1263740 - Skia seems to turn off subpixel AA at a certain font size

Status: RESOLVED WONTFIX

(Core :: Graphics, defect, P3)

Description

[Markus Stange [:mstange]]

STR:
 1. On a HiDPI display, look at the "Home" heading on https://github.com/mozilla/rr/wiki
 2. Look at the slightly smaller text below it.
 3. Be very confused about the inconsistent use of subpixel AA.

Jeff says they may be switching to path rendering for large fonts, and path rendering will just use regular gray-scale anti-aliasing.

Comment 1

[Mason Chang [Inactive] [:mchang]]

Might be hitting this - https://dxr.mozilla.org/mozilla-central/source/gfx/skia/skia/src/core/SkDraw.cpp#1660

which goes to https://dxr.mozilla.org/mozilla-central/source/gfx/skia/skia/src/core/SkDraw.cpp#1412

Comment 2

[Timur Davletshin]

Firefox 51beta2 on Linux (Skia) does not respect subpixel rendering settings in drop-down elements at least.

https://drive.google.com/file/d/0Bxs_utDd2nQgcHRuUDZxRkdDbk0/view?usp=sharing

Bottom line produced by FF51beta2, top line — FF50 release.

Comment 3

[Lee Salzman [:lsalzman]]

(In reply to Timur Irikovich Davletshin from comment #2)
> Firefox 51beta2 on Linux (Skia) does not respect subpixel rendering settings
> in drop-down elements at least.
> 
> https://drive.google.com/file/d/0Bxs_utDd2nQgcHRuUDZxRkdDbk0/view?usp=sharing
> 
> Bottom line produced by FF51beta2, top line — FF50 release.

I think maybe you are experiencing a separate issue unrelated to this bug, possibly bug 1316523. Can you try nightly and see if it is better there?

Comment 4

[Timur Davletshin]

(In reply to Lee Salzman [:lsalzman] from comment #3)
> (In reply to Timur Irikovich Davletshin from comment #2)
> > Firefox 51beta2 on Linux (Skia) does not respect subpixel rendering settings
> > in drop-down elements at least.
> > 
> > https://drive.google.com/file/d/0Bxs_utDd2nQgcHRuUDZxRkdDbk0/view?usp=sharing
> > 
> > Bottom line produced by FF51beta2, top line — FF50 release.
> 
> I think maybe you are experiencing a separate issue unrelated to this bug,
> possibly bug 1316523. Can you try nightly and see if it is better there?

I tried latest nightly build — issue remains the same. What I also discovered that all builds starting with current beta have the same behavior. Switching back to Cairo doesn't fix it. IMHO this was introduced somewhere between current stable (50) and all newer releases. Maybe as result of preparations to switch to Skia.

Comment 5

[Lee Salzman [:lsalzman]]

Given that this appears to be based on the fact that Skia beyond a certain size threshold renders glyphs as paths, which is not likely to change within Skia in the future, I am going to mark this as wontfix for now. If it turns out to be some other issue later, we can reopen it.