Firefox Aurora 34.0a2 2014-09-06 on Windows 8.1 with 125% font size on OS level Opening Preferences > Content > Fonts & Colors > Advanced shows a dialog Fonts in which the buttons OK, Cancel and Help at the bottom are cut off. Regression from bug 1035541 which removed the window dimensions? The issue doesn't occur on Firefox 33 Beta 1 (also dialog preferences) and not in the incontent preferences of Nightly (Gecko 35).

For me it's not logical, bug 1035541 removes the dialog width styling. With adding again the width, the height is correct. I think something in toolkit calculates the scaling wrong. I had similar effects with TB with embedded elements which are taller than their surrounding box and this ended in a scrollbar.

I see the same issue with FF34 on Win 7 and DPI at 125%. Regression range: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=63f44b4968c2&tochange=82df3654cd80

Not critical enough to block the release, so, not tracking. Richard, could you help here?

I don't think I can help. As wrote in comment 1, it's not logical with removing of the width definition the height is wrongly calculated. I would propose somebody from core should check if something with the calculation is wrong. And this happens only on scaled screens.

Yes, we have a similar problem in TB too, bug 789744. It looks like the XUL rendering core is somehow confused and doesn't know what the real size of the content is.