When is QGLWidget's paintGL called?

Question

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

When is that, specifically?

Answer 1

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! :-)