But now I have another question:My job was to catch pixels information when the QWindow do render() dynamically,and I got OpenGLFucntion::glRead() worked well,but it only work when the QWindow was exposed to the screen(When I minimize the window i stop animating and the rest paused rather than u expose the window again).My future work may require the QWindow not exposed.

Should I do render() in a sub thread to do this ? And if so ,what example can i use for reference or what should I pay attention to ? Thanks.