C++ LayerComposite类代码示例

bool
LayerTransactionParent::Attach(ShadowLayerParent* aLayerParent,
                               CompositableHost* aCompositable,
                               bool aIsAsync)
{
  if (!aCompositable) {
    return false;
  }

  Layer* baselayer = aLayerParent->AsLayer();
  if (!baselayer) {
    return false;
  }
  LayerComposite* layer = baselayer->AsLayerComposite();
  if (!layer) {
    return false;
  }

  Compositor* compositor
    = static_cast<LayerManagerComposite*>(aLayerParent->AsLayer()->Manager())->GetCompositor();

  if (!layer->SetCompositableHost(aCompositable)) {
    // not all layer types accept a compositable, see bug 967824
    return false;
  }
  aCompositable->Attach(aLayerParent->AsLayer(),
                        compositor,
                        aIsAsync
                          ? CompositableHost::ALLOW_REATTACH
                            | CompositableHost::KEEP_ATTACHED
                          : CompositableHost::NO_FLAGS);
  return true;
}

void
ContainerLayerComposite::CleanupResources()
{
  for (Layer* l = GetFirstChild(); l; l = l->GetNextSibling()) {
    LayerComposite* layerToCleanup = static_cast<LayerComposite*>(l->ImplData());
    layerToCleanup->CleanupResources();
  }
}

void
LayerTransactionParent::Attach(ShadowLayerParent* aLayerParent, CompositableParent* aCompositable)
{
  LayerComposite* layer = aLayerParent->AsLayer()->AsLayerComposite();
  MOZ_ASSERT(layer);

  Compositor* compositor
    = static_cast<LayerManagerComposite*>(aLayerParent->AsLayer()->Manager())->GetCompositor();

  CompositableHost* compositable = aCompositable->GetCompositableHost();
  MOZ_ASSERT(compositable);
  layer->SetCompositableHost(compositable);
  compositable->Attach(aLayerParent->AsLayer(), compositor);
}

void
LayerManagerComposite::ApplyOcclusionCulling(Layer* aLayer, nsIntRegion& aOpaqueRegion)
{
  nsIntRegion localOpaque;
  Matrix transform2d;
  bool isTranslation = false;
  // If aLayer has a simple transform (only an integer translation) then we
  // can easily convert aOpaqueRegion into pre-transform coordinates and include
  // that region.
  if (aLayer->GetLocalTransform().Is2D(&transform2d)) {
    if (transform2d.IsIntegerTranslation()) {
      isTranslation = true;
      localOpaque = aOpaqueRegion;
      localOpaque.MoveBy(-transform2d._31, -transform2d._32);
    }
  }

  // Subtract any areas that we know to be opaque from our
  // visible region.
  LayerComposite *composite = aLayer->AsLayerComposite();
  if (!localOpaque.IsEmpty()) {
    nsIntRegion visible = composite->GetShadowVisibleRegion();
    visible.Sub(visible, localOpaque);
    composite->SetShadowVisibleRegion(visible);
  }

  // Compute occlusions for our descendants (in front-to-back order) and allow them to
  // contribute to localOpaque.
  for (Layer* child = aLayer->GetLastChild(); child; child = child->GetPrevSibling()) {
    ApplyOcclusionCulling(child, localOpaque);
  }

  // If we have a simple transform, then we can add our opaque area into
  // aOpaqueRegion.
  if (isTranslation &&
      !aLayer->HasMaskLayers() &&
      aLayer->GetLocalOpacity() == 1.0f) {
    if (aLayer->GetContentFlags() & Layer::CONTENT_OPAQUE) {
      localOpaque.Or(localOpaque, composite->GetFullyRenderedRegion());
    }
    localOpaque.MoveBy(transform2d._31, transform2d._32);
    const Maybe<ParentLayerIntRect>& clip = aLayer->GetEffectiveClipRect();
    if (clip) {
      localOpaque.And(localOpaque, ParentLayerIntRect::ToUntyped(*clip));
    }
    aOpaqueRegion.Or(aOpaqueRegion, localOpaque);
  }
}

