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auto merge of #1971 : Constellation/servo/quick-fail-selector-matching, r=SimonSapin

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Restart selector matching from an appropriate selector

Introducing 3 matching failure statuses,

+ NotMatchedGlobally
+ NotMatchedAndRestartFromClosestDescendant
+ NotMatchedAndRestartFromClosestLaterSibling

When NotMatchedGlobally appears, stop selector matching completely since
the succeeding selector never matches.
It is raised when
+ Child selector cannot find the candidate element
+ Descendant selector cannot find the candidate element

When NotMatchedAndRestartFromClosestDescendant appears, the selector
matching does backtracking and restarts from the closest Descendant
selector.
It is raised when
+ NextSibling selector cannot find the candidate element.
+ LaterSibling selector cannot find the candidate element.
+ Child selector doesn't match on the found element.

When NotMatchedAndRestartFromClosestLaterSibling appears, the selector
matching does backtracking and restarts from the closest LaterSibling
selector.
It is raised when
+ NextSibling selector doesn't match on the found element.

For example, when the selector "d1 d2 a" is provided and we cannot *find*
an appropriate ancestor node for "d1", this selector matching raises
NotMatchedGlobally since even if "d2" is moved to more upper node, the
candidates for "d1" becomes less than before and d1 .

The next example is siblings. When the selector "b1 + b2 ~ d1 a" is
providied and we cannot *find* an appropriate brother node for b1,
the selector matching raises NotMatchedAndRestartFromClosestDescendant.
The selectors ("b1 + b2 ~") doesn't match and matching restart from "d1".

The additional example is child and sibling. When the selector
"b1 + c1 > b2 ~ d1 a" is provided and the selector "b1" doesn't match on
the element, this "b1" raises NotMatchedAndRestartFromClosestLaterSibling.
However since the selector "c1" raises
NotMatchedAndRestartFromClosestDescendant. So the selector
"b1 + c1 > b2 ~ " doesn't match and restart matching from "d1".
This commit is contained in:
bors-servo 2014-04-04 11:19:36 -04:00
commit 7ece5f92db
1 changed files with 96 additions and 12 deletions
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108
src/components/style/selector_matching.rs
View file

@ -527,19 +527,80 @@ fn matches_compound_selector<E:TElement,
element: &N,
shareable: &mut bool)
-> bool {
match matches_compound_selector_internal(selector, element, shareable) {
Matched => true,
_ => false
}
}
/// A result of selector matching, includes 3 failure types,
///
/// NotMatchedAndRestartFromClosestLaterSibling
/// NotMatchedAndRestartFromClosestDescendant
/// NotMatchedGlobally
///
/// When NotMatchedGlobally appears, stop selector matching completely since
/// the succeeding selectors never matches.
/// It is raised when
/// Child combinator cannot find the candidate element.
/// Descendant combinator cannot find the candidate element.
///
/// When NotMatchedAndRestartFromClosestDescendant appears, the selector
/// matching does backtracking and restarts from the closest Descendant
/// combinator.
/// It is raised when
/// NextSibling combinator cannot find the candidate element.
/// LaterSibling combinator cannot find the candidate element.
/// Child combinator doesn't match on the found element.
///
/// When NotMatchedAndRestartFromClosestLaterSibling appears, the selector
/// matching does backtracking and restarts from the closest LaterSibling
/// combinator.
/// It is raised when
/// NextSibling combinator doesn't match on the found element.
///
/// For example, when the selector "d1 d2 a" is provided and we cannot *find*
/// an appropriate ancestor node for "d1", this selector matching raises
/// NotMatchedGlobally since even if "d2" is moved to more upper node, the
/// candidates for "d1" becomes less than before and d1 .
///
/// The next example is siblings. When the selector "b1 + b2 ~ d1 a" is
/// providied and we cannot *find* an appropriate brother node for b1,
/// the selector matching raises NotMatchedAndRestartFromClosestDescendant.
/// The selectors ("b1 + b2 ~") doesn't match and matching restart from "d1".
///
/// The additional example is child and sibling. When the selector
/// "b1 + c1 > b2 ~ d1 a" is provided and the selector "b1" doesn't match on
/// the element, this "b1" raises NotMatchedAndRestartFromClosestLaterSibling.
/// However since the selector "c1" raises
/// NotMatchedAndRestartFromClosestDescendant. So the selector
/// "b1 + c1 > b2 ~ " doesn't match and restart matching from "d1".
enum SelectorMatchingResult {
Matched,
NotMatchedAndRestartFromClosestLaterSibling,
NotMatchedAndRestartFromClosestDescendant,
NotMatchedGlobally,
}
fn matches_compound_selector_internal<E:TElement,
N:TNode<E>>(
selector: &CompoundSelector,
element: &N,
shareable: &mut bool)
-> SelectorMatchingResult {
if !selector.simple_selectors.iter().all(|simple_selector| {
matches_simple_selector(simple_selector, element, shareable)
}) {
return false
return NotMatchedAndRestartFromClosestLaterSibling
}
match selector.next {
None => true,
None => Matched,
Some((ref next_selector, combinator)) => {
let (siblings, just_one) = match combinator {
Child => (false, true),
Descendant => (false, false),
NextSibling => (true, true),
LaterSibling => (true, false),
let (siblings, candidate_not_found) = match combinator {
Child => (false, NotMatchedGlobally),
Descendant => (false, NotMatchedGlobally),
NextSibling => (true, NotMatchedAndRestartFromClosestDescendant),
LaterSibling => (true, NotMatchedAndRestartFromClosestDescendant),
};
let mut node = (*element).clone();
loop {
@ -549,14 +610,37 @@ fn matches_compound_selector<E:TElement,
node.parent_node()
};
match next_node {
None => return false,
None => return candidate_not_found,
Some(next_node) => node = next_node,
}
if node.is_element() {
if matches_compound_selector(&**next_selector, &node, shareable) {
return true
} else if just_one {
return false
let result = matches_compound_selector_internal(&**next_selector,
&node,
shareable);
match (result, combinator) {
// Return the status immediately.
(Matched, _) => return result,
(NotMatchedGlobally, _) => return result,
// Upgrade the failure status to
// NotMatchedAndRestartFromClosestDescendant.
(_, Child) => return NotMatchedAndRestartFromClosestDescendant,
// Return the status directly.
(_, NextSibling) => return result,
// If the failure status is NotMatchedAndRestartFromClosestDescendant
// and combinator is LaterSibling, give up this LaterSibling matching
// and restart from the closest descendant combinator.
(NotMatchedAndRestartFromClosestDescendant, LaterSibling) => return result,
// The Descendant combinator and the status is
// NotMatchedAndRestartFromClosestLaterSibling or
// NotMatchedAndRestartFromClosestDescendant,
// or the LaterSibling combinator and the status is
// NotMatchedAndRestartFromClosestDescendant
// can continue to matching on the next candidate element.
_ => {},
}
}
}