Bug 1349418 - Remove checkerboarding code and just use an opaque background color behind root scroll frames. r=kats

gfx/layers/LayerAttributes.h

@@ -44,13 +44,6 @@ public:
   // All set methods return true if values changed, false otherwise.
   //
 
-  bool SetLayerBounds(const gfx::IntRect& aLayerBounds) {
-    if (mLayerBounds.IsEqualEdges(aLayerBounds)) {
-      return false;
-    }
-    mLayerBounds = aLayerBounds;
-    return true;
-  }
   bool SetPostScale(float aXScale, float aYScale) {
     if (mPostXScale == aXScale && mPostYScale == aYScale) {
       return false;
@@ -195,9 +188,6 @@ public:
   // Getters.
   //
 
-  const gfx::IntRect& LayerBounds() const {
-    return mLayerBounds;
-  }
   float PostXScale() const {
     return mPostXScale;
   }
@@ -265,8 +255,7 @@ public:
   }
 
   bool operator ==(const SimpleLayerAttributes& aOther) const {
-    return mLayerBounds == aOther.mLayerBounds &&
-           mTransform == aOther.mTransform &&
+    return mTransform == aOther.mTransform &&
            mTransformIsPerspective == aOther.mTransformIsPerspective &&
            mScrolledClip == aOther.mScrolledClip &&
            mPostXScale == aOther.mPostXScale &&
@@ -283,7 +272,6 @@ public:
   }
 
 private:
-  gfx::IntRect mLayerBounds;
   gfx::Matrix4x4 mTransform;
   bool mTransformIsPerspective;
   Maybe<LayerClip> mScrolledClip;

gfx/layers/Layers.cpp

@@ -576,8 +576,7 @@ Layer::CalculateScissorRect(const RenderTargetIntRect& aCurrentScissorRect)
     return currentClip;
   }
 
-  if (GetLocalVisibleRegion().IsEmpty() &&
-      !(AsHostLayer() && AsHostLayer()->NeedToDrawCheckerboarding())) {
+  if (GetLocalVisibleRegion().IsEmpty()) {
     // When our visible region is empty, our parent may not have created the
     // intermediate surface that we would require for correct clipping; however,
     // this does not matter since we are invisible.
@@ -1850,9 +1849,6 @@ Layer::PrintInfo(std::stringstream& aStream, const char* aPrefix)
   if (GetTransformIsPerspective()) {
     aStream << " [perspective]";
   }
-  if (!GetLayerBounds().IsEmpty()) {
-    AppendToString(aStream, GetLayerBounds(), " [bounds=", "]");
-  }
   if (!mVisibleRegion.IsEmpty()) {
     AppendToString(aStream, mVisibleRegion.ToUnknownRegion(), " [visible=", "]");
   } else {

gfx/layers/Layers.h

@@ -898,22 +898,6 @@ public:
     }
   }
 
-  /**
-   * CONSTRUCTION PHASE ONLY
-   * The union of the bounds of all the display item that got flattened
-   * into this layer. This is intended to be an approximation to the
-   * size of the layer if the nearest scrollable ancestor had an infinitely
-   * large displayport. Computing this more exactly is too expensive,
-   * but this approximation is sufficient for what we need to use it for.
-   */
-  virtual void SetLayerBounds(const gfx::IntRect& aLayerBounds)
-  {
-    if (mSimpleAttrs.SetLayerBounds(aLayerBounds)) {
-      MOZ_LAYERS_LOG_IF_SHADOWABLE(this, ("Layer::Mutated(%p) LayerBounds", this));
-      MutatedSimple();
-    }
-  }
-
   /**
    * CONSTRUCTION PHASE ONLY
    * Tell this layer which region will be visible. The visible region
@@ -1340,7 +1324,6 @@ public:
   const Maybe<LayerClip>& GetScrolledClip() const { return mSimpleAttrs.ScrolledClip(); }
   Maybe<ParentLayerIntRect> GetScrolledClipRect() const;
   uint32_t GetContentFlags() { return mSimpleAttrs.ContentFlags(); }
-  const gfx::IntRect& GetLayerBounds() const { return mSimpleAttrs.LayerBounds(); }
   const LayerIntRegion& GetVisibleRegion() const { return mVisibleRegion; }
   const ScrollMetadata& GetScrollMetadata(uint32_t aIndex) const;
   const FrameMetrics& GetFrameMetrics(uint32_t aIndex) const;

