WebCore/platform/graphics/ContextShadow.h

/*
 * Copyright (C) 2010 Sencha, Inc.
 * Copyright (C) 2010 Igalia S.L.
 *
 * 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 COMPUTER, 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
 * 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.
 */

#ifndef ContextShadow_h
#define ContextShadow_h

#include "Color.h"
#include "FloatRect.h"
#include "IntRect.h"
#include "RefCounted.h"

#if PLATFORM(CAIRO)
typedef struct _cairo cairo_t;
typedef struct _cairo_surface cairo_surface_t;
#elif PLATFORM(QT)
#include <QImage>
QT_BEGIN_NAMESPACE
class QPainter;
QT_END_NAMESPACE
#endif

namespace WebCore {

class AffineTransform;
class GraphicsContext;

#if PLATFORM(CAIRO)
typedef cairo_surface_t* PlatformImage;
typedef cairo_t* PlatformContext;
#elif PLATFORM(QT)
typedef QImage PlatformImage;
typedef QPainter* PlatformContext;
#else
typedef void* PlatformImage;
typedef void* PlatformContext;
#endif

// This is to track and keep the shadow state. We use this rather than
// using GraphicsContextState to allow possible optimizations (right now
// only to determine the shadow type, but in future it might covers things
// like cached scratch image, persistent shader, etc).

// This class should be copyable since GraphicsContextQt keeps a stack of
// the shadow state for savePlatformState and restorePlatformState.

class ContextShadow {
public:
    enum {
        NoShadow,
        SolidShadow,
        BlurShadow
    } m_type;

    Color m_color;
    int m_blurDistance;
    FloatSize m_offset;

    ContextShadow();
    ContextShadow(const Color&, float radius, const FloatSize& offset);

    bool mustUseContextShadow(GraphicsContext*);
    void clear();

    // The pair beginShadowLayer and endShadowLayer creates a temporary image
    // where the caller can draw onto, using the returned context. This context
    // must be used only to draw between the call to beginShadowLayer and
    // endShadowLayer.
    //
    // Note: multiple/nested shadow layers are NOT allowed.
    //
    // The current clip region will be used to optimize the size of the
    // temporary image. Thus, the original context should not change any
    // clipping until endShadowLayer. If the shadow will be completely outside
    // the clipping region, beginShadowLayer will return 0.
    //
    // The returned context will have the transformation matrix and clipping
    // properly initialized to start doing the painting (no need to account for
    // the shadow offset), however it will not have the same render hints, pen,
    // brush, etc as the passed context. This is intentional, usually shadows
    // have different properties than the shapes which cast them.
    //
    // Once endShadowLayer is called, the temporary image will be drawn with the
    // original context. If blur radius is specified, the shadow will be
    // filtered first.

    PlatformContext beginShadowLayer(GraphicsContext*, const FloatRect& layerArea);
    void endShadowLayer(GraphicsContext*);
    static void purgeScratchBuffer();

    void setShadowsIgnoreTransforms(bool enable) { m_shadowsIgnoreTransforms = enable; }
    bool shadowsIgnoreTransforms() const { return m_shadowsIgnoreTransforms; }
#if PLATFORM(CAIRO)
    void drawRectShadow(GraphicsContext* context, const IntRect& rect, const IntSize& topLeftRadius = IntSize(), const IntSize& topRightRadius = IntSize(), const IntSize& bottomLeftRadius = IntSize(), const IntSize& bottomRightRadius = IntSize());
#endif
#if PLATFORM(QT)
    QPointF offset() const { return QPointF(m_offset.width(), m_offset.height()); }
#endif

private:
    PlatformImage m_layerImage; // Buffer to where the temporary shadow will be drawn to.
    PlatformContext m_layerContext; // Context used to paint the shadow to the layer image.
    FloatRect m_sourceRect; // Sub-rect of m_layerImage that contains the shadow pixels.
    FloatPoint m_layerOrigin; // Top-left corner of the (possibly clipped) bounding rect to draw the shadow to.
    FloatPoint m_layerContextTranslation; // Translation to apply to m_layerContext for the shadow to be correctly clipped.
    bool m_shadowsIgnoreTransforms;

    void adjustBlurDistance(GraphicsContext*);
    void blurLayerImage(unsigned char*, const IntSize& imageSize, int stride);
    IntRect calculateLayerBoundingRect(GraphicsContext*, const FloatRect& layerArea, const IntRect& clipRect);

#if PLATFORM(CAIRO)
    void drawRectShadowWithoutTiling(GraphicsContext*, const IntRect& shadowRect, const IntSize& topLeftRadius, const IntSize& topRightRadius, const IntSize& bottomLeftRadius, const IntSize& bottomRightRadius, float alpha);
#endif
};

} // namespace WebCore

#endif // ContextShadow_h