If you change the height of the main window of our game, you will note that different widgets are resized in a different way. In particular, buttons retain their original height, and labels gain empty fields to the top and bottom of the text:
This is because each widget has a property called sizePolicy, which decides how a widget is to be resized by a layout. You can set separate size policies for horizontal and vertical directions. A button has a vertical size policy of Fixed by default, which means that the height of the widget will not change from the default height regardless of how much space there is available. A label ...