Remove right-click menu for backdrop (#616)

fix #606

spx-gui/src/components/editor/preview/stage-viewer/StageViewer.vue

@@ -47,6 +47,7 @@ import { useEditorCtx } from '../../EditorContextProvider.vue'
 import SpriteTransformer from './SpriteTransformer.vue'
 import SpriteItem from './SpriteItem.vue'
 import { MapMode } from '@/models/stage'
+import Konva from 'konva'
 
 const editorCtx = useEditorCtx()
 const conatiner = ref<HTMLElement | null>(null)
@@ -158,6 +159,12 @@ const menuPos = ref({ x: 0, y: 0 })
 
 function handleContextMenu(e: KonvaEventObject<MouseEvent>) {
  e.evt.preventDefault()
+
+ // Ignore right click on backdrop.
+ // Konva.Rect is a subclass of Konva.Shape.
+ // Currently we have all sprites as Konva.Shape and backdrop as Konva.Rect.
+ if (e.target instanceof Konva.Rect) return
+
  if (stageRef.value == null || e.target.parent == null) return
  const stage: Stage = stageRef.value.getStage()
  const pointerPos = stage.getPointerPosition()