Closed Bug 1553818 Opened 1 year ago Closed 1 year ago

Some sites such as seem to have blurrier fonts


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




Tracking Status
firefox-esr60 --- disabled
firefox-esr68 --- disabled
firefox67 --- wontfix
firefox68 --- wontfix
firefox69 --- verified
firefox70 --- verified


(Reporter: jan, Assigned: lsalzman)


(Blocks 1 open bug, Regressed 1 open bug, Regression, )


(Keywords: nightly-community, regression)


(5 files)

Attached image Screenshot.png

So I've enabled WR and I'm really loving it, the difference on heavier sites is very noticeable. However, I noticed some sites such as OcUK Forums seems to have blurrier fonts with WR enabled (WR off above, WR on below):

Turning WR off makes the text clear again. This does not happen to every site, all other sites I visit, fonts looks completely fine. It's just this website that for some reason I've noticed it.

Confirmed with 67 and 69 on Win10, GTX1060.

Blocks: wr-69
Priority: -- → P3

Hi, just wanted to add that was my Reddit/OcUK post, so to add more detail this is with FF 67 release with W10, GTX1080 Ti. I've also confirmed it with another PC using W10, AMD 5670.

Hey Lee - can you take a look at this please?

Flags: needinfo?(lsalzman)

If you disable WebRender, and you disable Direct2D as well so there is no HWA, what does it look like?

Flags: needinfo?(lsalzman) → needinfo?(jan)
Attached image basic,wr,d3d11.png
Flags: needinfo?(jan)
Summary: Some sites such as seems to have blurrier fonts → Some sites such as seem to have blurrier fonts

It seems like the result is consistent with what Skia rendering is giving us. Can you please also add in the about:support for the d3d11 case? I am also curious what the result looks like in Chromium, maybe closer to the Skia case?

Flags: needinfo?(jan)

(Win10 1809, GTX1060, 2560x1440, Dell UltraSharp U2515H (117.5 DPI))

Flags: needinfo?(jan)

Lee - any new ideas here?

Flags: needinfo?(lsalzman)

The font used is Verdana, which gets forced to use GDI rendering. In bug 1323587, Mason hard-coded the gamma to 2.3 for GDI fonts, based on a reading of Skia's code at However, it turns out that we rather need to use the ClearType value in the code nearby, which is a much lower gamma value by default, and in any case is a system parameter.

It turns out that our Skia and WebRender rendering of GDI fonts looks far bolder than the Direct2D reference case as a result. This has been the case since bug 1323587.

I have a fix in progress...

Flags: needinfo?(lsalzman)
Component: Graphics: WebRender → Graphics: Text
Priority: P3 → P1
Assignee: nobody → lsalzman
OS: Windows 10 → Windows
Regressed by: 1323587
Hardware: x86_64 → All
Pushed by
use GDI ClearType contrast for GDI font gamma. r=jrmuizel
Closed: 1 year ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla70
Has Regression Range: --- → yes
Has STR: --- → yes
Keywords: regression

Comment on attachment 9080168 [details]
Bug 1553818 - use GDI ClearType contrast for GDI font gamma. r?jrmuizel

Beta/Release Uplift Approval Request

  • User impact if declined: Windows users will see GDI fonts with incorrect gamma when using WebRender or Skia, that looks noticeably different than our normal output with the Direct2D backend.
  • Is this code covered by automated tests?: Yes
  • Has the fix been verified in Nightly?: Yes
  • Needs manual test from QE?: No
  • If yes, steps to reproduce:
  • List of other uplifts needed: bug 1568841
  • Risk to taking this patch: Low
  • Why is the change risky/not risky? (and alternatives if risky): GDI fonts under WebRender and Skia now more closely match the rendering output with our Direct2D backend.
  • String changes made/needed:
Attachment #9080168 - Flags: approval-mozilla-beta?

Comment on attachment 9080168 [details]
Bug 1553818 - use GDI ClearType contrast for GDI font gamma. r?jrmuizel

Fixes a regression in font rendering for some Windows users with WebRender enabled. Approved for 69.0b9.

Attachment #9080168 - Flags: approval-mozilla-beta? → approval-mozilla-beta+
Flags: qe-verify+
QA Contact: daniel.cicas
QA Whiteboard: [qa-triaged]


I can confirm that this issue is fixed on Fx 69.0b9 and Fx 70.0a1 BuildID: 20190731215544. I verified using Windows 10 x64 1050 GTX.

Regressions: 1578791
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