Javascript 鼠标按下事件未在文件中触发

未触发鼠标按下，但正在触发其他事件

paper.install(window)
paper.setup('canvas')
paper.view.onMouseDown = this.onMouseDown
paper.view.onMouseDrag = this.onMouseDrag
paper.view.onMouseUp = this.onMouseUp

但是当手动在画布中注册

mouseDown

事件时，它会按预期每次被触发

this.canvasComponent = this.$refs.canvas

this.canvasComponent.onmousedown = function (e) {
  console.log('Down fired')
}