Created attachment 776743 [details] Screen Shot 2013-07-17 at 00.32.13 .png User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:22.0) Gecko/20100101 Firefox/22.0 (Beta/Release) Build ID: 20130618035212 Steps to reproduce: The problem has to do with the zoom feature and websites that have drop-down menus. I changed the value of layout.css.devPixelsPerPx from -1.0 to 0.8 (also 0.9 and 1.0 for the purpose of testing), and was very satisfied with the zoom, except when I had to use drop-down menus with a mouse (keyboard access works). Actual results: In all cases for a value < 1.0, the menu doesn't appear where the drop-down menu is on the web page. It's further down and a bit off on the right, or way off on the right. In some cases (for a value < 1.0), selecting an element from the list produces no result, and in other cases (still for a value < 1.0) selecting an element from the list is possible only from the 6th or so element in order to select the 1st element in the list, and depending on the size of the drop-down menu, elements near the bottom can not be selected. I have tested with a few public sites. See attached screenshot when I clicked the "Version:" drop-down menu of this form. Expected results: The drop-down menu should not be off, selecting with the mouse should be possible and the element selected with the mouse should really be selected.
I'm not able to reproduce it with FF22 on Win 7. What's the dimensions/resolution of your display? And could you test with FF25 please? http://nightly.mozilla.org/ (make a new profile if you don't want to use the current one)
Addendum: I just noticed that videos embedded in web pages are black (sound is fine), for a value < 1.0 of layout.css.devPixelsPerPx.
(In reply to Loic from comment #1) > I'm not able to reproduce it with FF22 on Win 7. > > What's the dimensions/resolution of your display? Resolution: 1440 x 900 Pixel Depth: 32-Bit Color (ARGB8888) This is a 15-inch screen. > And could you test with FF25 please? http://nightly.mozilla.org/ > (make a new profile if you don't want to use the current one) I will, as soon as I can, and report back. Thank you.
(In reply to Loic from comment #1) > I'm not able to reproduce it with FF22 on Win 7. [...] > And could you test with FF25 please? http://nightly.mozilla.org/ > (make a new profile if you don't want to use the current one) I am able to reproduce all the above with FF25 nightly (25.0a1 (2013-07-17)) on Mac OS.
Confirming with Firefox Nightly on OS X. Changing the devPixelsPerPx value renders context menues and the URL bar incorrectly. Tested with a MacBook Pro Retina + External monitor. Second issue is that the UI is completely messed up if you would move the Firefox windows to the laptops display.
Created attachment 8452167 [details] devPixelsPerPx_panels_bug.png Related, this bug also impacts panels opened from the toolbar, eg. downloads…