[webkit-help] What is the situation regarding broken font rendering?

Simon Fraser simon.fraser at apple.com
Mon Sep 14 07:58:06 PDT 2015

> On Sep 14, 2015, at 4:08 AM, Jon Rimmer <jon.rimmer at gmail.com> wrote:
> Hi,
> As described in this bug:
> https://bugs.webkit.org/show_bug.cgi?id=23364 , Webkit's font
> rendering has been broken for over six years.
> What is going on with this issue? Despite assurances from Dean Jackson
> that it had not been forgotten, there has been no updates from Webkit
> engineers since 2010. You guys have been making a welcome effort
> recently around better project communication. I should hardly need to
> explain what a terrible impression it gives to promise users that an
> issue has not been forgotten, then seemingly forget about it for half
> a decade! If there has been a decision to leave this broken, should it
> at least not be communicated and explained to users?
> As it is, we have a web application that makes heavy use of
> transforms, transitions and animations, and it looks like garbage in
> Safari, and only Safari, due to the constant flickering of rendering.
> I am aware we can set -webkit-font-smoothing to force LCD antialiasing
> everywhere, but that would mean losing subpixel antialiasing in
> non-broken browsers that honour this property, and we have too many
> Chrome users who would balk at such a sudden degradation in rendering
> from what they're used to. I don't want leave the app looking like
> crap in Safari, but right now it feels like I have no choice but to do
> so. It would be nice to know whether there's any hope that Webkit's
> font rendering will eventually be fixed?

Just to clarify, this is an OSX-wide problem, and not specific to WebKit.
WebKit is dependent on underlying libraries for text rendering, graphics
and compositing, and this bug is a consequence of rendering text into
transparent textures, when the destination pixel colors are unknown.

Considerable engineering effort was spent earlier this year in trying to come
up with a solution to this problem. Some of this happened in WebKit[1], but
unfortunately we were not able to come up with a solution that worked well
in all cases. It’s still a high priority item for us, but we are very dependent on
other frameworks.

I did make an improvement which should make animations less likely to trigger
changes in text rendering[2]. Does your content still show lots of text flickers
in El Capitan or a recent WebKit nightly?


[1] https://bugs.webkit.org/show_bug.cgi?id=143508 <https://bugs.webkit.org/show_bug.cgi?id=143508>
[2] https://trac.webkit.org/r181515 <https://trac.webkit.org/r181515>

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