Bug 117074 – [CSS Regions] REGRESSION Incorrect layer clipping inside flow thread

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Andrei Bucur]

Created attachment 203444 [details]
Test case

fast/regions/overflow-size-change-with-stacking-context.html is failing for some time.

[Mihnea Ovidenie]

It fails from https://bugs.webkit.org/show_bug.cgi?id=76486 because the clip rects get transformed in RenderView coordinates - through associated render regions - while the layer bounds are still in flow thread coordinates (the flow thread is the root layer). Because of that, the intersection between the layer bounds and the clip rects fails and the layer is not displayed.

[Mihnea Ovidenie]

Created attachment 203697 [details]
Patch

[Dave Hyatt]

Comment on attachment 203697 [details]
Patch

r=me

[Mihnea Ovidenie]

Created attachment 203765 [details]
Patch for landing

[WebKit Commit Bot]

Comment on attachment 203765 [details]
Patch for landing

Clearing flags on attachment: 203765

Committed r151202: <http://trac.webkit.org/changeset/151202>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Alexandru Chiculita]

(In reply to comment #6)
> All reviewed patches have been landed.  Closing bug.

It's better if you just moved this functionality to
RenderFlowThread::mapLocalToContainer. 

That's for two reasons: 
1) the RenderFlowThread check will only be hit when there's a RenderFlowThread object
on the chain. 
2) other non-RenderBox objects will benefit from that change.

void RenderFlowThread::mapLocalToContainer(const RenderLayerModelObject*
repaintContainer, TransformState& transformState, MapCoordinatesFlags mode,
bool* wasFixed) const
{
    if (repaintContainer == this)
        return;

    // Transform from render flow coordinates into region coordinates.
    if (RenderRegion* region = mapFromFlowToRegion(transformState))
       
static_cast<RenderObject*>(region)->mapLocalToContainer(region->containerForRepaint(),
transformState, mode, wasFixed);
}

[Mihnea Ovidenie]

(In reply to comment #7)
> (In reply to comment #6)
> > All reviewed patches have been landed.  Closing bug.
> 
> It's better if you just moved this functionality to
> RenderFlowThread::mapLocalToContainer. 
> 
> That's for two reasons: 
> 1) the RenderFlowThread check will only be hit when there's a RenderFlowThread object
> on the chain. 
> 2) other non-RenderBox objects will benefit from that change.
> 
> void RenderFlowThread::mapLocalToContainer(const RenderLayerModelObject*
> repaintContainer, TransformState& transformState, MapCoordinatesFlags mode,
> bool* wasFixed) const
> {
>     if (repaintContainer == this)
>         return;
> 
>     // Transform from render flow coordinates into region coordinates.
>     if (RenderRegion* region = mapFromFlowToRegion(transformState))
> 
> static_cast<RenderObject*>(region)->mapLocalToContainer(region->containerForRepaint(),
> transformState, mode, wasFixed);
> }

Ok, i will fix in https://bugs.webkit.org/show_bug.cgi?id=117290

[Mihai Maerean]

> void RenderFlowThread::mapLocalToContainer(const RenderLayerModelObject* repaintContainer, TransformState& transformState, MapCoordinatesFlags mode, bool* wasFixed) const
> if (RenderRegion* region = mapFromFlowToRegion(transformState))
> static_cast<RenderObject*>(region)->mapLocalToContainer(region->containerForRepaint(),  transformState, mode, wasFixed);

You need to either make RenderRegion::mapLocalToContainer public or make RenderFlowThread a friend class RenderRegion in order to call mapLocalToContainer from RenderFlowThread (instead of using static_cast to RenderObject).