C++ HTMLCanvasElement类代码示例

void GraphicsContext3D::paintRenderingResultsToCanvas(CanvasRenderingContext* context, DrawingBuffer*)
{
    HTMLCanvasElement* canvas = context->canvas();
    ImageBuffer* imageBuffer = canvas->buffer();

    int rowBytes = m_currentWidth * 4;
    int totalBytes = rowBytes * m_currentHeight;

    OwnArrayPtr<unsigned char> pixels = adoptArrayPtr(new unsigned char[totalBytes]);
    if (!pixels)
        return;

    readRenderingResults(pixels.get(), totalBytes);

    if (!m_attrs.premultipliedAlpha) {
        for (int i = 0; i < totalBytes; i += 4) {
            // Premultiply alpha.
            pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
            pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
            pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
        }
    }

    paintToCanvas(pixels.get(), m_currentWidth, m_currentHeight,
                  canvas->width(), canvas->height(), imageBuffer->context()->platformContext());
}

void RenderHTMLCanvas::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
{
    GraphicsContext* context = paintInfo.context;

    LayoutRect contentRect = contentBoxRect();
    contentRect.moveBy(paintOffset);
    LayoutRect paintRect = replacedContentRect();
    paintRect.moveBy(paintOffset);

    bool clip = !contentRect.contains(paintRect);
    if (clip) {
        // Not allowed to overflow the content box.
        paintInfo.context->save();
        paintInfo.context->clip(pixelSnappedIntRect(contentRect));
    }

    // FIXME: InterpolationNone should be used if ImageRenderingOptimizeContrast is set.
    // See bug for more details: crbug.com/353716.
    InterpolationQuality interpolationQuality = style()->imageRendering() == ImageRenderingOptimizeContrast ? InterpolationLow : CanvasDefaultInterpolationQuality;

    HTMLCanvasElement* canvas = toHTMLCanvasElement(node());
    LayoutSize layoutSize = contentRect.size();
    if (style()->imageRendering() == ImageRenderingPixelated
        && (layoutSize.width() > canvas->width() || layoutSize.height() > canvas->height() || layoutSize == canvas->size())) {
        interpolationQuality = InterpolationNone;
    }

    InterpolationQuality previousInterpolationQuality = context->imageInterpolationQuality();
    context->setImageInterpolationQuality(interpolationQuality);
    canvas->paint(context, paintRect);
    context->setImageInterpolationQuality(previousInterpolationQuality);

    if (clip)
        context->restore();
}

  virtual nsRegion GetOpaqueRegion(nsDisplayListBuilder* aBuilder,
                                   bool* aSnap) override {
    *aSnap = false;
    nsHTMLCanvasFrame* f = static_cast<nsHTMLCanvasFrame*>(Frame());
    HTMLCanvasElement* canvas =
      HTMLCanvasElement::FromContent(f->GetContent());
    nsRegion result;
    if (canvas->GetIsOpaque()) {
      // OK, the entire region painted by the canvas is opaque. But what is
      // that region? It's the canvas's "dest rect" (controlled by the
      // object-fit/object-position CSS properties), clipped to the container's
      // content box (which is what GetBounds() returns). So, we grab those
      // rects and intersect them.
      nsRect constraintRect = GetBounds(aBuilder, aSnap);

      // Need intrinsic size & ratio, for ComputeObjectDestRect:
      nsIntSize canvasSize = f->GetCanvasSize();
      IntrinsicSize intrinsicSize = IntrinsicSizeFromCanvasSize(canvasSize);
      nsSize intrinsicRatio = IntrinsicRatioFromCanvasSize(canvasSize);

      const nsRect destRect =
        nsLayoutUtils::ComputeObjectDestRect(constraintRect,
                                             intrinsicSize, intrinsicRatio,
                                             f->StylePosition());
      return nsRegion(destRect.Intersect(constraintRect));
    }
    return result;
  }

void InspectorCanvasAgent::findFramesWithUninstrumentedCanvases()
{
    class NodeVisitor : public WrappedNodeVisitor {
    public:
        NodeVisitor(Page* page, FramesWithUninstrumentedCanvases& result)
            : m_page(page)
            , m_framesWithUninstrumentedCanvases(result)
        {
        }

        virtual void visitNode(Node* node) OVERRIDE
        {
            if (!node->hasTagName(HTMLNames::canvasTag) || !node->document() || !node->document()->frame())
                return;
            
