1553910 - ClearType pixel order not respected by WebRender

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Trevor Rowbotham [:rowbot]]

A reddit user has reported that when enabling webrender on Windows 7 with an nvidia GPU, they are seeing colorful fringes around all text.

https://www.reddit.com/r/firefox/comments/brw6c7/post_your_webrender_results/eoh8rqb?utm_source=share&utm_medium=web2x

Comment 1

[Jeff Muizelaar [:jrmuizel]]

A sc

Comment 2

[Trevor Rowbotham [:rowbot]]

User's about:support: https://pastebin.com/S09wpvS7
Screenshot comparison: https://imgur.com/a/dR6KO2z

Comment 3

[Trevor Rowbotham [:rowbot]]

I see in the supplied about:support, the ClearType Pixel Structure is BGR. Is that something that webrender handles or does it only support RGB for ClearType?

Comment 4

[Jeff Muizelaar [:jrmuizel]]

It seems like this is a problem on Win10 as well.

Comment 5

[Jeff Muizelaar [:jrmuizel]]

We also seem to have this problem if Direct2D is disabled.

Comment 6

[Jeff Muizelaar [:jrmuizel]]

This is handled in Skia here:

https://cs.chromium.org/chromium/src/third_party/skia/src/ports/SkScalerContext_win_dw.cpp?type=cs&q=fRec.fFlags+%26+SkScalerContext::kLCD_BGROrder_Flag&sq=package:chromium&g=0&l=1141

Lee, can you hook this up?

Comment 7

[Lee Salzman [:lsalzman]]

Attachment: Bug 1553910 - pass DWrite subpixel order into Skia and WebRender. r?jrmuizel

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dae9fa100abe
pass DWrite subpixel order into Skia and WebRender. r=jrmuizel

Comment 9

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/dae9fa100abe

Comment 10

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 9067467 [details]
Bug 1553910 - pass DWrite subpixel order into Skia and WebRender. r?jrmuizel

Beta/Release Uplift Approval Request

• User impact if declined: Color fringing on text on screens using a different subpixel order.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): This isn't too risky, it's mostly just plumbing some state around.
• String changes made/needed:

Comment 11

[Jeff Muizelaar [:jrmuizel]]

Julien, is possible to add something to 67 release notes about their being color fringing on text on screens with BGR pixel order when WebRender is enabled?

Comment 12

[Jeff Muizelaar [:jrmuizel]]

Some background on estimated impact of this issue:

• We only discovered the problem through a user that manually enabled WebRender on win7
• The problem has existed for the lifetime of WebRender (i.e it's been on Nightly since September 2018)
• The same problem happens when ever Direct2D is disabled. Direct2D is disabled for approx 25% of Windows users

Comment 13

[Ryan VanderMeulen [:RyanVM]]

Added as a known issue to the Fx67 release notes. Doesn't seem likely that we're going to try to backport this fix to a 67 dot release, though, so marking that as wontfix.

Comment 14

[Julien Cristau [:jcristau]]

Comment on attachment 9067467 [details]
Bug 1553910 - pass DWrite subpixel order into Skia and WebRender. r?jrmuizel

webrender fix for 68.0b6

Comment 15

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/releases/mozilla-beta/rev/7984ce01500a