Source/core/page/scrolling/ScrollingCoordinator.cpp

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This source file includes following definitions.
toWebLayer
create
m_lastMainThreadScrollingReasons
touchHitTestingEnabled
setShouldHandleScrollGestureOnMainThreadRegion
notifyLayoutUpdated
updateAfterCompositingChange
setLayerIsContainerForFixedPositionLayers
clearPositionConstraintExceptForLayer
computePositionConstraint
updateLayerPositionConstraint
willDestroyScrollableArea
removeWebScrollbarLayer
createScrollbarLayer
createSolidColorScrollbarLayer
detachScrollbarLayer
setupScrollbarLayer
addWebScrollbarLayer
getWebScrollbarLayer
scrollableAreaScrollbarLayerDidChange
scrollableAreaScrollLayerDidChange
makeLayerChildFrameMap
convertLayerRectsToEnclosingCompositedLayerRecursive
convertLayerRectsToEnclosingCompositedLayer
updateTouchEventTargetRectsIfNeeded
reset
setTouchEventTargetRects
touchEventTargetRectsDidChange
updateScrollParentForGraphicsLayer
updateClipParentForGraphicsLayer
willDestroyRenderLayer
setWheelEventHandlerCount
recomputeWheelEventHandlerCountForFrameView
setShouldUpdateScrollLayerPositionOnMainThread
pageDestroyed
coordinatesScrollingForFrameView
computeShouldHandleScrollGestureOnMainThreadRegion
accumulateDocumentTouchEventTargetRects
computeTouchEventTargetRects
computeCurrentWheelEventHandlerCount
frameViewWheelEventHandlerCountChanged
frameViewHasSlowRepaintObjectsDidChange
frameViewFixedObjectsDidChange
isForMainFrame
scrollLayerForFrameView
counterScrollingLayerForFrameView
frameViewRootLayerDidChange
handleWheelEventPhase
hasVisibleSlowRepaintViewportConstrainedObjects
mainThreadScrollingReasons
mainThreadScrollingReasonsAsText
mainThreadScrollingReasonsAsText
frameViewIsDirty
/*
 * 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
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * 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/FullscreenElementStack.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/frame/Settings.h"
#include "core/page/Page.h"
#include "core/plugins/PluginView.h"
#include "core/rendering/RenderGeometryMap.h"
#include "core/rendering/RenderView.h"
#include "core/rendering/compositing/CompositedLayerMapping.h"
#include "core/rendering/compositing/RenderLayerCompositor.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"
#include "platform/graphics/GraphicsLayer.h"
#if OS(MACOSX)
#include "platform/mac/ScrollAnimatorMac.h"
#endif
#include "platform/scroll/ScrollAnimator.h"
#include "platform/scroll/ScrollbarTheme.h"
#include "public/platform/Platform.h"
#include "public/platform/WebCompositorSupport.h"
#include "public/platform/WebLayerPositionConstraint.h"
#include "public/platform/WebScrollbarLayer.h"
#include "public/platform/WebScrollbarThemeGeometry.h"
#include "public/platform/WebScrollbarThemePainter.h"
#include "wtf/text/StringBuilder.h"

using blink::WebLayer;
using blink::WebLayerPositionConstraint;
using blink::WebRect;
using blink::WebScrollbarLayer;
using blink::WebVector;

namespace {

WebLayer* toWebLayer(WebCore::GraphicsLayer* layer)
{
    return layer ? layer->platformLayer() : 0;
}

} // namespace

namespace WebCore {

PassOwnPtr<ScrollingCoordinator> ScrollingCoordinator::create(Page* page)
{
    return adoptPtr(new ScrollingCoordinator(page));
}

ScrollingCoordinator::ScrollingCoordinator(Page* page)
    : m_page(page)
    , m_scrollGestureRegionIsDirty(false)
    , m_touchEventTargetRectsAreDirty(false)
    , m_shouldScrollOnMainThreadDirty(false)
    , m_wasFrameScrollable(false)
    , m_lastMainThreadScrollingReasons(0)
{
}

ScrollingCoordinator::~ScrollingCoordinator()
{
    ASSERT(!m_page);
    for (ScrollbarMap::iterator it = m_horizontalScrollbars.begin(); it != m_horizontalScrollbars.end(); ++it)
        GraphicsLayer::unregisterContentsLayer(it->value->layer());
    for (ScrollbarMap::iterator it = m_verticalScrollbars.begin(); it != m_verticalScrollbars.end(); ++it)
        GraphicsLayer::unregisterContentsLayer(it->value->layer());

}

bool ScrollingCoordinator::touchHitTestingEnabled() const
{
    RenderView* contentRenderer = m_page->mainFrame()->contentRenderer();
    Settings* settings = m_page->mainFrame()->document()->settings();
    return RuntimeEnabledFeatures::touchEnabled() && settings->compositorTouchHitTesting() && contentRenderer && contentRenderer->usesCompositing();
}

void ScrollingCoordinator::setShouldHandleScrollGestureOnMainThreadRegion(const Region& region)
{
    if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling())) {
        Vector<IntRect> rects = region.rects();
        WebVector<WebRect> webRects(rects.size());
        for (size_t i = 0; i < rects.size(); ++i)
            webRects[i] = rects[i];
        scrollLayer->setNonFastScrollableRegion(webRects);
    }
}

void ScrollingCoordinator::notifyLayoutUpdated()
{
    m_scrollGestureRegionIsDirty = true;
    m_touchEventTargetRectsAreDirty = true;
    m_shouldScrollOnMainThreadDirty = true;
}

