[Webkit-unassigned] [Bug 65627] [CSSRegions]RenderFlowThread should display its content using RenderRegion

Thu Aug 4 10:31:18 PDT 2011

https://bugs.webkit.org/show_bug.cgi?id=65627

Chiculita Alexandru <achicu at adobe.com> changed:

           What    |Removed                     |Added
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                 CC|                            |achicu at adobe.com

--- Comment #4 from Chiculita Alexandru <achicu at adobe.com>  2011-08-04 10:31:18 PST ---
We had a lot of discussions today related to how to render the layers.

Similar to columns we wanted to layout with the RenderFlowThread, but this time paint needs to happen inside the RenderRegions. 

Currently the RenderFlowThread is not collecting its layers, because there was a need to hide them initially. The idea was that we could somehow collect all the layers to inside the RenderRegion that actually needed to paint them, so that painting goes as normal. It seems like the code is pretty tightly integrated with the parent() and the renderer()->parent(), so it would need a serious amount of change in order to support that. It would also mean that a simple layer position change would need to recalculate the parent region.

On the other hand we can revert the RenderFlowThread to collect its layers and do the painting only if the RenderRegion is requesting it. One big issue that is still valid is about the GPU composited layers. Those are automatically created and painted in a different software stack. On some platforms we would need to create multiple GPU layers for the same GraphicLayer. That's because it needs to render in multiple place at the same time.

About clipping. I'm not sure which is the best way to do this. My current idea on that is to render by only clipping between regions. For example if a box is positioned between two regions, a part of it will render in the first region and the other part in the second region. Nothing will be painted outside the regions. However, if it is placed with "left:-40px" for example, it will not be clipped on the left margin of the region and will also paint outside of it. 

I'm sure the spec should specify how positioned objects are placed inside the flow and how are transforms going to affect them. More interesting would be to know what happens with positioned elements that are bigger then a region.

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