C++ HTMLCanvasElement::GetCurrentContextType方法代码示例

/* 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);
  }