600898 - text with RGBA colors (with alpha) has a visible pixel in the otherwise invisible space character when directwrite on and D2D off

Status: NEW

(Core :: Graphics, defect)

Description

[Asa Dotzler [:asa]]

Attachment: dots next to text

I'm seeing little black dots at word breaks on the Mozilla Labs Game On 2010 web page. I don't see them in other browsers. Tested with today's nightly build, hardware acceleration on, Windows 7. Screenshot attached

Comment 1

[Asa Dotzler [:asa]]

Attachment: zoomed dots

Comment 2

[Asa Dotzler [:asa]]

http://www.w3.org/Style/CSS/Test/CSS3/Color/current/html4/t040202-rgba-a0-6-a.htm is another example and a pretty simple testcase.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Does disabling dwrite or d2d change anything?

Comment 4

[Asa Dotzler [:asa]]

setting gfx.font_rendering.directwrite.enabled to false fixes this bug. Does that mean this bug belongs in the Graphics component?

Comment 5

[Boris Zbarsky [:bzbarsky]]

Yep.

Comment 6

[Asa Dotzler [:asa]]

looks like it's a problem for the text described in RGBa color. Something about the alpha channel is not being treated properly.

Comment 7

[Asa Dotzler [:asa]]

Mozilla Labs uses RGBa with decimal alpha values for its body text so it's all over the place at http://mozillalabs.com/

Comment 8

[Asa Dotzler [:asa]]

Attachment: testcase showing dots at bottom left corner of space characters

OK, it's the bottom left pixel of the space character. Here's a testcase

Comment 9

[Asa Dotzler [:asa]]

Attachment: working testcase showing dots at bottom left corner of space characters

Comment 10

[Asa Dotzler [:asa]]

Attachment: testcase showing RGBa alpha value of .5, 0, and 1.

Comment 11

[Bas Schouten (:bas.schouten)]

This should not block, this is only when using DirectWrite, but -not- Direct2D. This is never a default at the moment and fails a bunch of reftests. At the moment GDI rendering with DirectWrite is not something we really fully support yet. I might note this means you're apparently not getting D2D on your machine :).

Comment 12

[Joe Drew (not getting mail)]

Not blocking as per comment 11.

Comment 13

[Asa Dotzler [:asa]]

Apparently I had disabled D2D (not sure why :-) Things look correct when I have it turned on. Sorry for the false alarm.  Should we just wontfix this since that's not a supported (nor likely) configuration?

Comment 14

[Boris Zbarsky [:bzbarsky]]

If it's not a supported configuration, is there a good reason to allow users to enter it at all?

As in, should disabling d2d disable directwrite?