electron 完美拖拽 : 比 electron-drag 更优雅的实现

产品经理要求 electron window 下的工具条屏蔽鼠标右键。

window 下 electron 的原生拖拽(app-region:drag)会吃掉点击事件，没法做右键屏蔽。必须自己手工实现拖拽才行。

如果使用 mousemove 事件实现需求 ，在鼠标快速移动的时候，会超出窗体范围，导致窗体不再跟随鼠标移动。

我基于 pointer event 实现了这个需求，用 setPointerCapture 可以捕获 BrowserWindow 之外的鼠标位置，效果很完美。

此方案比 electron-drag 的方案更优 : 它有平台相关的二进制依赖，升级打包都会变得麻烦。

我发现网上还没有人提过这种方案，所以写博客记录并分享一下。

实现方案的代码差异如下，仅够参考。核心代码是 web/src/lib/drag.coffee 和 main/ipc/drag.coffee。

web/src/lib/drag.coffee

import $on from '~/lib/on.coffee'
import ipc from '~/lib/ipc.coffee'
import platform from '@/config/platform.mjs'

{drag:{setBounds,getBounds}} = ipc
pointermove = 'pointermove'
IGNORE = new Set('SELECT BUTTON A INPUT TEXTAREA'.split ' ')
{round} = Math
export default main = (elem)=>
  if platform!='win32'
    return

  elem.style.appRegion = 'no-drag'

  moving = false

  init_w = init_h = init_x = init_y = init_top = init_left = undefined

  _move = (e)=>
    {screenX,screenY} = e
    setBounds(
      round screenX-init_x+init_left
      round screenY-init_y+init_top
      init_w
      init_h
    )
    return

  down = (e)=>
    if moving
      return
    if e.button!=0 # 鼠标左键
      return
    {target} = e
    p = e.target
    loop
      {nodeName} = p
      if IGNORE.has nodeName
        return
      if nodeName == 'BODY'
        break
      p = p.parentNode
    moving = true
    {screenX:init_x,screenY:init_y} = e

    elem.setPointerCapture e.pointerId
    elem.addEventListener pointermove,_move

    {
      x:init_left
      y:init_top
      height:init_h
      width:init_w
    } = await getBounds()

    console.log  await getBounds()
    return

  up = (e)=>
    if moving
      await _move(e)
      elem.releasePointerCapture e.pointerId
      elem.removeEventListener pointermove,_move
      moving = false
    return

  $on elem,{
    lostpointercapture:up
    pointercancel:up
    pointerdown:down
    pointerup:up
  }

  return

main/ipc/drag.coffee

export getBounds = ->
  @sender.getOwnerBrowserWindow().getBounds()

export setBounds = (x,y,width,height)->
  win = @sender.getOwnerBrowserWindow()
  # 不用 setPosition 是因为 https://github.com/electron/electron/issues/9477 browserWindow.setPosition(x,y) changed window size (windows/linux) with non default scaleLevel (125% for example)
  win.setBounds {
    x:Math.round(x)
    y:Math.round(y)
    width
    height
  }
  return

main/ipc.coffee

`export * as drag from './ipc/drag.coffee'`

web/src/page/recbar.vue

<template lang="pug">
-nav(:class="{ pause }")
nav(:class="{ pause }" ref="nav")
</template>

<script lang="coffee">
import drag from '~/lib/drag.coffee'
nav = shallowRef()
export default {
setup: =>
  onMounted =>
    drag(nav.value)
    return
  {
    nav
  }
}
</script>

main/boot.coffee

_handle = (k, v)=>
  if v instanceof Function
    ipcMain.handle k.join('.'), (e,args)=>
      v.apply(e,args)

  for [name,func] from Object.entries v
    _handle [...k, name], func

  return

for [k,v] from Object.entries ipc
  _handle([k], v)

web/src/lib/_on.coffee

export default (elem, dict)=>
  for event,func of dict
    elem.addEventListener(event, func)
  =>
    for event,func of dict
      elem.removeEventListener(event, func)

web/src/lib/on.coffee

import $on from './_on.coffee'
export default (elem, dict)=>
  unbind = $on elem, dict
  onUnmounted unbind
  unbind