603337 - border-radius plus overflow!=visible forces grayscale font anti-aliasing

Status: VERIFIED FIXED

(Core :: Layout, defect)

Description

[Ilja Sekler]

User-Agent:       Mozilla/5.0 (X11; Linux i686; rv:2.0b8pre) Gecko/20100101 Firefox/4.0b8pre
Build Identifier: Mozilla/5.0 (X11; Linux i686; rv:2.0b8pre) Gecko/20100101 Firefox/4.0b8pre

In some circumstances (see $URL; another example: "Reviews" on <https://addons.mozilla.org/en-US/firefox/addon/6622/>), CSS property 'border-radius' forces grayscale anti-aliasing instead of subpixel one, used everywhere else.


Reproducible: Always

Steps to Reproduce:

1. Setup your desktop environment to use subpixel anti-aliasing
2. Load the $URL
 
Actual Results:  
The text in the richlistbox on the left side of the page ("Get Add-ons", "Extensions", "Appearance", "Plugins") and in #view-port-container on the right one is rendered using grayscale anti-aliasing.

Expected Results:  
Subpixel AA everywhere.


When setting all values for border-*-radius in #view-port-container and in .category:-moz-locale-dir(ltr) to 1px or less, font rendering switches to subpixel.

This might be closely related or a dupe of <https://bugzilla.mozilla.org/show_bug.cgi?id=363861>, but border style as trigger doesn't look very obvious to me.

Built from <http://hg.mozilla.org/mozilla-central/rev/5a41a70eb631>.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Can we get a reduced testcase? It's unclear how widespread this bug is going to be.

Comment 2

[Ilja Sekler]

Attachment: Reduced Testcase

It turns out to be a combination of border-radius > 1px with "overflow: hidden" which triggers grayscale anti-aliasing on trunk.

Chromium 7.0.536.0 behaves the same, Firefox 3.6 is not affected.

Comment 3

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Should be fixed by bug 613040.

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Please retest now that bug 628745 has been fixed.

Comment 5

[Asa Dotzler [:asa]]

this does appear fixed with the 628745 changes. I see sub-pixel aa in the testcase using windows 7.

Comment 6

[Ilja Sekler]

Attachment: New behavior: grayscale only when text is clipped

The 4x magnified screenshot should just illustrate the tradeoff in the fix. Such insane cases as on the screenshot might be quite rare in the wild, and if an uncompromising solution would have cost too much speed, I am very happy with the tradeoff.

Confirming FIXED on Linux, Mozilla/5.0 (X11; Linux i686; rv:2.0b11pre) Gecko/20110127 Firefox/4.0b11pre built from <http://hg.mozilla.org/mozilla-central/rev/2df909c5921d>.

Thanks a lot!

Comment 7

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Yeah, that's expected. Like you, we hope such things are rare in the wild :-).

Comment 8

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Although we'll actually do a complete fix post-FF4.

Comment 9

[Aleksei Perepelkin [:chaos]]

Verified with Mozilla/5.0 (X11; Linux i686; rv:2.0b12pre) Gecko/20110204 Firefox/4.0b12pre