[Webkit-unassigned] [Bug 39857] New: GIFs loop one time too few

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=39857

           Summary: GIFs loop one time too few
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Images
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: pkasting at google.com
                CC: mrowe at apple.com


Created an attachment (id=57281)
 --> (https://bugs.webkit.org/attachment.cgi?id=57281)
Image with a loop count of "1"

The Netscape extension to GIF89a that adds a loop count to animated images is interpreted differently by Firefox/IE vs. Safari/Opera.  According to http://mxr.mozilla.org/mozilla-central/source/modules/libpr0n/src/imgContainer.cpp (see SetLoopCount()), the loop count is intended to mean "how many times should this loop after animating through once".  Thus a loop count of "1" means that the animation should be displayed a total of 2 times.  Firefox and IE both behave this way.

Safari/Opera, on the other hand, treat the loop count as the number of total times to loop.  Thus they display non-infinitely-looping GIFs with one fewer cycle compared to Firefox/IE.  The attached image specifies a loop count of 1 and thus can be used to compare the browsers' behavior.

Chrome currently matches Safari/Opera; I intend to fix this in a separate bug.  This bug is about fixing Safari.

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