Source/WebCore/rendering/RenderLayerCompositor.h

/*
 * Copyright (C) 2009 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. ``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 COMPUTER, INC. OR
 * 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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#ifndef RenderLayerCompositor_h
#define RenderLayerCompositor_h

#include "ChromeClient.h"
#include "RenderLayer.h"
#include "RenderLayerBacking.h"

namespace WebCore {

#define PROFILE_LAYER_REBUILD 0

class GraphicsLayer;
class RenderEmbeddedObject;
class RenderPart;
#if ENABLE(VIDEO)
class RenderVideo;
#endif

enum CompositingUpdateType {
    CompositingUpdateAfterLayoutOrStyleChange,
    CompositingUpdateOnPaitingOrHitTest,
    CompositingUpdateOnScroll
};

// RenderLayerCompositor manages the hierarchy of
// composited RenderLayers. It determines which RenderLayers
// become compositing, and creates and maintains a hierarchy of
// GraphicsLayers based on the RenderLayer painting order.
// 
// There is one RenderLayerCompositor per RenderView.

class RenderLayerCompositor : public GraphicsLayerClient {
public:
    RenderLayerCompositor(RenderView*);
    ~RenderLayerCompositor();

    // Return true if this RenderView is in "compositing mode" (i.e. has one or more
    // composited RenderLayers)
    bool inCompositingMode() const { return m_compositing; }
    // This will make a compositing layer at the root automatically, and hook up to
    // the native view/window system.
    void enableCompositingMode(bool enable = true);
    
    // Returns true if the accelerated compositing is enabled
    bool hasAcceleratedCompositing() const { return m_hasAcceleratedCompositing; }

    bool canRender3DTransforms() const;

    // Copy the accelerated compositing related flags from Settings
    void cacheAcceleratedCompositingFlags();

    // Called when the layer hierarchy needs to be updated (compositing layers have been
    // created, destroyed or re-parented).
    void setCompositingLayersNeedRebuild(bool needRebuild = true);
    bool compositingLayersNeedRebuild() const { return m_compositingLayersNeedRebuild; }

    // Controls whether or not to consult geometry when deciding which layers need
    // to be composited. Defaults to true.
    void setCompositingConsultsOverlap(bool b) { m_compositingConsultsOverlap = b; }
    bool compositingConsultsOverlap() const { return m_compositingConsultsOverlap; }
    
    // GraphicsLayers buffer state, which gets pushed to the underlying platform layers
    // at specific times.
    void scheduleLayerFlush();
    void flushPendingLayerChanges();
    bool isFlushingLayers() const { return m_flushingLayers; }
    
    // flushPendingLayerChanges() flushes the entire GraphicsLayer tree, which can cross frame boundaries.
    // This call returns the rootmost compositor that is being flushed (including self).
    RenderLayerCompositor* enclosingCompositorFlushingLayers() const;
    
    // Rebuild the tree of compositing layers
    void updateCompositingLayers(CompositingUpdateType = CompositingUpdateAfterLayoutOrStyleChange, RenderLayer* updateRoot = 0);
    // This is only used when state changes and we do not exepect a style update or layout to happen soon (e.g. when
    // we discover that an iframe is overlapped during painting).
    void scheduleCompositingLayerUpdate();
    bool compositingLayerUpdatePending() const;
    
    // Update the compositing state of the given layer. Returns true if that state changed.
    enum CompositingChangeRepaint { CompositingChangeRepaintNow, CompositingChangeWillRepaintLater };
    bool updateLayerCompositingState(RenderLayer*, CompositingChangeRepaint = CompositingChangeRepaintNow);

    // Update the geometry for compositing children of compositingAncestor.
    void updateCompositingDescendantGeometry(RenderLayer* compositingAncestor, RenderLayer* layer, RenderLayerBacking::UpdateDepth);
    
    // Whether layer's backing needs a graphics layer to do clipping by an ancestor (non-stacking-context parent with overflow).
    bool clippedByAncestor(RenderLayer*) const;
    // Whether layer's backing needs a graphics layer to clip z-order children of the given layer.
    bool clipsCompositingDescendants(const RenderLayer*) const;

    // Whether the given layer needs an extra 'contents' layer.
    bool needsContentsCompositingLayer(const RenderLayer*) const;
    // Return the bounding box required for compositing layer and its childern, relative to ancestorLayer.
    // If layerBoundingBox is not 0, on return it contains the bounding box of this layer only.
    IntRect calculateCompositedBounds(const RenderLayer* layer, const RenderLayer* ancestorLayer);

