When is QGLWidget's paintGL called?

qt opengl rendering qglwidget
Nomis Raserf picture Nomis Raserf · Jul 17, 2013 · Viewed 9.3k times · Source

All I can find is "whenever the widget needs to be painted."

When is that, specifically?

Answer

peppe picture peppe · Jul 17, 2013

When you call updateGL() on your widget (or update()), or just Qt decides to redraw your widget. Reasons why Qt might choose to ask for a redraw include:

  • your widget gets resized
  • your widget is hidden and shown again
  • your widget is minimized and then restored
  • something else is put in front of your widget and then moved away
  • the Moon is in the third quarter
  • a distant butterfly had flapped its wings
  • ...

In short, you have very little control about when Qt asks for a repaint. Just be sure to paint fast! :-)

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