From 30d4df57785de9208898c5011637d9c13402d6b7 Mon Sep 17 00:00:00 2001
From: Ehsan Akhgari <ehsan@mozilla.com>
Date: Sat, 29 Jul 2017 02:43:39 -0400
Subject: [PATCH] Bug 1385538 - Avoid dynamic memory allocation for
 EditorBase::mSelState; r=masayuki

---
 editor/libeditor/EditorBase.cpp             |  5 ++---
 editor/libeditor/EditorBase.h               |  4 ++--
 editor/libeditor/PlaceholderTransaction.cpp | 20 +++++++-------------
 editor/libeditor/PlaceholderTransaction.h   |  7 +++----
 4 files changed, 14 insertions(+), 22 deletions(-)

diff --git a/editor/libeditor/EditorBase.cpp b/editor/libeditor/EditorBase.cpp
index 235d03abc505..b5b22631455b 100644
--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -128,7 +128,6 @@ using namespace widget;
 
 EditorBase::EditorBase()
   : mPlaceholderName(nullptr)
-  , mSelState(nullptr)
   , mModCount(0)
   , mFlags(0)
   , mUpdateCount(0)
@@ -974,7 +973,7 @@ EditorBase::BeginPlaceHolderTransaction(nsIAtom* aName)
     mPlaceholderName = aName;
     RefPtr<Selection> selection = GetSelection();
     if (selection) {
-      mSelState = MakeUnique<SelectionState>();
+      mSelState.emplace();
       mSelState->SaveSelection(selection);
       // Composition transaction can modify multiple nodes and it merges text
       // node for ime into single text node.
@@ -1039,7 +1038,7 @@ EditorBase::EndPlaceHolderTransaction()
       if (mPlaceholderName == nsGkAtoms::IMETxnName) {
         mRangeUpdater.DropSelectionState(*mSelState);
       }
-      mSelState = nullptr;
+      mSelState.reset();
     }
     // We might have never made a placeholder if no action took place.
     if (mPlaceholderTransaction) {
diff --git a/editor/libeditor/EditorBase.h b/editor/libeditor/EditorBase.h
index 339c48021bf7..8bd52151ab7f 100644
--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -7,10 +7,10 @@
 #define mozilla_EditorBase_h
 
 #include "mozilla/Assertions.h"         // for MOZ_ASSERT, etc.
+#include "mozilla/Maybe.h"              // for Maybe
 #include "mozilla/OwningNonNull.h"      // for OwningNonNull
 #include "mozilla/SelectionState.h"     // for RangeUpdater, etc.
 #include "mozilla/StyleSheet.h"         // for StyleSheet
-#include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"            // for WeakPtr
 #include "mozilla/dom/Text.h"
 #include "nsCOMPtr.h"                   // for already_AddRefed, nsCOMPtr
@@ -1133,7 +1133,7 @@ protected:
   // Name of placeholder transaction.
   nsIAtom* mPlaceholderName;
   // Saved selection state for placeholder transaction batching.
-  mozilla::UniquePtr<SelectionState> mSelState;
+  mozilla::Maybe<SelectionState> mSelState;
   // IME composition this is not null between compositionstart and
   // compositionend.
   RefPtr<TextComposition> mComposition;
diff --git a/editor/libeditor/PlaceholderTransaction.cpp b/editor/libeditor/PlaceholderTransaction.cpp
index 142a85075ff2..8f1fb812d30a 100644
--- a/editor/libeditor/PlaceholderTransaction.cpp
+++ b/editor/libeditor/PlaceholderTransaction.cpp
@@ -19,12 +19,12 @@ using namespace dom;
 PlaceholderTransaction::PlaceholderTransaction(
                           EditorBase& aEditorBase,
                           nsIAtom* aName,
-                          UniquePtr<SelectionState> aSelState)
+                          Maybe<SelectionState>&& aSelState)
   : mAbsorb(true)
   , mForwarding(nullptr)
   , mCompositionTransaction(nullptr)
   , mCommitted(false)
-  , mStartSel(Move(aSelState))
+  , mStartSel(Move(*aSelState))
   , mEditorBase(&aEditorBase)
 {
   mName = aName;
@@ -38,19 +38,15 @@ NS_IMPL_CYCLE_COLLECTION_CLASS(PlaceholderTransaction)
 
 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(PlaceholderTransaction,
                                                 EditAggregateTransaction)
-  if (tmp->mStartSel) {
-    ImplCycleCollectionUnlink(*tmp->mStartSel);
-  }
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mEditorBase);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mStartSel);
   NS_IMPL_CYCLE_COLLECTION_UNLINK(mEndSel);
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(PlaceholderTransaction,
                                                   EditAggregateTransaction)
-  if (tmp->mStartSel) {
-    ImplCycleCollectionTraverse(cb, *tmp->mStartSel, "mStartSel", 0);
-  }
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEditorBase);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStartSel);
   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEndSel);
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
@@ -78,12 +74,10 @@ PlaceholderTransaction::UndoTransaction()
   nsresult rv = EditAggregateTransaction::UndoTransaction();
   NS_ENSURE_SUCCESS(rv, rv);
 
-  NS_ENSURE_TRUE(mStartSel, NS_ERROR_NULL_POINTER);
-
   // now restore selection
   RefPtr<Selection> selection = mEditorBase->GetSelection();
   NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
-  return mStartSel->RestoreSelection(selection);
+  return mStartSel.RestoreSelection(selection);
 }
 
 NS_IMETHODIMP
@@ -222,11 +216,11 @@ PlaceholderTransaction::StartSelectionEquals(SelectionState* aSelState,
   // determine if starting selection matches the given selection state.
   // note that we only care about collapsed selections.
   NS_ENSURE_TRUE(aResult && aSelState, NS_ERROR_NULL_POINTER);
-  if (!mStartSel->IsCollapsed() || !aSelState->IsCollapsed()) {
+  if (!mStartSel.IsCollapsed() || !aSelState->IsCollapsed()) {
     *aResult = false;
     return NS_OK;
   }
-  *aResult = mStartSel->IsEqual(aSelState);
+  *aResult = mStartSel.IsEqual(aSelState);
   return NS_OK;
 }
 
diff --git a/editor/libeditor/PlaceholderTransaction.h b/editor/libeditor/PlaceholderTransaction.h
index d97c06814339..5b726b994505 100644
--- a/editor/libeditor/PlaceholderTransaction.h
+++ b/editor/libeditor/PlaceholderTransaction.h
@@ -8,7 +8,7 @@
 
 #include "EditAggregateTransaction.h"
 #include "mozilla/EditorUtils.h"
-#include "mozilla/UniquePtr.h"
+#include "mozilla/Maybe.h"
 #include "nsIAbsorbingTransaction.h"
 #include "nsIDOMNode.h"
 #include "nsCOMPtr.h"
@@ -33,7 +33,7 @@ public:
   NS_DECL_ISUPPORTS_INHERITED
 
   PlaceholderTransaction(EditorBase& aEditorBase, nsIAtom* aName,
-                         UniquePtr<SelectionState> aSelState);
+                         Maybe<SelectionState>&& aSelState);
 
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(PlaceholderTransaction,
                                            EditAggregateTransaction)
@@ -81,8 +81,7 @@ protected:
   // at the end.  This is so that UndoTransaction() and RedoTransaction() can
   // restore the selection properly.
 
-  // Use a pointer because this is constructed before we exist.
-  UniquePtr<SelectionState> mStartSel;
+  SelectionState mStartSel;
   SelectionState mEndSel;
 
   // The editor for this transaction.