void ScrollingCoordinator::updateAfterCompositingChange()
{
    TRACE_EVENT0("input", "ScrollingCoordinator::updateAfterCompositingChange");

    if (m_scrollGestureRegionIsDirty) {
        // Compute the region of the page where we can't handle scroll gestures and mousewheel events
        // on the impl thread. This currently includes:
        // 1. All scrollable areas, such as subframes, overflow divs and list boxes, whose composited
        // scrolling are not enabled. We need to do this even if the frame view whose layout was updated
        // is not the main frame.
        // 2. Resize control areas, e.g. the small rect at the right bottom of div/textarea/iframe when
        // CSS property "resize" is enabled.
        // 3. Plugin areas.
        Region shouldHandleScrollGestureOnMainThreadRegion = computeShouldHandleScrollGestureOnMainThreadRegion(m_page->mainFrame(), IntPoint());
        setShouldHandleScrollGestureOnMainThreadRegion(shouldHandleScrollGestureOnMainThreadRegion);
        m_scrollGestureRegionIsDirty = false;
    }

    if (m_touchEventTargetRectsAreDirty) {
        updateTouchEventTargetRectsIfNeeded();
        m_touchEventTargetRectsAreDirty = false;
    }

    FrameView* frameView = m_page->mainFrame()->view();
    bool frameIsScrollable = frameView && frameView->isScrollable();
    if (m_shouldScrollOnMainThreadDirty || m_wasFrameScrollable != frameIsScrollable) {
        setShouldUpdateScrollLayerPositionOnMainThread(mainThreadScrollingReasons());
        m_shouldScrollOnMainThreadDirty = false;
    }
    m_wasFrameScrollable = frameIsScrollable;

    // The mainFrame view doesn't get included in the FrameTree below, so we
    // update its size separately.
    if (WebLayer* scrollingWebLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : 0) {
        scrollingWebLayer->setBounds(frameView->contentsSize());
        // If there is a fullscreen element, set the scroll clip layer to 0 so main frame won't scroll.
        Element* fullscreenElement = FullscreenElementStack::fullscreenElementFrom(*(m_page->mainFrame()->document()));
        if (fullscreenElement)
            scrollingWebLayer->setScrollClipLayer(0);
        else
            scrollingWebLayer->setScrollClipLayer(toWebLayer(frameView->layerForContainer()));
    }

    const FrameTree& tree = m_page->mainFrame()->tree();
    for (const LocalFrame* child = tree.firstChild(); child; child = child->tree().nextSibling()) {
        if (WebLayer* scrollLayer = toWebLayer(child->view()->layerForScrolling()))
            scrollLayer->setBounds(child->view()->contentsSize());
    }
}

void ScrollingCoordinator::setLayerIsContainerForFixedPositionLayers(GraphicsLayer* layer, bool enable)
{
    if (WebLayer* scrollableLayer = toWebLayer(layer))
        scrollableLayer->setIsContainerForFixedPositionLayers(enable);
}

static void clearPositionConstraintExceptForLayer(GraphicsLayer* layer, GraphicsLayer* except)
{
    if (layer && layer != except && toWebLayer(layer))
        toWebLayer(layer)->setPositionConstraint(WebLayerPositionConstraint());
}

static WebLayerPositionConstraint computePositionConstraint(const RenderLayer* layer)
{
    ASSERT(layer->hasCompositedLayerMapping());
    do {
        if (layer->renderer()->style()->position() == FixedPosition) {
            const RenderObject* fixedPositionObject = layer->renderer();
            bool fixedToRight = !fixedPositionObject->style()->right().isAuto();
            bool fixedToBottom = !fixedPositionObject->style()->bottom().isAuto();
            return WebLayerPositionConstraint::fixedPosition(fixedToRight, fixedToBottom);
        }

        layer = layer->parent();

        // Composited layers that inherit a fixed position state will be positioned with respect to the nearest compositedLayerMapping's GraphicsLayer.
        // So, once we find a layer that has its own compositedLayerMapping, we can stop searching for a fixed position RenderObject.
    } while (layer && !layer->hasCompositedLayerMapping());
    return WebLayerPositionConstraint();
}

void ScrollingCoordinator::updateLayerPositionConstraint(RenderLayer* layer)
{
    ASSERT(layer->hasCompositedLayerMapping());
    CompositedLayerMappingPtr compositedLayerMapping = layer->compositedLayerMapping();
    GraphicsLayer* mainLayer = compositedLayerMapping->localRootForOwningLayer();

    // Avoid unnecessary commits
    clearPositionConstraintExceptForLayer(compositedLayerMapping->ancestorClippingLayer(), mainLayer);
    clearPositionConstraintExceptForLayer(compositedLayerMapping->mainGraphicsLayer(), mainLayer);

    if (WebLayer* scrollableLayer = toWebLayer(mainLayer))
        scrollableLayer->setPositionConstraint(computePositionConstraint(layer));
}

void ScrollingCoordinator::willDestroyScrollableArea(ScrollableArea* scrollableArea)
{
    removeWebScrollbarLayer(scrollableArea, HorizontalScrollbar);
    removeWebScrollbarLayer(scrollableArea, VerticalScrollbar);
}

void ScrollingCoordinator::removeWebScrollbarLayer(ScrollableArea* scrollableArea, ScrollbarOrientation orientation)
{
    ScrollbarMap& scrollbars = orientation == HorizontalScrollbar ? m_horizontalScrollbars : m_verticalScrollbars;
    if (OwnPtr<WebScrollbarLayer> scrollbarLayer = scrollbars.take(scrollableArea))
        GraphicsLayer::unregisterContentsLayer(scrollbarLayer->layer());
}

static PassOwnPtr<WebScrollbarLayer> createScrollbarLayer(Scrollbar* scrollbar)
{
    ScrollbarTheme* theme = scrollbar->theme();
    blink::WebScrollbarThemePainter painter(theme, scrollbar);
    OwnPtr<blink::WebScrollbarThemeGeometry> geometry(blink::WebScrollbarThemeGeometryNative::create(theme));

