Add EventHandlerRegistry

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 
 #include "core/page/scrolling/ScrollingCoordinator.h"
 
 #include "RuntimeEnabledFeatures.h"
 #include "core/dom/Document.h"
+#include "core/dom/EventHandlerRegistry.h"
 #include "core/dom/Node.h"
-#include "core/dom/WheelController.h"
 #include "core/html/HTMLElement.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/page/Page.h"
 #include "core/frame/Settings.h"
 #include "platform/TraceEvent.h"
 #include "platform/exported/WebScrollbarImpl.h"
 #include "platform/exported/WebScrollbarThemeGeometryNative.h"
 #include "platform/geometry/Region.h"
 #include "platform/geometry/TransformState.h"
@@ skipping 572 matching lines @@
 {
     m_layersWithTouchRects.remove(layer);
 }
 
 void ScrollingCoordinator::setWheelEventHandlerCount(unsigned count)
 {
     if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling()))
         scrollLayer->setHaveWheelEventHandlers(count > 0);
 }
 
+void ScrollingCoordinator::setScrollEventHandlerCount(unsigned count)
+{
+    if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling()))
+        scrollLayer->setHaveScrollEventHandlers(count > 0);
+}
+
 void ScrollingCoordinator::recomputeWheelEventHandlerCountForFrameView(FrameView*)
 {
     setWheelEventHandlerCount(computeCurrentWheelEventHandlerCount());
 }
 
+void ScrollingCoordinator::recomputeScrollEventHandlerCountForFrameView(FrameView*)

[Rick Byers, 2014/03/24 14:27:59]

What you're doing here seems conceptually similar to the code in
Document::didAdd/Remove/ClearTouchEventHandler that calls
frameHost->chrome().client().needTouchEvents(true/false) whenever we transition
between no handlers and some handlers.  Can we generalize that somehow?

One option is having the EventHandlerRegistry chain between documents the way
the touch handler stuff does today (so any number of handlers in a child
document count as one handler in the parent) and then expose an API for when it
changes.

Alternately, if it's simpler I'm not opposed to walking the frame tree to
compute this when needed (should always be cheap), but then we should probably
do the same for the touch handlers.

One thing you may want to think about is the impact on out-of-process iframes /
site-isolation.  I haven't figured out yet how the touch handler tracking needs
to change for site-isolation, but if you're refactoring all this then it
probably makes sense to have some idea for how it'll eventually handle site
isolation.  I'm guessing having an outside process compute the document-wide
view will fit much better with the site-isolation model.

+{
+    setScrollEventHandlerCount(computeCurrentScrollEventHandlerCount());
+}
+
 void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons reasons)
 {
     if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling())) {
         m_lastMainThreadScrollingReasons = reasons;
         scrollLayer->setShouldScrollOnMainThread(reasons);
     }
 }
 
 void ScrollingCoordinator::pageDestroyed()
 {
@@ skipping 143 matching lines @@
 
     accumulateDocumentTouchEventTargetRects(rects, document);
 }
 
 unsigned ScrollingCoordinator::computeCurrentWheelEventHandlerCount()
 {
     unsigned wheelEventHandlerCount = 0;
 
     for (LocalFrame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
         if (frame->document())
-            wheelEventHandlerCount += WheelController::from(*frame->document())->wheelEventHandlerCount();
+            wheelEventHandlerCount += EventHandlerRegistry::from(*frame->document())->wheelEventHandlerCount();
     }
 
     return wheelEventHandlerCount;
 }
 
+unsigned ScrollingCoordinator::computeCurrentScrollEventHandlerCount()
+{
+    unsigned scrollEventHandlerCount = 0;
+
+    for (LocalFrame* frame = m_page->mainFrame(); frame; frame = frame->tree().traverseNext()) {
+        if (frame->document())
+            scrollEventHandlerCount += EventHandlerRegistry::from(*frame->document())->scrollEventHandlerCount();
+    }
+
+    return scrollEventHandlerCount;
+}
+
 void ScrollingCoordinator::frameViewWheelEventHandlerCountChanged(FrameView* frameView)
 {
     ASSERT(isMainThread());
     ASSERT(m_page);
 
     recomputeWheelEventHandlerCountForFrameView(frameView);
 }
 
+void ScrollingCoordinator::frameViewScrollEventHandlerCountChanged(FrameView* frameView)
+{
+    ASSERT(isMainThread());
+    ASSERT(m_page);
+
+    recomputeScrollEventHandlerCountForFrameView(frameView);
+}
+
 void ScrollingCoordinator::frameViewHasSlowRepaintObjectsDidChange(FrameView* frameView)
 {
     ASSERT(isMainThread());
     ASSERT(m_page);
 
     if (!coordinatesScrollingForFrameView(frameView))
         return;
 
     m_shouldScrollOnMainThreadDirty = true;
 }
@@ skipping 30 matching lines @@
 void ScrollingCoordinator::frameViewRootLayerDidChange(FrameView* frameView)
 {
     ASSERT(isMainThread());
     ASSERT(m_page);
 
     if (!coordinatesScrollingForFrameView(frameView))
         return;
 
     notifyLayoutUpdated();
     recomputeWheelEventHandlerCountForFrameView(frameView);
+    recomputeScrollEventHandlerCountForFrameView(frameView);
 }
 
 #if OS(MACOSX)
 void ScrollingCoordinator::handleWheelEventPhase(PlatformWheelEventPhase phase)
 {
     ASSERT(isMainThread());
 
     if (!m_page)
         return;
 
@@ skipping 75 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : 0)
         return blink::WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace WebCore