fix object is null and the application exit and not check lead to crash.

src/slic3r/GUI/GUI_App.cpp

@@ -5974,7 +5974,9 @@ void GUI_App::open_preferences(size_t open_on_tab, const std::string& highlight_
         // so we put it into an inner scope
         PreferencesDialog dlg(mainframe, open_on_tab, highlight_option);
         dlg.ShowModal();
-        this->plater_->get_current_canvas3D()->force_set_focus();
+        GLCanvas3D* canvas = this->plater_->get_current_canvas3D();
+        if (canvas)
+            canvas->force_set_focus();
         // BBS
         //app_layout_changed = dlg.settings_layout_changed();
 #if ENABLE_GCODE_LINES_ID_IN_H_SLIDER

src/slic3r/GUI/MainFrame.cpp

@@ -501,8 +501,11 @@ DPIFrame(NULL, wxID_ANY, "", wxDefaultPosition, wxDefaultSize, BORDERLESS_FRAME_
 //FIXME maybe this is useful for __WXGTK3__ as well?
 #if __APPLE__
     Bind(wxEVT_MOVE, [](wxMoveEvent& event) {
-        wxGetApp().plater()->get_current_canvas3D()->set_as_dirty();
+        GLCanvas3D* canvas = wxGetApp().plater()->get_current_canvas3D();
-        wxGetApp().plater()->get_current_canvas3D()->request_extra_frame();
+        if (canvas) {
+            canvas->set_as_dirty();
+            canvas->request_extra_frame();
+        }
         event.Skip();
     });
 #endif
@@ -2240,7 +2243,9 @@ static wxMenu* generate_help_menu()
 
     append_menu_item(helpMenu, wxID_ANY, _L("Show Tip of the Day"), _L("Show Tip of the Day"), [](wxCommandEvent&) {
         wxGetApp().plater()->get_dailytips()->open();
-        wxGetApp().plater()->get_current_canvas3D()->set_as_dirty();
+        GLCanvas3D* canvas = wxGetApp().plater()->get_current_canvas3D();
+        if (canvas)
+            canvas->set_as_dirty();
         });
 
     // Report a bug
@@ -2514,8 +2519,11 @@ void MainFrame::init_menubar_as_editor()
 
     auto handle_key_event = [](wxKeyEvent& evt) {
         if (wxGetApp().imgui()->update_key_data(evt)) {
-            wxGetApp().plater()->get_current_canvas3D()->render();
+            GLCanvas3D* canvas = wxGetApp().plater()->get_current_canvas3D();
-            return true;
+            if (canvas) {
+                canvas->render();
+                return true;
+            }
         }
         return false;
     };

src/slic3r/GUI/Plater.cpp

@@ -1903,11 +1903,14 @@ void Sidebar::update_presets(Preset::Type preset_type)
         }
 
         Preset& printer_preset = wxGetApp().preset_bundle->printers.get_edited_preset();
-        if (auto printer_structure_opt = printer_preset.config.option<ConfigOptionEnum<PrinterStructure>>("printer_structure")) {
+        GLCanvas3D* canvas = wxGetApp().plater()->get_current_canvas3D();
-            wxGetApp().plater()->get_current_canvas3D()->get_arrange_settings().align_to_y_axis = (printer_structure_opt->value == PrinterStructure::psI3);
+        if (canvas) {
+            if (auto printer_structure_opt = printer_preset.config.option<ConfigOptionEnum<PrinterStructure>>("printer_structure")) {
+                canvas->get_arrange_settings().align_to_y_axis = (printer_structure_opt->value == PrinterStructure::psI3);
+            }
+            else
+                canvas->get_arrange_settings().align_to_y_axis = false;
         }
-        else
-            wxGetApp().plater()->get_current_canvas3D()->get_arrange_settings().align_to_y_axis = false;
 
         break;
     }
@@ -2749,9 +2752,12 @@ void Sidebar::update_ui_from_settings()
     // BBS
     //p->object_manipulation->update_ui_from_settings();
     // update Cut gizmo, if it's open
-    p->plater->canvas3D()->update_gizmos_on_off_state();
+    GLCanvas3D* canvas = p->plater->canvas3D();
-    p->plater->set_current_canvas_as_dirty();
+    if (canvas) {
-    p->plater->get_current_canvas3D()->request_extra_frame();
+        canvas->update_gizmos_on_off_state();
+        p->plater->set_current_canvas_as_dirty();        
+        p->plater->get_current_canvas3D()->request_extra_frame();
+    }
 #if 0
     p->object_list->apply_volumes_order();
 #endif
@@ -5671,7 +5677,13 @@ Selection& Plater::priv::get_selection()
 
