User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:49.0) Gecko/20100101 Firefox/49.0 Build ID: 20160920074044 Steps to reproduce: Using Ubuntu 16.04 LTS, I upgraded from Firefox 48 to Firefox 49 when offered. Actual results: After the upgrade, the default zoom level is 100%, whereas it was 150% in Firefox 48 and previous versions, because I set the system scaling to 1.5 in the Ubuntu system settings. Expected results: The default zoom level should still follow the system scaling, i.e. be at 150% on my system.
More detailed reproduction steps: - Install Ubuntu 16.04 LTS and all currently available updates, except for Firefox updates - Go to Ubuntu System Settings -> Displays and set "Scale for menu and title bars" to 1.5 - Start Firefox, click the menu button on the upper right, and note that the zoom level is at 150% - Close Firefox and update to the latest Firefox version (49.0) offered through Ubuntu updates - Start Firefox, click the menu button on the upper right, and note that the zoom level is not at 100%. Firefox no longer follows the System Scaling.
(In reply to robert_s from comment #1) > - Start Firefox, click the menu button on the upper right, and note that the > zoom level is not at 100%. Typo: Make that "now" rather than "not".
After downgrading to Firefox 45.0, I realize I made a mistake: Firefox was always showing a default zoom level of 100%. But, in Firefox 45.0, the tabs and toolbar buttons were bigger, and so were the rendered web pages. Comparing screenshots, I found that I need to set the zoom level to 133% in Firefox 49.0 to achieve the same visual result of web pages that Firefox 45.0 showed at 100%. The tabs and the toolbar buttons are still smaller than in 45.0.
I found out that changing the setting layout.css.devPixelsPerPx in about:config from the default (-1.0) to 2.0 in Firefox 49.0 produces the same visual result of tabs, tool bar and web pages that Firefox 45.0 produced at the default setting. From what I understand, -1.0 means "use system scaling". Why did this result in 2.0 in Firefox 45.0 through 48.0, and suddenly results in 1.0 in Firefox 49.0?
Jonathan, do you have an idea about the change of layout.css.devPixelsPerPx in FF49?
Component: Untriaged → Widget: Gtk
Product: Firefox → Core
(In reply to robert_s from comment #1) > More detailed reproduction steps: > > - Install Ubuntu 16.04 LTS and all currently available updates, except for > Firefox updates > - Go to Ubuntu System Settings -> Displays and set "Scale for menu and title > bars" to 1.5 > - Start Firefox, click the menu button on the upper right, and note that the > zoom level is at 150% > - Close Firefox and update to the latest Firefox version (49.0) offered > through Ubuntu updates > - Start Firefox, click the menu button on the upper right, and note that the > zoom level is not at 100%. Firefox no longer follows the System Scaling. Unfortunately, GTK3 supports integer scale only by HiDPI API. But we won't support float scale by X such as bug 1211547 yet.
On my system running Ubuntu 15.10, Firefox 49 currently reports a devicePixelRatio of 1.5. There seem to be two scales, a per-monitor "Scale for menu and title bars" which can be set in the Screen Display settings panel (currently set to 1.5 for both my monitors); and then a separate "Scaling Factor" for fonts that can be adjusted in the Tweaks tool (mine is 1.5 here, too). But these interact with each other in ways that I don't fully understand at this point, and if they're substantially different from each other then things start to look a little odd. Note that IIRC, our Gtk widget backend doesn't yet support per-monitor DPI, so I don't know exactly how things get resolved if there are multiple screens and they're configured with different scale factors.
Up until Firefox 48, the _per-monitor_ scaling was used. I know for sure, because I'm using Ubuntu 16.04 LTS on a USB stick which I use on different computers/monitors. One setup (with a UHD monitor) has the scaling factor in the screen display settings set to 1.5, the other one (with a FHD monitor) has it set to 1.0. Up until Firefox 48, it automatically adjusted to the computer/monitor I was currently using. Firefox 49 has lost this ability. Now I have to enter about:config each time I switch the computer and change the devPixels setting manually. For me, this is a serious regression.
hey Johnathan, any ideas as to why we lost the ability to update automatically per comment 8?
Robert, please try to track down what regressed in 49 using our regression tool. http://mozilla.github.io/mozregression/
Thanks for making me take a long hard look with the regression tool. It turns out that the scaling is not broken, but was rather FIXED: In Firefox 45.0 through 48.0, setting the scaling factor in Ubuntu System Settings to 1.5 resulted in Firefox using layout.css.devPixelsPerPx = 2.0, which was apparently more upscaling than it should have been. FireFox 49.0 fixed that, and now a scaling factor of 1.5 in Ubuntu System Settings results in Firefox using layout.css.devPixelsPerPx = 1.5. I had so gotten used to the incorrect 2.0 scaling that when I saw everything being smaller than before, I thought the scaling was not working at all. Sorry for the misconception.
Status: UNCONFIRMED → RESOLVED
Last Resolved: 2 years ago
Resolution: --- → INVALID
You need to log in before you can comment on or make changes to this bug.