    // Repaint the appropriate layers when the given RenderLayer starts or stops being composited.
    void repaintOnCompositingChange(RenderLayer*);
    
    // Notify us that a layer has been added or removed
    void layerWasAdded(RenderLayer* parent, RenderLayer* child);
    void layerWillBeRemoved(RenderLayer* parent, RenderLayer* child);

    // Get the nearest ancestor layer that has overflow or clip, but is not a stacking context
    RenderLayer* enclosingNonStackingClippingLayer(const RenderLayer* layer) const;

    // Repaint parts of all composited layers that intersect the given absolute rectangle.
    void repaintCompositedLayersAbsoluteRect(const IntRect&);

    RenderLayer* rootRenderLayer() const;
    GraphicsLayer* rootPlatformLayer() const;

    enum RootLayerAttachment {
        RootLayerUnattached,
        RootLayerAttachedViaChromeClient,
        RootLayerAttachedViaEnclosingFrame
    };

    RootLayerAttachment rootLayerAttachment() const { return m_rootLayerAttachment; }
    void updateRootLayerAttachment();
    void updateRootLayerPosition();
    
    void didMoveOnscreen();
    void willMoveOffscreen();
    
    void didStartAcceleratedAnimation(CSSPropertyID);
    
#if ENABLE(VIDEO)
    // Use by RenderVideo to ask if it should try to use accelerated compositing.
    bool canAccelerateVideoRendering(RenderVideo*) const;
#endif

    // Walk the tree looking for layers with 3d transforms. Useful in case you need
    // to know if there is non-affine content, e.g. for drawing into an image.
    bool has3DContent() const;
    
    // Most platforms connect compositing layer trees between iframes and their parent document.
    // Some (currently just Mac) allow iframes to do their own compositing.
    static bool allowsIndependentlyCompositedFrames(const FrameView*);
    bool shouldPropagateCompositingToEnclosingFrame() const;

    HTMLFrameOwnerElement* enclosingFrameElement() const;

    static RenderLayerCompositor* frameContentsCompositor(RenderPart*);
    // Return true if the layers changed.
    static bool parentFrameContentLayers(RenderPart*);

    // Update the geometry of the layers used for clipping and scrolling in frames.
    void frameViewDidChangeLocation(const IntPoint& contentsOffset);
    void frameViewDidChangeSize();
    void frameViewDidScroll(const IntPoint& = IntPoint());

    String layerTreeAsText(bool showDebugInfo = false);

    // These are named to avoid conflicts with the functions in GraphicsLayerClient
    // These return the actual internal variables.
    bool compositorShowDebugBorders() const { return m_showDebugBorders; }
    bool compositorShowRepaintCounter() const { return m_showRepaintCounter; }

    void updateContentsScale(float, RenderLayer* = 0);

    GraphicsLayer* layerForHorizontalScrollbar() const { return m_layerForHorizontalScrollbar.get(); }
    GraphicsLayer* layerForVerticalScrollbar() const { return m_layerForVerticalScrollbar.get(); }
    GraphicsLayer* layerForScrollCorner() const { return m_layerForScrollCorner.get(); }

private:
    // GraphicsLayerClient Implementation
    virtual void notifyAnimationStarted(const GraphicsLayer*, double) { }
    virtual void notifySyncRequired(const GraphicsLayer*) { scheduleLayerFlush(); }
    virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect&);

    // These calls return false always. They are saying that the layers associated with this client
    // (the clipLayer and scrollLayer) should never show debugging info.
    virtual bool showDebugBorders() const { return false; }
    virtual bool showRepaintCounter() const { return false; }
    
    // Whether the given RL needs a compositing layer.
    bool needsToBeComposited(const RenderLayer*) const;
    // Whether the layer has an intrinsic need for compositing layer.
    bool requiresCompositingLayer(const RenderLayer*) const;
    // Whether the layer could ever be composited.
    bool canBeComposited(const RenderLayer*) const;

    // Make or destroy the backing for this layer; returns true if backing changed.
    bool updateBacking(RenderLayer*, CompositingChangeRepaint shouldRepaint);