    OwnPtr<WebScrollbarLayer> scrollbarLayer = adoptPtr(blink::Platform::current()->compositorSupport()->createScrollbarLayer(new blink::WebScrollbarImpl(scrollbar), painter, geometry.leakPtr()));
    GraphicsLayer::registerContentsLayer(scrollbarLayer->layer());
    return scrollbarLayer.release();
}

PassOwnPtr<WebScrollbarLayer> ScrollingCoordinator::createSolidColorScrollbarLayer(ScrollbarOrientation orientation, int thumbThickness, bool isLeftSideVerticalScrollbar)
{
    blink::WebScrollbar::Orientation webOrientation = (orientation == HorizontalScrollbar) ? blink::WebScrollbar::Horizontal : blink::WebScrollbar::Vertical;
    OwnPtr<WebScrollbarLayer> scrollbarLayer = adoptPtr(blink::Platform::current()->compositorSupport()->createSolidColorScrollbarLayer(webOrientation, thumbThickness, isLeftSideVerticalScrollbar));
    GraphicsLayer::registerContentsLayer(scrollbarLayer->layer());
    return scrollbarLayer.release();
}

static void detachScrollbarLayer(GraphicsLayer* scrollbarGraphicsLayer)
{
    ASSERT(scrollbarGraphicsLayer);

    scrollbarGraphicsLayer->setContentsToPlatformLayer(0);
    scrollbarGraphicsLayer->setDrawsContent(true);
}

static void setupScrollbarLayer(GraphicsLayer* scrollbarGraphicsLayer, WebScrollbarLayer* scrollbarLayer, WebLayer* scrollLayer, WebLayer* containerLayer)
{
    ASSERT(scrollbarGraphicsLayer);
    ASSERT(scrollbarLayer);

    if (!scrollLayer) {
        detachScrollbarLayer(scrollbarGraphicsLayer);
        return;
    }
    scrollbarLayer->setScrollLayer(scrollLayer);
    scrollbarLayer->setClipLayer(containerLayer);
    scrollbarGraphicsLayer->setContentsToPlatformLayer(scrollbarLayer->layer());
    scrollbarGraphicsLayer->setDrawsContent(false);
}

WebScrollbarLayer* ScrollingCoordinator::addWebScrollbarLayer(ScrollableArea* scrollableArea, ScrollbarOrientation orientation, PassOwnPtr<blink::WebScrollbarLayer> scrollbarLayer)
{
    ScrollbarMap& scrollbars = orientation == HorizontalScrollbar ? m_horizontalScrollbars : m_verticalScrollbars;
    return scrollbars.add(scrollableArea, scrollbarLayer).storedValue->value.get();
}

WebScrollbarLayer* ScrollingCoordinator::getWebScrollbarLayer(ScrollableArea* scrollableArea, ScrollbarOrientation orientation)
{
    ScrollbarMap& scrollbars = orientation == HorizontalScrollbar ? m_horizontalScrollbars : m_verticalScrollbars;
    return scrollbars.get(scrollableArea);
}

void ScrollingCoordinator::scrollableAreaScrollbarLayerDidChange(ScrollableArea* scrollableArea, ScrollbarOrientation orientation)
{
// FIXME: Instead of hardcode here, we should make a setting flag.
#if OS(MACOSX)
    static const bool platformSupportsCoordinatedScrollbar = ScrollAnimatorMac::canUseCoordinatedScrollbar();
    static const bool platformSupportsMainFrameOnly = false; // Don't care.
#elif OS(ANDROID)
    static const bool platformSupportsCoordinatedScrollbar = true;
    static const bool platformSupportsMainFrameOnly = false;
#else
    static const bool platformSupportsCoordinatedScrollbar = true;
    static const bool platformSupportsMainFrameOnly = true;
#endif
    if (!platformSupportsCoordinatedScrollbar)
        return;

    bool isMainFrame = isForMainFrame(scrollableArea);
    if (!isMainFrame && platformSupportsMainFrameOnly)
        return;

    GraphicsLayer* scrollbarGraphicsLayer = orientation == HorizontalScrollbar
        ? scrollableArea->layerForHorizontalScrollbar()
        : scrollableArea->layerForVerticalScrollbar();

    if (scrollbarGraphicsLayer) {
        Scrollbar* scrollbar = orientation == HorizontalScrollbar ? scrollableArea->horizontalScrollbar() : scrollableArea->verticalScrollbar();
        if (scrollbar->isCustomScrollbar()) {
            detachScrollbarLayer(scrollbarGraphicsLayer);
            return;
        }

        WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, orientation);
        if (!scrollbarLayer) {
            Settings* settings = m_page->mainFrame()->document()->settings();

            OwnPtr<WebScrollbarLayer> webScrollbarLayer;
            if (settings->useSolidColorScrollbars()) {
                ASSERT(RuntimeEnabledFeatures::overlayScrollbarsEnabled());
                webScrollbarLayer = createSolidColorScrollbarLayer(orientation, scrollbar->theme()->thumbThickness(scrollbar), scrollableArea->shouldPlaceVerticalScrollbarOnLeft());
            } else {
                webScrollbarLayer = createScrollbarLayer(scrollbar);
            }
            scrollbarLayer = addWebScrollbarLayer(scrollableArea, orientation, webScrollbarLayer.release());
        }

