Fix bug #242044 - Reduce number of allocations by nsSpaceManager::PushState

layout/base/src/nsSpaceManager.cpp

@@ -133,7 +133,7 @@ nsSpaceManager::~nsSpaceManager()
 
   NS_ASSERTION(!mSavedStates, "states remaining on state stack");
 
-  while (mSavedStates){
+  while (mSavedStates && mSavedStates != &mAutoState){
     SpaceManagerState *state = mSavedStates;
     mSavedStates = state->mNext;
     delete state;
@@ -979,7 +979,13 @@ nsSpaceManager::PushState()
   // Allowing mFloatDamage to accumulate the damage incurred during both
   // reflows ensures that nothing gets missed.
 
-  SpaceManagerState *state = new SpaceManagerState;
+  SpaceManagerState *state;
+
+  if(mSavedStates) {
+    state = new SpaceManagerState;
+  } else {
+    state = &mAutoState;
+  }
 
   NS_ASSERTION(state, "PushState() failed!");
 
@@ -994,6 +1000,8 @@ nsSpaceManager::PushState()
 
   if (mFrameInfoMap) {
     state->mLastFrame = mFrameInfoMap->mFrame;
+  } else {
+    state->mLastFrame = nsnull;
   }
 
   // Now that we've saved our state, add it to mSavedStates.
@@ -1038,11 +1046,14 @@ nsSpaceManager::PopState()
   mLowestTop = mSavedStates->mLowestTop;
 
   // Now that we've restored our state, pop the topmost
-  // state and delete it.
+  // state and delete it.  Make sure not to delete the mAutoState element
+  // as it is embeded in this class
 
   SpaceManagerState *state = mSavedStates;
   mSavedStates = mSavedStates->mNext;
+  if(state != &mAutoState) {
     delete state;
+  }
 }
 
 nscoord

layout/base/src/nsSpaceManager.h

@@ -332,9 +332,6 @@ protected:
     nscoord mXMost;
     nscoord mLowestTop;
     SpaceManagerState *mNext;
-
-    SpaceManagerState() : mX(0), mY(0), mLastFrame(nsnull), mNext(nsnull) {}
-    ~SpaceManagerState() {}
   };
 
 public:
@@ -411,6 +408,7 @@ protected:
   nsIntervalSet   mFloatDamage;
 
   SpaceManagerState *mSavedStates;
+  SpaceManagerState mAutoState;
 
 protected:
   FrameInfo* GetFrameInfoFor(nsIFrame* aFrame);

layout/generic/nsSpaceManager.cpp

@@ -133,7 +133,7 @@ nsSpaceManager::~nsSpaceManager()
 
   NS_ASSERTION(!mSavedStates, "states remaining on state stack");
 
-  while (mSavedStates){
+  while (mSavedStates && mSavedStates != &mAutoState){
     SpaceManagerState *state = mSavedStates;
     mSavedStates = state->mNext;
     delete state;
@@ -979,7 +979,13 @@ nsSpaceManager::PushState()
   // Allowing mFloatDamage to accumulate the damage incurred during both
   // reflows ensures that nothing gets missed.
 
-  SpaceManagerState *state = new SpaceManagerState;
+  SpaceManagerState *state;
+
+  if(mSavedStates) {
+    state = new SpaceManagerState;
+  } else {
+    state = &mAutoState;
+  }
 
   NS_ASSERTION(state, "PushState() failed!");
 
@@ -994,6 +1000,8 @@ nsSpaceManager::PushState()
 
   if (mFrameInfoMap) {
     state->mLastFrame = mFrameInfoMap->mFrame;
+  } else {
+    state->mLastFrame = nsnull;
   }
 
   // Now that we've saved our state, add it to mSavedStates.
@@ -1038,11 +1046,14 @@ nsSpaceManager::PopState()
   mLowestTop = mSavedStates->mLowestTop;
 
   // Now that we've restored our state, pop the topmost
-  // state and delete it.
+  // state and delete it.  Make sure not to delete the mAutoState element
+  // as it is embeded in this class
 
   SpaceManagerState *state = mSavedStates;
   mSavedStates = mSavedStates->mNext;
+  if(state != &mAutoState) {
     delete state;
+  }
 }
 
 nscoord

layout/generic/nsSpaceManager.h

@@ -332,9 +332,6 @@ protected:
     nscoord mXMost;
     nscoord mLowestTop;
     SpaceManagerState *mNext;
-
-    SpaceManagerState() : mX(0), mY(0), mLastFrame(nsnull), mNext(nsnull) {}
-    ~SpaceManagerState() {}
   };
 
 public:
@@ -411,6 +408,7 @@ protected:
   nsIntervalSet   mFloatDamage;
 
   SpaceManagerState *mSavedStates;
+  SpaceManagerState mAutoState;
 
 protected:
   FrameInfo* GetFrameInfoFor(nsIFrame* aFrame);