1296788 - Consider removing -moz-osx-font-smoothing

Status: RESOLVED WONTFIX

(Core :: Layout: Text and Fonts, defect)

Description

[Thomas Wisniewski]

This feature is non-standard, limited to OSX, hidden behind a preference (layout.css.osx-font-smoothing.enabled), and font-smooth was itself removed from the spec years ago.

Is there a reason to keep it around, or would it be better to remove it entirely (aside from any parts that might be necessary to emulate -webkit-font-smoothing, if any?)

Comment 1

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to Thomas Wisniewski from comment #0)
> This feature is non-standard, limited to OSX, hidden behind a preference
> (layout.css.osx-font-smoothing.enabled)

That preference is enabled by default on Mac.

> Is there a reason to keep it around,

Find the bug where we added it, and see why we added it?

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

(In reply to David Baron :dbaron: ⌚️UTC-7 (review requests must explain patch) from comment #1)
> Find the bug where we added it, and see why we added it?

(You should be able to do this with "hg annotate" or "git blame", or perhaps by searching bugzilla.)

Comment 3

[Thomas Wisniewski]

Thanks. hg annotate gives me bug 857142, which mentions that there were problems at the time with some fonts appearing worse in Firefox on OSX than in WebKit (before version 28 when this was released).

:jfkthame, what do you think? Is this still a good setting to keep around, or have things advanced to the point where it's time to re-evaluate things?

Comment 4

[Jonathan Kew [:jfkthame]]

Nothing has changed significantly since that time, AFAICT. The rendering of light-on-dark glyphs still tends to appear excessively "fat" on OS X, unless -moz-osx-font-smoothing:grayscale is used to disable subpixel antialiasing. So the use case is unchanged, and sites that depend on this (e.g. to make their icon fonts render cleanly in toolbars that use white-on-dark glyphs) will regress if we remove it.

Simple testcase (for OS X):

  data:text/html,<span style="font:12px arial">Hello World<br>
                 <span style="background:black;color:white">Hello World<br>
                 <span style="-moz-osx-font-smoothing:grayscale">Hello World

Here, the glyphs in middle line (which has white-on-black rendering, but does not force grayscale AA) appear fatter/bolder than those on the other two lines. This may be OK for text readability in some cases, but it plays havoc with people's icon fonts.

Comment 5

[Xidorn Quan [:xidorn] UTC+11]

Given we have been adding -webkit-prefixed things, could we probably rename it to -webkit-font-smoothing, so that page works on Safari would get Firefox support for free? (We can still disable it on systems other than macOS by default.)

Comment 6

[Thomas Wisniewski]

If we're truly stuck with this then I'd rather resuscitate the font-smooth standard... but then I don't know if the Firefox and WebKit versions could even be aligned in a standard way.

Comment 7

[Jonathan Kew [:jfkthame]]

(In reply to Xidorn Quan [:xidorn] (UTC+10) from comment #5)
> Given we have been adding -webkit-prefixed things, could we probably rename
> it to -webkit-font-smoothing, so that page works on Safari would get Firefox
> support for free? (We can still disable it on systems other than macOS by
> default.)

We probably shouldn't drop the -moz-prefixed version, but maybe aliasing it to -webkit-font-smoothing would make sense. Though if we're going to do that, we should look at what happens on other platforms to see what effect the webkit property has there, and decide whether we should do the same. At the time we implemented this, the big pain point was OS X, and it didn't seem important elsewhere, but I don't know if anything has changed in that regard.