Steps: - Updated to firefox 20.0 on ubuntu 12.04.1. - Created new profile (using firefox -P). - Modified layout.css.devpixelsperpx to 1.1. Result: Address bar suggestions (history urls), file/edit/... menu popups, search box now are all shown incompletely (see screenshots): - address bar doesn't show history, only a tiny stub, same for search box - menu popups look like they don't have enough space to display all items All of these were working fine on firefox 19.0. I've tested on 2 machines with ubuntu 12.04.1, one of which is a fresh install. Apparently there are minor issues on windows as well: on windows 7, firefox 20, changing layout.css.devpixelsperpx makes a solid black band show instead of the gradient shadow behind the address bar.

(In reply to harjoc from comment #0) > Apparently there are minor issues on windows as well: on windows 7, firefox > 20, changing layout.css.devpixelsperpx makes a solid black band show instead > of the gradient shadow behind the address bar. You're right, I observe that with Firefox 23 on Win 7. In addition, when you're typing something in the location bar, the drop-down menu is opening gradually from top to bottom with a large blank area at the end with missing URL entries. Regression range: m-c good=2013-02-26 bad=2013-02-27 http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=73f0c5b00572&tochange=e7632ab657e5

Regression window Good: http://hg.mozilla.org/mozilla-central/rev/739f20de3c1e Mozilla/5.0 (X11; Linux i686; rv:20.0) Gecko/20121207 Firefox/20.0 ID:20121207030741 Bad: http://hg.mozilla.org/mozilla-central/rev/b7fab17d30b7 Mozilla/5.0 (X11; Linux i686; rv:20.0) Gecko/20121208 Firefox/20.0 ID:20121208030937 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=739f20de3c1e&tochange=b7fab17d30b7 Triggered by: ac48e5c365e2 Jonathan Kew — bug 814434 - use global display pixels for window positioning/sizing for consistency across mixed-resolution screens. r=smichaud

I'm pretty sure this will turn out to be the same as bug 840881. There are currently several things that are a bit broken if you change devPixelsPerPx - the workaround is to leave it untouched! On Windows, at least, it should no longer be needed to scale things properly for hi-dpi displays.

Mozilla/5.0 (X11; Linux i686; rv:25.0) Gecko/20130728 Firefox/25.0 I am unable to reproduce this on Firefox 23 beta 9 (buildID: 20130725195523) or latest Nightly (buildID: 20130728030204). Probably was fixed along with bug 840881.

Seems fixed here as well on firefox 21 - ubuntu standard package (I'm the initial reporter). Thanks.