Question

How do I preview what the size of widgets in a window will be after the layout rules are applied, before I actually show() the widget window? It seems all sizes are 100×30 before that initial show() command. How do I go around that?

Answer 1

The invalidate() worked for me.

Notice that if you do the following it would work as asked here (at least it seems to be fine in my code):

widget->show();
widget->layout()->invalidate();
widget->hide();

This doesn’t show the widget on the screen since you don’t relinquish control back to the queue until the hide() happens. In between, the invalidate() computes the correct positions.