Disallow polygon2D editing if internal vertices exists, as suggested in #24853

editor/plugins/abstract_polygon_2d_editor.cpp

@@ -297,6 +297,12 @@ bool AbstractPolygon2DEditor::forward_gui_input(const Ref<InputEvent> &p_event)
 
 	if (mb.is_valid()) {
 
+		String cant_edit = _why_cant_edit_polygon();
+		if (cant_edit != String()) {
+			EditorNode::get_singleton()->show_warning(cant_edit);
+			return true;
+		}
+
 		Transform2D xform = canvas_item_editor->get_canvas_transform() * _get_node()->get_global_transform();
 
 		Vector2 gpoint = mb->get_position();

editor/plugins/abstract_polygon_2d_editor.h

@@ -134,6 +134,8 @@ protected:
 	virtual bool _has_resource() const;
 	virtual void _create_resource();
 
+	virtual String _why_cant_edit_polygon() const { return String(); }
+
 public:
 	bool forward_gui_input(const Ref<InputEvent> &p_event);
 	void forward_canvas_draw_over_viewport(Control *p_overlay);

editor/plugins/polygon_2d_editor_plugin.cpp

@@ -52,6 +52,16 @@ Vector2 Polygon2DEditor::_get_offset(int p_idx) const {
 	return node->get_offset();
 }
 
+String Polygon2DEditor::_why_cant_edit_polygon() const {
+
+	if (node->get_internal_vertex_count() > 0) {
+
+		return TTR("Polygon 2D has internal vertices, so it can no longer be edited in the viewport.");
+	}
+
+	return String();
+}
+
 int Polygon2DEditor::_get_polygon_count() const {
 	if (node->get_internal_vertex_count() > 0) {
 		return 0; //do not edit if internal vertices exist

editor/plugins/polygon_2d_editor_plugin.h

@@ -152,6 +152,7 @@ protected:
 	virtual void _set_node(Node *p_polygon);
 
 	virtual Vector2 _get_offset(int p_idx) const;
+	virtual String _why_cant_edit_polygon() const;
 
 	virtual bool _has_uv() const { return true; };
 	virtual void _commit_action();