Remap paint after mesh boolean (from context menu)

src/slic3r/GUI/GUI_ObjectList.cpp

@@ -3225,6 +3225,22 @@ void ObjectList::boolean()
     Plater::TakeSnapshot snapshot(wxGetApp().plater(), "boolean");
 
     ModelObject* object = (*m_objects)[obj_idxs.front()];
+
+    const bool keep_painting = wxGetApp().app_config->get_bool("keep_painting");
+    std::vector<std::optional<TriangleSelector::SavedPainting>> saved_paintings;
+    if (keep_painting) {
+        // Save painting of all the positive parts
+        saved_paintings.reserve(object->volumes.size());
+        for (const ModelVolume* vol : object->volumes) {
+            if (vol && vol->mesh_ptr() && vol->is_model_part() && vol->is_any_painted()) {
+                saved_paintings.emplace_back(vol->save_painting());
+                if (saved_paintings.back()) {
+                    saved_paintings.back()->mesh.transform(vol->get_matrix(), true);
+                }
+            }
+        }
+    }
+
     TriangleMesh mesh = Plater::combine_mesh_fff(*object, -1, [this](const std::string& msg) {return wxGetApp().notification_manager()->push_plater_error_notification(msg); });
 
     // add mesh to model as a new object, keep the original object's name and config
@@ -3236,6 +3252,29 @@ void ObjectList::boolean()
         new_object->add_instance();
     ModelVolume* new_volume = new_object->add_volume(mesh);
 
+    // Remap paint
+    if (keep_painting) {
+        for (auto& saved_painting : saved_paintings) {
+            if (saved_painting) {
+                // For each original painted volume, we need to apply to each instance
+                // because we merged all instances into one in `combine_mesh_fff`
+
+                // First we save the non-instance-translated mesh
+                TriangleMesh vols_mesh(std::move(saved_painting->mesh));
+                
+                for (const ModelInstance* i : object->instances) {
+                    // Then for each instance, we apply the paint at the given instance place
+                    saved_painting->mesh = vols_mesh;
+                    saved_painting->mesh.transform(i->get_matrix());
+
+                    // Then paint it
+                    new_volume->restore_painting(saved_painting, true);
+                }
+
+            }
+        }
+    }
+
     // BBS: ensure on bed but no need to ensure locate in the center around origin
     new_object->ensure_on_bed();
     new_object->center_around_origin();

src/slic3r/GUI/Plater.cpp

@@ -15108,7 +15108,7 @@ TriangleMesh Plater::combine_mesh_fff(const ModelObject& mo, int instance_id, st
     }
 
     if (instance_id == -1) {
-        TriangleMesh vols_mesh(mesh);
+        TriangleMesh vols_mesh(std::move(mesh));
         mesh = TriangleMesh();
         for (const ModelInstance* i : mo.instances) {
             TriangleMesh m = vols_mesh;