[Webkit-unassigned] [Bug 88386] New: shouldSuppressPaintingLayer shouldn't be called on every RenderLayers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=88386

           Summary: shouldSuppressPaintingLayer shouldn't be called on
                    every RenderLayers
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jchaffraix at webkit.org
                CC: simon.fraser at apple.com, jamesr at chromium.org


After doing some archeology (see r16129), the code is used to avoid FOUCs by preventing paints to propagate to child RenderLayers (meaning that there will be a flash to white instead). It was later extended to allow for paints suppression. All the conditions that the function checks are tied to the document - the exception being that it checks for child layer - which means that instead of having a fixed cost per paint phase, it's a cost per RenderLayer::paintLayer. On http://dglazkov.github.com/performance-tests/biggrid.html, this is an ~8 - 10% cost as we need to do a lot of paintLayer calls.

At the time the function was introduced, it's unclear if the painting went through a single point as it does now but we can easily move the code to the FrameView now.

Patch forthcoming.

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