            Frame* frame = node->document()->frame();
            if (frame->page() != m_page)
                return;

            HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(node);
            if (canvas->renderingContext())
                m_framesWithUninstrumentedCanvases.set(frame, true);
        }

    private:

/* static */ already_AddRefed<ImageBitmap>
ImageBitmap::CreateInternal(nsIGlobalObject* aGlobal, HTMLCanvasElement& aCanvasEl,
                            const Maybe<IntRect>& aCropRect, ErrorResult& aRv)
{
  if (aCanvasEl.Width() == 0 || aCanvasEl.Height() == 0) {
    aRv.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
    return nullptr;
  }

  RefPtr<SourceSurface> surface = GetSurfaceFromElement(aGlobal, aCanvasEl, aRv);

  if (NS_WARN_IF(aRv.Failed())) {
    return nullptr;
  }

  // Crop the source surface if needed.
  RefPtr<SourceSurface> croppedSurface;
  IntRect cropRect = aCropRect.valueOr(IntRect());

  // If the HTMLCanvasElement's rendering context is WebGL, then the snapshot
  // we got from the HTMLCanvasElement is a DataSourceSurface which is a copy
  // of the rendering context. We handle cropping in this case.
  if ((aCanvasEl.GetCurrentContextType() == CanvasContextType::WebGL1 ||
       aCanvasEl.GetCurrentContextType() == CanvasContextType::WebGL2) &&
      aCropRect.isSome()) {
    // The _surface_ must be a DataSourceSurface.
    MOZ_ASSERT(surface->GetType() == SurfaceType::DATA,
               "The snapshot SourceSurface from WebGL rendering contest is not \
               DataSourceSurface.");
    RefPtr<DataSourceSurface> dataSurface = surface->GetDataSurface();
    croppedSurface = CropAndCopyDataSourceSurface(dataSurface, cropRect);
    cropRect.MoveTo(0, 0);
  }

JSValue JSHTMLCanvasElement::getContext(ExecState* exec)
{
    HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(impl());
    const String& contextId = exec->argument(0).toString(exec)->value(exec);
    
    RefPtr<CanvasContextAttributes> attrs;
#if ENABLE(WEBGL)
    if (HTMLCanvasElement::is3dType(contextId)) {
        get3DContextAttributes(exec, attrs);
        if (exec->hadException())
            return jsUndefined();
    }
#endif
    
    CanvasRenderingContext* context = canvas->getContext(contextId, attrs.get());
    if (!context)
        return jsNull();
    JSValue jsValue = toJS(exec, globalObject(), WTF::getPtr(context));
    if (InspectorInstrumentation::canvasAgentEnabled(canvas->document())) {
        ScriptObject contextObject(exec, jsValue.getObject());
        ScriptObject wrapped;
        if (context->is2d())
            wrapped = InspectorInstrumentation::wrapCanvas2DRenderingContextForInstrumentation(canvas->document(), contextObject);
#if ENABLE(WEBGL)
        else if (context->is3d())
            wrapped = InspectorInstrumentation::wrapWebGLRenderingContextForInstrumentation(canvas->document(), contextObject);
#endif
        if (!wrapped.hasNoValue())
            return wrapped.jsValue();
    }
    return jsValue;
}

static void heightAttrSetter(v8::Local<v8::String> name, v8::Local<v8::Value> value, const v8::AccessorInfo& info)
{
    HTMLCanvasElement* imp = V8HTMLCanvasElement::toNative(info.Holder());
    int v = toInt32(value);
    imp->setHeight(v);
    return;
}

bool RenderHTMLCanvas::requiresLayer() const
{
    if (RenderReplaced::requiresLayer())
        return true;
    
    HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(node());
    return canvas && canvas->renderingContext() && canvas->renderingContext()->isAccelerated();
}

PassRefPtr<Image> CSSCanvasValue::image(RenderObject* renderer, const IntSize& /*size*/)
{
    ASSERT(clients().contains(renderer));
    HTMLCanvasElement* elt = element(renderer->document());
    if (!elt || !elt->buffer())
        return 0;
    return elt->copiedImage();
}

