Bug 1128225 (Part 3) - Add infrastructure for tracking draw results in geometry items. r=tn

layout/base/FrameLayerBuilder.cpp

@@ -4732,6 +4732,31 @@ FrameLayerBuilder::DumpRetainedLayerTree(LayerManager* aManager, std::stringstre
   aManager->Dump(aStream, "", aDumpHtml);
 }
 
+nsDisplayItemGeometry*
+FrameLayerBuilder::GetMostRecentGeometry(nsDisplayItem* aItem)
+{
+  typedef nsTArray<DisplayItemData*> DataArray;
+
+  // Retrieve the array of DisplayItemData associated with our frame.
+  FrameProperties properties = aItem->Frame()->Properties();
+  auto dataArray =
+    static_cast<DataArray*>(properties.Get(LayerManagerDataProperty()));
+  if (!dataArray) {
+    return nullptr;
+  }
+
+  // Find our display item data, if it exists, and return its geometry.
+  uint32_t itemPerFrameKey = aItem->GetPerFrameKey();
+  for (uint32_t i = 0; i < dataArray->Length(); i++) {
+    DisplayItemData* data = dataArray->ElementAt(i);
+    if (data->GetDisplayItemKey() == itemPerFrameKey) {
+      return data->GetGeometry();
+    }
+  }
+
+  return nullptr;
+}
+
 gfx::Rect
 CalculateBounds(const nsTArray<DisplayItemClip::RoundedRect>& aRects, int32_t A2D)
 {

layout/base/FrameLayerBuilder.h

@@ -275,6 +275,17 @@ public:
    */
   static void DumpRetainedLayerTree(LayerManager* aManager, std::stringstream& aStream, bool aDumpHtml = false);
 
+  /**
+   * Returns the most recently allocated geometry item for the given display
+   * item.
+   *
+   * XXX(seth): The current implementation must iterate through all display
+   * items allocated for this display item's frame. This may lead to O(n^2)
+   * behavior in some situations.
+   */
+  static nsDisplayItemGeometry* GetMostRecentGeometry(nsDisplayItem* aItem);
+
+
   /******* PRIVATE METHODS to FrameLayerBuilder.cpp ********/
   /* These are only in the public section because they need
    * to be called by file-scope helper functions in FrameLayerBuilder.cpp.
@@ -398,6 +409,7 @@ public:
 
     uint32_t GetDisplayItemKey() { return mDisplayItemKey; }
     Layer* GetLayer() { return mLayer; }
+    nsDisplayItemGeometry* GetGeometry() const { return mGeometry.get(); }
     void Invalidate() { mIsInvalid = true; }
 
   private:

layout/base/nsDisplayListInvalidation.h

@@ -7,6 +7,8 @@
 #define NSDISPLAYLISTINVALIDATION_H_
 
 #include "mozilla/Attributes.h"
+#include "FrameLayerBuilder.h"
+#include "imgIContainer.h"
 #include "nsRect.h"
 #include "nsColor.h"
 #include "gfxRect.h"
@@ -71,6 +73,63 @@ public:
   nsRect mBorderRect;
 };
 
+/**
+ * nsImageGeometryMixin is a mixin for geometry items that draw images. Geometry
+ * items that include this mixin can track drawing results and use that
+ * information to inform invalidation decisions.
+ *
+ * This mixin uses CRTP; its template parameter should be the type of the class
+ * that is inheriting from it. See nsDisplayItemGenericImageGeometry for an
+ * example.
+ */
+template <typename T>
+class nsImageGeometryMixin
+{
+public:
+  explicit nsImageGeometryMixin(nsDisplayItem* aItem)
+    : mLastDrawResult(mozilla::image::DrawResult::NOT_READY)
+  {
+    auto lastGeometry =
+      static_cast<T*>(mozilla::FrameLayerBuilder::GetMostRecentGeometry(aItem));
+    if (lastGeometry) {
+      mLastDrawResult = lastGeometry->LastDrawResult();
+    }
+  }
+
+  static void UpdateDrawResult(nsDisplayItem* aItem,
+                               mozilla::image::DrawResult aResult)
+  {
+    auto lastGeometry =
+      static_cast<T*>(mozilla::FrameLayerBuilder::GetMostRecentGeometry(aItem));
+    if (lastGeometry) {
+      lastGeometry->mLastDrawResult = aResult;
+    }
+  }
+
+  mozilla::image::DrawResult LastDrawResult() const { return mLastDrawResult; }
+
+private:
+  mozilla::image::DrawResult mLastDrawResult;
+};
+
+/**
+ * nsDisplayItemGenericImageGeometry is a generic geometry item class that
+ * includes nsImageGeometryMixin.
+ *
+ * This should be sufficient for most display items that draw images.
+ */
+class nsDisplayItemGenericImageGeometry
+  : public nsDisplayItemGenericGeometry
+  , public nsImageGeometryMixin<nsDisplayItemGenericImageGeometry>
+{
+public:
+  nsDisplayItemGenericImageGeometry(nsDisplayItem* aItem,
+                                    nsDisplayListBuilder* aBuilder)
+    : nsDisplayItemGenericGeometry(aItem, aBuilder)
+    , nsImageGeometryMixin(aItem)
+  { }
+};
+
 class nsDisplayItemBoundsGeometry : public nsDisplayItemGeometry
 {
 public: