I think I found a better way to solve the button-height problem, that should be safe: I found a routine that can request the nominal dimensions of a fontSet. And I now use that info to trim the size of the buttons, rather than adapting the text-widget height to the buttons. This should avoid problems with vertical alignment of the text in the text-edits, and it makes the buttons transform to a reasonable size.
Only the spacing in the pull-down menus looks unnaturally large now. But the menu items seem to resist vertical sizing, so I guess we have to live with that. My exploring also dug up a way to control distance of widgets to their reference neighbor. I use that now to position the checkboxes, and make the spin-control buttons touch each other. This whole operation all in all results in a much nicer layout of the dialogs (in so far they are generated by GenericPopUp). And it is much more robust against font-size changes too, as I derive heights and distances from the fontSet parameters. I pushed the patch to Savannah master. everything there can go into 4.6.0.
