Bug 1267438 - Give layers an optional scrolled clip that is scrolled by all scroll frames associated with the layer. r=mstange

MozReview-Commit-ID: EGqVZuISSZQ

--HG--
extra : rebase_source : cf1e70734524cb740cb0cb64190d5a780d2b692f
extra : amend_source : b91d3f887a78da248950289fa8917db5fa62910b
extra : source : 54cb97cee6810ec56308d1f2f66e5b8fda02da3e
extra : histedit_source : dc982f0a16e8c2c042c260bc56252425cc6f76c4

gfx/layers/FrameMetrics.h

@@ -725,6 +725,8 @@ private:
   Maybe<size_t> mMaskLayerIndex;
 };
 
+typedef Maybe<LayerClip> MaybeLayerClip;  // for passing over IPDL
+
 /**
  * Metadata about a scroll frame that's stored in the layer tree for use by
  * the compositor (including APZ). This includes the scroll frame's FrameMetrics,

gfx/layers/Layers.cpp

@@ -1100,6 +1100,8 @@ Layer::GetCombinedClipRect() const
 {
   Maybe<ParentLayerIntRect> clip = GetClipRect();
 
+  clip = IntersectMaybeRects(clip, GetScrolledClipRect());
+
   for (size_t i = 0; i < mScrollMetadata.Length(); i++) {
     clip = IntersectMaybeRects(clip, mScrollMetadata[i].GetClipRect());
   }
@@ -1902,6 +1904,9 @@ Layer::PrintInfo(std::stringstream& aStream, const char* aPrefix)
   if (mClipRect) {
     AppendToString(aStream, *mClipRect, " [clip=", "]");
   }
+  if (mScrolledClip) {
+    AppendToString(aStream, mScrolledClip->GetClipRect(), " [scrolled-clip=", "]");
+  }
   if (1.0 != mPostXScale || 1.0 != mPostYScale) {
     aStream << nsPrintfCString(" [postScale=%g, %g]", mPostXScale, mPostYScale).get();
   }

gfx/layers/Layers.h

@@ -1035,6 +1035,26 @@ public:
     }
   }
 
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Set an optional scrolled clip on the layer.
+   * The scrolled clip, if present, consists of a clip rect and an optional mask.
+   * This scrolled clip is always scrolled by all scroll frames associated with
+   * this layer. (By contrast, the scroll clips stored in ScrollMetadata are
+   * only scrolled by scroll frames above that ScrollMetadata, and the layer's
+   * mClipRect is always fixed to the layer contents (which may or may not be
+   * scrolled by some of the scroll frames associated with the layer, depending
+   * on whether the layer is fixed).)
+   */
+  void SetScrolledClip(const Maybe<LayerClip>& aScrolledClip)
+  {
+    if (mScrolledClip != aScrolledClip) {
+      MOZ_LAYERS_LOG_IF_SHADOWABLE(this, ("Layer::Mutated(%p) ScrolledClip", this));
+      mScrolledClip = aScrolledClip;
+      Mutated();
+    }
+  }
+
   /**
    * CONSTRUCTION PHASE ONLY
    * Set a layer to mask this layer.
@@ -1281,6 +1301,7 @@ public:
   float GetOpacity() { return mOpacity; }
   gfx::CompositionOp GetMixBlendMode() const { return mMixBlendMode; }
   const Maybe<ParentLayerIntRect>& GetClipRect() const { return mClipRect; }
+  const Maybe<LayerClip>& GetScrolledClip() const { return mScrolledClip; }
   uint32_t GetContentFlags() { return mContentFlags; }
   const gfx::IntRect& GetLayerBounds() const { return mLayerBounds; }
   const LayerIntRegion& GetVisibleRegion() const { return mVisibleRegion; }
@@ -1850,6 +1871,7 @@ protected:
   gfx::CompositionOp mMixBlendMode;
   bool mForceIsolatedGroup;
   Maybe<ParentLayerIntRect> mClipRect;
+  Maybe<LayerClip> mScrolledClip;
   gfx::IntRect mTileSourceRect;
   gfx::TiledIntRegion mInvalidRegion;
   nsTArray<RefPtr<AsyncPanZoomController> > mApzcs;

gfx/layers/ipc/LayerTransactionParent.cpp

@@ -343,6 +343,7 @@ LayerTransactionParent::RecvUpdate(InfallibleTArray<Edit>&& cset,
       layer->SetContentFlags(common.contentFlags());
       layer->SetOpacity(common.opacity());
       layer->SetClipRect(common.useClipRect() ? Some(common.clipRect()) : Nothing());
+      layer->SetScrolledClip(common.scrolledClip());
       layer->SetBaseTransform(common.transform().value());
       layer->SetTransformIsPerspective(common.transformIsPerspective());
       layer->SetPostScale(common.postXScale(), common.postYScale());

gfx/layers/ipc/LayersMessages.ipdlh

@@ -45,6 +45,7 @@ using struct mozilla::layers::ScrollMetadata from "FrameMetrics.h";
 using mozilla::layers::FrameMetrics::ViewID from "FrameMetrics.h";
 using struct mozilla::layers::FenceHandle from "mozilla/layers/FenceUtils.h";
 using mozilla::layers::LayersBackend from "mozilla/layers/LayersTypes.h";
+using mozilla::layers::MaybeLayerClip from "FrameMetrics.h";
 
 namespace mozilla {
 namespace layers {
@@ -218,6 +219,7 @@ struct CommonLayerAttributes {
   float opacity;
   bool useClipRect;
   ParentLayerIntRect clipRect;
+  MaybeLayerClip scrolledClip;
   bool isFixedPosition;
   uint64_t fixedPositionScrollContainerId;
   LayerPoint fixedPositionAnchor;

gfx/layers/ipc/ShadowLayers.cpp

@@ -828,6 +828,7 @@ ShadowLayerForwarder::EndTransaction(InfallibleTArray<EditReply>* aReplies,
     common.useClipRect() = !!mutant->GetClipRect();
     common.clipRect() = (common.useClipRect() ?
                          *mutant->GetClipRect() : ParentLayerIntRect());
+    common.scrolledClip() = mutant->GetScrolledClip();
     common.isFixedPosition() = mutant->GetIsFixedPosition();
     if (mutant->GetIsFixedPosition()) {
       common.fixedPositionScrollContainerId() = mutant->GetFixedPositionScrollContainerId();