[Webkit-unassigned] [Bug 61557] New: [REGRESSION] recalcStyle for display:inline to display:none transition has complexity N^2 where N is the number of child Text nodes.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=61557

           Summary: [REGRESSION] recalcStyle for display:inline to
                    display:none transition has complexity N^2 where N is
                    the number of child Text nodes.
           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: loislo at chromium.org
                CC: eric at webkit.org, hyatt at apple.com, mitz at webkit.org
            Blocks: 60959


Created an attachment (id=95037)
 --> (https://bugs.webkit.org/attachment.cgi?id=95037&action=review)
test. It adds 50 new text nodes and dumps time/(count^2) at each iteration

The regression was introduced at http://trac.webkit.org/changeset/84166

When I change display:inline to display:none then
1) Node::detach() will be called for each child node;
2) repaint will be called for each child node's renderer for invalidating the affected area;
3) RenderText::clippedOverflowRectForRepaint was changed in the patch. As result parent RenderInline renderer object will be returned instead of RenderBlock in the old code
4) RenderInline::culledInlineVisualOverflowBoundingBox of the parent node's renderer will be called for each child node
  but it has a cycle over all the child node's renderers
  RenderInline::culledInlineBoundingBox has the same cycle too.

1>    webkit.dll!WebCore::RenderInline::culledInlineBoundingBox(const WebCore::RenderInline * container=0x0d9ed9bc)  Line 782    C++
2     webkit.dll!WebCore::RenderInline::culledInlineVisualOverflowBoundingBox()  Line 890 + 0x10 bytes    C++
3     webkit.dll!WebCore::RenderInline::linesVisualOverflowBoundingBox()  Line 931 + 0xc bytes    C++
4     webkit.dll!WebCore::RenderInline::clippedOverflowRectForRepaint(WebCore::RenderBoxModelObject * repaintContainer=0x00000000)  Line 967    C++
5     webkit.dll!WebCore::RenderText::clippedOverflowRectForRepaint(WebCore::RenderBoxModelObject * repaintContainer=0x00000000)  Line 1357 + 0x1a bytes    C++
6     webkit.dll!WebCore::RenderObject::repaint(bool immediate=false)  Line 1208 + 0x32 bytes    C++
7     webkit.dll!WebCore::RenderObjectChildList::removeChildNode(WebCore::RenderObject * owner=0x0d9ed9bc, WebCore::RenderObject * oldChild=0x0da64c3c, bool fullRemove=true)  Line 80    C++
8     webkit.dll!WebCore::RenderObject::removeChild(WebCore::RenderObject * oldChild=0x0da64c3c)  Line 334    C++
9     webkit.dll!WebCore::RenderObject::remove()  Line 764 + 0x42 bytes    C++
10     webkit.dll!WebCore::RenderObject::destroy()  Line 2070    C++
11     webkit.dll!WebCore::RenderText::destroy()  Line 201    C++
12     webkit.dll!WebCore::Node::detach()  Line 1367 + 0x1d bytes    C++
13     webkit.dll!WebCore::ContainerNode::detach()  Line 761 + 0x12 bytes    C++
14     webkit.dll!WebCore::Element::detach()  Line 1026    C++
15     webkit.dll!WebCore::Element::recalcStyle(WebCore::Node::StyleChange change=NoChange)  Line 1090 + 0x12 bytes    C++


Should I just revert it or add something like 

while (container->isRenderInline() && container->parent())
    container = container->parent();

into RenderText::clippedOverflowRectForRepaint

Another idea with caching the rect looks much more complex.

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