[Webkit-unassigned] [Bug 64321] New: Changing url cursor at runtime causes flickering

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=64321

           Summary: Changing url cursor at runtime causes flickering
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Windows XP
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: ananta at chromium.org
                CC: fishd at chromium.org


This bug was originally logged as a Chromium bug. http://code.google.com/p/chromium/issues/detail?id=87488.

The steps copied from the chromium report are as below:-

1. create a custom, animating cursor with a canvas
2. update the cursor w/ document.style.cursor = 'url('+canvas.toDataURL()+'), pointer' (do this repeatedly)
3. notice occasional flickering where the cursor is replaced with the default for a very brief moment before the new custom cursor is rendered.

Some debugging revealed that the flicker happens because the code to set the cursor runs at times before the webkit cursor cache is populated
with the new cursor image. As a result the cursor reverts back to the default pointer cursor for a brief moment, thus causing the flicker.

Ideas from Darin Fisher:- 

1. Webkit could use the previous cursor image while the new cursor is fetched.
2. Data urls could be processed synchronously.

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