On Mac setting the window to a very large vertical size makes the window display in that size and stretch outside the dektop borders.

On Windows the window is resized to a much smaller window before it is displayed.

It would be expected that large window sizes would work similarly on both platforms.

This can make ui designed in Designer look differently on Mac and Windows.

Reproducible with the following steps in Designer.

• Create a new Widget
• set the geometry to height 3000
• add some widgets
• preview
  On Windows, the widget is compressed to fit the desktop size.
  On Mac, the widget is not compressed and the height 3000 is used.