[Webkit-unassigned] [Bug 106841] [Compositor][Mac] Layers with preserve-3d should not intersect with layers without preserve-3d

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=106841





--- Comment #4 from Alexandru Chiculita <achicu at adobe.com>  2013-01-14 16:54:39 PST ---
It looks like two different bugs. That bug reproduces in both Chromium and Safari and is due to the fact that the parent 3d rendering context is determined using the GraphicsLayers tree instead of using the parent containing block. In that case, adding a simple transform on the "plane" elements looks like fixing the problem. Maybe for that one, the fix would be to force graphics layer creation for layers that have a different transform-style from their parents. 

This bug only reproduces in Safari.

Here are some links into the specification: http://www.w3.org/TR/css3-transforms/

> A 3D rendering context is established by a a transformable element whose computed value 
> for ‘transform-style’ is ‘preserve-3d’, and which itself is not part of a 3D rendering context.
> Note that such an element is always a containing block. An element that establishes a 3D
> rendering context also participates in that context.

So in this case the "preserve-3d" layer creates a 3d rendering context and participates in it. However, it should be a different 3d rendering context than the 3d rendering contexts that other sibling layers might create. In this case it looks like the first preserve-3d layer will propagate its own 3d redering context to the parent layer, so next layers will just inherit the same one. Most probably the fix would be to create another level of CALayers in the compositor for layers that have "preserve-3d" and create the 3d rendering context (not just propagate it), so that siblings are separated correctly.

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