        // Root layer non-overlay scrollbars should be marked opaque to disable
        // blending.
        bool isOpaqueScrollbar = !scrollbar->isOverlayScrollbar();
        if (!scrollbarGraphicsLayer->contentsOpaque())
            scrollbarGraphicsLayer->setContentsOpaque(isMainFrame && isOpaqueScrollbar);
        scrollbarLayer->layer()->setOpaque(scrollbarGraphicsLayer->contentsOpaque());

        WebLayer* scrollLayer = toWebLayer(scrollableArea->layerForScrolling());
        WebLayer* containerLayer = toWebLayer(scrollableArea->layerForContainer());
        setupScrollbarLayer(scrollbarGraphicsLayer, scrollbarLayer, scrollLayer, containerLayer);
    } else
        removeWebScrollbarLayer(scrollableArea, orientation);
}

bool ScrollingCoordinator::scrollableAreaScrollLayerDidChange(ScrollableArea* scrollableArea)
{
    GraphicsLayer* scrollLayer = scrollableArea->layerForScrolling();

    if (scrollLayer) {
        // With pinch virtual viewport we no longer need to special case the main frame.
        bool pinchVirtualViewportEnabled = m_page->mainFrame()->document()->settings()->pinchVirtualViewportEnabled();
        bool layerScrollShouldFireGraphicsLayerDidScroll = isForMainFrame(scrollableArea) && !pinchVirtualViewportEnabled;
        scrollLayer->setScrollableArea(scrollableArea, layerScrollShouldFireGraphicsLayerDidScroll);
    }

    WebLayer* webLayer = toWebLayer(scrollableArea->layerForScrolling());
    WebLayer* containerLayer = toWebLayer(scrollableArea->layerForContainer());
    if (webLayer) {
        webLayer->setScrollClipLayer(containerLayer);
        webLayer->setScrollPosition(IntPoint(scrollableArea->scrollPosition() - scrollableArea->minimumScrollPosition()));
        webLayer->setBounds(scrollableArea->contentsSize());
        bool canScrollX = scrollableArea->userInputScrollable(HorizontalScrollbar);
        bool canScrollY = scrollableArea->userInputScrollable(VerticalScrollbar);
        webLayer->setUserScrollable(canScrollX, canScrollY);
    }
    if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, HorizontalScrollbar)) {
        GraphicsLayer* horizontalScrollbarLayer = scrollableArea->layerForHorizontalScrollbar();
        if (horizontalScrollbarLayer)
            setupScrollbarLayer(horizontalScrollbarLayer, scrollbarLayer, webLayer, containerLayer);
    }
    if (WebScrollbarLayer* scrollbarLayer = getWebScrollbarLayer(scrollableArea, VerticalScrollbar)) {
        GraphicsLayer* verticalScrollbarLayer = scrollableArea->layerForVerticalScrollbar();
        if (verticalScrollbarLayer)
            setupScrollbarLayer(verticalScrollbarLayer, scrollbarLayer, webLayer, containerLayer);
    }

    return !!webLayer;
}

// In order to do a DFS cross-frame walk of the RenderLayer tree, we need to know which
// RenderLayers have child frames inside of them. This computes a mapping for the
// current frame which we can consult while walking the layers of that frame.
// Whenever we descend into a new frame, a new map will be created.
typedef HashMap<const RenderLayer*, Vector<const LocalFrame*> > LayerFrameMap;
static void makeLayerChildFrameMap(const LocalFrame* currentFrame, LayerFrameMap* map)
{
    map->clear();
    const FrameTree& tree = currentFrame->tree();
    for (const LocalFrame* child = tree.firstChild(); child; child = child->tree().nextSibling()) {
        const RenderObject* ownerRenderer = child->ownerRenderer();
        if (!ownerRenderer)
            continue;
        const RenderLayer* containingLayer = ownerRenderer->enclosingLayer();
        LayerFrameMap::iterator iter = map->find(containingLayer);
        if (iter == map->end())
            map->add(containingLayer, Vector<const LocalFrame*>()).storedValue->value.append(child);
        else
            iter->value.append(child);
    }
}

static void convertLayerRectsToEnclosingCompositedLayerRecursive(
    const RenderLayer* curLayer,
    const LayerHitTestRects& layerRects,
    LayerHitTestRects& compositorRects,
    RenderGeometryMap& geometryMap,
    HashSet<const RenderLayer*>& layersWithRects,
    LayerFrameMap& layerChildFrameMap)
{
    // Project any rects for the current layer
    LayerHitTestRects::const_iterator layerIter = layerRects.find(curLayer);
    if (layerIter != layerRects.end()) {
        // Find the enclosing composited layer when it's in another document (for non-composited iframes).
        RenderLayer* compositedLayer = 0;
        for (const RenderLayer* layer = layerIter->key; !compositedLayer;) {
            compositedLayer = layer->enclosingCompositingLayerForRepaint();
            if (!compositedLayer) {
                RenderObject* owner = layer->renderer()->frame()->ownerRenderer();
                if (!owner)
                    break;
                layer = owner->enclosingLayer();
            }
        }
        if (!compositedLayer) {
            // Since this machinery is used only when accelerated compositing is enabled, we expect
            // that every layer should have an enclosing composited layer.
            ASSERT_NOT_REACHED();
            return;
        }

