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

    TransformationMatrix mapping;
    mapping.translate(-m_transformedSourceRect.x(), -m_transformedSourceRect.y());
    if (m_transformMode == Untransform){ 
        // Compute the inverse mapping from the canvas space to the
        // coordinate space of our bitmap.
        mapping = m_orgTransform.inverse() * mapping;
    }
    compositeToCopy(*m_destContext, *m_drawContext, mapping);

    // Save the reference layer so we can tell what changed.
    SkCanvas referenceCanvas(*m_referenceBitmap);
    referenceCanvas.drawBitmap(bitmapForContext(*m_drawContext), 0, 0);
    // Layer rect represents the part of the original layer.
}

void TransparencyWin::setupLayerForTextComposite()
{
    ASSERT(m_transformMode == KeepTransform);
    // Fall through to filling with white.
    setupLayerForWhiteLayer();
}

void TransparencyWin::setupLayerForWhiteLayer()
{
    initializeNewContext();
    m_drawContext->fillRect(IntRect(IntPoint(0, 0), m_layerSize), Color::white);
    // Layer rect represents the part of the original layer.
}

void TransparencyWin::setupTransform(const IntRect& region)
{
    switch (m_transformMode) {
    case KeepTransform:
        setupTransformForKeepTransform(region);
        break;
    case Untransform:
        setupTransformForUntransform();
        break;
    case ScaleTransform:
        setupTransformForScaleTransform();
        break;
    }
}

void TransparencyWin::setupTransformForKeepTransform(const IntRect& region)
{
    if (m_layerMode != NoLayer) {
        // Need to save things since we're modifying the transform.
        m_drawContext->save();
        m_savedOnDrawContext = true;

        // Account for the fact that the layer may be offset from the
        // original. This only happens when we create a layer that has the
        // same coordinate space as the parent.
        TransformationMatrix xform;
        xform.translate(-m_transformedSourceRect.x(), -m_transformedSourceRect.y());

        // We're making a layer, so apply the old transform to the new one
        // so it's maintained. We know the new layer has the identity
        // transform now, we we can just multiply it.
        xform = m_orgTransform * xform;
        m_drawContext->concatCTM(xform);
    }
    m_drawRect = m_sourceRect;
}

void TransparencyWin::setupTransformForUntransform()
{
    ASSERT(m_layerMode != NoLayer);
    // We now have a new layer with the identity transform, which is the
    // Untransformed space we'll use for drawing.
    m_drawRect = IntRect(IntPoint(0, 0), m_layerSize);
}

void TransparencyWin::setupTransformForScaleTransform()
{
    if (m_layerMode == NoLayer) {
        // Need to save things since we're modifying the layer.
        m_drawContext->save();
        m_savedOnDrawContext = true;

        // Undo the transform on the current layer when we're re-using the
        // current one.
        m_drawContext->concatCTM(m_drawContext->getCTM().inverse());

        // We're drawing to the original layer with just a different size.
        m_drawRect = m_transformedSourceRect;
    } else {
        // Just go ahead and use the layer's coordinate space to draw into.
        // It will have the scaled size, and an identity transform loaded.
        m_drawRect = IntRect(IntPoint(0, 0), m_layerSize);
    }
}

void TransparencyWin::setTextCompositeColor(Color color)
{
    m_textCompositeColor = color;
}

void TransparencyWin::initializeNewContext()
{
    int pixelSize = m_layerSize.width() * m_layerSize.height();
    if (pixelSize > maxCachedBufferPixelSize) {
        // Create a 1-off buffer for drawing into. We only need the reference
        // buffer if we're making an OpaqueCompositeLayer.
        bool needReferenceBitmap = m_layerMode == OpaqueCompositeLayer;
        m_ownedBuffers.set(new OwnedBuffers(m_layerSize, needReferenceBitmap));

        m_layerBuffer = m_ownedBuffers->destBitmap();
        m_drawContext = m_layerBuffer->context();
        if (needReferenceBitmap)
            m_referenceBitmap = m_ownedBuffers->referenceBitmap();
        return;
    }

    if (m_cachedBuffers && m_cachedBuffers->canHandleSize(m_layerSize)) {
        // We can re-use the existing buffer. We don't need to clear it since
        // all layer modes will clear it in their initialization.
        m_layerBuffer = m_cachedBuffers->destBitmap();
        m_drawContext = m_cachedBuffers->destBitmap()->context();
        bitmapForContext(*m_drawContext).eraseARGB(0, 0, 0, 0);
        m_referenceBitmap = m_cachedBuffers->referenceBitmap();
        m_referenceBitmap->eraseARGB(0, 0, 0, 0);
        return;
    }

