I see, that "IMPORTANT! QPainter can paint on QWidget only in paintEvent(QPaintEvent*). " (from Wiki qt)
How to draw rectangle or text on click button?
Goal: application magnifier glass, it must

• read pixmap from desktop : pixmap = screen->grabWindow(0);
  how to read only part of pixmap and often refreshing?
  next, I must onMouseMove, read small rectangle near mouse pointer to pixmap, next draw not in paintEvent in my application form N times greater, draw scaled bitmap.
  I must capture mouse, it must receive mouse messages, even if mouse is far from application window.

]]>https://forum.qt.io/topic/139238/paint-on-widget-not-in-paintevent-and-magnifierRSS for NodeThu, 05 Nov 2026 01:21:56 GMTSun, 11 Sep 2022 17:57:44 GMT60Hi
The tricky part is the drag a rect outside the Qt application.
I used the transparent window solution as talked about here
http://www.ifnamemain.com/posts/2014/Jul/11/screen_capture_1/

]]>https://forum.qt.io/post/728238https://forum.qt.io/post/728238Sun, 11 Sep 2022 18:03:25 GMT