CompositingReasons RenderHTMLCanvas::additionalCompositingReasons() const
{
    HTMLCanvasElement* canvas = toHTMLCanvasElement(node());
    if (canvas->renderingContext() && canvas->renderingContext()->isAccelerated())
        return CompositingReasonCanvas;

    return CompositingReasonNone;
}

    /* PreTransactionCallback gets called by the Layers code every time the
     * WebGL canvas is going to be composited.
     */
    static void PreTransactionCallback(void* data)
    {
        WebGLContextUserData* userdata = static_cast<WebGLContextUserData*>(data);
        HTMLCanvasElement* canvas = userdata->mContent;
        WebGLContext* context = static_cast<WebGLContext*>(canvas->GetContextAtIndex(0));

        // Present our screenbuffer, if needed.
        context->PresentScreenBuffer();
    }

void V8HTMLCanvasElement::getContextMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
{
    v8::Handle<v8::Object> holder = info.Holder();
    v8::Isolate* isolate = info.GetIsolate();
    HTMLCanvasElement* impl = V8HTMLCanvasElement::toNative(holder);
    TOSTRING_VOID(V8StringResource<>, contextIdResource, info[0]);
    String contextId = contextIdResource;
    RefPtr<CanvasContextAttributes> attributes = nullptr;
    if (contextId == "webgl" || contextId == "experimental-webgl") {
        RefPtr<WebGLContextAttributes> webGLAttributes = WebGLContextAttributes::create();
        if (info.Length() > 1 && info[1]->IsObject()) {
            v8::Handle<v8::Object> jsAttributes = info[1]->ToObject();
            v8::Handle<v8::String> alpha = v8AtomicString(isolate, "alpha");
            if (jsAttributes->Has(alpha) && !isUndefinedOrNull(jsAttributes->Get(alpha)))
                webGLAttributes->setAlpha(jsAttributes->Get(alpha)->BooleanValue());
            v8::Handle<v8::String> depth = v8AtomicString(isolate, "depth");
            if (jsAttributes->Has(depth) && !isUndefinedOrNull(jsAttributes->Get(depth)))
                webGLAttributes->setDepth(jsAttributes->Get(depth)->BooleanValue());
            v8::Handle<v8::String> stencil = v8AtomicString(isolate, "stencil");
            if (jsAttributes->Has(stencil) && !isUndefinedOrNull(jsAttributes->Get(stencil)))
                webGLAttributes->setStencil(jsAttributes->Get(stencil)->BooleanValue());
            v8::Handle<v8::String> antialias = v8AtomicString(isolate, "antialias");
            if (jsAttributes->Has(antialias) && !isUndefinedOrNull(jsAttributes->Get(antialias)))
                webGLAttributes->setAntialias(jsAttributes->Get(antialias)->BooleanValue());
            v8::Handle<v8::String> premultipliedAlpha = v8AtomicString(isolate, "premultipliedAlpha");
            if (jsAttributes->Has(premultipliedAlpha) && !isUndefinedOrNull(jsAttributes->Get(premultipliedAlpha)))
                webGLAttributes->setPremultipliedAlpha(jsAttributes->Get(premultipliedAlpha)->BooleanValue());
            v8::Handle<v8::String> preserveDrawingBuffer = v8AtomicString(isolate, "preserveDrawingBuffer");
            if (jsAttributes->Has(preserveDrawingBuffer) && !isUndefinedOrNull(jsAttributes->Get(preserveDrawingBuffer)))
                webGLAttributes->setPreserveDrawingBuffer(jsAttributes->Get(preserveDrawingBuffer)->BooleanValue());
            v8::Handle<v8::String> failIfMajorPerformanceCaveat = v8AtomicString(isolate, "failIfMajorPerformanceCaveat");
            if (jsAttributes->Has(failIfMajorPerformanceCaveat) && !isUndefinedOrNull(jsAttributes->Get(failIfMajorPerformanceCaveat)))
                webGLAttributes->setFailIfMajorPerformanceCaveat(jsAttributes->Get(failIfMajorPerformanceCaveat)->BooleanValue());
        }
        attributes = webGLAttributes;
    } else {
        RefPtr<Canvas2DContextAttributes> canvas2DAttributes = Canvas2DContextAttributes::create();
        attributes = canvas2DAttributes;
    }
    CanvasRenderingContext* result = impl->getContext(contextId, attributes.get());
    if (!result) {
        v8SetReturnValueNull(info);
        return;
    }
    if (result->is2d()) {
        v8::Handle<v8::Value> v8Result = toV8(toCanvasRenderingContext2D(result), info.Holder(), info.GetIsolate());
        v8SetReturnValue(info, v8Result);
        return;
    }
    if (result->is3d()) {
        v8::Handle<v8::Value> v8Result = toV8(toWebGLRenderingContext(result), info.Holder(), info.GetIsolate());
        v8SetReturnValue(info, v8Result);
        return;
    }
    ASSERT_NOT_REACHED();
    v8SetReturnValueNull(info);
}