 Selection& Plater::priv::get_curr_selection()
 {
-    return get_current_canvas3D()->get_selection();
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (!canvas) {
+        // During destruction, return a reference to a static empty selection
+        static Selection empty_selection;
+        return empty_selection;
+    }
+    return canvas->get_selection();
 }
 
 int Plater::priv::get_selected_object_idx() const
@@ -5701,10 +5713,15 @@ void Plater::priv::selection_changed()
     }
 
     // forces a frame render to update the view (to avoid a missed update if, for example, the context menu appears)
-    if (get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView) {
+    GLCanvas3D* canvas = get_current_canvas3D();
-        assemble_view->render();
+    if (canvas) {
-    } else {
+        if (canvas->get_canvas_type() == GLCanvas3D::CanvasAssembleView) {
-        view3D->render();
+            if (assemble_view)
+                assemble_view->render();
+        } else {
+            if (view3D)
+                view3D->render();
+        }
     }
 }
 
@@ -6473,7 +6490,10 @@ bool Plater::priv::replace_volume_with_stl(int object_idx, int volume_idx, const
         return false;
     }
 
-    wxBusyInfo info(_L("Replace from:") + " " + from_u8(path), q->get_current_canvas3D()->get_wxglcanvas());
+    GLCanvas3D* canvas = q->get_current_canvas3D();
+    if (!canvas)
+        return false;
+    wxBusyInfo info(_L("Replace from:") + " " + from_u8(path), canvas->get_wxglcanvas());
 
     if (!snapshot.empty())
         q->take_snapshot(snapshot);
@@ -6770,7 +6790,10 @@ void Plater::priv::reload_from_disk()
             if (color_dlg.ShowModal() != wxID_OK) { filament_ids.clear(); }
         };
         wxBusyCursor wait;
-        wxBusyInfo info(_L("Reload from:") + " " + from_u8(path), q->get_current_canvas3D()->get_wxglcanvas());
+        GLCanvas3D* canvas = q->get_current_canvas3D();
+        if (!canvas)
+            return false;
+        wxBusyInfo info(_L("Reload from:") + " " + from_u8(path), canvas->get_wxglcanvas());
 
         Model new_model;
         try
@@ -9396,7 +9419,13 @@ void Plater::priv::take_snapshot(const std::string& snapshot_name, const UndoRed
             tower.rotation = proj_cfg.opt_float("wipe_tower_rotation_angle");
         }
     }
-    const GLGizmosManager& gizmos = get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_gizmos_manager() : view3D->get_canvas3d()->get_gizmos_manager();
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (!canvas) {
+        // During destruction, skip snapshot
+        return;
+    }
+    
+    const GLGizmosManager& gizmos = canvas->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_gizmos_manager() : view3D->get_canvas3d()->get_gizmos_manager();
 
     if (snapshot_type == UndoRedo::SnapshotType::ProjectSeparator)
         this->undo_redo_stack().clear();
@@ -9430,7 +9459,9 @@ void Plater::priv::undo()
     // BBS: undo-redo until modify record
     while (--it_current != snapshots.begin() && !snapshot_modifies_project(*it_current));
     if (it_current == snapshots.begin()) return;
-    if (get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView) {
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (!canvas) return;
+    if (canvas->get_canvas_type() == GLCanvas3D::CanvasAssembleView) {
         if (it_current->snapshot_data.snapshot_type != UndoRedo::SnapshotType::GizmoAction &&
             it_current->snapshot_data.snapshot_type != UndoRedo::SnapshotType::EnteringGizmo &&
             it_current->snapshot_data.snapshot_type != UndoRedo::SnapshotType::LeavingGizmoNoAction &&
@@ -9538,9 +9569,13 @@ void Plater::priv::undo_redo_to(std::vector<UndoRedo::Snapshot>::const_iterator
     // Make a copy of the snapshot, undo/redo could invalidate the iterator
     const UndoRedo::Snapshot snapshot_copy = *it_snapshot;
     // Do the jump in time.
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (!canvas) return;
+    
+    bool is_assemble = canvas->get_canvas_type() == GLCanvas3D::CanvasAssembleView;
     if (it_snapshot->timestamp < this->undo_redo_stack().active_snapshot_time() ?
-        this->undo_redo_stack().undo(model, get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_selection() : this->view3D->get_canvas3d()->get_selection(), get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_gizmos_manager() : this->view3D->get_canvas3d()->get_gizmos_manager(), this->partplate_list, top_snapshot_data, it_snapshot->timestamp) :
+        this->undo_redo_stack().undo(model, is_assemble ? assemble_view->get_canvas3d()->get_selection() : this->view3D->get_canvas3d()->get_selection(), is_assemble ? assemble_view->get_canvas3d()->get_gizmos_manager() : this->view3D->get_canvas3d()->get_gizmos_manager(), this->partplate_list, top_snapshot_data, it_snapshot->timestamp) :
-        this->undo_redo_stack().redo(model, get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_gizmos_manager() : this->view3D->get_canvas3d()->get_gizmos_manager(), this->partplate_list, it_snapshot->timestamp)) {
+        this->undo_redo_stack().redo(model, is_assemble ? assemble_view->get_canvas3d()->get_gizmos_manager() : this->view3D->get_canvas3d()->get_gizmos_manager(), this->partplate_list, it_snapshot->timestamp)) {
         if (printer_technology_changed) {
             // Switch to the other printer technology. Switch to the last printer active for that particular technology.
             AppConfig *app_config = wxGetApp().app_config;
@@ -9618,7 +9653,11 @@ void Plater::priv::undo_redo_to(std::vector<UndoRedo::Snapshot>::const_iterator
 
