DoubleSlider: Implemented code for check of used extruders for MustiAsSingle mode

src/libslic3r/GCode/ToolOrdering.cpp

@@ -486,7 +486,8 @@ void ToolOrdering::assign_custom_gcodes(const Print &print)
 			print_z_below = it_lt_below->print_z;
 		if (custom_gcode.print_z > print_z_below + 0.5 * EPSILON) {
 			// The custom G-code applies to the current layer.
-			if (custom_gcode.gcode != ColorChangeCode || extruder_printing_above[unsigned(custom_gcode.extruder - 1)])
+			if ( custom_gcode.gcode != ColorChangeCode || 
+                (custom_gcode.extruder <= num_extruders && extruder_printing_above[unsigned(custom_gcode.extruder - 1)]))
 				// If it is color change, it will actually be useful as the exturder above will print.
         		lt.custom_gcode = &custom_gcode;
 			// Consume that custom G-code event.

src/libslic3r/Print.hpp

@@ -382,6 +382,7 @@ public:
 
     // Accessed by SupportMaterial
     const PrintRegion*  get_region(size_t idx) const  { return m_regions[idx]; }
+    const ToolOrdering& get_tool_ordering() const { return m_wipe_tower_data.tool_ordering; }   // #ys_FIXME just for testing
 
 protected:
     // methods for handling regions

src/slic3r/GUI/wxExtensions.cpp

@@ -5,6 +5,7 @@
 
 #include "libslic3r/Utils.hpp"
 #include "libslic3r/Model.hpp"
+#include "libslic3r/Print.hpp"
 
 #include <wx/sizer.h>
 #include <wx/bmpcbox.h>
@@ -3487,7 +3488,25 @@ int DoubleSlider::get_extruder_for_tick(int tick)
 std::set<int> DoubleSlider::get_used_extruders_for_tick(int tick)
 {
     if (m_mode == mmMultiExtruder)
-        return {}; // #ys_FIXME: correct fill used_extruders_for_tick for mmMultiExtruder
+    {
+        // #ys_FIXME: get tool ordering from _correct_ place
+        const Slic3r::ToolOrdering& tool_ordering = Slic3r::GUI::wxGetApp().plater()->fff_print().get_tool_ordering();
+
+        if (tool_ordering.empty())
+            return {};
+
+        std::set<int> used_extruders;
+
+        auto it_layer_tools = std::lower_bound(tool_ordering.begin(), tool_ordering.end(), Slic3r::LayerTools(m_values[tick]));
+        for (; it_layer_tools != tool_ordering.end(); it_layer_tools++)
+        {
+            const std::vector<unsigned>& extruders = it_layer_tools->extruders;
+            for (const auto& extruder : extruders)
+                used_extruders.emplace(extruder+1);
+        }
+
+        return used_extruders;
+    }
 
     const int default_initial_extruder = m_mode == mmMultiAsSingle ? std::max(m_only_extruder, 1) : 1;
     if (m_ticks.empty())