/* static */ bool
LayerManagerComposite::AddMaskEffect(Layer* aMaskLayer, EffectChain& aEffects, bool aIs3D)
{
  if (!aMaskLayer) {
    return false;
  }
  LayerComposite* maskLayerComposite = static_cast<LayerComposite*>(aMaskLayer->ImplData());
  if (!maskLayerComposite->GetCompositableHost()) {
    NS_WARNING("Mask layer with no compositable host");
    return false;
  }

  gfx::Matrix4x4 transform;
  ToMatrix4x4(aMaskLayer->GetEffectiveTransform(), transform);
  return maskLayerComposite->GetCompositableHost()->AddMaskEffect(aEffects, transform, aIs3D);
}

static void
BuildBackgroundPatternFor(ContainerLayer* aContainer,
                          Layer* aShadowRoot,
                          const ViewConfig& aConfig,
                          const gfxRGBA& aColor,
                          LayerManager* aManager,
                          nsIFrame* aFrame)
{
  LayerComposite* shadowRoot = aShadowRoot->AsLayerComposite();
  gfxMatrix t;
  if (!shadowRoot->GetShadowTransform().Is2D(&t)) {
    return;
  }

  // Get the rect bounding the shadow content, transformed into the
  // same space as |aFrame|
  nsIntRect contentBounds = shadowRoot->GetShadowVisibleRegion().GetBounds();
  gfxRect contentVis(contentBounds.x, contentBounds.y,
                     contentBounds.width, contentBounds.height);
  gfxRect localContentVis(t.Transform(contentVis));
  // Round *in* here because this area is punched out of the background
  localContentVis.RoundIn();
  nsIntRect localIntContentVis(localContentVis.X(), localContentVis.Y(),
                               localContentVis.Width(), localContentVis.Height());

  // Get the frame's rect
  nscoord auPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
  nsIntRect frameRect = aFrame->GetRect().ToOutsidePixels(auPerDevPixel);

  // If the shadow tree covers the frame rect, don't bother building
  // the background, it wouldn't be visible
  if (localIntContentVis.Contains(frameRect)) {
    return;
  }
  nsRefPtr<ColorLayer> layer = aManager->CreateColorLayer();
  layer->SetColor(aColor);

  // The visible area of the background is the frame's area minus the
  // content area
  nsIntRegion bgRgn(frameRect);
  bgRgn.Sub(bgRgn, localIntContentVis);
  bgRgn.MoveBy(-frameRect.TopLeft());
  layer->SetVisibleRegion(bgRgn);

  aContainer->InsertAfter(layer, nullptr);
}

static void
TranslateShadowLayer2D(Layer* aLayer,
                       const gfxPoint& aTranslation)
{
  // This layer might also be a scrollable layer and have an async transform.
  // To make sure we don't clobber that, we start with the shadow transform.
  // Any adjustments to the shadow transform made in this function in previous
  // frames have been cleared in ClearAsyncTransforms(), so such adjustments
  // will not compound over successive frames.
  Matrix layerTransform;
  if (!aLayer->GetLocalTransform().Is2D(&layerTransform)) {
    return;
  }

  // Apply the 2D translation to the layer transform.
  layerTransform._31 += aTranslation.x;
  layerTransform._32 += aTranslation.y;

  // The transform already takes the resolution scale into account.  Since we
  // will apply the resolution scale again when computing the effective
  // transform, we must apply the inverse resolution scale here.
  Matrix4x4 layerTransform3D = Matrix4x4::From2D(layerTransform);
  if (ContainerLayer* c = aLayer->AsContainerLayer()) {
    layerTransform3D.Scale(1.0f/c->GetPreXScale(),
                           1.0f/c->GetPreYScale(),
                           1);
  }
  layerTransform3D = layerTransform3D *
    Matrix4x4().Scale(1.0f/aLayer->GetPostXScale(),
                      1.0f/aLayer->GetPostYScale(),
                      1);

