561637 - reftests/bidi/visualmarquee.html and reftests/bidi/logicalmarquee fail on OSX

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect)

Description

[Simon Montagu :smontagu]

Attachment: Test image

This looks like an anti-aliasing issue

Comment 1

[Simon Montagu :smontagu]

Attachment: Reference image

Comment 2

[Jonathan Kew [:jfkthame]]

Simplified testcase: load into adjacent tabs

Test
  data:text/html,<marquee scrollamount="0" behavior="alternate">X</marquee>

Reference
  data:text/html,<div style="text-align:right">X</div>

Then flip back and forth; the X can be seen to move by approximately (not exactly) one pixel, with the <marquee> version being slightly further from the right edge of the window.

This also occurs on Windows7 when DirectWrite is enabled (see bug 578127), but does not occur using the GDI font path.

Comment 3

[Simon Montagu :smontagu]

Attachment: Fix

Forcing text-align: left fixes this for me locally.

Comment 4

[Jonathan Kew [:jfkthame]]

(In reply to comment #3)
> Created attachment 457279 [details] [diff] [review]
> Fix
> 
> Forcing text-align: left fixes this for me locally.

Yes, this also appears to fix the failure on windows with dwrite.

However, it's not clear to me what these Hebrew marquee tests were specifically trying to address, and whether forcing left-alignment means we're no longer testing the same issues.

Comment 5

[Simon Montagu :smontagu]

Thanks for the pointer, Jonathan. Similar issues seem to have come up in the past, e.g. in the reftests for bug 336736 and bug 404553. The work-arounds used there don't help here because the point of the test is to verify that reordering doesn't break on XBL bound anonymous content (cf. bug 558403 comment 17). I'll check in attachment 457279 [details] [diff] [review] if it passes on tryserver.

Comment 6

[Simon Montagu :smontagu]

http://hg.mozilla.org/mozilla-central/rev/2c01b0ceb712