[Webkit-unassigned] [Bug 57269] New: REGRESSION (r82151): Every WKView paint now makes an extra copy of the painted bits

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=57269

           Summary: REGRESSION (r82151): Every WKView paint now makes an
                    extra copy of the painted bits
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Windows 7
            Status: NEW
          Keywords: NeedsRadar, PlatformOnly, Regression
          Severity: Normal
          Priority: P2
         Component: Platform
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: aroben at apple.com
                CC: andersca at apple.com, sam at webkit.org


r82151 changed ShareableBitmap::paint to use CGBitmapContextCreateImage in its implementation, rather than creating an image using a custom data provider. On Mac, CGBitmapContextCreateImage uses a copy-on-write implementation, but on Windows it just copies the data. This means that we're now making an extra copy of every pixel that we paint into a WKView.

This is likely a performance regression, though that has not been confirmed.

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