551611 - Animated GIF No Longer Combines Correctly

Status: RESOLVED DUPLICATE of bug 513749

(Core :: Graphics: ImageLib, defect)

Description

[Stephen]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6

Since upgrading from Firefox 3.5.x to 3.6, animated gifs that use the combine option no longer combine properly. The images seen in the example URL, for "hot topics" on a forum, contain 5 frames each. The result is an image that appears to be glitching, with transparencies overwriting the pixels beneath them, rather than following the combine metric to continue showing the pixels form the last frame. The initial frame features a full diamond shape with a jewel in the center. Subsequent frames only change that central jewel. Thus, the points of the diamond remain present while the center flickers. In addition, it appears to completely clear the image for a frame when it's meant to wrap back around to the beginning.

Reproducible: Always

Steps to Reproduce:
1. Locate topic with sufficient number of posts in forum.
2. Observe post icon on left.
Actual Results:  
The image glitches, with transparency acting like a solid color. This does not happen in other browsers, including older versions of Firefox.

Expected Results:  
The image should combine frames, so that only solid pixels of the new frame overwrite pixels in the old frame, with all the other old pixels remaining.

This error was produced on a fresh install of Firefox, with vanilla settings. It has been reproduced by other members of the community linked to in the example.

Comment 1

[Boris Zbarsky [:bzbarsky]]

Hmm.  This seems to work ok for me on Mac.  Martijn, can you reproduce on Windows?

Comment 2

[Stephen]

I've added a screenshot of two of the different states for easier reference.

http://www.psypokes.com/forums/images/ffbug.png

Comment 3

[Martijn Wargers (dead)]

I can reproduce this on windows (7) for 3.6, but not on current trunk.
I don't see this in a 2009-01-04 build, so I guess it was fixed somewhere in 2008 (I don't have those builds on my machine, atm).

Comment 4

[Boris Zbarsky [:bzbarsky]]

> I can reproduce this on windows (7) for 3.6, but not on current trunk.

I just retested on Mac in a 1.9.2 branch build, and I definitely see the problem there.  I'll hunt down a range.

Comment 5

[Boris Zbarsky [:bzbarsky]]

Actually, it's more likely that it was introduced after 2009-01-04.  A Mac 2009-08-13 (branch date) mac m-c nightly shows the bug.

Comment 6

[Boris Zbarsky [:bzbarsky]]

OK.  On m-c, the bug got fixed in this checkin range: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=75af94f85a98&tochange=3cab7a0c2c3d

Looks like bug 513749 got fixed in that range and sure looks a lot like this bug.  Should be fixed in the 1.9.2.2 update.

Comment 7

[Boris Zbarsky [:bzbarsky]]

And confirmed that today's 1.9.2 build doesn't have the problem.