Added a limitation on the number of usable extruders in the multi-material gizmo. If a printer has more extruders than this limit, a notification about it is shown.

src/slic3r/GUI/Gizmos/GLGizmoMmuSegmentation.cpp

@@ -8,6 +8,7 @@
 #include "slic3r/GUI/BitmapCache.hpp"
 #include "slic3r/GUI/format.hpp"
 #include "slic3r/GUI/GUI_ObjectList.hpp"
+#include "slic3r/GUI/NotificationManager.hpp"
 #include "libslic3r/PresetBundle.hpp"
 #include "libslic3r/Model.hpp"
 
@@ -16,6 +17,22 @@
 
 namespace Slic3r::GUI {
 
+static inline void show_notification_extruders_limit_exceeded()
+{
+    wxGetApp()
+        .plater()
+        ->get_notification_manager()
+        ->push_notification(NotificationType::MmSegmentationExceededExtrudersLimit, NotificationManager::NotificationLevel::RegularNotification,
+                            GUI::format(_L("Your printer has more extruders than the multi-material painting gizmo supports. For this reason, only the "
+                                           "first %1% extruders will be able to be used for painting."), GLGizmoMmuSegmentation::EXTRUDERS_LIMIT));
+}
+
+void GLGizmoMmuSegmentation::on_opening()
+{
+    if (wxGetApp().extruders_edited_cnt() > int(GLGizmoMmuSegmentation::EXTRUDERS_LIMIT))
+        show_notification_extruders_limit_exceeded();
+}
+
 void GLGizmoMmuSegmentation::on_shutdown()
 {
     m_parent.use_slope(false);
@@ -132,6 +149,9 @@ void GLGizmoMmuSegmentation::set_painter_gizmo_data(const Selection &selection)
     ModelObject *model_object         = m_c->selection_info()->model_object();
     int          prev_extruders_count = int(m_original_extruders_colors.size());
     if (prev_extruders_count != wxGetApp().extruders_edited_cnt() || get_extruders_colors() != m_original_extruders_colors) {
+        if (wxGetApp().extruders_edited_cnt() > int(GLGizmoMmuSegmentation::EXTRUDERS_LIMIT))
+            show_notification_extruders_limit_exceeded();
+
         this->init_extruders_data();
         // Reinitialize triangle selectors because of change of extruder count need also change the size of GLIndexedVertexArray
         if (prev_extruders_count != wxGetApp().extruders_edited_cnt())
@@ -158,7 +178,7 @@ static void render_extruders_combo(const std::string                       &labe
     ImGui::BeginGroup();
     ImVec2 combo_pos = ImGui::GetCursorScreenPos();
     if (ImGui::BeginCombo(label.c_str(), "")) {
-        for (size_t extruder_idx = 0; extruder_idx < extruders.size(); ++extruder_idx) {
+        for (size_t extruder_idx = 0; extruder_idx < std::min(extruders.size(), GLGizmoMmuSegmentation::EXTRUDERS_LIMIT); ++extruder_idx) {
             ImGui::PushID(int(extruder_idx));
             ImVec2 start_position = ImGui::GetCursorScreenPos();
 

src/slic3r/GUI/Gizmos/GLGizmoMmuSegmentation.hpp

@@ -36,6 +36,12 @@ public:
 
     void set_painter_gizmo_data(const Selection& selection) override;
 
+    // TriangleSelector::serialization/deserialization has a limit to store 19 different states.
+    // EXTRUDER_LIMIT + 1 states are used to storing the painting because also uncolored triangles are stored.
+    // When increasing EXTRUDER_LIMIT, it needs to ensure that TriangleSelector::serialization/deserialization
+    // will be also extended to support additional states, requiring at least one state to remain free out of 19 states.
+    static const constexpr size_t EXTRUDERS_LIMIT = 16;
+
 protected:
     std::array<float, 4> get_cursor_sphere_left_button_color() const override;
     std::array<float, 4> get_cursor_sphere_right_button_color() const override;
@@ -63,7 +69,7 @@ private:
     void update_model_object() const override;
     void update_from_model_object() override;
 
-    void on_opening() override {}
+    void on_opening() override;
     void on_shutdown() override;
     PainterGizmoType get_painter_type() const override;
 

src/slic3r/GUI/NotificationManager.hpp

@@ -87,7 +87,9 @@ enum class NotificationType
     DesktopIntegrationSuccess,
     DesktopIntegrationFail,
     UndoDesktopIntegrationSuccess,
-    UndoDesktopIntegrationFail
+    UndoDesktopIntegrationFail,
+    // Notification that a printer has more extruders than are supported by MM Gizmo/segmentation.
+    MmSegmentationExceededExtrudersLimit
 
 };