LayerAncestorClippingStack.h   [plain text]

/*
 * Copyright (C) 2019 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:
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 * 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
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 */

#pragma once

#include "LayoutRect.h"
#include "RenderLayer.h"
#include "ScrollTypes.h"
#include <wtf/Vector.h>
#include <wtf/WeakPtr.h>

namespace WTF {
class TextStream;
}

namespace WebCore {

class ScrollingCoordinator;

struct CompositedClipData {
    CompositedClipData(RenderLayer* layer, LayoutRect rect, bool isOverflowScrollEntry)
        : clippingLayer(makeWeakPtr(layer))
        , clipRect(rect)
        , isOverflowScroll(isOverflowScrollEntry)
    {
    }

    bool operator==(const CompositedClipData& other) const
    {
        return clippingLayer == other.clippingLayer
            && clipRect == other.clipRect
            && isOverflowScroll == other.isOverflowScroll;
    }
    
    bool operator!=(const CompositedClipData& other) const
    {
        return !(*this == other);
    }

    WeakPtr<RenderLayer> clippingLayer; // For scroller entries, the scrolling layer. For other entries, the most-descendant layer that has a clip.
    LayoutRect clipRect; // In the coordinate system of the RenderLayer that owns the stack.
    bool isOverflowScroll { false };
};


// This class encapsulates the set of layers and their scrolling tree nodes representing clipping in the layer's containing block ancestry,
// but not in its paint order ancestry.
class LayerAncestorClippingStack {
    WTF_MAKE_FAST_ALLOCATED;
public:
    LayerAncestorClippingStack(Vector<CompositedClipData>&&);
    ~LayerAncestorClippingStack() = default;

    bool hasAnyScrollingLayers() const;
    
    bool equalToClipData(const Vector<CompositedClipData>&) const;
    bool updateWithClipData(ScrollingCoordinator*, Vector<CompositedClipData>&&);

    void clear(ScrollingCoordinator*);
    void detachFromScrollingCoordinator(ScrollingCoordinator&);

    void updateScrollingNodeLayers(ScrollingCoordinator&);

    GraphicsLayer* firstClippingLayer() const;
    GraphicsLayer* lastClippingLayer() const;
    ScrollingNodeID lastOverflowScrollProxyNodeID() const;
    
    bool update(LayerAncestorClippingStack&&);
    
    struct ClippingStackEntry {
        CompositedClipData clipData;
        ScrollingNodeID overflowScrollProxyNodeID { 0 }; // The node for repositioning the scrolling proxy layer.
        RefPtr<GraphicsLayer> clippingLayer;
    };

    Vector<ClippingStackEntry>& stack() { return m_stack; }
    const Vector<ClippingStackEntry>& stack() const { return m_stack; }

private:
    // Order is ancestors to descendants.
    Vector<ClippingStackEntry> m_stack;
};

TextStream& operator<<(TextStream&, const LayerAncestorClippingStack&);

} // namespace WebCore