Created attachment 197180 [details]
Screen shots of a dialog on Windows and Linux computers

In Linux, Libre renders dialog edit controls (including the edit of a combo-box) incorrectly. The width is as defined in the IDE but the height is much greater than as defined. This is not done to accommodate the text, whose characters are much shorter than the oversized frame. I turn off native rendering [hDlg.getPeer().setProperty("NativeWidgetLook", False)] in order to be able to dynamically change label background color. If I don't do this, the edit controls are rendered somewhat differently but still incorrectly. I create my dialogs in Windows, where all Libre versions on several test computers render them exactly as defined. I also test them on two Linux computers. In the one with Libre 6.4.7.2 on ubuntuMATE 20.04 the edits are two pixels taller than as defined. In the one with  Libre 24.2.6.2 on ubuntuMATE 24.04 they are five pixels taller. The attached document (ODT file) contains screen shots of the same dialog on two Linux and two Windows computers, all with different display resolutions and Libre versions.