Source/web/painting/PaintAggregator.h

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * in the documentation and/or other materials provided with the
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#ifndef PaintAggregator_h
#define PaintAggregator_h

#include "core/platform/graphics/IntPoint.h"
#include "core/platform/graphics/IntRect.h"
#include "wtf/Vector.h"

namespace WebKit {

// This class is responsible for aggregating multiple invalidation and scroll
// commands to produce a scroll and repaint sequence.
class PaintAggregator {
public:
    // This structure describes an aggregation of invalidateRect and scrollRect
    // calls. If |scrollRect| is non-empty, then that rect should be scrolled
    // by the amount specified by |scrollDelta|. If |paintRects| is non-empty,
    // then those rects should be repainted. If |scrollRect| and |paintRects|
    // are non-empty, then scrolling should be performed before repainting.
    // |scrollDelta| can only specify scrolling in one direction (i.e., the x
    // and y members cannot both be non-zero).
    struct PendingUpdate {
        PendingUpdate();
        ~PendingUpdate();

        // Returns the rect damaged by scrolling within |scrollRect| by
        // |scrollDelta|. This rect must be repainted.
        WebCore::IntRect calculateScrollDamage() const;

        // Returns the smallest rect containing all paint rects.
        WebCore::IntRect calculatePaintBounds() const;

        WebCore::IntPoint scrollDelta;
        WebCore::IntRect scrollRect;
        WTF::Vector<WebCore::IntRect> paintRects;
    };

    // There is a PendingUpdate if invalidateRect or scrollRect were called and
    // ClearPendingUpdate was not called.
    bool hasPendingUpdate() const;
    void clearPendingUpdate();

    // Fills |update| and clears the pending update.
    void popPendingUpdate(PendingUpdate*);

    // The given rect should be repainted.
    void invalidateRect(const WebCore::IntRect&);

    // The given rect should be scrolled by the given amounts.
    void scrollRect(int dx, int dy, const WebCore::IntRect& clipRect);

private:
    WebCore::IntRect scrollPaintRect(const WebCore::IntRect& paintRect, int dx, int dy) const;
    bool shouldInvalidateScrollRect(const WebCore::IntRect&) const;
    void invalidateScrollRect();
    void combinePaintRects();

    PendingUpdate m_update;
};

} // namespace WebKit

#endif