gfx/layers/client/ClientTiledPaintedLayer.cpp

@@ -169,7 +169,7 @@ ClientTiledPaintedLayer::BeginPaint()
   ParentLayerToLayerMatrix4x4 transformDisplayPortToLayer =
     GetTransformToAncestorsParentLayer(this, displayPortAncestor).Inverse();
 
-  LayerRect layerBounds = ViewAs<LayerPixel>(Rect(GetLayerBounds()));
+  LayerRect layerBounds(GetVisibleRegion().GetBounds());
 
   // Compute the critical display port that applies to this layer in the
   // LayoutDevice space of this layer, but only if there is no OMT animation

gfx/layers/client/TiledContentClient.cpp

@@ -1218,7 +1218,7 @@ ClientMultiTiledLayerBuffer::ComputeProgressiveUpdateRegion(const nsIntRegion& a
     GetCompositorSideCompositionBounds(scrollAncestor,
                                        aPaintData->mTransformToCompBounds,
                                        viewTransform,
-                                       ViewAs<LayerPixel>(Rect(mPaintedLayer.GetLayerBounds())));
+                                       LayerRect(mPaintedLayer.GetVisibleRegion().GetBounds()));
 
   if (!transformedCompositionBounds) {
     aPaintData->mPaintFinished = true;

gfx/layers/composite/ContainerLayerComposite.cpp

@@ -212,8 +212,7 @@ ContainerPrepare(ContainerT* aContainer,
     // We don't want to skip container layers because otherwise their mPrepared
     // may be null which is not allowed.
     if (!layerToRender->GetLayer()->AsContainerLayer()) {
-      if (!layerToRender->GetLayer()->IsVisible() &&
-          !layerToRender->NeedToDrawCheckerboarding(nullptr)) {
+      if (!layerToRender->GetLayer()->IsVisible()) {
         CULLING_LOG("Sublayer %p has no effective visible region\n", layerToRender->GetLayer());
         continue;
       }
@@ -423,24 +422,6 @@ RenderLayers(ContainerT* aContainer, LayerManagerComposite* aManager,
       }
     }
 
-    Color color;
-    if (layerToRender->NeedToDrawCheckerboarding(&color)) {
-      if (gfxPrefs::APZHighlightCheckerboardedAreas()) {
-        color = Color(255 / 255.f, 188 / 255.f, 217 / 255.f, 1.f); // "Cotton Candy"
-      }
-      // Ideally we would want to intersect the checkerboard region from the APZ with the layer bounds
-      // and only fill in that area. However the layer bounds takes into account the base translation
-      // for the painted layer whereas the checkerboard region does not. One does not simply
-      // intersect areas in different coordinate spaces. So we do this a little more permissively
-      // and only fill in the background when we know there is checkerboard, which in theory
-      // should only occur transiently.
-      EffectChain effectChain(layer);
-      effectChain.mPrimaryEffect = new EffectSolidColor(color);
-      aManager->GetCompositor()->DrawGeometry(gfx::Rect(layer->GetLayerBounds()), clipRect,
-                                              effectChain, layer->GetEffectiveOpacity(),
-                                              layer->GetEffectiveTransform(), Nothing());
-    }
-
     if (layerToRender->HasLayerBeenComposited()) {
       // Composer2D will compose this layer so skip GPU composition
       // this time. The flag will be reset for the next composition phase

gfx/layers/composite/LayerManagerComposite.cpp

@@ -1501,35 +1501,6 @@ LayerComposite::HasStaleCompositor() const
   return mCompositeManager->GetCompositor() != mCompositor;
 }
 