 void Plater::priv::update_after_undo_redo(const UndoRedo::Snapshot& snapshot, bool /* temp_snapshot_was_taken */)
 {
-    get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ? assemble_view->get_canvas3d()->get_selection().clear() : this->view3D->get_canvas3d()->get_selection().clear();
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (!canvas) return;
+    
+    bool is_assemble = canvas->get_canvas_type() == GLCanvas3D::CanvasAssembleView;
+    is_assemble ? assemble_view->get_canvas3d()->get_selection().clear() : this->view3D->get_canvas3d()->get_selection().clear();
     // Update volumes from the deserializd model, always stop / update the background processing (for both the SLA and FFF technologies).
     this->update((unsigned int)UpdateParams::FORCE_BACKGROUND_PROCESSING_UPDATE | (unsigned int)UpdateParams::POSTPONE_VALIDATION_ERROR_MESSAGE);
     // Release old snapshots if the memory allocated is excessive. This may remove the top most snapshot if jumping to the very first snapshot.
@@ -9627,10 +9666,10 @@ void Plater::priv::update_after_undo_redo(const UndoRedo::Snapshot& snapshot, bo
     // triangle meshes may have gotten released from the scene or the background processing, therefore now being calculated into the Undo / Redo stack size.
         this->undo_redo_stack().release_least_recently_used();
     //YS_FIXME update obj_list from the deserialized model (maybe store ObjectIDs into the tree?) (no selections at this point of time)
-        get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ?
+        is_assemble ?
             assemble_view->get_canvas3d()->get_selection().set_deserialized(GUI::Selection::EMode(this->undo_redo_stack().selection_deserialized().mode), this->undo_redo_stack().selection_deserialized().volumes_and_instances) :
             this->view3D->get_canvas3d()->get_selection().set_deserialized(GUI::Selection::EMode(this->undo_redo_stack().selection_deserialized().mode), this->undo_redo_stack().selection_deserialized().volumes_and_instances);
-    get_current_canvas3D()->get_canvas_type() == GLCanvas3D::CanvasAssembleView ?
+    is_assemble ?
         assemble_view->get_canvas3d()->get_gizmos_manager().update_after_undo_redo(snapshot) :
         this->view3D->get_canvas3d()->get_gizmos_manager().update_after_undo_redo(snapshot);
 
@@ -11309,7 +11348,9 @@ void Plater::load_gcode(const wxString& filename)
     p->preview->reload_print(false, m_only_gcode);
     wxGetApp().mainframe->select_tab(MainFrame::tpPreview);
     p->set_current_panel(p->preview, true);
-    p->get_current_canvas3D()->render();
+    GLCanvas3D* canvas = p->get_current_canvas3D();
+    if (canvas)
+        canvas->render();
     //p->notification_manager->bbl_show_plateinfo_notification(into_u8(_L("Preview only mode for gcode file.")));
 
     wxBusyCursor wait;
@@ -12309,7 +12350,9 @@ void Plater::set_selected_visible(bool visible)
     Plater::TakeSnapshot snapshot(this, "Set Selected Objects Visible in AssembleView");
     get_ui_job_worker().cancel_all();
 
-    p->get_current_canvas3D()->set_selected_visible(visible);
+    GLCanvas3D* canvas = p->get_current_canvas3D();
+    if (canvas)
+        canvas->set_selected_visible(visible);
 }
 
 
@@ -12329,7 +12372,9 @@ void Plater::remove_selected()
 
     //BBS delete current selected
     // p->view3D->delete_selected();
-    p->get_current_canvas3D()->delete_selected();
+    GLCanvas3D* canvas = p->get_current_canvas3D();
+    if (canvas)
+        canvas->delete_selected();
 }
 
 void Plater::increase_instances(size_t num)
@@ -14644,7 +14689,9 @@ void Plater::changed_object(ModelObject &object){
     p->schedule_background_process();
         
     // Check outside bed
-    get_current_canvas3D()->requires_check_outside_state();
+    GLCanvas3D* canvas = get_current_canvas3D();
+    if (canvas)
+        canvas->requires_check_outside_state();
 }
 
 void Plater::changed_object(int obj_idx)