[Webkit-unassigned] [Bug 95440] New: testing img.complete without waiting for decoding is wrong

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=95440

           Summary: testing img.complete without waiting for decoding is
                    wrong
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jussi.kukkonen at intel.com


I was trying to fix HTMLImageElement.complete (so it would return false when the image was not decodable), and realised the tests that use it are also wrong.

img.complete may (and should) change while the script is running. If we want to check the "final" value we can't do it when script execution starts: the image may not be loaded/decoded yet at that time. We should check img.complete only after decoding should be complete.

Fixing this reliably wasn't as easy as I hoped:
 * it seems even for inlined uri-data images, the decoding is still done in parallel with script execution
 * same goes for img.onload: checking for img.complete from the onload handler gives flaky results
...at least these were my results with the WIP patch in bug 28832

A timeout is an inherently flaky solution but still the best I could think of... with small images (like the testrunner ones) the decoding seems to take only milliseconds. I'll upload a patch with a timeout but I'd be happy with a better solution if anyone has one.

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