-static bool
-LayerHasCheckerboardingAPZC(Layer* aLayer, Color* aOutColor)
-{
-  bool answer = false;
-  for (LayerMetricsWrapper i(aLayer, LayerMetricsWrapper::StartAt::BOTTOM); i; i = i.GetParent()) {
-    if (!i.Metrics().IsScrollable()) {
-      continue;
-    }
-    if (i.GetApzc() && i.GetApzc()->IsCurrentlyCheckerboarding()) {
-      if (aOutColor) {
-        *aOutColor = i.Metadata().GetBackgroundColor();
-      }
-      answer = true;
-      break;
-    }
-    break;
-  }
-  return answer;
-}
-
-bool
-LayerComposite::NeedToDrawCheckerboarding(gfx::Color* aOutCheckerboardingColor)
-{
-  return GetLayer()->Manager()->AsyncPanZoomEnabled() &&
-         (GetLayer()->GetContentFlags() & Layer::CONTENT_OPAQUE) &&
-         GetLayer()->IsOpaqueForVisibility() &&
-         LayerHasCheckerboardingAPZC(GetLayer(), aOutCheckerboardingColor);
-}
-
 #ifndef MOZ_HAVE_PLATFORM_SPECIFIC_LAYER_BUFFERS
 
 /*static*/ bool

gfx/layers/composite/LayerManagerComposite.h

@@ -589,12 +589,6 @@ public:
   bool GetShadowTransformSetByAnimation() { return mShadowTransformSetByAnimation; }
   bool GetShadowOpacitySetByAnimation() { return mShadowOpacitySetByAnimation; }
 
-  /**
-   * Return true if a checkerboarding background color needs to be drawn
-   * for this layer.
-   */
-  virtual bool NeedToDrawCheckerboarding(gfx::Color* aOutCheckerboardingColor = nullptr) { return false; }
-
 protected:
   HostLayerManager* mCompositorManager;
 
@@ -694,8 +688,6 @@ public:
    */
   virtual nsIntRegion GetFullyRenderedRegion();
 
-  virtual bool NeedToDrawCheckerboarding(gfx::Color* aOutCheckerboardingColor = nullptr);
-
 protected:
   LayerManagerComposite* mCompositeManager;
 

layout/base/PresShell.cpp

@@ -5313,20 +5313,29 @@ PresShell::AddCanvasBackgroundColorItem(nsDisplayListBuilder& aBuilder,
   // color background behind a scrolled transparent background. Instead,
   // we'll try to move the color background into the scrolled content
   // by making nsDisplayCanvasBackground paint it.
+  bool addedScrollingBackgroundColor = false;
   if (!aFrame->GetParent()) {
     nsIScrollableFrame* sf =
       aFrame->PresContext()->PresShell()->GetRootScrollFrameAsScrollable();
     if (sf) {
       nsCanvasFrame* canvasFrame = do_QueryFrame(sf->GetScrolledFrame());
       if (canvasFrame && canvasFrame->IsVisibleForPainting(&aBuilder)) {
-        if (AddCanvasBackgroundColor(aList, canvasFrame, bgcolor, mHasCSSBackgroundColor))
-          return;
+        addedScrollingBackgroundColor =
+          AddCanvasBackgroundColor(aList, canvasFrame, bgcolor, mHasCSSBackgroundColor);
       }
     }
   }
 
