Color mixing feature (#15347)

# Description

This PR ports the color mixing feature from BambuStudio.
The port is based on the previous work by @ianalexis in #15231.
This PR completes the port and fixes various bugs.

Several improvements were also made during the porting process.

WIP


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src/slic3r/GUI/PartPlate.cpp

@@ -6,6 +6,7 @@
 #include <sstream>
 #include <regex>
 #include "libslic3r/MultiNozzleUtils.hpp"
+#include "libslic3r/FilamentMixer.hpp"
 #include <future>
 #include <glad/gl.h>
 #include <boost/algorithm/string.hpp>
@@ -1675,6 +1676,25 @@ std::vector<int> PartPlate::get_extruders(bool conside_custom_gcode) const
 	std::sort(plate_extruders.begin(), plate_extruders.end());
 	auto it_end = std::unique(plate_extruders.begin(), plate_extruders.end());
 	plate_extruders.resize(std::distance(plate_extruders.begin(), it_end));
+
+	// Expand mixed filament slots to their physical components. A mixed slot is virtual and
+	// is never loaded into a tray, so callers (AMS mapping, filament checks) must see the
+	// physical filaments it resolves to instead.
+	{
+		auto& project_config = wxGetApp().preset_bundle->project_config;
+		auto* is_mixed_opt = project_config.option<ConfigOptionBools>("filament_is_mixed");
+		auto* comp_strs_opt = project_config.option<ConfigOptionStrings>("filament_mixed_components");
+		if (is_mixed_opt && comp_strs_opt && has_any_mixed_filament(is_mixed_opt->values)) {
+			std::vector<unsigned int> ext_0based;
+			for (int e : plate_extruders)
+				if (e >= 1) ext_0based.push_back((unsigned int)(e - 1));
+			auto expanded = expand_mixed_filaments(ext_0based, is_mixed_opt->values, comp_strs_opt->values);
+			plate_extruders.clear();
+			for (unsigned int e : expanded)
+				plate_extruders.push_back((int)(e + 1));
+		}
+	}
+
 	return plate_extruders;
 }
 
@@ -1836,6 +1856,24 @@ std::vector<int> PartPlate::get_extruders_under_cli(bool conside_custom_gcode, D
     std::sort(plate_extruders.begin(), plate_extruders.end());
     auto it_end = std::unique(plate_extruders.begin(), plate_extruders.end());
     plate_extruders.resize(std::distance(plate_extruders.begin(), it_end));
+
+    // Expand mixed filament slots to their physical components. A mixed slot is virtual and
+    // is never loaded into a tray, so callers (AMS mapping, filament checks) must see the
+    // physical filaments it resolves to instead.
+    {
+        auto* is_mixed_opt = full_config.option<ConfigOptionBools>("filament_is_mixed");
+        auto* comp_strs_opt = full_config.option<ConfigOptionStrings>("filament_mixed_components");
+        if (is_mixed_opt && comp_strs_opt && has_any_mixed_filament(is_mixed_opt->values)) {
+            std::vector<unsigned int> ext_0based;
+            for (int e : plate_extruders)
+                if (e >= 1) ext_0based.push_back((unsigned int)(e - 1));
+            auto expanded = expand_mixed_filaments(ext_0based, is_mixed_opt->values, comp_strs_opt->values);
+            plate_extruders.clear();
+            for (unsigned int e : expanded)
+                plate_extruders.push_back((int)(e + 1));
+        }
+    }
+
     return plate_extruders;
 }
 
@@ -1889,6 +1927,25 @@ std::vector<int> PartPlate::get_extruders_without_support(bool conside_custom_gc
 	std::sort(plate_extruders.begin(), plate_extruders.end());
 	auto it_end = std::unique(plate_extruders.begin(), plate_extruders.end());
 	plate_extruders.resize(std::distance(plate_extruders.begin(), it_end));
+
+	// Expand mixed filament slots to their physical components. A mixed slot is virtual and
+	// is never loaded into a tray, so callers (AMS mapping, filament checks) must see the
+	// physical filaments it resolves to instead.
+	{
+		auto& project_config = wxGetApp().preset_bundle->project_config;
+		auto* is_mixed_opt = project_config.option<ConfigOptionBools>("filament_is_mixed");
+		auto* comp_strs_opt = project_config.option<ConfigOptionStrings>("filament_mixed_components");
+		if (is_mixed_opt && comp_strs_opt && has_any_mixed_filament(is_mixed_opt->values)) {
+			std::vector<unsigned int> ext_0based;
+			for (int e : plate_extruders)
+				if (e >= 1) ext_0based.push_back((unsigned int)(e - 1));
+			auto expanded = expand_mixed_filaments(ext_0based, is_mixed_opt->values, comp_strs_opt->values);
+			plate_extruders.clear();
+			for (unsigned int e : expanded)
+				plate_extruders.push_back((int)(e + 1));
+		}
+	}
+
 	return plate_extruders;
 }
 
@@ -1990,6 +2047,50 @@ bool PartPlate::check_tpu_printable_status(const DynamicPrintConfig & config, co
 	return true;
 }
 
