C++ GraphicsContext::beginTransparencyLayer方法代码示例

void FindPageOverlay::drawRect(GraphicsContext& graphicsContext, const IntRect& dirtyRect)
{
    Vector<IntRect> rects = rectsForTextMatches();
    ASSERT(!rects.isEmpty());

    FrameView* frameView = webPage()->corePage()->mainFrame()->view();

    int width = frameView->width();
    if (frameView->verticalScrollbar())
        width -= frameView->verticalScrollbar()->width();
    int height = frameView->height();
    if (frameView->horizontalScrollbar())
        height -= frameView->horizontalScrollbar()->height();
    
    IntRect paintRect = intersection(dirtyRect, IntRect(0, 0, width, height));
    if (paintRect.isEmpty())
        return;

    graphicsContext.beginTransparencyLayer(1);
    graphicsContext.setCompositeOperation(CompositeCopy);

    // Draw the background.
    graphicsContext.fillRect(paintRect, overlayBackgroundColor(), sRGBColorSpace);

    // FIXME: Draw the holes.

    graphicsContext.endTransparencyLayer();
}

void RenderEmbeddedObject::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    if (!showsUnavailablePluginIndicator())
        return;

    if (paintInfo.phase == PaintPhaseSelection)
        return;

    GraphicsContext* context = paintInfo.context;
    if (context->paintingDisabled())
        return;

    FloatRect contentRect;
    FloatRect indicatorRect;
    FloatRect replacementTextRect;
    FloatRect arrowRect;
    FontCascade font;
    TextRun run("");
    float textWidth;
    if (!getReplacementTextGeometry(paintOffset, contentRect, indicatorRect, replacementTextRect, arrowRect, font, run, textWidth))
        return;

    Path background;
    background.addRoundedRect(indicatorRect, FloatSize(replacementTextRoundedRectRadius, replacementTextRoundedRectRadius));

    GraphicsContextStateSaver stateSaver(*context);
    context->clip(contentRect);
    context->setFillColor(m_unavailablePluginIndicatorIsPressed ? replacementTextRoundedRectPressedColor() : replacementTextRoundedRectColor(), style().colorSpace());
    context->fillPath(background);

    Path strokePath;
    FloatRect strokeRect(indicatorRect);
    strokeRect.inflate(1);
    strokePath.addRoundedRect(strokeRect, FloatSize(replacementTextRoundedRectRadius + 1, replacementTextRoundedRectRadius + 1));

    context->setStrokeColor(unavailablePluginBorderColor(), style().colorSpace());
    context->setStrokeThickness(2);
    context->strokePath(strokePath);

    const FontMetrics& fontMetrics = font.fontMetrics();
    float labelX = roundf(replacementTextRect.location().x() + replacementTextRoundedRectLeftTextMargin);
    float labelY = roundf(replacementTextRect.location().y() + (replacementTextRect.size().height() - fontMetrics.height()) / 2 + fontMetrics.ascent() + replacementTextRoundedRectTopTextMargin);
    context->setFillColor(replacementTextColor(), style().colorSpace());
    context->drawBidiText(font, run, FloatPoint(labelX, labelY));

    if (shouldUnavailablePluginMessageBeButton(document(), m_pluginUnavailabilityReason)) {
        arrowRect.inflate(-replacementArrowCirclePadding);

        context->beginTransparencyLayer(1.0);
        context->setFillColor(replacementTextColor(), style().colorSpace());
        context->fillEllipse(arrowRect);

        context->setCompositeOperation(CompositeClear);
        drawReplacementArrow(context, arrowRect);
        context->endTransparencyLayer();
    }
}

void InlinePainter::paintOutline(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    RenderStyle* styleToUse = m_renderInline.style();
    if (!styleToUse->hasOutline())
        return;

    LayoutRect bounds;
    if (RuntimeEnabledFeatures::slimmingPaintEnabled()) {
        // FIXME: Use tighter bounds.
        RenderBlock* cb = m_renderInline.containingBlock();
        bounds = cb->visualOverflowRect();
        bounds.moveBy(paintOffset);
    }
    RenderDrawingRecorder recorder(paintInfo.context, m_renderInline, paintInfo.phase, bounds);
    if (recorder.canUseCachedDrawing())
        return;

    if (styleToUse->outlineStyleIsAuto()) {
        if (RenderTheme::theme().shouldDrawDefaultFocusRing(&m_renderInline)) {
            // Only paint the focus ring by hand if the theme isn't able to draw the focus ring.
            ObjectPainter(m_renderInline).paintFocusRing(paintInfo, paintOffset, styleToUse);
        }
        return;
    }

    if (styleToUse->outlineStyle() == BNONE)
        return;

    Vector<LayoutRect> rects;

    rects.append(LayoutRect());
    for (InlineFlowBox* curr = m_renderInline.firstLineBox(); curr; curr = curr->nextLineBox()) {
        RootInlineBox& root = curr->root();
        LayoutUnit top = std::max<LayoutUnit>(root.lineTop(), curr->logicalTop());
        LayoutUnit bottom = std::min<LayoutUnit>(root.lineBottom(), curr->logicalBottom());
        rects.append(LayoutRect(curr->x(), top, curr->logicalWidth(), bottom - top));
    }
    rects.append(LayoutRect());

