[Webkit-unassigned] [Bug 39123] New: Unneeded fillRect call in RenderBoxModelObject::paintFillLayerExtended

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=39123

           Summary: Unneeded fillRect call in
                    RenderBoxModelObject::paintFillLayerExtended
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: Enhancement
          Priority: P4
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: pgalizia at codeaurora.org


For SVN version 59242 of RenderBoxModelObject (and earlier):

In the RenderBoxModelObject::paintFillLayerExtended method, there's a call to fillRect for the baseColor (line 587), then another one a few lines later for bgColor (line 594).  If the alpha of the bgColor is set to the max value (i.e., no blending), then the first fillRect for baseColor should be unnecessary.

Example: starting at line 581:
#####################################
        // If we have an alpha and we are painting the root element, go ahead and blend with the base background color.
        if (isOpaqueRoot) {
            Color baseColor = view()->frameView()->baseBackgroundColor();
            if (baseColor.alpha() > 0) {
                context->save();
                context->setCompositeOperation(CompositeCopy);
                context->fillRect(rect, baseColor, style()->colorSpace()); // Can we check here for bgColor's alpha, and drop the draw if 0xff?
                context->restore();
            } else
                context->clearRect(rect);
        }

        if (bgColor.isValid() && bgColor.alpha() > 0)
            context->fillRect(rect, bgColor, style()->colorSpace());  /// If this has alpha 0xff, for example, that should make the above
#####################################                  


We do have a proposed patch for that, which will be attached shortly.

Found on an ARM-based system, but should be applicable across all platforms.

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