问题
All I can find is "whenever the widget needs to be painted."
When is that, specifically?
回答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! :-)
来源：https://stackoverflow.com/questions/17710514/when-is-qglwidgets-paintgl-called