Created attachment 8894665 [details] Screenshot from 2017-08-07 16-54-32.png User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20170807113452 Steps to reproduce: 1. Go to a website in Nightly, the two that I've tested and confirmed are The Verge (https://theverge.com) and Google Inbox (https://inbox.google.com) 2. Look at the body text on the page. I use infinality & Debian 9 if that matters. The issue doesn't occur on Chrome. Actual results: Blocky, old-looking fonts. Expected results: Smooth font rendering.
I can't reproduce it on Ubuntu 16.04. Jonathan, do you have any idea about it?
It looks like antialiasing (font smoothing) is turned off, which is generally controlled via system-level preferences or fontconfig settings -- exactly where to find them depends on the desktop environment being used, I guess. I believe Firefox pays more attention to these settings than Chrome, which might explain why things look different there (I wouldn't be surprised if Chrome applies smoothing regardless of OS-level settings). (Also possibly relevant: what specific font is being used, as determined by the Fonts panel in the devtools Element Inspector?)
Created attachment 8905175 [details] sample1.png Same problem. RGB anti-aliasing and hinting don't work on some sites. System settings: anti-aliasing: enabled, subpixel rendering type: RGB, hinting style: slight. System: Kubuntu 16.04.3, 64-bit. Nightly 57.0a1 (2017-09-06).
Created attachment 8907959 [details] Screenshot from 2017-09-14 06-17-45.png Another example. Ubuntu 16.04.3 LTS.
Any chance of running mozregression  on this? Sounds like a recent problem.  http://mozilla.github.io/mozregression/quickstart.html
Created attachment 8909142 [details] sample2.png I can't reproduce this problem using mozregression. But I did some tests. Results are in the picture. System settings of anti-aliasing are work for GUI in all versions of Firefox, but not for sites rendering.
This reproduces with a clean profile?