        LayerHitTestRects::iterator compIter = compositorRects.find(compositedLayer);
        Vector<LayoutRect>* compIterValue;
        if (compIter == compositorRects.end())
            compIterValue = &compositorRects.add(compositedLayer, Vector<LayoutRect>()).storedValue->value;
        else
            compIterValue = &compIter->value;
        // Transform each rect to the co-ordinate space of it's enclosing composited layer.
        for (size_t i = 0; i < layerIter->value.size(); ++i) {
            LayoutRect rect = layerIter->value[i];
            if (compositedLayer != curLayer) {
                FloatQuad compositorQuad = geometryMap.mapToContainer(rect, compositedLayer->renderer());
                rect = LayoutRect(compositorQuad.boundingBox());
                // If the enclosing composited layer itself is scrolled, we have to undo the subtraction
                // of its scroll offset since we want the offset relative to the scrolling content, not
                // the element itself.
                if (compositedLayer->renderer()->hasOverflowClip())
                    rect.move(compositedLayer->renderBox()->scrolledContentOffset());
            }
            compIterValue->append(rect);
        }
    }

    // Walk child layers of interest
    for (const RenderLayer* childLayer = curLayer->firstChild(); childLayer; childLayer = childLayer->nextSibling()) {
        if (layersWithRects.contains(childLayer)) {
            geometryMap.pushMappingsToAncestor(childLayer, curLayer);
            convertLayerRectsToEnclosingCompositedLayerRecursive(childLayer, layerRects, compositorRects, geometryMap, layersWithRects, layerChildFrameMap);
            geometryMap.popMappingsToAncestor(curLayer);
        }
    }

    // If this layer has any frames of interest as a child of it, walk those (with an updated frame map).
    LayerFrameMap::iterator mapIter = layerChildFrameMap.find(curLayer);
    if (mapIter != layerChildFrameMap.end()) {
        for (size_t i = 0; i < mapIter->value.size(); i++) {
            const LocalFrame* childFrame = mapIter->value[i];
            const RenderLayer* childLayer = childFrame->view()->renderView()->layer();
            if (layersWithRects.contains(childLayer)) {
                LayerFrameMap newLayerChildFrameMap;
                makeLayerChildFrameMap(childFrame, &newLayerChildFrameMap);
                geometryMap.pushMappingsToAncestor(childLayer, curLayer);
                convertLayerRectsToEnclosingCompositedLayerRecursive(childLayer, layerRects, compositorRects, geometryMap, layersWithRects, newLayerChildFrameMap);
                geometryMap.popMappingsToAncestor(curLayer);
            }
        }
    }
}

static void convertLayerRectsToEnclosingCompositedLayer(LocalFrame* mainFrame, const LayerHitTestRects& layerRects, LayerHitTestRects& compositorRects)
{
    TRACE_EVENT0("input", "ScrollingCoordinator::convertLayerRectsToEnclosingCompositedLayer");
    bool touchHandlerInChildFrame = false;

    // We have a set of rects per RenderLayer, we need to map them to their bounding boxes in their
    // enclosing composited layer. To do this most efficiently we'll walk the RenderLayer tree using
    // RenderGeometryMap. First record all the branches we should traverse in the tree (including
    // all documents on the page).
    HashSet<const RenderLayer*> layersWithRects;
    for (LayerHitTestRects::const_iterator layerIter = layerRects.begin(); layerIter != layerRects.end(); ++layerIter) {
        const RenderLayer* layer = layerIter->key;
        do {
            if (!layersWithRects.add(layer).isNewEntry)
                break;

            if (layer->parent()) {
                layer = layer->parent();
            } else if (RenderObject* parentDocRenderer = layer->renderer()->frame()->ownerRenderer()) {
                layer = parentDocRenderer->enclosingLayer();
                touchHandlerInChildFrame = true;
            }
        } while (layer);
    }

    // Now walk the layer projecting rects while maintaining a RenderGeometryMap
    MapCoordinatesFlags flags = UseTransforms;
    if (touchHandlerInChildFrame)
        flags |= TraverseDocumentBoundaries;
    RenderLayer* rootLayer = mainFrame->contentRenderer()->layer();
    RenderGeometryMap geometryMap(flags);
    geometryMap.pushMappingsToAncestor(rootLayer, 0);
    LayerFrameMap layerChildFrameMap;
    makeLayerChildFrameMap(mainFrame, &layerChildFrameMap);
    convertLayerRectsToEnclosingCompositedLayerRecursive(rootLayer, layerRects, compositorRects, geometryMap, layersWithRects, layerChildFrameMap);
}

void ScrollingCoordinator::updateTouchEventTargetRectsIfNeeded()
{
    TRACE_EVENT0("input", "ScrollingCoordinator::updateTouchEventTargetRectsIfNeeded");

    if (!touchHitTestingEnabled())
        return;

    LayerHitTestRects touchEventTargetRects;
    computeTouchEventTargetRects(touchEventTargetRects);
    setTouchEventTargetRects(touchEventTargetRects);
}

void ScrollingCoordinator::reset()
{
    m_horizontalScrollbars.clear();
    m_verticalScrollbars.clear();
    m_layersWithTouchRects.clear();
    m_wasFrameScrollable = false;

    // This is retained for testing.
    m_lastMainThreadScrollingReasons = 0;
    setShouldUpdateScrollLayerPositionOnMainThread(m_lastMainThreadScrollingReasons);
}