    // Repaint the given rect (which is layer's coords), and regions of child layers that intersect that rect.
    void recursiveRepaintLayerRect(RenderLayer* layer, const IntRect& rect);

    typedef HashMap<RenderLayer*, IntRect> OverlapMap;
    static void addToOverlapMap(OverlapMap&, RenderLayer*, IntRect& layerBounds, bool& boundsComputed);
    static bool overlapsCompositedLayers(OverlapMap&, const IntRect& layerBounds);

    void updateCompositingLayersTimerFired(Timer<RenderLayerCompositor>*);

#if ENABLE(COMPOSITED_FIXED_ELEMENTS)
    bool checkForPositionedElements(Vector<RenderLayer*>* list);
#endif

    // Returns true if any layer's compositing changed
    void computeCompositingRequirements(RenderLayer*, OverlapMap*, struct CompositingState&, bool& layersChanged);
    
    // Recurses down the tree, parenting descendant compositing layers and collecting an array of child layers for the current compositing layer.
    void rebuildCompositingLayerTree(RenderLayer* layer, const struct CompositingState&, Vector<GraphicsLayer*>& childGraphicsLayersOfEnclosingLayer);

    // Recurses down the tree, updating layer geometry only.
    void updateLayerTreeGeometry(RenderLayer*);
    
    // Hook compositing layers together
    void setCompositingParent(RenderLayer* childLayer, RenderLayer* parentLayer);
    void removeCompositedChildren(RenderLayer*);

    bool layerHas3DContent(const RenderLayer*) const;

    void ensureRootPlatformLayer();
    void destroyRootPlatformLayer();

    void attachRootPlatformLayer(RootLayerAttachment);
    void detachRootPlatformLayer();
    
    void rootLayerAttachmentChanged();

    void updateOverflowControlsLayers();

    void scheduleNeedsStyleRecalc(Element*);
    void notifyIFramesOfCompositingChange();

    // Whether a running transition or animation enforces the need for a compositing layer.
    bool requiresCompositingForAnimation(RenderObject*) const;
    bool requiresCompositingForTransform(RenderObject*) const;
    bool requiresCompositingForVideo(RenderObject*) const;
    bool requiresCompositingForCanvas(RenderObject*) const;
    bool requiresCompositingForPlugin(RenderObject*) const;
    bool requiresCompositingForFrame(RenderObject*) const;
    bool requiresCompositingWhenDescendantsAreCompositing(RenderObject*) const;
    bool requiresCompositingForFullScreen(RenderObject*) const;

#if PLATFORM(ANDROID)
    // Whether we are using layers for new android features (overflow support, fixed elements)
    bool requiresCompositingForAndroidLayers(const RenderLayer* layer) const;
#endif

    bool requiresScrollLayer(RootLayerAttachment) const;
    bool requiresHorizontalScrollbarLayer() const;
    bool requiresVerticalScrollbarLayer() const;
    bool requiresScrollCornerLayer() const;

private:
    RenderView* m_renderView;
    OwnPtr<GraphicsLayer> m_rootPlatformLayer;
    Timer<RenderLayerCompositor> m_updateCompositingLayersTimer;

    bool m_hasAcceleratedCompositing;
    ChromeClient::CompositingTriggerFlags m_compositingTriggers;

    bool m_showDebugBorders;
    bool m_showRepaintCounter;
    bool m_compositingConsultsOverlap;

    // When true, we have to wait until layout has happened before we can decide whether to enter compositing mode,
    // because only then do we know the final size of plugins and iframes.
    // FIXME: once set, this is never cleared.
    mutable bool m_compositingDependsOnGeometry;

    bool m_compositing;
    bool m_compositingLayersNeedRebuild;
    bool m_flushingLayers;
    bool m_forceCompositingMode;

    RootLayerAttachment m_rootLayerAttachment;

    // Enclosing clipping layer for iframe content
    OwnPtr<GraphicsLayer> m_clipLayer;
    OwnPtr<GraphicsLayer> m_scrollLayer;

    // Enclosing layer for overflow controls and the clipping layer
    OwnPtr<GraphicsLayer> m_overflowControlsHostLayer;

    // Layers for overflow controls
    OwnPtr<GraphicsLayer> m_layerForHorizontalScrollbar;
    OwnPtr<GraphicsLayer> m_layerForVerticalScrollbar;
    OwnPtr<GraphicsLayer> m_layerForScrollCorner;
#if PROFILE_LAYER_REBUILD
    int m_rootLayerUpdateCount;
#endif
};


} // namespace WebCore

#endif // RenderLayerCompositor_h