-  aList.AppendNewToBottom(
-    new (&aBuilder) nsDisplaySolidColor(&aBuilder, aFrame, aBounds, bgcolor));
+  if (!addedScrollingBackgroundColor ||
+      (nsLayoutUtils::UsesAsyncScrolling(aFrame) && NS_GET_A(bgcolor) == 255)) {
+    // With async scrolling, we'd like to have two instances of the background
+    // color: one that scrolls with the content (for the reasons stated above),
+    // and one underneath which does not scroll with the content, but which can
+    // be shown during checkerboarding and overscroll.
+    // We can only do that if the color is opaque.
+    aList.AppendNewToBottom(
+      new (&aBuilder) nsDisplaySolidColor(&aBuilder, aFrame, aBounds, bgcolor));
+  }
 }
 
 static bool IsTransparentContainerElement(nsPresContext* aPresContext)

layout/painting/FrameLayerBuilder.cpp

@@ -660,10 +660,6 @@ public:
    * in mItemClip).
    */
   void UpdateCommonClipCount(const DisplayItemClip& aCurrentClip);
-  /**
-   * The union of all the bounds of the display items in this layer.
-   */
-  nsIntRect mBounds;
   /**
    * The region of visible content above the layer and below the
    * next PaintedLayerData currently in the stack, if any.
@@ -3241,10 +3237,6 @@ void ContainerState::FinishPaintedLayerData(PaintedLayerData& aData, FindOpaqueB
     SetOuterVisibleRegionForLayer(layer, data->mVisibleRegion);
   }
 
-  nsIntRect layerBounds = data->mBounds;
-  layerBounds.MoveBy(-GetTranslationForPaintedLayer(data->mLayer));
-  layer->SetLayerBounds(layerBounds);
-
 #ifdef MOZ_DUMP_PAINTING
   if (!data->mLog.IsEmpty()) {
     if (PaintedLayerData* containingPld = mLayerBuilder->GetContainingPaintedLayerData()) {
@@ -3441,10 +3433,6 @@ PaintedLayerData::Accumulate(ContainerState* aState,
 {
   FLB_LOG_PAINTED_LAYER_DECISION(this, "Accumulating dp=%s(%p), f=%p against pld=%p\n", aItem->Name(), aItem, aItem->Frame(), this);
 
-  bool snap;
-  nsRect itemBounds = aItem->GetBounds(aState->mBuilder, &snap);
-  mBounds = mBounds.Union(aState->ScaleToOutsidePixels(itemBounds, snap));
-
   if (aState->mBuilder->NeedToForceTransparentSurfaceForItem(aItem)) {
     mForceTransparentSurface = true;
   }
@@ -3766,7 +3754,7 @@ ContainerState::GetDisplayPortForAnimatedGeometryRoot(AnimatedGeometryRoot* aAni
   mLastDisplayPortAGR = aAnimatedGeometryRoot;
 
   nsIScrollableFrame* sf = nsLayoutUtils::GetScrollableFrameFor(*aAnimatedGeometryRoot);
-  if (sf == nullptr) {
+  if (sf == nullptr || nsLayoutUtils::UsesAsyncScrolling(*aAnimatedGeometryRoot)) {
     mLastDisplayPortRect = nsRect();
     return mLastDisplayPortRect;
   }

layout/reftests/async-scrolling/checkerboard-2-ref.html

@@ -1,6 +1,7 @@
 <!DOCTYPE HTML>
 <html>
 <body style="background-color: green; overflow:hidden">
+  <div style="position:fixed; left: 0px; top: 0px; width: 100px; height: 500px; background-color: purple; z-index: -1"></div>
   <div style="position:absolute; left: 0px; top: 0px; background-color: yellow; width: 100px; height: 200px"></div>
   <div style="position:fixed; left: 10px; top: 10px; width: 10px; height: 10px; background-color: blue"></div>
 </body>

layout/reftests/async-scrolling/checkerboard-3-ref.html

@@ -1,5 +1,6 @@
 <!DOCTYPE HTML>
 <html>
 <body style="background-color: green; overflow:hidden">
+  <div style="position:fixed; left: 0px; top: 0px; width: 100px; height: 500px; background-color: purple; z-index: -1"></div>
   <div style="position:fixed; left: 10px; top: 10px; width: 10px; height: 10px; background-color: blue"></div>
 </body>