "S";
-                }
-                gcode << (255.0 * speed / 100.0);
-            }
-            if (this->config.gcode_comments) gcode << " ; enable fan";
-            gcode << "\n";
-        }
-    }
-    return gcode.str();
-}
-
 std::string GCodeWriter::set_acceleration(unsigned int acceleration)
 {
     // Clamp the acceleration to the allowed maximum.
@@ -611,4 +576,43 @@ std::string GCodeWriter::unlift()
     return gcode;
 }
 
+std::string GCodeWriter::set_fan(const GCodeFlavor gcode_flavor, bool gcode_comments, unsigned int speed)
+{
+    std::ostringstream gcode;
+    if (speed == 0) {
+        switch (gcode_flavor) {
+        case gcfTeacup:
+            gcode << "M106 S0"; break;
+        case gcfMakerWare:
+        case gcfSailfish:
+            gcode << "M127";    break;
+        default:
+            gcode << "M107";    break;
+        }
+        if (gcode_comments)
+            gcode << " ; disable fan";
+        gcode << "\n";
+    } else {
+        switch (gcode_flavor) {
+        case gcfMakerWare:
+        case gcfSailfish:
+            gcode << "M126";    break;
+        case gcfMach3:
+        case gcfMachinekit:
+            gcode << "M106 P" << 255.0 * speed / 100.0; break;
+        default:
+            gcode << "M106 S" << 255.0 * speed / 100.0; break;
+        }
+        if (gcode_comments) 
+            gcode << " ; enable fan";
+        gcode << "\n";
+    }
+    return gcode.str();
+}
+
+std::string GCodeWriter::set_fan(unsigned int speed) const
+{
+    return GCodeWriter::set_fan(this->config.gcode_flavor, this->config.gcode_comments, speed);
+}
+
 }
diff --git a/src/libslic3r/GCodeWriter.hpp b/src/libslic3r/GCodeWriter.hpp
index 2de95ecc5..dd602ca80 100644
--- a/src/libslic3r/GCodeWriter.hpp
+++ b/src/libslic3r/GCodeWriter.hpp
@@ -18,7 +18,7 @@ public:
     GCodeWriter() : 
         multiple_extruders(false), m_extrusion_axis("E"), m_extruder(nullptr),
         m_single_extruder_multi_material(false),
-        m_last_acceleration(0), m_max_acceleration(0), m_last_fan_speed(0), 
+        m_last_acceleration(0), m_max_acceleration(0),
         m_last_bed_temperature(0), m_last_bed_temperature_reached(true), 
         m_lifted(0)
         {}
@@ -42,7 +42,6 @@ public:
     std::string postamble() const;
     std::string set_temperature(unsigned int temperature, bool wait = false, int tool = -1) const;
     std::string set_bed_temperature(unsigned int temperature, bool wait = false);
-    std::string set_fan(unsigned int speed, bool dont_save = false);
     std::string set_acceleration(unsigned int acceleration);
     std::string reset_e(bool force = false);
     std::string update_progress(unsigned int num, unsigned int tot, bool allow_100 = false) const;
@@ -69,6 +68,12 @@ public:
     std::string unlift();
     Vec3d       get_position() const { return m_pos; }
 
+    // To be called by the CoolingBuffer from another thread.
+    static std::string set_fan(const GCodeFlavor gcode_flavor, bool gcode_comments, unsigned int speed);
+    // To be called by the main thread. It always emits the G-code, it does not remember the previous state.
+    // Keeping the state is left to the CoolingBuffer, which runs asynchronously on another thread.
+    std::string set_fan(unsigned int speed) const;
+
 private:
 	// Extruders are sorted by their ID, so that binary search is possible.
     std::vector<Extruder> m_extruders;
@@ -79,7 +84,6 @@ private:
     // Limit for setting the acceleration, to respect the machine limits set for the Marlin firmware.
     // If set to zero, the limit is not in action.
     unsigned int    m_max_acceleration;
-    unsigned int    m_last_fan_speed;
     unsigned int    m_last_bed_temperature;
     bool            m_last_bed_temperature_reached;
     double          m_lifted;
diff --git a/t/cooling.t b/t/cooling.t
index 2f444cf9d..a7720fd07 100644
--- a/t/cooling.t
+++ b/t/cooling.t
@@ -132,7 +132,7 @@ $config->set('disable_fan_first_layers',    [ 0 ]);
             'fan_below_layer_time'      => [ $print_time2 + 1, $print_time2 + 1 ], 
             'slowdown_below_layer_time' => [ $print_time2 + 2, $print_time2 + 2 ]
         });
-    $buffer->gcodegen->set_extruders([ 0, 1 ]);
+    $gcodegen->set_extruders([ 0, 1 ]);
     my $gcode = $buffer->process_layer($gcode1 . "T1\nG1 X0 E1 F3000\n", 0);
     like $gcode, qr/^M106/, 'fan is activated for the 1st tool';
     like $gcode, qr/.*M107/, 'fan is disabled for the 2nd tool';
diff --git a/xs/xsp/GCode.xsp b/xs/xsp/GCode.xsp
index 78a5dde37..4c2583894 100644
--- a/xs/xsp/GCode.xsp
+++ b/xs/xsp/GCode.xsp
@@ -10,7 +10,6 @@
     CoolingBuffer(GCode* gcode)
         %code{% RETVAL = new CoolingBuffer(*gcode); %};
     ~CoolingBuffer();
-    Ref<GCode> gcodegen();
     std::string process_layer(std::string gcode, size_t layer_id)
         %code{% RETVAL = THIS->process_layer(std::move(gcode), layer_id, true); %};