  LayerComposite* layerComposite = aLayer->AsLayerComposite();
  layerComposite->SetShadowTransform(layerTransform3D);
  layerComposite->SetShadowTransformSetByAnimation(false);

  const nsIntRect* clipRect = aLayer->GetClipRect();
  if (clipRect) {
    nsIntRect transformedClipRect(*clipRect);
    transformedClipRect.MoveBy(aTranslation.x, aTranslation.y);
    layerComposite->SetShadowClipRect(&transformedClipRect);
  }
}

void
LayerTransactionParent::Attach(ShadowLayerParent* aLayerParent,
                               CompositableParent* aCompositable,
                               bool aIsAsyncVideo)
{
  LayerComposite* layer = aLayerParent->AsLayer()->AsLayerComposite();
  MOZ_ASSERT(layer);

  Compositor* compositor
    = static_cast<LayerManagerComposite*>(aLayerParent->AsLayer()->Manager())->GetCompositor();

  CompositableHost* compositable = aCompositable->GetCompositableHost();
  MOZ_ASSERT(compositable);
  layer->SetCompositableHost(compositable);
  compositable->Attach(aLayerParent->AsLayer(),
                       compositor,
                       aIsAsyncVideo
                         ? CompositableHost::ALLOW_REATTACH
                           | CompositableHost::KEEP_ATTACHED
                         : CompositableHost::NO_FLAGS);
}

static void
TranslateShadowLayer2D(Layer* aLayer,
                       const gfxPoint& aTranslation)
{
  gfxMatrix layerTransform;
  if (!GetBaseTransform2D(aLayer, &layerTransform)) {
    return;
  }

  // Apply the 2D translation to the layer transform.
  layerTransform.x0 += aTranslation.x;
  layerTransform.y0 += aTranslation.y;

  // The transform already takes the resolution scale into account.  Since we
  // will apply the resolution scale again when computing the effective
  // transform, we must apply the inverse resolution scale here.
  gfx3DMatrix layerTransform3D = gfx3DMatrix::From2D(layerTransform);
  if (ContainerLayer* c = aLayer->AsContainerLayer()) {
    layerTransform3D.Scale(1.0f/c->GetPreXScale(),
                           1.0f/c->GetPreYScale(),
                           1);
  }
  layerTransform3D.ScalePost(1.0f/aLayer->GetPostXScale(),
                             1.0f/aLayer->GetPostYScale(),
                             1);

  LayerComposite* layerComposite = aLayer->AsLayerComposite();
  layerComposite->SetShadowTransform(layerTransform3D);
  layerComposite->SetShadowTransformSetByAnimation(false);

  const nsIntRect* clipRect = aLayer->GetClipRect();
  if (clipRect) {
    nsIntRect transformedClipRect(*clipRect);
    transformedClipRect.MoveBy(aTranslation.x, aTranslation.y);
    layerComposite->SetShadowClipRect(&transformedClipRect);
  }
}

// Go down the composite layer tree, setting properties to match their
// content-side counterparts.
static void
SetShadowProperties(Layer* aLayer)
{
  // FIXME: Bug 717688 -- Do these updates in LayerTransactionParent::RecvUpdate.
  LayerComposite* layerComposite = aLayer->AsLayerComposite();
  // Set the layerComposite's base transform to the layer's base transform.
  layerComposite->SetShadowTransform(aLayer->GetBaseTransform());
  layerComposite->SetShadowTransformSetByAnimation(false);
  layerComposite->SetShadowVisibleRegion(aLayer->GetVisibleRegion());
  layerComposite->SetShadowClipRect(aLayer->GetClipRect());
  layerComposite->SetShadowOpacity(aLayer->GetOpacity());

  for (Layer* child = aLayer->GetFirstChild();
      child; child = child->GetNextSibling()) {
    SetShadowProperties(child);
  }
}

// ContainerRender is shared between RefLayer and ContainerLayer
template<class ContainerT> void
ContainerRender(ContainerT* aContainer,
                LayerManagerComposite* aManager,
                const nsIntRect& aClipRect)
{
  /**
   * Setup our temporary surface for rendering the contents of this container.
   */
  RefPtr<CompositingRenderTarget> surface;

  Compositor* compositor = aManager->GetCompositor();

