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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/176864">176864</a></dd>
<dt>Author</dt> <dd>benjamin@webkit.org</dd>
<dt>Date</dt> <dd>2014-12-05 12:58:08 -0800 (Fri, 05 Dec 2014)</dd>
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<h3>Log Message</h3>
<pre>Fix style sharing with the "type" and "readonly" attributes
https://bugs.webkit.org/show_bug.cgi?id=139283
Patch by Benjamin Poulain <bpoulain@apple.com> on 2014-12-05
Reviewed by Antti Koivisto.
Source/WebCore:
There are two bugs adressed with this patch:
1) The attributes "type" and "readonly" where only handled correctly
for input elements. For everything else, they could incorrectly
be ignored for style sharing.
2) The handling of attributes was incorrect for selector lists, leading
to various bugs (incorrect style sharing in some cases, disabling
style sharing on valid cases).
For [1], the problem was that attribute checking had been limited to
StyleResolver::canShareStyleWithControl(). That function is for handling
the special states of input element. For any other element, the attributes
were simply ignored.
For [2], there were a bunch of small problems. First, containsUncommonAttributeSelector()
was not recursive, which caused it to ignored any nested selector list. This used to be
correct but since we have advanced selectors we can no longer assumed selectors are not nested.
A second issue was that any attribute in a selector list was causing us to fall back
to the slow case. Now that we have the fast :matches(), we really don't want that.
The function containsUncommonAttributeSelector() was transformed into a recursive function
tracking where we are in the selector.
At the entry point, we start with the flag "startsOnRightmostElement" set to true. The flag is then
updated on the stack of each recursive call.
For example, "webkit > is:matches(freaking > awesome)". We evalute "is" with the flag to true, then recurse
into evaluating "freaking > awesome" with the flag still set to true. When we evalute ">", the flag
is set to false to evaluate any following selectors.
After evaluating "freaking > awesome", we go back to our previous stack frame, and the flag
is back to true and we can continue evaluating with the curren top level state.