Bug 1521644 - Create nsDisplayAsyncZoom which creates a ContainerLayer that is marked as an async zoom container. r=mattwoodrow

Differential Revision: https://phabricator.services.mozilla.com/D17175

--HG--
extra : moz-landing-system : lando

layout/painting/nsDisplayItemTypesList.h

@@ -4,6 +4,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 // IWYU pragma: private, include "nsDisplayList.h"
+DECLARE_DISPLAY_ITEM_TYPE(ASYNC_ZOOM, TYPE_RENDERS_NO_IMAGES)
 DECLARE_DISPLAY_ITEM_TYPE(ALT_FEEDBACK, 0)
 DECLARE_DISPLAY_ITEM_TYPE(BACKGROUND, TYPE_IS_CONTENTFUL)
 DECLARE_DISPLAY_ITEM_TYPE(THEMED_BACKGROUND, TYPE_RENDERS_NO_IMAGES)

layout/painting/nsDisplayList.cpp

@@ -7155,6 +7155,32 @@ bool nsDisplayZoom::ComputeVisibility(nsDisplayListBuilder* aBuilder,
   return retval;
 }
 
+nsDisplayAsyncZoom::nsDisplayAsyncZoom(
+    nsDisplayListBuilder* aBuilder, nsIFrame* aFrame, nsDisplayList* aList,
+    const ActiveScrolledRoot* aActiveScrolledRoot,
+    mozilla::layers::FrameMetrics::ViewID aViewID)
+    : nsDisplayOwnLayer(aBuilder, aFrame, aList, aActiveScrolledRoot),
+      mViewID(aViewID) {
+  MOZ_COUNT_CTOR(nsDisplayAsyncZoom);
+}
+
+#ifdef NS_BUILD_REFCNT_LOGGING
+nsDisplayAsyncZoom::~nsDisplayAsyncZoom() {
+  MOZ_COUNT_DTOR(nsDisplayAsyncZoom);
+}
+#endif
+
+already_AddRefed<Layer> nsDisplayAsyncZoom::BuildLayer(
+    nsDisplayListBuilder* aBuilder, LayerManager* aManager,
+    const ContainerLayerParameters& aContainerParameters) {
+  RefPtr<Layer> layer =
+      nsDisplayOwnLayer::BuildLayer(aBuilder, aManager, aContainerParameters);
+
+  layer->SetIsAsyncZoomContainer(Some(mViewID));
+
+  return layer.forget();
+}
+
 ///////////////////////////////////////////////////
 // nsDisplayTransform Implementation
 //

layout/painting/nsDisplayList.h

@@ -6112,6 +6112,43 @@ class nsDisplayZoom : public nsDisplaySubDocument {
   int32_t mAPD, mParentAPD;
 };
 
+/**
+ * nsDisplayAsyncZoom is used for APZ zooming. It wraps the contents of the
+ * root content document's scroll frame, including fixed position content. It
+ * does not contain the scroll frame's scrollbars. It is clipped to the scroll
+ * frame's scroll port clip. It is not scrolled; only its non-fixed contents
+ * are scrolled. This item creates a container layer.
+ */
+class nsDisplayAsyncZoom : public nsDisplayOwnLayer {
+ public:
+  nsDisplayAsyncZoom(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
+                     nsDisplayList* aList,
+                     const ActiveScrolledRoot* aActiveScrolledRoot,
+                     mozilla::layers::FrameMetrics::ViewID aViewID);
+  nsDisplayAsyncZoom(nsDisplayListBuilder* aBuilder,
+                     const nsDisplayAsyncZoom& aOther)
+      : nsDisplayOwnLayer(aBuilder, aOther), mViewID(aOther.mViewID) {
+    MOZ_COUNT_CTOR(nsDisplayAsyncZoom);
+  }
+
+#ifdef NS_BUILD_REFCNT_LOGGING
+  virtual ~nsDisplayAsyncZoom();
+#endif
+
+  virtual already_AddRefed<Layer> BuildLayer(
+      nsDisplayListBuilder* aBuilder, LayerManager* aManager,
+      const ContainerLayerParameters& aContainerParameters) override;
+  NS_DISPLAY_DECL_NAME("AsyncZoom", TYPE_ASYNC_ZOOM)
+  virtual LayerState GetLayerState(
+      nsDisplayListBuilder* aBuilder, LayerManager* aManager,
+      const ContainerLayerParameters& aParameters) override {
+    return mozilla::LAYER_ACTIVE_FORCE;
+  }
+
+ protected:
+  mozilla::layers::FrameMetrics::ViewID mViewID;
+};
+
 /**
  * A base class for different effects types.
  */