  RefPtr<CompositingRenderTarget> previousTarget = compositor->GetCurrentRenderTarget();

  nsIntRect visibleRect = aContainer->GetEffectiveVisibleRegion().GetBounds();

  float opacity = aContainer->GetEffectiveOpacity();

  bool needsSurface = aContainer->UseIntermediateSurface();
  bool surfaceCopyNeeded;
  aContainer->DefaultComputeSupportsComponentAlphaChildren(&surfaceCopyNeeded);
  if (needsSurface) {
    SurfaceInitMode mode = INIT_MODE_CLEAR;
    gfx::IntRect surfaceRect = gfx::IntRect(visibleRect.x, visibleRect.y,
                                            visibleRect.width, visibleRect.height);
    // we're about to create a framebuffer backed by textures to use as an intermediate
    // surface. What to do if its size (as given by framebufferRect) would exceed the
    // maximum texture size supported by the GL? The present code chooses the compromise
    // of just clamping the framebuffer's size to the max supported size.
    // This gives us a lower resolution rendering of the intermediate surface (children layers).
    // See bug 827170 for a discussion.
    int32_t maxTextureSize = compositor->GetMaxTextureSize();
    surfaceRect.width = std::min(maxTextureSize, surfaceRect.width);
    surfaceRect.height = std::min(maxTextureSize, surfaceRect.height);
    if (aContainer->GetEffectiveVisibleRegion().GetNumRects() == 1 &&
        (aContainer->GetContentFlags() & Layer::CONTENT_OPAQUE))
    {
      mode = INIT_MODE_NONE;
    }

    if (surfaceCopyNeeded) {
      gfx::IntPoint sourcePoint = gfx::IntPoint(visibleRect.x, visibleRect.y);

      gfx::Matrix4x4 transform = aContainer->GetEffectiveTransform();
      DebugOnly<gfx::Matrix> transform2d;
      MOZ_ASSERT(transform.Is2D(&transform2d) && !gfx::ThebesMatrix(transform2d).HasNonIntegerTranslation());
      sourcePoint += gfx::IntPoint(transform._41, transform._42);

      sourcePoint -= compositor->GetCurrentRenderTarget()->GetOrigin();

      surface = compositor->CreateRenderTargetFromSource(surfaceRect, previousTarget, sourcePoint);
    } else {
      surface = compositor->CreateRenderTarget(surfaceRect, mode);
    }

    if (!surface) {
      return;
    }

    compositor->SetRenderTarget(surface);
  } else {
    surface = previousTarget;
  }

  nsAutoTArray<Layer*, 12> children;
  aContainer->SortChildrenBy3DZOrder(children);

  // If this is a scrollable container layer, and it's overscrolled, the layer's
  // contents are transformed in a way that would leave blank regions in the
  // composited area. If the layer has a background color, fill these areas
  // with the background color by drawing a rectangle of the background color
  // over the entire composited area before drawing the container contents.
  if (AsyncPanZoomController* apzc = aContainer->GetAsyncPanZoomController()) {
    // Make sure not to do this on a "scrollinfo" layer (one with an empty visible
    // region) because it's just a placeholder for APZ purposes.
    if (apzc->IsOverscrolled() && !aContainer->GetVisibleRegion().IsEmpty()) {
      gfxRGBA color = aContainer->GetBackgroundColor();
      // If the background is completely transparent, there's no point in
      // drawing anything for it. Hopefully the layers behind, if any, will
      // provide suitable content for the overscroll effect.
      if (color.a != 0.0) {
        EffectChain effectChain(aContainer);
        effectChain.mPrimaryEffect = new EffectSolidColor(ToColor(color));
        gfx::Rect clipRect(aClipRect.x, aClipRect.y, aClipRect.width, aClipRect.height);
        Compositor* compositor = aManager->GetCompositor();
        compositor->DrawQuad(compositor->ClipRectInLayersCoordinates(clipRect),
            clipRect, effectChain, opacity, Matrix4x4());
      }
    }
  }

