C++ Layer::GetFrameMetrics方法代码示例

void
ClientTiledThebesLayer::GetAncestorLayers(Layer** aOutScrollAncestor,
                                          Layer** aOutDisplayPortAncestor)
{
  Layer* scrollAncestor = nullptr;
  Layer* displayPortAncestor = nullptr;
  for (Layer* ancestor = this; ancestor; ancestor = ancestor->GetParent()) {
    const FrameMetrics& metrics = ancestor->GetFrameMetrics();
    if (!scrollAncestor && metrics.GetScrollId() != FrameMetrics::NULL_SCROLL_ID) {
      scrollAncestor = ancestor;
    }
    if (!metrics.mDisplayPort.IsEmpty()) {
      displayPortAncestor = ancestor;
      // Any layer that has a displayport must be scrollable, so we can break
      // here.
      break;
    }
  }
  if (aOutScrollAncestor) {
    *aOutScrollAncestor = scrollAncestor;
  }
  if (aOutDisplayPortAncestor) {
    *aOutDisplayPortAncestor = displayPortAncestor;
  }
}

void
ClientTiledThebesLayer::BeginPaint()
{
  mPaintData.mLowPrecisionPaintCount = 0;
  mPaintData.mPaintFinished = false;
  mPaintData.mCompositionBounds.SetEmpty();
  mPaintData.mCriticalDisplayPort.SetEmpty();

  if (!GetBaseTransform().Is2D()) {
    // Give up if there is a complex CSS transform on the layer. We might
    // eventually support these but for now it's too complicated to handle
    // given that it's a pretty rare scenario.
    return;
  }

  // Get the metrics of the nearest scrollable layer and the nearest layer
  // with a displayport.
  Layer* scrollAncestor = nullptr;
  Layer* displayPortAncestor = nullptr;
  GetAncestorLayers(&scrollAncestor, &displayPortAncestor);

  if (!displayPortAncestor || !scrollAncestor) {
    // No displayport or scroll ancestor, so we can't do progressive rendering.
#if defined(MOZ_WIDGET_ANDROID) || defined(MOZ_B2G)
    // Both Android and b2g are guaranteed to have a displayport set, so this
    // should never happen.
    NS_WARNING("Tiled Thebes layer with no scrollable container ancestor");
#endif
    return;
  }

  TILING_LOG("TILING %p: Found scrollAncestor %p and displayPortAncestor %p\n", this,
    scrollAncestor, displayPortAncestor);

  const FrameMetrics& scrollMetrics = scrollAncestor->GetFrameMetrics();
  const FrameMetrics& displayportMetrics = displayPortAncestor->GetFrameMetrics();

  // Calculate the transform required to convert ParentLayer space of our
  // display port ancestor to the Layer space of this layer.
  gfx::Matrix4x4 transformDisplayPortToLayer =
    GetTransformToAncestorsParentLayer(this, displayPortAncestor);
  transformDisplayPortToLayer.Invert();

  // Note that below we use GetZoomToParent() in a number of places. Because this
  // code runs on the client side, the mTransformScale field of the FrameMetrics
  // will not have been set. This can result in incorrect values being returned
  // by GetZoomToParent() when we have CSS transforms set on some of these layers.
  // This code should be audited and updated as part of fixing bug 993525.

  // Compute the critical display port that applies to this layer in the
  // LayoutDevice space of this layer.
  ParentLayerRect criticalDisplayPort =
    (displayportMetrics.mCriticalDisplayPort * displayportMetrics.GetZoomToParent())
    + displayportMetrics.mCompositionBounds.TopLeft();
  mPaintData.mCriticalDisplayPort = RoundedOut(
    ApplyParentLayerToLayerTransform(transformDisplayPortToLayer, criticalDisplayPort));
  TILING_LOG("TILING %p: Critical displayport %s\n", this, Stringify(mPaintData.mCriticalDisplayPort).c_str());

  // Store the resolution from the displayport ancestor layer. Because this is Gecko-side,
  // before any async transforms have occurred, we can use the zoom for this.
  mPaintData.mResolution = displayportMetrics.GetZoomToParent();
  TILING_LOG("TILING %p: Resolution %f\n", this, mPaintData.mResolution.scale);

  // Store the applicable composition bounds in this layer's Layer units.
  mPaintData.mTransformToCompBounds =
    GetTransformToAncestorsParentLayer(this, scrollAncestor);
  gfx::Matrix4x4 transformToBounds = mPaintData.mTransformToCompBounds;
  transformToBounds.Invert();
  mPaintData.mCompositionBounds = ApplyParentLayerToLayerTransform(
    transformToBounds, scrollMetrics.mCompositionBounds);
  TILING_LOG("TILING %p: Composition bounds %s\n", this, Stringify(mPaintData.mCompositionBounds).c_str());