+// A mixed-color filament alternates between its components constantly. On a single-nozzle
+// printer every one of those switches is a full filament change plus a purge, so warn before
+// slicing. Multi-nozzle printers keep the components loaded at once and are not affected.
+bool PartPlate::check_single_extruder_mixed_filament_risk(const DynamicPrintConfig &config, std::string &warning_text) const
+{
+    warning_text.clear();
+
+    auto *nozzle_diameter_opt = config.option<ConfigOptionFloatsNullable>("nozzle_diameter");
+    if (!nozzle_diameter_opt || nozzle_diameter_opt->values.size() > 1)
+        return false;
+
+    auto *is_mixed_opt = wxGetApp().preset_bundle->project_config.option<ConfigOptionBools>("filament_is_mixed");
+    if (!is_mixed_opt || !has_any_mixed_filament(is_mixed_opt->values))
+        return false;
+
+    auto is_mixed_slot = [&](int extruder_1based) {
+        size_t idx = (size_t)(extruder_1based - 1);
+        return idx < is_mixed_opt->values.size() && is_mixed_opt->values[idx];
+    };
+
+    const std::string mixed_warn_msg = _u8L("Printing mixed-color filament on a single-extruder printer requires frequent filament changes and flushing, "
+                                            "which may significantly increase waste and the risk of nozzle / waste-chute clogging.");
+
+    for (int obj_idx = 0; obj_idx < (int)m_model->objects.size(); ++obj_idx) {
+        if (!contain_instance_totally(obj_idx, 0))
+            continue;
+        ModelObject *mo = m_model->objects[obj_idx];
+        int obj_ext = mo->config.has("extruder") ? mo->config.extruder() : 1;
+        if (is_mixed_slot(obj_ext)) {
+            warning_text = mixed_warn_msg;
+            return true;
+        }
+        for (ModelVolume *mv : mo->volumes) {
+            int vol_ext = mv->config.has("extruder") ? mv->config.extruder() : obj_ext;
+            if (is_mixed_slot(vol_ext)) {
+                warning_text = mixed_warn_msg;
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
 bool PartPlate::check_mixture_of_pla_and_petg(const DynamicPrintConfig &config)
 {
     bool has_pla = false;
@@ -6384,6 +6485,31 @@ int PartPlateList::store_to_3mf_structure(PlateDataPtrs& plate_data_list, bool w
 					}
 					//parse filament info
 					plate_data_item->parse_filament_info(m_plate_list[i]->get_slice_result());
+
+					// Record mixed (virtual) filaments actually used on this plate.
+					// Source is ToolOrdering::used_mixed_filaments (slots that appeared in
+					// layer tools before resolve), persisted on GCodeProcessorResult / Print —
+					// not print->extruders() which only reflects assignment.
+					{
+						std::vector<unsigned int> used_mixed;
+						if (auto *slice_result = m_plate_list[i]->get_slice_result())
+							used_mixed = slice_result->used_mixed_filaments;
+						if (used_mixed.empty() && print)
+							used_mixed = print->get_slice_used_mixed_filaments();
+						if (!used_mixed.empty() && print) {
+							const auto &fila_types  = print->config().filament_type.values;
+							const auto &fila_colors = print->config().filament_colour.values;
+							const auto &fila_comps  = print->config().filament_mixed_components.values;
+							for (unsigned int fid : used_mixed) {
+								PlateMixedFilamentInfo mixed_info;
+								mixed_info.id = (int) fid + 1;
+								if (fid < fila_types.size())  mixed_info.type       = fila_types[fid];
+								if (fid < fila_colors.size()) mixed_info.color      = fila_colors[fid];
+								if (fid < fila_comps.size())  mixed_info.components = fila_comps[fid];
+								plate_data_item->mixed_filaments_info.push_back(mixed_info);
+							}
+						}
+					}
 				} else {
 					BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << "slice result = " << m_plate_list[i]->get_slice_result()
 										<< ", result valid = " << m_plate_list[i]->is_slice_result_valid();
@@ -6450,6 +6576,13 @@ int PartPlateList::load_from_3mf_structure(PlateDataPtrs& plate_data_list, int f
 		m_plate_list[index]->slice_filaments_info = plate_data_list[i]->slice_filaments_info;
 		gcode_result->warnings = plate_data_list[i]->warnings;
         gcode_result->filament_maps = plate_data_list[i]->filament_maps;
+		gcode_result->used_mixed_filaments.clear();
+		for (const auto &mixed_info : plate_data_list[i]->mixed_filaments_info) {
+			if (mixed_info.id > 0)
+				gcode_result->used_mixed_filaments.push_back(static_cast<unsigned int>(mixed_info.id - 1));
+		}
+		if (Print *print = dynamic_cast<Print*>(fff_print))
+			print->set_slice_used_mixed_filaments(gcode_result->used_mixed_filaments);
 
         // Reconstruct the device-side nozzle grouping from the loaded 3mf so
         // the monitor/preview can map filaments to physical nozzles.