723657 - document.normalize() causes slight rendering difference in the "f" character

Status: RESOLVED WORKSFORME

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

Description

[Jesse Ruderman]

Attachment: testcase (two text nodes; click to normalize)

The difference is very hard to see without screen zoom.

Comment 1

[Jesse Ruderman]

Attachment: "before" screenshot

Comment 2

[Jesse Ruderman]

Attachment: "after" screenshot

Comment 3

[Jesse Ruderman]

The "after" image is slightly darker where the two letters meet.

4 pixels differ (max channel difference: 42)

Comment 4

[Jesse Ruderman]

Linux only?

Comment 5

[Jonathan Kew [:jfkthame]]

Sounds like perhaps an antialiasing artifact, where the difference is caused by one of the cases being painted in a single operation, and the other in two separate operations; where the subpixel antialiasing of the two glyphs overlaps, this can lead to slightly different results.

Comment 6

[Jesse Ruderman]

Is it a bug in Firefox?  A bug in Linux?  Something I should just teach my fuzzer to deal with?  (Which won't be hard, thanks to the "max channel difference" feature of nsIDOMWindowUtils.compareCanvases.)

Comment 7

[Jonathan Kew [:jfkthame]]

I'm not entirely sure yet. I'll try to figure out more definitely what's happening - comment 5 is really just speculation. What font is being used in your case (in case I have trouble reproducing it)?

Comment 8

[Jesse Ruderman]

Seems to be an Ubuntu font named "serif".

Comment 9

[Ryan VanderMeulen (PTO, back July 27)]

Is this something that still happens/matters?

Comment 10

[Jonathan Kew [:jfkthame]]

I can't readily seem to reproduce it, and it doesn't sound like it would really matter anyhow... Jesse, is this an issue we should look into at all, or just dismiss it?

Comment 11

[Ryan VanderMeulen (PTO, back July 27)]

Jesse is gone. Let's just call this WFM.