  /**
   * Render this container's contents.
   */
  for (uint32_t i = 0; i < children.Length(); i++) {
    LayerComposite* layerToRender = static_cast<LayerComposite*>(children.ElementAt(i)->ImplData());

    if (layerToRender->GetLayer()->GetEffectiveVisibleRegion().IsEmpty() &&
        !layerToRender->GetLayer()->AsContainerLayer()) {
//.........这里部分代码省略.........

void
LayerManagerComposite::PostProcessLayers(Layer* aLayer,
                                         nsIntRegion& aOpaqueRegion,
                                         LayerIntRegion& aVisibleRegion)
{
  nsIntRegion localOpaque;
  Matrix transform2d;
  Maybe<nsIntPoint> integerTranslation;
  // If aLayer has a simple transform (only an integer translation) then we
  // can easily convert aOpaqueRegion into pre-transform coordinates and include
  // that region.
  if (aLayer->GetLocalTransform().Is2D(&transform2d)) {
    if (transform2d.IsIntegerTranslation()) {
      integerTranslation = Some(TruncatedToInt(transform2d.GetTranslation()));
      localOpaque = aOpaqueRegion;
      localOpaque.MoveBy(-*integerTranslation);
    }
  }

  // Save the value of localOpaque, which currently stores the region obscured
  // by siblings (and uncles and such), before our descendants contribute to it.
  nsIntRegion obscured = localOpaque;

  // Recurse on our descendants, in front-to-back order. In this process:
  //  - Occlusions are computed for them, and they contribute to localOpaque.
  //  - They recalculate their visible regions, and accumulate them into
  //    descendantsVisibleRegion.
  LayerIntRegion descendantsVisibleRegion;
  for (Layer* child = aLayer->GetLastChild(); child; child = child->GetPrevSibling()) {
    PostProcessLayers(child, localOpaque, descendantsVisibleRegion);
  }

  // Recalculate our visible region.
  LayerComposite* composite = aLayer->AsLayerComposite();
  LayerIntRegion visible = composite->GetShadowVisibleRegion();

  // If we have descendants, throw away the visible region stored on this
  // layer, and use the region accumulated by our descendants instead.
  if (aLayer->GetFirstChild()) {
    visible = descendantsVisibleRegion;
  }

  // Subtract any areas that we know to be opaque.
  if (!obscured.IsEmpty()) {
    visible.SubOut(LayerIntRegion::FromUnknownRegion(obscured));
  }

  composite->SetShadowVisibleRegion(visible);

  // Transform the newly calculated visible region into our parent's space,
  // apply our clip to it (if any), and accumulate it into |aVisibleRegion|
  // for the caller to use.
  ParentLayerIntRegion visibleParentSpace = TransformTo<ParentLayerPixel>(
      aLayer->GetLocalTransform(), visible);
  if (const Maybe<ParentLayerIntRect>& clipRect = composite->GetShadowClipRect()) {
    visibleParentSpace.AndWith(*clipRect);
  }
  aVisibleRegion.OrWith(ViewAs<LayerPixel>(visibleParentSpace,
      PixelCastJustification::MovingDownToChildren));

  // If we have a simple transform, then we can add our opaque area into
  // aOpaqueRegion.
  if (integerTranslation &&
      !aLayer->HasMaskLayers() &&
      aLayer->IsOpaqueForVisibility()) {
    if (aLayer->GetContentFlags() & Layer::CONTENT_OPAQUE) {
      localOpaque.OrWith(composite->GetFullyRenderedRegion());
    }
    localOpaque.MoveBy(*integerTranslation);
    const Maybe<ParentLayerIntRect>& clip = aLayer->GetEffectiveClipRect();
    if (clip) {
      localOpaque.AndWith(clip->ToUnknownRect());
    }
    aOpaqueRegion.OrWith(localOpaque);
  }
}

static bool
SampleAnimations(Layer* aLayer, TimeStamp aPoint)
{
  AnimationArray& animations = aLayer->GetAnimations();
  InfallibleTArray<AnimData>& animationData = aLayer->GetAnimationData();

  bool activeAnimations = false;

  for (uint32_t i = animations.Length(); i-- !=0; ) {
    Animation& animation = animations[i];
    AnimData& animData = animationData[i];

    activeAnimations = true;