  // Calculate the scroll offset since the last transaction
  mPaintData.mScrollOffset = displayportMetrics.GetScrollOffset() * displayportMetrics.GetZoomToParent();
  TILING_LOG("TILING %p: Scroll offset %s\n", this, Stringify(mPaintData.mScrollOffset).c_str());
}

float
LayerManagerComposite::ComputeRenderIntegrity()
{
  // We only ever have incomplete rendering when progressive tiles are enabled.
  Layer* root = GetRoot();
  if (!gfxPrefs::UseProgressiveTilePainting() || !root) {
    return 1.f;
  }

  const FrameMetrics& rootMetrics = root->GetFrameMetrics();
  ParentLayerIntRect bounds = RoundedToInt(rootMetrics.mCompositionBounds);
  nsIntRect screenRect(bounds.x,
                       bounds.y,
                       bounds.width,
                       bounds.height);

  float lowPrecisionMultiplier = 1.0f;
  float highPrecisionMultiplier = 1.0f;

#ifdef MOZ_ANDROID_OMTC
  // Use the transform on the primary scrollable layer and its FrameMetrics
  // to find out how much of the viewport the current displayport covers
  Layer* primaryScrollable = GetPrimaryScrollableLayer();
  if (primaryScrollable) {
    // This is derived from the code in
    // AsyncCompositionManager::TransformScrollableLayer
    const FrameMetrics& metrics = primaryScrollable->GetFrameMetrics();
    Matrix4x4 transform = primaryScrollable->GetEffectiveTransform();
    transform.ScalePost(metrics.mResolution.scale, metrics.mResolution.scale, 1);

    // Clip the screen rect to the document bounds
    Rect documentBounds =
      transform.TransformBounds(Rect(metrics.mScrollableRect.x - metrics.GetScrollOffset().x,
                                     metrics.mScrollableRect.y - metrics.GetScrollOffset().y,
                                     metrics.mScrollableRect.width,
                                     metrics.mScrollableRect.height));
    documentBounds.RoundOut();
    screenRect = screenRect.Intersect(nsIntRect(documentBounds.x, documentBounds.y,
                                                documentBounds.width, documentBounds.height));

    // If the screen rect is empty, the user has scrolled entirely into
    // over-scroll and so we can be considered to have full integrity.
    if (screenRect.IsEmpty()) {
      return 1.0f;
    }

    // Work out how much of the critical display-port covers the screen
    bool hasLowPrecision = false;
    if (!metrics.mCriticalDisplayPort.IsEmpty()) {
      hasLowPrecision = true;
      highPrecisionMultiplier =
        GetDisplayportCoverage(metrics.mCriticalDisplayPort, transform, screenRect);
    }

    // Work out how much of the display-port covers the screen
    if (!metrics.mDisplayPort.IsEmpty()) {
      if (hasLowPrecision) {
        lowPrecisionMultiplier =
          GetDisplayportCoverage(metrics.mDisplayPort, transform, screenRect);
      } else {
        lowPrecisionMultiplier = highPrecisionMultiplier =
          GetDisplayportCoverage(metrics.mDisplayPort, transform, screenRect);
      }
    }
  }

  // If none of the screen is covered, we have zero integrity.
  if (highPrecisionMultiplier <= 0.0f && lowPrecisionMultiplier <= 0.0f) {
    return 0.0f;
  }
#endif // MOZ_ANDROID_OMTC

  nsIntRegion screenRegion(screenRect);
  nsIntRegion lowPrecisionScreenRegion(screenRect);
  Matrix4x4 transform;
  ComputeRenderIntegrityInternal(root, screenRegion,
                                 lowPrecisionScreenRegion, transform);

  if (!screenRegion.IsEqual(screenRect)) {
    // Calculate the area of the region. All rects in an nsRegion are
    // non-overlapping.
    float screenArea = screenRect.width * screenRect.height;
    float highPrecisionIntegrity = screenRegion.Area() / screenArea;
    float lowPrecisionIntegrity = 1.f;
    if (!lowPrecisionScreenRegion.IsEqual(screenRect)) {
      lowPrecisionIntegrity = lowPrecisionScreenRegion.Area() / screenArea;
    }

    return ((highPrecisionIntegrity * highPrecisionMultiplier) +
            (lowPrecisionIntegrity * lowPrecisionMultiplier)) / 2;
  }

  return 1.f;
}