From 87e8ddba66464d25ef4b6f68caaa181489545902 Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <email@mattatobin.com>
Date: Tue, 3 May 2022 08:56:38 -0500
Subject: [Layout:Base] Back out the change to vector for DisplayLists because
 win7-7 is a moron.

---
 layout/base/FrameLayerBuilder.cpp | 75 ++++++++++++---------------------------
 1 file changed, 22 insertions(+), 53 deletions(-)

diff --git a/layout/base/FrameLayerBuilder.cpp b/layout/base/FrameLayerBuilder.cpp
index 993572cf3..d38b17adc 100644
--- a/layout/base/FrameLayerBuilder.cpp
+++ b/layout/base/FrameLayerBuilder.cpp
@@ -162,12 +162,7 @@ void
 FrameLayerBuilder::DisplayItemData::AddFrame(nsIFrame* aFrame)
 {
   MOZ_RELEASE_ASSERT(mLayer);
-  
-  // Make sure we don't add duplicate frames as we're storing these as vectors.
-  // See UXP Issue #1860
-  if (!mFrameList.Contains(aFrame)) {
-    mFrameList.AppendElement(aFrame);
-  }
+  mFrameList.AppendElement(aFrame);
 
   nsTArray<DisplayItemData*>* array =
     aFrame->GetProperty(FrameLayerBuilder::LayerManagerDataProperty());
@@ -333,7 +328,8 @@ public:
   void Dump(const char *aPrefix = "") {
     printf_stderr("%sLayerManagerData %p\n", aPrefix, this);
 
-    for (auto& data : mDisplayItems) {
+    for (auto iter = mDisplayItems.Iter(); !iter.Done(); iter.Next()) {
+      FrameLayerBuilder::DisplayItemData* data = iter.Get()->GetKey();
 
       nsAutoCString prefix;
       prefix += aPrefix;
@@ -392,7 +388,7 @@ public:
 #ifdef DEBUG_DISPLAY_ITEM_DATA
   LayerManagerData *mParent;
 #endif
-  std::vector<RefPtr<FrameLayerBuilder::DisplayItemData> > mDisplayItems;
+  nsTHashtable<nsRefPtrHashKey<FrameLayerBuilder::DisplayItemData> > mDisplayItems;
   bool mInvalidateAllLayers;
 };
 
@@ -1975,12 +1971,7 @@ FrameLayerBuilder::RemoveFrameFromLayerManager(const nsIFrame* aFrame,
       }
     }
 
-    auto it = std::find(data->mParent->mDisplayItems.begin(),
-                        data->mParent->mDisplayItems.end(),
-                        data);
-    MOZ_ASSERT(it != data->mParent->mDisplayItems.end());
-    std::iter_swap(it, data->mParent->mDisplayItems.end() - 1);
-    data->mParent->mDisplayItems.pop_back();
+    data->mParent->mDisplayItems.RemoveEntry(data);
   }
 
   arrayCopy.Clear();
@@ -2033,40 +2024,27 @@ FrameLayerBuilder::WillEndTransaction()
   NS_ASSERTION(data, "Must have data!");
 
   // Update all the frames that used to have layers.
-  auto iter = data->mDisplayItems.begin();
-  while (iter != data->mDisplayItems.end()) {
-    DisplayItemData* did = iter->get();
-    if (!did->mUsed) {
+  for (auto iter = data->mDisplayItems.Iter(); !iter.Done(); iter.Next()) {
+    DisplayItemData* data = iter.Get()->GetKey();
+    if (!data->mUsed) {
       // This item was visible, but isn't anymore.
-      PaintedLayer* t = did->mLayer->AsPaintedLayer();
-      if (t && did->mGeometry) {
+      PaintedLayer* t = data->mLayer->AsPaintedLayer();
+      if (t && data->mGeometry) {
 #ifdef MOZ_DUMP_PAINTING
         if (nsLayoutUtils::InvalidationDebuggingIsEnabled()) {
-          printf_stderr("Invalidating unused display item (%i) belonging to frame %p from layer %p\n", did->mDisplayItemKey, did->mFrameList[0], t);
+          printf_stderr("Invalidating unused display item (%i) belonging to frame %p from layer %p\n", data->mDisplayItemKey, data->mFrameList[0], t);
         }
 #endif
         InvalidatePostTransformRegion(t,
-                                      did->mGeometry->ComputeInvalidationRegion(),
-                                      did->mClip,
+                                      data->mGeometry->ComputeInvalidationRegion(),
+                                      data->mClip,
                                       GetLastPaintOffset(t));
       }
 
-      did->ClearAnimationCompositorState();
-
-      // Remove this item. Swapping it with the last element first is
-      // quicker than erasing from the middle.
-      if (iter != data->mDisplayItems.end() - 1) {
-        std::iter_swap(iter, data->mDisplayItems.end() - 1);
-        data->mDisplayItems.pop_back();
-      } else {
-        data->mDisplayItems.pop_back();
-        break;
-      }
-
-      // Don't increment iter because we still need to process the item which was moved.
+      data->ClearAnimationCompositorState();
+      iter.Remove();
     } else {
-      ComputeGeometryChangeForItem(did);
-      iter++;
+      ComputeGeometryChangeForItem(data);
     }
   }
 
@@ -4822,7 +4800,7 @@ FrameLayerBuilder::StoreDataForFrame(nsDisplayItem* aItem, Layer* aLayer, LayerS
 
   data->BeginUpdate(aLayer, aState, mContainerLayerGeneration, aItem);
 
-  lmd->mDisplayItems.push_back(data);
+  lmd->mDisplayItems.PutEntry(data);
   return data;
 }
 
@@ -4846,7 +4824,7 @@ FrameLayerBuilder::StoreDataForFrame(nsIFrame* aFrame,
 
   data->BeginUpdate(aLayer, aState, mContainerLayerGeneration);
 
-  lmd->mDisplayItems.push_back(data);
+  lmd->mDisplayItems.PutEntry(data);
 }
 
 FrameLayerBuilder::ClippedDisplayItem::ClippedDisplayItem(nsDisplayItem* aItem,
@@ -5580,19 +5558,10 @@ FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
       flattenToSingleLayer = true;
 
       // Restore DisplayItemData
-      auto iter = data->mDisplayItems.begin();
-      while (iter != data->mDisplayItems.end()) {
-        DisplayItemData* did = iter->get();
-        if (did->mUsed && did->mContainerLayerGeneration >= mContainerLayerGeneration) {
-          if (iter != data->mDisplayItems.end() - 1) {
-            std::iter_swap(iter, data->mDisplayItems.end() - 1);
-            data->mDisplayItems.pop_back();
-          } else {
-            data->mDisplayItems.pop_back();
-            break;
-          }
-        } else {
-          iter++;
+      for (auto iter = data->mDisplayItems.Iter(); !iter.Done(); iter.Next()) {
+        DisplayItemData* data = iter.Get()->GetKey();
+        if (data->mUsed && data->mContainerLayerGeneration >= mContainerLayerGeneration) {
+          iter.Remove();
         }
       }
 
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