    TimeDuration elapsedDuration = aPoint - animation.startTime();
    // Skip animations that are yet to start.
    //
    // Currently, this should only happen when the refresh driver is under test
    // control and is made to produce a time in the past or is restored from
    // test control causing it to jump backwards in time.
    //
    // Since activeAnimations is true, this could mean we keep compositing
    // unnecessarily during the delay, but so long as this only happens while
    // the refresh driver is under test control that should be ok.
    if (elapsedDuration.ToSeconds() < 0) {
      continue;
    }

    AnimationTiming timing;
    timing.mIterationDuration = animation.duration();
    // Currently animations run on the compositor have their delay factored
    // into their start time, hence the delay is effectively zero.
    timing.mDelay = TimeDuration(0);
    timing.mIterationCount = animation.iterationCount();
    timing.mDirection = animation.direction();
    // Animations typically only run on the compositor during their active
    // interval but if we end up sampling them outside that range (for
    // example, while they are waiting to be removed) we currently just
    // assume that we should fill.
    timing.mFillMode = NS_STYLE_ANIMATION_FILL_MODE_BOTH;

    ComputedTiming computedTiming =
      dom::Animation::GetComputedTimingAt(
        Nullable<TimeDuration>(elapsedDuration), timing);

    NS_ABORT_IF_FALSE(0.0 <= computedTiming.mTimeFraction &&
                      computedTiming.mTimeFraction <= 1.0,
                      "time fraction should be in [0-1]");

    int segmentIndex = 0;
    AnimationSegment* segment = animation.segments().Elements();
    while (segment->endPortion() < computedTiming.mTimeFraction) {
      ++segment;
      ++segmentIndex;
    }

    double positionInSegment =
      (computedTiming.mTimeFraction - segment->startPortion()) /
      (segment->endPortion() - segment->startPortion());

    double portion =
      animData.mFunctions[segmentIndex]->GetValue(positionInSegment);

    // interpolate the property
    Animatable interpolatedValue;
    SampleValue(portion, animation, animData.mStartValues[segmentIndex],
                animData.mEndValues[segmentIndex], &interpolatedValue);
    LayerComposite* layerComposite = aLayer->AsLayerComposite();
    switch (animation.property()) {
    case eCSSProperty_opacity:
    {
      layerComposite->SetShadowOpacity(interpolatedValue.get_float());
      break;
    }
    case eCSSProperty_transform:
    {
      Matrix4x4 matrix = interpolatedValue.get_ArrayOfTransformFunction()[0].get_TransformMatrix().value();
      if (ContainerLayer* c = aLayer->AsContainerLayer()) {
        matrix = matrix * Matrix4x4().Scale(c->GetInheritedXScale(),
                                            c->GetInheritedYScale(),
                                            1);
      }
      layerComposite->SetShadowTransform(matrix);
      layerComposite->SetShadowTransformSetByAnimation(true);
      break;
    }
    default:
      NS_WARNING("Unhandled animated property");
    }
  }

  for (Layer* child = aLayer->GetFirstChild(); child;
       child = child->GetNextSibling()) {
    activeAnimations |= SampleAnimations(child, aPoint);
  }

  return activeAnimations;
}

// Go down shadow layer tree and apply transformations for scrollable layers.
static void
TransformShadowTree(nsDisplayListBuilder* aBuilder, nsFrameLoader* aFrameLoader,
                    nsIFrame* aFrame, Layer* aLayer,
                    const ViewTransform& aTransform,
                    float aTempScaleDiffX = 1.0,
                    float aTempScaleDiffY = 1.0)
{
  LayerComposite* shadow = aLayer->AsLayerComposite();
  shadow->SetShadowClipRect(aLayer->GetClipRect());
  shadow->SetShadowVisibleRegion(aLayer->GetVisibleRegion());
  shadow->SetShadowOpacity(aLayer->GetOpacity());

  const FrameMetrics* metrics = GetFrameMetrics(aLayer);

