[Webkit-unassigned] [Bug 133359] [CSS Grid Layout] Upgrade align-self and align-items parsing to CSS 3

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=133359


Javier Fernandez <jfernandez at igalia.com> changed:

           What    |Removed                     |Added
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                 CC|                            |hyatt at apple.com




--- Comment #23 from Javier Fernandez <jfernandez at igalia.com>  2014-07-31 17:15:27 PST ---
It seems that my approach of resolving the "auto" values during the CSS Cascade have some limitations, which caused some mathhml layout tests to fail.

This is the Box Aligment specification I'm following in my mplementation:

  - http://dev.w3.org/csswg/css-align-3/

The root cause of these failires is that mathml layout code changes the value of the alignItems property on several renders. I expected that to force a style recalculation, as it happens when properties are changed through javascript. This is controlled by the WebCore::Style::determineChange, which now it forces a Dettach whenever the change affects to the alignItems property.

The intention of my patch was to avoid logic duplication of this "auto" resolution, since both grid an flex share the same logic. Also, the CSScomputedStyleDeclaration needs to implement exactly the same logic. Besides, now, according to the last specs, the default value of all the properties is "auto", so when resolving the "alignSelf", it's not enough to refer to the parent's alignItem; this has to be resolved too.

To complicate things even more,  there is now a "legacy"  keyword that forces the "justifyItems" property to be inherited by all the descendants. All this logic seems to be naturally implemented in the css cascade, which also would simplify the resolution implemented by the renders. 

However, there are several issues on this approach; first of all, the anonymous renderers are not part of the css cascade resolution. Also, several renders derive from RenderFelxibleBoxm but they don't specify the appropriated display value, which is what the css cascade use to discriminate between different elements. Finally, changes in the alignItem performed in the layout phase should trigger, somehow, a style recalc at least in the subtree.

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