Combo boxes have more space above/below in 5.12.2 than 5.9.7 on the Mac.

In Qt 5.12.2, combo boxes on the Mac seem to have a few extra pixels of spacing above and below them, which means that layouts with a mixture of buttons and combo boxes don't always have consistent spacing.

See the attached UI file and screenshots from Qt Designer. In 5.9.7, there is a consistent 13-pixel spacing between all of the buttons and combo boxes. In 5.12.2, the buttons are still spaced 13 pixels apart, but there's a 16-pixel space between the combo box and the buttons.

Similarly, if you delete the combo box from the horizontal layout at the bottom of this UI file, the layout's height decreases by a few pixels in 5.12.2. This didn't happen in 5.9.7.

It's not a major functional issue, and I'm not sure whether the change is intended behavior or not, but most of the layouts I've been working with seem to look better using the more consistent spacing of 5.9.7.