Rework MediaQueryMatcher to batch up listener notification

Source/core/css/MediaQueryList.cpp

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Library General Public License for more details.
  *
  *  You should have received a copy of the GNU Library General Public License
  *  along with this library; see the file COPYING.LIB.  If not, write to
  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  *  Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/css/MediaQueryList.h"
 
 #include "core/css/MediaList.h"
 #include "core/css/MediaQueryEvaluator.h"
 #include "core/css/MediaQueryListListener.h"
 #include "core/css/MediaQueryMatcher.h"
 
 namespace WebCore {
 
-PassRefPtrWillBeRawPtr<MediaQueryList> MediaQueryList::create(PassRefPtrWillBeRawPtr<MediaQueryMatcher> vector, PassRefPtrWillBeRawPtr<MediaQuerySet> media, bool matches)
+PassRefPtrWillBeRawPtr<MediaQueryList> MediaQueryList::create(PassRefPtrWillBeRawPtr<MediaQueryMatcher> matcher, PassRefPtrWillBeRawPtr<MediaQuerySet> media)
 {
-    return adoptRefWillBeNoop(new MediaQueryList(vector, media, matches));
+    return adoptRefWillBeNoop(new MediaQueryList(matcher, media));
 }
 
-MediaQueryList::MediaQueryList(PassRefPtrWillBeRawPtr<MediaQueryMatcher> vector, PassRefPtrWillBeRawPtr<MediaQuerySet> media, bool matches)
-    : m_matcher(vector)
+MediaQueryList::MediaQueryList(PassRefPtrWillBeRawPtr<MediaQueryMatcher> matcher, PassRefPtrWillBeRawPtr<MediaQuerySet> media)
+    : m_matcher(matcher)
     , m_media(media)
-    , m_evaluationRound(m_matcher->evaluationRound())
-    , m_changeRound(m_evaluationRound - 1) // m_evaluationRound and m_changeRound initial values must be different.
-    , m_matches(matches)
+    , m_matchesDirty(true)
+    , m_matches(false)
 {
+    m_matcher->addMediaQueryList(this);
+    updateMatches();
 }
 
-DEFINE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(MediaQueryList)
+MediaQueryList::~MediaQueryList()
+{
+    // FIXME: Figure out how to deal with this in oilpan.

[Mads Ager (chromium), 2014/06/26 06:06:22]

Right, this will not work for the oilpan build since m_matcher can be dead in
the same GC cycle and could therefore already be destructed. If we cannot avoid
tie together the destruction and unregistration of the object we should use
Oilpan weakness.

In order to do that: guard this with #if !ENABLE(OILPAN) and update the
MediaQueryMatcher collection to use RawPtrWillBeWeakMember instead of
RawPtrWillBeMember. Then oilpan will remove the list from the collection when it
dies automatically.

[cbiesinger, 2014/06/26 20:27:59]

Done.

+    m_matcher->removeMediaQueryList(this);
+}
 
 String MediaQueryList::media() const
 {
     return m_media->mediaText();
 }
 
 void MediaQueryList::addListener(PassRefPtrWillBeRawPtr<MediaQueryListListener> listener)
 {
     if (!listener)
         return;
 
-    m_matcher->addListener(listener, this);
+    listener->setMediaQueryList(this);
+    m_listeners.add(listener);
 }
 
 void MediaQueryList::removeListener(PassRefPtrWillBeRawPtr<MediaQueryListListener> listener)
 {
     if (!listener)
         return;
 
-    m_matcher->removeListener(listener.get(), this);
+    RefPtrWillBeRawPtr<MediaQueryList> protect(this);
+    listener->clearMediaQueryList();
+
+    for (ListenerList::iterator i = m_listeners.begin(), end = m_listeners.end(); i != end; ++i) {
+        // We can't just use m_listeners.remove() here, because we get a new wrapper for the
+        // listener callback every time. We have to use MediaQueryListListener::operator==.
+        if (**i == *listener.get()) {
+            m_listeners.remove(i);
+            break;
+        }
+    }
 }
 
-bool MediaQueryList::evaluate(MediaQueryEvaluator* evaluator)
+void MediaQueryList::documentDetached()
 {
-    if (m_evaluationRound != m_matcher->evaluationRound() && evaluator)
-        setMatches(evaluator->eval(m_media.get()));
-    return m_changeRound == m_matcher->evaluationRound();
+    m_listeners.clear();
 }
 
-void MediaQueryList::setMatches(bool newValue)
+void MediaQueryList::mediaFeaturesChanged(WillBeHeapVector<RefPtrWillBeMember<MediaQueryListListener> >* toNotify)
 {
-    m_evaluationRound = m_matcher->evaluationRound();
+    m_matchesDirty = true;
+    if (updateMatches()) {

[esprehn, 2014/06/26 05:43:24]

early return.

if (!updateMatches())
  return;
for (...)
  toNotify->append(*i);

then you don't need any braces at all.

[cbiesinger, 2014/06/26 20:27:59]

Done.

+        for (ListenerList::const_iterator i = m_listeners.begin(), end = m_listeners.end(); i != end; ++i) {
+            toNotify->append(*i);
+        }
+    }
+}
 
-    if (newValue == m_matches)
-        return;
-
-    m_matches = newValue;
-    m_changeRound = m_evaluationRound;
+bool MediaQueryList::updateMatches()
+{
+    m_matchesDirty = false;
+    if (m_matches != m_matcher->evaluate(m_media.get())) {
+        m_matches = !m_matches;
+        return true;
+    }
+    return false;
 }
 
 bool MediaQueryList::matches()
 {
-    if (m_evaluationRound != m_matcher->evaluationRound())
-        setMatches(m_matcher->evaluate(m_media.get()));
+    updateMatches();
     return m_matches;
 }
 
 void MediaQueryList::trace(Visitor* visitor)
 {
     visitor->trace(m_matcher);
     visitor->trace(m_media);
+    visitor->trace(m_listeners);
 }
 
 }