    Color outlineColor = m_renderInline.resolveColor(styleToUse, CSSPropertyOutlineColor);
    bool useTransparencyLayer = outlineColor.hasAlpha();

    GraphicsContext* graphicsContext = paintInfo.context;
    if (useTransparencyLayer) {
        graphicsContext->beginTransparencyLayer(static_cast<float>(outlineColor.alpha()) / 255);
        outlineColor = Color(outlineColor.red(), outlineColor.green(), outlineColor.blue());
    }

    for (unsigned i = 1; i < rects.size() - 1; i++)
        paintOutlineForLine(graphicsContext, paintOffset, rects.at(i - 1), rects.at(i), rects.at(i + 1), outlineColor);

    if (useTransparencyLayer)
        graphicsContext->endLayer();
}

void PageOverlay::drawRect(GraphicsContext& graphicsContext, const IntRect& dirtyRect)
{
    // If the dirty rect is outside the bounds, ignore it.
    IntRect paintRect = intersection(dirtyRect, bounds());
    if (paintRect.isEmpty())
        return;

    GraphicsContextStateSaver stateSaver(graphicsContext);
    graphicsContext.beginTransparencyLayer(1);
    graphicsContext.setCompositeOperation(CompositeCopy);

    m_client->drawRect(this, graphicsContext, paintRect);

    graphicsContext.endTransparencyLayer();
}

void CrossfadeGeneratedImage::drawCrossfade(GraphicsContext& context)
{
    // Draw nothing if either of the images hasn't loaded yet.
    if (m_fromImage == Image::nullImage() || m_toImage == Image::nullImage())
        return;

    GraphicsContextStateSaver stateSaver(context);

    context.clip(FloatRect(FloatPoint(), m_crossfadeSize));
    context.beginTransparencyLayer(1);

    drawCrossfadeSubimage(context, m_fromImage, CompositeSourceOver, 1 - m_percentage, m_crossfadeSize);
    drawCrossfadeSubimage(context, m_toImage, CompositePlusLighter, m_percentage, m_crossfadeSize);

    context.endTransparencyLayer();
}

void SVGImage::draw(GraphicsContext& context, const FloatRect& dstRect, const FloatRect& srcRect, CompositeOperator compositeOp, BlendMode blendMode, ImageOrientationDescription)
{
    if (!m_page)
        return;

    FrameView* view = frameView();
    ASSERT(view);

    GraphicsContextStateSaver stateSaver(context);
    context.setCompositeOperation(compositeOp, blendMode);
    context.clip(enclosingIntRect(dstRect));

    float alpha = context.alpha();
    bool compositingRequiresTransparencyLayer = compositeOp != CompositeSourceOver || blendMode != BlendModeNormal || alpha < 1;
    if (compositingRequiresTransparencyLayer) {
        context.beginTransparencyLayer(alpha);
        context.setCompositeOperation(CompositeSourceOver, BlendModeNormal);
    }

    FloatSize scale(dstRect.width() / srcRect.width(), dstRect.height() / srcRect.height());
    
    // We can only draw the entire frame, clipped to the rect we want. So compute where the top left
    // of the image would be if we were drawing without clipping, and translate accordingly.
    FloatSize topLeftOffset(srcRect.location().x() * scale.width(), srcRect.location().y() * scale.height());
    FloatPoint destOffset = dstRect.location() - topLeftOffset;

    context.translate(destOffset.x(), destOffset.y());
    context.scale(scale);

    view->resize(containerSize());

    if (!m_url.isEmpty())
        view->scrollToFragment(m_url);
    
    if (view->needsLayout())
        view->layout();

    view->paint(context, intersection(context.clipBounds(), enclosingIntRect(srcRect)));

    if (compositingRequiresTransparencyLayer)
        context.endTransparencyLayer();

    stateSaver.restore();

    if (imageObserver())
        imageObserver()->didDraw(this);
}

static void drawCrossfadeSubimage(GraphicsContext& context, Image* image, CompositeOperator operation, float opacity, const FloatSize& targetSize)
{
    FloatSize imageSize = image->size();

    // SVGImage resets the opacity when painting, so we have to use transparency layers to accurately paint one at a given opacity.
    bool useTransparencyLayer = image->isSVGImage();

    GraphicsContextStateSaver stateSaver(context);

    context.setCompositeOperation(operation);

    if (useTransparencyLayer)
        context.beginTransparencyLayer(opacity);
    else
        context.setAlpha(opacity);

    if (targetSize != imageSize)
        context.scale(FloatSize(targetSize.width() / imageSize.width(), targetSize.height() / imageSize.height()));
    context.drawImage(image, ColorSpaceDeviceRGB, IntPoint());

    if (useTransparencyLayer)
        context.endTransparencyLayer();
}

void BeginTransparencyLayer::apply(GraphicsContext& context) const
{
    context.beginTransparencyLayer(m_opacity);
}