    // Create a new cached buffer.
    if (m_cachedBuffers)
      delete m_cachedBuffers;
    m_cachedBuffers = new OwnedBuffers(m_layerSize, true);

    m_layerBuffer = m_cachedBuffers->destBitmap();
    m_drawContext = m_cachedBuffers->destBitmap()->context();
    m_referenceBitmap = m_cachedBuffers->referenceBitmap();
}

void TransparencyWin::compositeOpaqueComposite()
{
    SkCanvas* destCanvas = canvasForContext(*m_destContext);
    destCanvas->save();

    SkBitmap* bitmap = const_cast<SkBitmap*>(
        &bitmapForContext(*m_layerBuffer->context()));
    
    // This function will be called for WhiteLayer as well, which we don't want
    // to change.
    if (m_layerMode == OpaqueCompositeLayer) {
        // Fix up our bitmap, making it contain only the pixels which changed
        // and transparent everywhere else.
        SkAutoLockPixels sourceLock(*m_referenceBitmap);
        SkAutoLockPixels lock(*bitmap);
        for (int y = 0; y < bitmap->height(); y++) {
            uint32_t* source = m_referenceBitmap->getAddr32(0, y);
            uint32_t* dest = bitmap->getAddr32(0, y);
            for (int x = 0; x < bitmap->width(); x++) {
                // Clear out any pixels that were untouched.
                if (dest[x] == source[x])
                    dest[x] = 0;
                else
                    dest[x] |= (0xFF << SK_A32_SHIFT);
            }
        }
    } else
        makeLayerOpaque();

    SkRect destRect;
    if (m_transformMode != Untransform) {
        // We want to use Untransformed space.
        //
        // Note that we DON'T call m_layerBuffer->image() here. This actually
        // makes a copy of the image, which is unnecessary and slow. Instead, we
        // just draw the image from inside the destination context.
        SkMatrix identity;
        identity.reset();
        destCanvas->setMatrix(identity);

        destRect.set(m_transformedSourceRect.x(), m_transformedSourceRect.y(), m_transformedSourceRect.right(), m_transformedSourceRect.bottom());
    } else
        destRect.set(m_sourceRect.x(), m_sourceRect.y(), m_sourceRect.right(), m_sourceRect.bottom());

    SkPaint paint;
    paint.setFilterBitmap(true);
    paint.setAntiAlias(true);

    // Note that we need to specify the source layer subset, since the bitmap
    // may have been cached and it could be larger than what we're using.
    SkIRect sourceRect = { 0, 0, m_layerSize.width(), m_layerSize.height() };
    destCanvas->drawBitmapRect(*bitmap, &sourceRect, destRect, &paint);
    destCanvas->restore();
}

void TransparencyWin::compositeTextComposite()
{
    const SkBitmap& bitmap = m_layerBuffer->context()->platformContext()->canvas()->getTopPlatformDevice().accessBitmap(true);
    SkColor textColor = m_textCompositeColor.rgb();
    for (int y = 0; y < m_layerSize.height(); y++) {
        uint32_t* row = bitmap.getAddr32(0, y);
        for (int x = 0; x < m_layerSize.width(); x++) {
            // The alpha is the average of the R, G, and B channels.
            int alpha = (SkGetPackedR32(row[x]) + SkGetPackedG32(row[x]) + SkGetPackedB32(row[x])) / 3;

            // Apply that alpha to the text color and write the result.
            row[x] = SkAlphaMulQ(textColor, SkAlpha255To256(255 - alpha));
        }
    }

    // Now the layer has text with the proper color and opacity.
    SkCanvas* destCanvas = canvasForContext(*m_destContext);

    // We want to use Untransformed space (see above)
    SkMatrix identity;
    identity.reset();
    destCanvas->setMatrix(identity);
    SkRect destRect = { m_transformedSourceRect.x(), m_transformedSourceRect.y(), m_transformedSourceRect.right(), m_transformedSourceRect.bottom() };

    // Note that we need to specify the source layer subset, since the bitmap
    // may have been cached and it could be larger than what we're using.
    SkIRect sourceRect = { 0, 0, m_layerSize.width(), m_layerSize.height() };
    destCanvas->drawBitmapRect(bitmap, &sourceRect, destRect, 0);
    destCanvas->restore();
}

void TransparencyWin::makeLayerOpaque()
{
    SkBitmap& bitmap = const_cast<SkBitmap&>(m_drawContext->platformContext()->
        canvas()->getTopPlatformDevice().accessBitmap(true));
    for (int y = 0; y < m_layerSize.height(); y++) {
        uint32_t* row = bitmap.getAddr32(0, y);
        for (int x = 0; x < m_layerSize.width(); x++)
            row[x] |= 0xFF000000;
    }
}

} // namespace WebCore