[Webkit-unassigned] [Bug 101303] New: Fixed position elements that are out of view still end up forcing non-threaded scrolling

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=101303

           Summary: Fixed position elements that are out of view still end
                    up forcing non-threaded scrolling
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: bdakin at apple.com


http://trac.webkit.org/changeset/133536 made it so that pages with position:fixed elements can scroll on the scrolling thread. However, pages with out-of-viewport fixed position elements are still failing to scroll on the scrolling thread because we don't create layers for the out-of-view elements.

This issues is tracked by these tests:
platform/mac/tiled-drawing/fixed/fixed-position-out-of-view.html
platform/mac/tiled-drawing/fixed/fixed-position-out-of-view-negative-zindex.html

If you comment out these lines in RenderLayerCompositor::requiresCompositingForPosition(), then we do create the layers and the bug goes away:
    // Fixed position elements that are invisible in the current view don't get their own layer.
    FrameView* frameView = m_renderView->frameView();
    if (frameView && !layer->absoluteBoundingBox().intersects(IntRect(IntPoint(frameView->scrollOffsetForFixedPosition()), frameView->layoutSize())))
        return false;

-- 
Configure bugmail: https://bugs.webkit.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the assignee for the bug.