  gfx3DMatrix shadowTransform = aLayer->GetTransform();
  ViewTransform layerTransform = aTransform;

  if (metrics && metrics->IsScrollable()) {
    const ViewID scrollId = metrics->mScrollId;
    const nsContentView* view =
      aFrameLoader->GetCurrentRemoteFrame()->GetContentView(scrollId);
    NS_ABORT_IF_FALSE(view, "Array of views should be consistent with layer tree");
    const gfx3DMatrix& currentTransform = aLayer->GetTransform();

    const ViewConfig& config = view->GetViewConfig();
    // With temporary scale we should compensate translation
    // using temporary scale value
    aTempScaleDiffX *= GetXScale(shadowTransform) * config.mXScale;
    aTempScaleDiffY *= GetYScale(shadowTransform) * config.mYScale;
    ViewTransform viewTransform = ComputeShadowTreeTransform(
      aFrame, aFrameLoader, metrics, view->GetViewConfig(),
      aTempScaleDiffX, aTempScaleDiffY
    );

    // Apply the layer's own transform *before* the view transform
    shadowTransform = gfx3DMatrix(viewTransform) * currentTransform;

    layerTransform = viewTransform;
    if (metrics->IsRootScrollable()) {
      // Apply the translation *before* we do the rest of the transforms.
      nsIntPoint offset = GetContentRectLayerOffset(aFrame, aBuilder);
      shadowTransform = shadowTransform *
          gfx3DMatrix::Translation(float(offset.x), float(offset.y), 0.0);
    }
  }

  if (aLayer->GetIsFixedPosition() &&
      !aLayer->GetParent()->GetIsFixedPosition()) {
    // Alter the shadow transform of fixed position layers in the situation
    // that the view transform's scroll position doesn't match the actual
    // scroll position, due to asynchronous layer scrolling.
    float offsetX = layerTransform.mTranslation.x;
    float offsetY = layerTransform.mTranslation.y;
    ReverseTranslate(shadowTransform, gfxPoint(offsetX, offsetY));
    const nsIntRect* clipRect = shadow->GetShadowClipRect();
    if (clipRect) {
      nsIntRect transformedClipRect(*clipRect);
      transformedClipRect.MoveBy(-offsetX, -offsetY);
      shadow->SetShadowClipRect(&transformedClipRect);
    }
  }

  // The transform already takes the resolution scale into account.  Since we
  // will apply the resolution scale again when computing the effective
  // transform, we must apply the inverse resolution scale here.
  if (ContainerLayer* c = aLayer->AsContainerLayer()) {
    shadowTransform.Scale(1.0f/c->GetPreXScale(),
                          1.0f/c->GetPreYScale(),
                          1);
  }
  shadowTransform.ScalePost(1.0f/aLayer->GetPostXScale(),
                            1.0f/aLayer->GetPostYScale(),
                            1);

  shadow->SetShadowTransform(shadowTransform);
  for (Layer* child = aLayer->GetFirstChild();
       child; child = child->GetNextSibling()) {
    TransformShadowTree(aBuilder, aFrameLoader, aFrame, child, layerTransform,
                        aTempScaleDiffX, aTempScaleDiffY);
  }
}

void
AsyncCompositionManager::TransformScrollableLayer(Layer* aLayer, const LayoutDeviceToLayerScale& aResolution)
{
  LayerComposite* layerComposite = aLayer->AsLayerComposite();
  ContainerLayer* container = aLayer->AsContainerLayer();

  const FrameMetrics& metrics = container->GetFrameMetrics();
  // We must apply the resolution scale before a pan/zoom transform, so we call
  // GetTransform here.
  const gfx3DMatrix& currentTransform = aLayer->GetTransform();
  gfx3DMatrix oldTransform = currentTransform;

  gfx3DMatrix treeTransform;

  CSSToLayerScale geckoZoom = metrics.mDevPixelsPerCSSPixel * aResolution;

