[Webkit-unassigned] [Bug 258351] New: [LBSE] Erroneous/unncessary repainting when viewBox is used on <svg> elements

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=258351

            Bug ID: 258351
           Summary: [LBSE] Erroneous/unncessary repainting when viewBox is
                    used on <svg> elements
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: SVG
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: zimmermann at kde.org
                CC: sabouhallawa at apple.com, zimmermann at kde.org

Created attachment 466775

  --> https://bugs.webkit.org/attachment.cgi?id=466775&action=review

Slow SVG

This used to work in the downstream PoC - but since the implementations are way different nowadays, we need to re-investigate.
Currently when viewBox is enabled, the accelerated transform animation performance is artifically lower, since there are unnecessary repaints triggered, but not when viewBoxis omitted -- one sees only compositing steps, no painting (no increase of layer repaint counters, etc)

Testcase (fast w/o viewBox, try enabling viewBox).
<?xml version="1.0" encoding="utf-8"?>
<svg xmlns="http://www.w3.org/2000/svg" fooviewBox="0 0 800 600" width="100%" height="100%">
<style type="text/css">
path#demoScene1 {
    transform-origin: 50% 50%;
    animation: rotateAroundCenterAnimationFrames 2s linear 0s infinite;
}

@keyframes rotateAroundCenterAnimationFrames {
    0% { transform: rotate(0deg); }
   50% { transform: rotate(180deg); }
  100% { transform: rotate(359deg); }
}
</style>
<path id="demoScene1" d="m233.58,47.875c0,7.476-2.158,8.743-8.992,8.743-6.972,0-9.123-1.268-9.123-8.743,0-6.714,2.151-7.723,9.123-7.723,6.834,0.001,8.992,1.01,8.992,7.723zm-1.27,65.47c0,9.976,4.809,15.219,4.809,15.219s-6.383,5.037-11.303,5.037c-6.464,0-9.215-11.614-9.215-16.417v-50.182h15.709v46.343z"/>
</svg>

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