void JSHTMLCanvasElement::markChildren(MarkStack& markStack)
{
    Base::markChildren(markStack);

    HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(impl());
    JSGlobalData& globalData = *Heap::heap(this)->globalData();

    markDOMObjectWrapper(markStack, globalData, canvas->renderingContext());
}

void GraphicsContext3DInternal::paintRenderingResultsToCanvas(CanvasRenderingContext* context)
{
    HTMLCanvasElement* canvas = context->canvas();
    ImageBuffer* imageBuffer = canvas->buffer();
    unsigned char* pixels = 0;
#if PLATFORM(SKIA)
    const SkBitmap* canvasBitmap = imageBuffer->context()->platformContext()->bitmap();
    const SkBitmap* readbackBitmap = 0;
    ASSERT(canvasBitmap->config() == SkBitmap::kARGB_8888_Config);
    if (canvasBitmap->width() == m_impl->width() && canvasBitmap->height() == m_impl->height()) {
        // This is the fastest and most common case. We read back
        // directly into the canvas's backing store.
        readbackBitmap = canvasBitmap;
        m_resizingBitmap.reset();
    } else {
        // We need to allocate a temporary bitmap for reading back the
        // pixel data. We will then use Skia to rescale this bitmap to
        // the size of the canvas's backing store.
        if (m_resizingBitmap.width() != m_impl->width() || m_resizingBitmap.height() != m_impl->height()) {
            m_resizingBitmap.setConfig(SkBitmap::kARGB_8888_Config,
                                       m_impl->width(),
                                       m_impl->height());
            if (!m_resizingBitmap.allocPixels())
                return;
        }
        readbackBitmap = &m_resizingBitmap;
    }

    // Read back the frame buffer.
    SkAutoLockPixels bitmapLock(*readbackBitmap);
    pixels = static_cast<unsigned char*>(readbackBitmap->getPixels());
#elif PLATFORM(CG)
    if (m_renderOutput)
        pixels = m_renderOutput;
#else
#error Must port to your platform
#endif

    m_impl->readBackFramebuffer(pixels, 4 * m_impl->width() * m_impl->height());

#if PLATFORM(SKIA)
    if (m_resizingBitmap.readyToDraw()) {
        // We need to draw the resizing bitmap into the canvas's backing store.
        SkCanvas canvas(*canvasBitmap);
        SkRect dst;
        dst.set(SkIntToScalar(0), SkIntToScalar(0), SkIntToScalar(canvasBitmap->width()), SkIntToScalar(canvasBitmap->height()));
        canvas.drawBitmapRect(m_resizingBitmap, 0, dst);
    }
#elif PLATFORM(CG)
    if (m_renderOutput && context->is3d()) {
        WebGLRenderingContext* webGLContext = static_cast<WebGLRenderingContext*>(context);
        webGLContext->graphicsContext3D()->paintToCanvas(m_renderOutput, m_impl->width(), m_impl->height(), canvas->width(), canvas->height(), imageBuffer->context()->platformContext());
    }
#else
#error Must port to your platform
#endif
}

    /** DidTransactionCallback gets called by the Layers code everytime the WebGL canvas gets composite,
      * so it really is the right place to put actions that have to be performed upon compositing
      */
    static void DidTransactionCallback(void* aData)
    {
        WebGLContextUserData *userdata = static_cast<WebGLContextUserData*>(aData);
        HTMLCanvasElement *canvas = userdata->mContent;
        WebGLContext *context = static_cast<WebGLContext*>(canvas->GetContextAtIndex(0));

        // Mark ourselves as no longer invalidated.
        context->MarkContextClean();

        context->UpdateLastUseIndex();
    }