// Note that in principle this could be called more often than computeTouchEventTargetRects, for
// example during a non-composited scroll (although that's not yet implemented - crbug.com/261307).
void ScrollingCoordinator::setTouchEventTargetRects(const LayerHitTestRects& layerRects)
{
    TRACE_EVENT0("input", "ScrollingCoordinator::setTouchEventTargetRects");

    LayerHitTestRects compositorRects;
    convertLayerRectsToEnclosingCompositedLayer(m_page->mainFrame(), layerRects, compositorRects);

    HashSet<const RenderLayer*> oldLayersWithTouchRects;
    m_layersWithTouchRects.swap(oldLayersWithTouchRects);

    for (LayerHitTestRects::const_iterator iter = compositorRects.begin(); iter != compositorRects.end(); ++iter) {
        const RenderLayer* layer = iter->key;
        WebVector<WebRect> webRects(iter->value.size());
        for (size_t i = 0; i < iter->value.size(); ++i)
            webRects[i] = enclosingIntRect(iter->value[i]);
        // This should be ensured by convertLayerRectsToEnclosingCompositedLayer above.
        ASSERT(layer->hasCompositedLayerMapping());
        CompositedLayerMappingPtr compositedLayerMapping = layer->compositedLayerMapping();
        // If the layer is using composited scrolling, then it's the contents that these
        // rects apply to.
        GraphicsLayer* graphicsLayer = compositedLayerMapping->scrollingContentsLayer();
        if (!graphicsLayer)
            graphicsLayer = compositedLayerMapping->mainGraphicsLayer();
        graphicsLayer->platformLayer()->setTouchEventHandlerRegion(webRects);
        oldLayersWithTouchRects.remove(layer);
        m_layersWithTouchRects.add(layer);
    }

    // If there are any layers left that we haven't updated, clear them out.
    for (HashSet<const RenderLayer*>::iterator it = oldLayersWithTouchRects.begin(); it != oldLayersWithTouchRects.end(); ++it) {
        // FIXME: This is a bug. What's happening here is that we're clearing touch regions for
        // layers that we didn't visit above. That assumes a 1:1 mapping between RenderLayer and
        // the graphics layer that owns the touch rects. This is false in the case of
        // HasOwnBackingButPaintsIntoAncestor and will be extra-false in the world of squashing.
        if ((*it)->hasCompositedLayerMapping()) {
            GraphicsLayer* graphicsLayer = (*it)->compositedLayerMapping()->scrollingContentsLayer();
            if (!graphicsLayer)
                graphicsLayer = (*it)->compositedLayerMapping()->mainGraphicsLayer();
            graphicsLayer->platformLayer()->setTouchEventHandlerRegion(WebVector<WebRect>());
        }
    }
}

void ScrollingCoordinator::touchEventTargetRectsDidChange()
{
    if (!touchHitTestingEnabled())
        return;

    // Wait until after layout to update.
    if (m_page->mainFrame()->view()->needsLayout())
        return;

    // FIXME: scheduleAnimation() is just a method of forcing the compositor to realize that it
    // needs to commit here. We should expose a cleaner API for this.
    RenderView* renderView = m_page->mainFrame()->contentRenderer();
    if (renderView && renderView->compositor() && renderView->compositor()->inCompositingMode())
        m_page->mainFrame()->view()->scheduleAnimation();

    m_touchEventTargetRectsAreDirty = true;
}

void ScrollingCoordinator::updateScrollParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent)
{
    WebLayer* scrollParentWebLayer = 0;
    if (parent && parent->hasCompositedLayerMapping())
        scrollParentWebLayer = toWebLayer(parent->compositedLayerMapping()->parentForSublayers());

    child->setScrollParent(scrollParentWebLayer);
}

void ScrollingCoordinator::updateClipParentForGraphicsLayer(GraphicsLayer* child, RenderLayer* parent)
{
    WebLayer* clipParentWebLayer = 0;
    if (parent && parent->hasCompositedLayerMapping())
        clipParentWebLayer = toWebLayer(parent->compositedLayerMapping()->parentForSublayers());

    child->setClipParent(clipParentWebLayer);
}

void ScrollingCoordinator::willDestroyRenderLayer(RenderLayer* layer)
{
    m_layersWithTouchRects.remove(layer);
}

void ScrollingCoordinator::setWheelEventHandlerCount(unsigned count)
{
    if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling()))
        scrollLayer->setHaveWheelEventHandlers(count > 0);
}

void ScrollingCoordinator::recomputeWheelEventHandlerCountForFrameView(FrameView*)
{
    setWheelEventHandlerCount(computeCurrentWheelEventHandlerCount());
}

void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons reasons)
{
    if (WebLayer* scrollLayer = toWebLayer(m_page->mainFrame()->view()->layerForScrolling())) {
        m_lastMainThreadScrollingReasons = reasons;
        scrollLayer->setShouldScrollOnMainThread(reasons);
    }
}

void ScrollingCoordinator::pageDestroyed()
{
    ASSERT(m_page);
    m_page = 0;
}

bool ScrollingCoordinator::coordinatesScrollingForFrameView(FrameView* frameView) const
{
    ASSERT(isMainThread());
    ASSERT(m_page);

    // We currently only handle the main frame.
    if (&frameView->frame() != m_page->mainFrame())
        return false;

    // We currently only support composited mode.
    RenderView* renderView = m_page->mainFrame()->contentRenderer();
    if (!renderView)
        return false;
    return renderView->usesCompositing();
}

Region ScrollingCoordinator::computeShouldHandleScrollGestureOnMainThreadRegion(const LocalFrame* frame, const IntPoint& frameLocation) const
{
    Region shouldHandleScrollGestureOnMainThreadRegion;
    FrameView* frameView = frame->view();
    if (!frameView)
        return shouldHandleScrollGestureOnMainThreadRegion;

