[Webkit-unassigned] [Bug 43809] New: Degraded performance updating <tspan> due to excessive repaint

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=43809

           Summary: Degraded performance updating <tspan> due to excessive
                    repaint
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh Intel
        OS/Version: Mac OS X 10.6
            Status: UNCONFIRMED
          Severity: Enhancement
          Priority: P2
         Component: SVG
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: tonysung at asia.apple.com
                CC: zimmermann at kde.org


Open the attached test case, which by default shows 60 lines of text and which the first line of text is updated continuously with a setTimeout(func, 0) call.

There're 3 cases, where the DOM structures are all the same but having the first 2, 60, or 200 <tspan> visible. In the test cases all except the first <tspan> is static.

Compare the frame rates of the 3 cases with the help of QuartzDebug. The more number of visible <tspan> we have, the slower the frame rate it is, even though we're changing only one of the <tspan> in all 3 cases.

Enabling "Flash Screen Updates" in QuartzDebug suggests that the browser is repainting all <tspan> including those which haven't been changed.

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