在UI窗口没有任何改动的情况下，view的painevent()接口不停地被调用，导致UI窗口不停地被重绘，最终导致真正要操作UI的时候很卡（比如拖动边框等）
检查你的代码哪里是否反复调用repaint()或update()
From Qt Documentation
A paint event is a request to repaint all or part of a widget. It can happen for one of the following reasons:
- repaint() or update() was invoked,
- the widget was obscured and has now been uncovered, or
- many other reasons.