    IntPoint offset = frameLocation;
    offset.moveBy(frameView->frameRect().location());

    if (const FrameView::ScrollableAreaSet* scrollableAreas = frameView->scrollableAreas()) {
        for (FrameView::ScrollableAreaSet::const_iterator it = scrollableAreas->begin(), end = scrollableAreas->end(); it != end; ++it) {
            ScrollableArea* scrollableArea = *it;
            // Composited scrollable areas can be scrolled off the main thread.
            if (scrollableArea->usesCompositedScrolling())
                continue;
            IntRect box = scrollableArea->scrollableAreaBoundingBox();
            box.moveBy(offset);
            shouldHandleScrollGestureOnMainThreadRegion.unite(box);
        }
    }

    // We use GestureScrollBegin/Update/End for moving the resizer handle. So we mark these
    // small resizer areas as non-fast-scrollable to allow the scroll gestures to be passed to
    // main thread if they are targeting the resizer area. (Resizing is done in EventHandler.cpp
    // on main thread).
    if (const FrameView::ResizerAreaSet* resizerAreas = frameView->resizerAreas()) {
        for (FrameView::ResizerAreaSet::const_iterator it = resizerAreas->begin(), end = resizerAreas->end(); it != end; ++it) {
            RenderBox* box = *it;
            IntRect bounds = box->absoluteBoundingBoxRect();
            IntRect corner = box->layer()->scrollableArea()->touchResizerCornerRect(bounds);
            corner.moveBy(offset);
            shouldHandleScrollGestureOnMainThreadRegion.unite(corner);
        }
    }

    if (const HashSet<RefPtr<Widget> >* children = frameView->children()) {
        for (HashSet<RefPtr<Widget> >::const_iterator it = children->begin(), end = children->end(); it != end; ++it) {
            if (!(*it)->isPluginView())
                continue;

            PluginView* pluginView = toPluginView((*it).get());
            if (pluginView->wantsWheelEvents())
                shouldHandleScrollGestureOnMainThreadRegion.unite(pluginView->frameRect());
        }
    }

    const FrameTree& tree = frame->tree();
    for (LocalFrame* subFrame = tree.firstChild(); subFrame; subFrame = subFrame->tree().nextSibling())
        shouldHandleScrollGestureOnMainThreadRegion.unite(computeShouldHandleScrollGestureOnMainThreadRegion(subFrame, offset));

    return shouldHandleScrollGestureOnMainThreadRegion;
}

static void accumulateDocumentTouchEventTargetRects(LayerHitTestRects& rects, const Document* document)
{
    ASSERT(document);
    if (!document->touchEventTargets())
        return;

    const TouchEventTargetSet* targets = document->touchEventTargets();

    // If there's a handler on the document, html or body element (fairly common in practice),
    // then we can quickly mark the entire document and skip looking at any other handlers.
    // Note that technically a handler on the body doesn't cover the whole document, but it's
    // reasonable to be conservative and report the whole document anyway.
    for (TouchEventTargetSet::const_iterator iter = targets->begin(); iter != targets->end(); ++iter) {
        Node* target = iter->key;
        if (target == document || target == document->documentElement() || target == document->body()) {
            if (RenderObject* renderer = document->renderer()) {
                renderer->computeLayerHitTestRects(rects);
            }
            return;
        }
    }

    for (TouchEventTargetSet::const_iterator iter = targets->begin(); iter != targets->end(); ++iter) {
        const Node* target = iter->key;
        if (!target->inDocument())
            continue;

        if (target->isDocumentNode()) {
            ASSERT(target != document);
            accumulateDocumentTouchEventTargetRects(rects, toDocument(target));
        } else if (RenderObject* renderer = target->renderer()) {
            // If the set also contains one of our ancestor nodes then processing
            // this node would be redundant.
            bool hasTouchEventTargetAncestor = false;
            for (Node* ancestor = target->parentNode(); ancestor && !hasTouchEventTargetAncestor; ancestor = ancestor->parentNode()) {
                if (targets->contains(ancestor))
                    hasTouchEventTargetAncestor = true;
            }
            if (!hasTouchEventTargetAncestor) {
                // Walk up the tree to the outermost non-composited scrollable layer.
                RenderLayer* enclosingNonCompositedScrollLayer = 0;
                for (RenderLayer* parent = renderer->enclosingLayer(); parent && parent->compositingState() == NotComposited; parent = parent->parent()) {
                    if (parent->scrollsOverflow())
                        enclosingNonCompositedScrollLayer = parent;
                }

                // Report the whole non-composited scroll layer as a touch hit rect because any
                // rects inside of it may move around relative to their enclosing composited layer
                // without causing the rects to be recomputed. Non-composited scrolling occurs on
                // the main thread, so we're not getting much benefit from compositor touch hit
                // testing in this case anyway.
                if (enclosingNonCompositedScrollLayer)
                    enclosingNonCompositedScrollLayer->computeSelfHitTestRects(rects);

                renderer->computeLayerHitTestRects(rects);
            }
        }
    }

}

void ScrollingCoordinator::computeTouchEventTargetRects(LayerHitTestRects& rects)
{
    TRACE_EVENT0("input", "ScrollingCoordinator::computeTouchEventTargetRects");
    ASSERT(touchHitTestingEnabled());

    Document* document = m_page->mainFrame()->document();
    if (!document || !document->view())
        return;

