transparencywin.cpp

linux下开源浏览器WebKit的源码,市面上的很多商用浏览器都是移植自WebKit

/*
 * Copyright (C) 2009 Google 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:
 * 
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
 * OWNER 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,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "config.h"
#include <windows.h>

#include "GraphicsContext.h"
#include "ImageBuffer.h"
#include "PlatformContextSkia.h"
#include "SimpleFontData.h"
#include "TransformationMatrix.h"
#include "TransparencyWin.h"

#include "SkColorPriv.h"
#include "skia/ext/platform_canvas.h"

namespace WebCore {

namespace {

// The maximum size in pixels of the buffer we'll keep around for drawing text
// into. Buffers larger than this will be destroyed when we're done with them.
const int maxCachedBufferPixelSize = 65536;

inline skia::PlatformCanvas* canvasForContext(const GraphicsContext& context)
{
    return context.platformContext()->canvas();
}

inline const SkBitmap& bitmapForContext(const GraphicsContext& context)
{
    return canvasForContext(context)->getTopPlatformDevice().accessBitmap(false);
}

void compositeToCopy(const GraphicsContext& sourceLayers,
                     GraphicsContext& destContext,
                     const TransformationMatrix& matrix)
{
    // Make a list of all devices. The iterator goes top-down, and we want
    // bottom-up. Note that each layer can also have an offset in canvas
    // coordinates, which is the (x, y) position.
    struct DeviceInfo {
        DeviceInfo(SkDevice* d, int lx, int ly)
            : device(d)
            , x(lx)
            , y(ly) {}
        SkDevice* device;
        int x;
        int y;
    };
    Vector<DeviceInfo> devices;
    SkCanvas* sourceCanvas = canvasForContext(sourceLayers);
    SkCanvas::LayerIter iter(sourceCanvas, false);
    while (!iter.done()) {
        devices.append(DeviceInfo(iter.device(), iter.x(), iter.y()));
        iter.next();
    }

    // Create a temporary canvas for the compositing into the destination.
    SkBitmap* destBmp = const_cast<SkBitmap*>(&bitmapForContext(destContext));
    SkCanvas destCanvas(*destBmp);
    destCanvas.setMatrix(matrix);

    for (int i = devices.size() - 1; i >= 0; i--) {
        const SkBitmap& srcBmp = devices[i].device->accessBitmap(false);

        SkRect destRect;
        destRect.fLeft = devices[i].x;
        destRect.fTop = devices[i].y;
        destRect.fRight = destRect.fLeft + srcBmp.width();
        destRect.fBottom = destRect.fTop + srcBmp.height();

        destCanvas.drawBitmapRect(srcBmp, 0, destRect);
    }
}

}  // namespace

// If either of these pointers is non-null, both must be valid and point to
// bitmaps of the same size.
class TransparencyWin::OwnedBuffers {
public:
    OwnedBuffers(const IntSize& size, bool needReferenceBuffer)
    {
        m_destBitmap.adopt(ImageBuffer::create(size, false));

        if (needReferenceBuffer) {
            m_referenceBitmap.setConfig(SkBitmap::kARGB_8888_Config, size.width(), size.height());
            m_referenceBitmap.allocPixels();
            m_referenceBitmap.eraseARGB(0, 0, 0, 0);
        }
    }

    ImageBuffer* destBitmap() { return m_destBitmap.get(); }

    // This bitmap will be empty if you don't specify needReferenceBuffer to the
    // constructor.
    SkBitmap* referenceBitmap() { return &m_referenceBitmap; }

    // Returns whether the current layer will fix a buffer of the given size.
    bool canHandleSize(const IntSize& size) const
    {
        return m_destBitmap->size().width() >= size.width() && m_destBitmap->size().height() >= size.height();
    }

private:
    // The destination bitmap we're drawing into.
    OwnPtr<ImageBuffer> m_destBitmap;

    // This could be an ImageBuffer but this is an optimization. Since this is
    // only ever used as a reference, we don't need to make a full
    // PlatformCanvas using Skia on Windows. Just allocating a regular SkBitmap
    // is much faster since it's just a Malloc rather than a GDI call.
    SkBitmap m_referenceBitmap;
};

TransparencyWin::OwnedBuffers* TransparencyWin::m_cachedBuffers = 0;

TransparencyWin::TransparencyWin()
    : m_destContext(0)
    , m_orgTransform()
    , m_layerMode(NoLayer)
    , m_transformMode(KeepTransform)
    , m_drawContext(0)
    , m_savedOnDrawContext(false)
    , m_layerBuffer(0)
    , m_referenceBitmap(0)
{
}

TransparencyWin::~TransparencyWin()
{
    // Matches the save() in initializeNewTextContext (or the constructor for
    // SCALE) to put the context back into the same state we found it.
    if (m_savedOnDrawContext)
        m_drawContext->restore();

    switch (m_layerMode) {
    case NoLayer:
        break;
    case OpaqueCompositeLayer:
    case WhiteLayer:
        compositeOpaqueComposite();
        break;
    case TextComposite:
        compositeTextComposite();
        break;
    }
}

void TransparencyWin::init(GraphicsContext* dest,
                           LayerMode layerMode,
                           TransformMode transformMode,
                           const IntRect& region) {
    m_destContext = dest;
    m_orgTransform = dest->getCTM();
    m_layerMode = layerMode;
    m_transformMode = transformMode;
    m_sourceRect = region;

    computeLayerSize();
    setupLayer();
    setupTransform(region);
}

void TransparencyWin::computeLayerSize()
{
    if (m_transformMode == Untransform) {
        // The meaning of the "transformed" source rect is a little ambigous
        // here. The rest of the code doesn't care about it in the Untransform
        // case since we're using our own happy coordinate system. So we set it
        // to be the source rect since that matches how the code below actually
        // uses the variable: to determine how to translate things to account
        // for the offset of the layer.
        m_transformedSourceRect = m_sourceRect;
        m_layerSize = IntSize(m_sourceRect.width(), m_sourceRect.height());
    } else {
        m_transformedSourceRect = m_orgTransform.mapRect(m_sourceRect);
        m_layerSize = IntSize(m_transformedSourceRect.width(), m_transformedSourceRect.height());
    }
}

void TransparencyWin::setupLayer()
{
    switch (m_layerMode) {
    case NoLayer:
        setupLayerForNoLayer();
        break;
    case OpaqueCompositeLayer:
        setupLayerForOpaqueCompositeLayer();
        break;
    case TextComposite:
        setupLayerForTextComposite();
        break;
    case WhiteLayer:
        setupLayerForWhiteLayer();
        break;
    }
}

void TransparencyWin::setupLayerForNoLayer()
{
    m_drawContext = m_destContext;  // Draw to the source context.
}

void TransparencyWin::setupLayerForOpaqueCompositeLayer()
{
    initializeNewContext();