CefPython中SendMouseWheelEvent后续页面加载失效问题求助

使用CEF Python 66.1调用SendMouseWheelEvent向浏览器传递鼠标滚动指令时，仅在首次页面加载时生效，后续页面加载后无法正常工作，除非用真实鼠标手动滚动一次。

测试脚本说明：

• 测试1：调用JS的scrollBy方法，每次页面加载后都能正常滚动
• 测试2：调用SendMouseWheelEvent，仅首次页面加载时有效

测试代码（errorrep.py）：

from cefpython3 import cefpython as cef
import time
from threading import Thread
import errorrep

mybrowser = None

def main():
    cef.Initialize()
    browser = cef.CreateBrowserSync(url="https://stackoverflow.com/")
    browser.SetClientHandler(LoadHandler())
    errorrep.mybrowser = browser
    cef.MessageLoop()
    del browser
    cef.Shutdown()


class LoadHandler(object):
    def OnLoadingStateChange(self, browser, is_loading, **_):
        if not is_loading:
            Thread(target=test).start()


def test():
  print("Page loading is complete!")
  for i in range(5):
    print('scrolling')
    # test 1
    errorrep.mybrowser.ExecuteJavascript(jsCode="""scrollBy(0,25)""")
    # test 2
    # errorrep.mybrowser.SendMouseWheelEvent(0,0,0,-120, cef.EVENTFLAG_NONE)
    time.sleep(1)
  print('opening new page, clicking on the logo link')
  errorrep.mybrowser.ExecuteJavascript(jsCode="""document.getElementsByClassName('s-topbar--logo js-gps-track')[0].click();""")


if __name__ == '__main__':
    main()

1. 确保浏览器获得输入焦点 #

后续页面加载后，浏览器可能失去输入焦点，导致模拟的滚轮事件不被响应。发送滚轮事件前先调用SetFocus(True)让浏览器获得焦点：

errorrep.mybrowser.SetFocus(True)
errorrep.mybrowser.SendMouseWheelEvent(0,0,0,-120, cef.EVENTFLAG_NONE)

2. 在CEF主线程执行事件发送 #

CEF的大部分API调用需要在消息循环所在的主线程执行，当前用Thread启动测试函数存在线程安全问题。改用cef.PostTask将滚轮事件发送逻辑放到主线程执行：

def send_wheel_event(browser):
    browser.SetFocus(True)
    browser.SendMouseWheelEvent(0, 0, 0, -120, cef.EVENTFLAG_NONE)

# 在test函数中替换原测试2代码
cef.PostTask(cef.TID_UI, send_wheel_event, errorrep.mybrowser)

3. 修正滚轮事件的坐标参数 #

SendMouseWheelEvent的前两个参数是鼠标坐标，需确保坐标落在页面可视区域内。可以获取浏览器窗口尺寸，传入中间位置坐标：

def send_wheel_event(browser):
    browser.SetFocus(True)
    # 获取浏览器客户端区域尺寸
    window_rect = browser.GetWindowInfo().GetClientRect()
    x = (window_rect['right'] - window_rect['left']) // 2
    y = (window_rect['bottom'] - window_rect['top']) // 2
    browser.SendMouseWheelEvent(x, y, 0, -120, cef.EVENTFLAG_NONE)

完整修正后的test函数示例 #

def test():
    print("Page loading is complete!")
    for i in range(5):
        print('scrolling')
        # 替换test1为test2的修正逻辑
        def send_wheel():
            errorrep.mybrowser.SetFocus(True)
            window_rect = errorrep.mybrowser.GetWindowInfo().GetClientRect()
            x = (window_rect['right'] - window_rect['left']) // 2
            y = (window_rect['bottom'] - window_rect['top']) // 2
            errorrep.mybrowser.SendMouseWheelEvent(x, y, 0, -120, cef.EVENTFLAG_NONE)
        cef.PostTask(cef.TID_UI, send_wheel)
        time.sleep(1)
    print('opening new page, clicking on the logo link')
    errorrep.mybrowser.ExecuteJavascript(jsCode="""document.getElementsByClassName('s-topbar--logo js-gps-track')[0].click();""")

内容的提问来源于stack exchange，提问作者Flora42