    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();
    }

    return wheelEventHandlerCount;
}

void ScrollingCoordinator::frameViewWheelEventHandlerCountChanged(FrameView* frameView)
{
    ASSERT(isMainThread());
    ASSERT(m_page);

    recomputeWheelEventHandlerCountForFrameView(frameView);
}

void ScrollingCoordinator::frameViewHasSlowRepaintObjectsDidChange(FrameView* frameView)
{
    ASSERT(isMainThread());
    ASSERT(m_page);

    if (!coordinatesScrollingForFrameView(frameView))
        return;

    m_shouldScrollOnMainThreadDirty = true;
}

void ScrollingCoordinator::frameViewFixedObjectsDidChange(FrameView* frameView)
{
    ASSERT(isMainThread());
    ASSERT(m_page);

    if (!coordinatesScrollingForFrameView(frameView))
        return;

    m_shouldScrollOnMainThreadDirty = true;
}

bool ScrollingCoordinator::isForMainFrame(ScrollableArea* scrollableArea) const
{
    return scrollableArea == m_page->mainFrame()->view();
}

GraphicsLayer* ScrollingCoordinator::scrollLayerForFrameView(FrameView* frameView)
{
    RenderView* renderView = frameView->frame().contentRenderer();
    if (!renderView)
        return 0;
    return renderView->compositor()->scrollLayer();
}

GraphicsLayer* ScrollingCoordinator::counterScrollingLayerForFrameView(FrameView*)
{
    return 0;
}

void ScrollingCoordinator::frameViewRootLayerDidChange(FrameView* frameView)
{
    ASSERT(isMainThread());
    ASSERT(m_page);

    if (!coordinatesScrollingForFrameView(frameView))
        return;

    notifyLayoutUpdated();
    recomputeWheelEventHandlerCountForFrameView(frameView);
}

#if OS(MACOSX)
void ScrollingCoordinator::handleWheelEventPhase(PlatformWheelEventPhase phase)
{
    ASSERT(isMainThread());

    if (!m_page)
        return;

    FrameView* frameView = m_page->mainFrame()->view();
    if (!frameView)
        return;

    frameView->scrollAnimator()->handleWheelEventPhase(phase);
}
#endif

bool ScrollingCoordinator::hasVisibleSlowRepaintViewportConstrainedObjects(FrameView* frameView) const
{
    const FrameView::ViewportConstrainedObjectSet* viewportConstrainedObjects = frameView->viewportConstrainedObjects();
    if (!viewportConstrainedObjects)
        return false;

    for (FrameView::ViewportConstrainedObjectSet::const_iterator it = viewportConstrainedObjects->begin(), end = viewportConstrainedObjects->end(); it != end; ++it) {
        RenderObject* viewportConstrainedObject = *it;
        if (!viewportConstrainedObject->isBoxModelObject() || !viewportConstrainedObject->hasLayer())
            return true;
        RenderLayer* layer = toRenderBoxModelObject(viewportConstrainedObject)->layer();
        // Any explicit reason that a fixed position element is not composited shouldn't cause slow scrolling.
        if (layer->compositingState() != PaintsIntoOwnBacking && layer->viewportConstrainedNotCompositedReason() == RenderLayer::NoNotCompositedReason)
            return true;

        // Composited layers that actually paint into their enclosing ancestor
        // must also force main thread scrolling.
        if (layer->compositingState() == HasOwnBackingButPaintsIntoAncestor)
            return true;
    }
    return false;
}

MainThreadScrollingReasons ScrollingCoordinator::mainThreadScrollingReasons() const
{
    // The main thread scrolling reasons are applicable to scrolls of the main
    // frame. If it does not exist or if it is not scrollable, there is no
    // reason to force main thread scrolling.
    FrameView* frameView = m_page->mainFrame()->view();
    if (!frameView)
        return static_cast<MainThreadScrollingReasons>(0);

    MainThreadScrollingReasons mainThreadScrollingReasons = (MainThreadScrollingReasons)0;

    if (frameView->hasSlowRepaintObjects())
        mainThreadScrollingReasons |= HasSlowRepaintObjects;
    if (hasVisibleSlowRepaintViewportConstrainedObjects(frameView))
        mainThreadScrollingReasons |= HasNonLayerViewportConstrainedObjects;

    return mainThreadScrollingReasons;
}

String ScrollingCoordinator::mainThreadScrollingReasonsAsText(MainThreadScrollingReasons reasons)
{
    StringBuilder stringBuilder;

    if (reasons & ScrollingCoordinator::HasSlowRepaintObjects)
        stringBuilder.append("Has slow repaint objects, ");
    if (reasons & ScrollingCoordinator::HasViewportConstrainedObjectsWithoutSupportingFixedLayers)
        stringBuilder.append("Has viewport constrained objects without supporting fixed layers, ");
    if (reasons & ScrollingCoordinator::HasNonLayerViewportConstrainedObjects)
        stringBuilder.append("Has non-layer viewport-constrained objects, ");

    if (stringBuilder.length())
        stringBuilder.resize(stringBuilder.length() - 2);
    return stringBuilder.toString();
}

String ScrollingCoordinator::mainThreadScrollingReasonsAsText() const
{
    ASSERT(m_page->mainFrame()->document()->lifecycle().state() >= DocumentLifecycle::CompositingClean);
    return mainThreadScrollingReasonsAsText(m_lastMainThreadScrollingReasons);
}

bool ScrollingCoordinator::frameViewIsDirty() const
{
    FrameView* frameView = m_page->mainFrame()->view();
    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
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root/Source/core/page/scrolling/ScrollingCoordinator.cpp

DEFINITIONS