  LayerIntPoint scrollOffsetLayerPixels = RoundedToInt(metrics.mScrollOffset * geckoZoom);

  if (mIsFirstPaint) {
    mContentRect = metrics.mScrollableRect;
    SetFirstPaintViewport(scrollOffsetLayerPixels,
                          geckoZoom,
                          mContentRect);
    mIsFirstPaint = false;
  } else if (!metrics.mScrollableRect.IsEqualEdges(mContentRect)) {
    mContentRect = metrics.mScrollableRect;
    SetPageRect(mContentRect);
  }

  // We synchronise the viewport information with Java after sending the above
  // notifications, so that Java can take these into account in its response.
  // Calculate the absolute display port to send to Java
  LayerIntRect displayPort = RoundedToInt(
    (metrics.mCriticalDisplayPort.IsEmpty()
      ? metrics.mDisplayPort
      : metrics.mCriticalDisplayPort
    ) * geckoZoom);
  displayPort += scrollOffsetLayerPixels;

  LayerMargin fixedLayerMargins(0, 0, 0, 0);
  ScreenPoint offset(0, 0);

  // Ideally we would initialize userZoom to AsyncPanZoomController::CalculateResolution(metrics)
  // but this causes a reftest-ipc test to fail (see bug 883646 comment 27). The reason for this
  // appears to be that metrics.mZoom is poorly initialized in some scenarios. In these scenarios,
  // however, we can assume there is no async zooming in progress and so the following statement
  // works fine.
  CSSToScreenScale userZoom(metrics.mDevPixelsPerCSSPixel.scale * metrics.mResolution.scale);
  ScreenPoint userScroll = metrics.mScrollOffset * userZoom;
  SyncViewportInfo(displayPort, geckoZoom, mLayersUpdated,
                   userScroll, userZoom, fixedLayerMargins,
                   offset);
  mLayersUpdated = false;

  // Apply the render offset
  mLayerManager->GetCompositor()->SetScreenRenderOffset(offset);

  // Handle transformations for asynchronous panning and zooming. We determine the
  // zoom used by Gecko from the transformation set on the root layer, and we
  // determine the scroll offset used by Gecko from the frame metrics of the
  // primary scrollable layer. We compare this to the user zoom and scroll
  // offset in the view transform we obtained from Java in order to compute the
  // transformation we need to apply.
  LayerToScreenScale zoomAdjust = userZoom / geckoZoom;

  LayerIntPoint geckoScroll(0, 0);
  if (metrics.IsScrollable()) {
    geckoScroll = scrollOffsetLayerPixels;
  }

  LayerPoint translation = (userScroll / zoomAdjust) - geckoScroll;
  treeTransform = gfx3DMatrix(ViewTransform(-translation, userZoom / metrics.mDevPixelsPerCSSPixel));

  // The transform already takes the resolution scale into account.  Since we
  // will apply the resolution scale again when computing the effective
  // transform, we must apply the inverse resolution scale here.
  gfx3DMatrix computedTransform = treeTransform * currentTransform;
  computedTransform.Scale(1.0f/container->GetPreXScale(),
                          1.0f/container->GetPreYScale(),
                          1);
  computedTransform.ScalePost(1.0f/container->GetPostXScale(),
                              1.0f/container->GetPostYScale(),
                              1);
  layerComposite->SetShadowTransform(computedTransform);
  NS_ASSERTION(!layerComposite->GetShadowTransformSetByAnimation(),
               "overwriting animated transform!");

  // Apply resolution scaling to the old transform - the layer tree as it is
  // doesn't have the necessary transform to display correctly.
  oldTransform.Scale(aResolution.scale, aResolution.scale, 1);

  // Make sure that overscroll and under-zoom are represented in the old
  // transform so that fixed position content moves and scales accordingly.
  // These calculations will effectively scale and offset fixed position layers
  // in screen space when the compensatory transform is performed in
  // AlignFixedLayersForAnchorPoint.
  ScreenRect contentScreenRect = mContentRect * userZoom;
  gfxPoint3D overscrollTranslation;
  if (userScroll.x < contentScreenRect.x) {
    overscrollTranslation.x = contentScreenRect.x - userScroll.x;
//.........这里部分代码省略.........