Text in fonts too bold or blurry in Firefox on macOS Mojave?

submitted by u/WerewolfAX to r/social

Hello Dear Firefox Community!

Since the last update of Firefox Developer Edition to v66.0b1 (64Bit) on macOS Mojave I’ve got a weird problem: It looks like the browser shifts the font-weight definition up on every website for one step. So what used to be 200 is now 300, 300 is 400 and so on. When I roll back to the previous version everything works fine again. Looks like the font rendering is broken since the update.

Is it just me or was there a change and maybe a bug with the font rendering?

Currently I only had the possibility to test it on macOS Mojave (10.14.2) so unfortunately I can’t say if other operating systems are also affected by this. My other regular Firefox installation (stable, v64.0.2) on the same devices also still work as expected, so I don’t think it’s an OS related issue, especially because I can fix it by rolling back one FF Dev version.

I attach a little screenshot to maybe show you the problem a bit better:Left side is a screenshot from the previous Firefox Developer Edition version, right side is the 66.0b1.If you look at the screenshot in full size you see that the font on the right looks a bit bolder but still anti-aliased - the fonts just feel a bit “blurry” in person in comparison. And it adds some unnecessary weight on some pages and looks weird especially where the font size is quite small.

I already tried to purge caches to make sure there are no corrupt data there, tried a new user profile and fiddled with the hardware acceleration settings, but no changes there.

Thanks in advance for your help or feedback to that problem!

u/yoasif

It looks like this is the issue - but it looks like it is a fix.

Have you played with any of the font smoothing settings in Mojave? I know there were changes around that. Also, it may be significant if you are on an external high DPI display vs. one built in to a Mac.

This fixes a bug in Firefox. Compare the text to Safari - Firefox is respecting your platform setting instead of doing its own thing.

Most Mac users want that.

You can disable font smoothing if you prefer that look.

FYI, if you are on a non-retina display, you will need to wait until Firefox 66 for a further fix (I guess developers are mostly on laptops with high DPI).

Context

In the macOS Mojave 10.14 release, Apple removed support for subpixel anti-aliasing but kept “dilation” (bolding) for standard pixel density displays. Concurrently, the Firefox 2D rendering code (Skia) included a bug that disabled gamma conversion, making fonts look thinner.

Mozilla shipped a fix for this in Firefox 66 to match the platform vendor (Apple).

This was a platform change, so users differed on which behavior they ended up preferring; while many users seemed to gravitate towards disabling font smoothing, on my low-DPI MacBook Air running Catalina, I still have font smoothing enabled. Clearly, Apple wants its customers on high-DPI displays, however – with fewer hacks for making text look better on lower DPI displays.

If you liked this material, please consider supporting me. You can also message me on Mastodon.