Bug 594983. Look inside display sublists to determine whether there is text for the layer. r=roc,a=blocking

layout/base/FrameLayerBuilder.cpp

@@ -884,24 +884,6 @@ ContainerState::PopThebesLayerData()
   mThebesLayerDataStack.RemoveElementAt(lastIndex);
 }
 
-static PRBool
-IsText(nsDisplayItem* aItem) {
-  switch (aItem->GetType()) {
-  case nsDisplayItem::TYPE_TEXT:
-  case nsDisplayItem::TYPE_BULLET:
-  case nsDisplayItem::TYPE_HEADER_FOOTER:
-#ifdef MOZ_MATHML
-  case nsDisplayItem::TYPE_MATHML_CHAR_FOREGROUND:
-#endif
-#ifdef MOZ_XUL
-  case nsDisplayItem::TYPE_XUL_TEXT_BOX:
-#endif
-    return PR_TRUE;
-  default:
-    return PR_FALSE;
-  }
-}
-
 void
 ContainerState::ThebesLayerData::Accumulate(nsDisplayListBuilder* aBuilder,
                                             nsDisplayItem* aItem,
@@ -941,7 +923,7 @@ ContainerState::ThebesLayerData::Accumulate(nsDisplayListBuilder* aBuilder,
     if (tmp.GetNumRects() <= 4) {
       mOpaqueRegion = tmp;
     }
-  } else if (IsText(aItem)) {
+  } else if (aItem->HasText()) {
     mHasText = PR_TRUE;
     if (!mOpaqueRegion.Contains(aVisibleRect)) {
       mHasTextOverTransparent = PR_TRUE;

layout/base/nsDisplayList.cpp

@@ -1160,6 +1160,16 @@ PRBool nsDisplayWrapList::ChildrenCanBeInactive(nsDisplayListBuilder* aBuilder,
   return PR_TRUE;
 }
 
+PRBool nsDisplayWrapList::HasText()
+{
+  for (nsDisplayItem* i = mList.GetBottom(); i; i = i->GetAbove()) {
+    if (i->HasText()) {
+      return PR_TRUE;
+    }
+  }
+  return PR_FALSE;
+}
+
 static nsresult
 WrapDisplayList(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
                 nsDisplayList* aList, nsDisplayWrapper* aWrapper) {

layout/base/nsDisplayList.h

@@ -659,6 +659,12 @@ public:
     return mToReferenceFrame;
   }
 
+  /**
+   * Checks if this display item (or any children) contains text that might 
+   * be rendered with subpixel antialiasing.
+   */
+  virtual PRBool HasText() { return PR_FALSE; }
+
 protected:
   friend class nsDisplayList;
   
@@ -1115,6 +1121,14 @@ public:
     mPaint(mFrame, aCtx, mVisibleRect, ToReferenceFrame());
   }
   NS_DISPLAY_DECL_NAME(mName, mType)
+
+  virtual PRBool HasText() {
+    if (mType == nsDisplayItem::TYPE_HEADER_FOOTER) {
+      return PR_TRUE;
+    } else {
+      return PR_FALSE;
+    }
+  }
 protected:
   PaintCallback mPaint;
 #ifdef DEBUG
@@ -1467,6 +1481,8 @@ public:
     return PR_FALSE;
   }
   NS_DISPLAY_DECL_NAME("WrapList", TYPE_WRAP_LIST)
+
+  virtual PRBool HasText();
                                     
   virtual nsDisplayList* GetList() { return &mList; }
   
@@ -1751,6 +1767,8 @@ public:
 
   NS_DISPLAY_DECL_NAME("nsDisplayTransform", TYPE_TRANSFORM);
 
+  virtual PRBool HasText() { return mStoredList.HasText(); }
+
 #ifdef NS_DEBUG
   nsDisplayWrapList* GetStoredList() { return &mStoredList; }
 #endif

layout/generic/nsBulletFrame.cpp

@@ -202,6 +202,8 @@ public:
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      nsIRenderingContext* aCtx);
   NS_DISPLAY_DECL_NAME("Bullet", TYPE_BULLET)
+
+  virtual PRBool HasText() { return PR_TRUE; }
 };
 
 void nsDisplayBullet::Paint(nsDisplayListBuilder* aBuilder,

layout/generic/nsTextFrameThebes.cpp

@@ -3977,6 +3977,8 @@ public:
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      nsIRenderingContext* aCtx);
   NS_DISPLAY_DECL_NAME("Text", TYPE_TEXT)
+
+  virtual PRBool HasText() { return PR_TRUE; }
 };
 
 void

layout/mathml/nsMathMLChar.cpp

@@ -2016,6 +2016,8 @@ public:
 
   NS_DISPLAY_DECL_NAME("MathMLCharForeground", TYPE_MATHML_CHAR_FOREGROUND)
 
+  virtual PRBool HasText() { return PR_TRUE; }
+
 private:
   nsMathMLChar* mChar;
   PRPackedBool  mIsSelected;

layout/xul/base/src/nsTextBoxFrame.cpp

@@ -346,6 +346,8 @@ public:
                      nsIRenderingContext* aCtx);
   virtual nsRect GetBounds(nsDisplayListBuilder* aBuilder);
   NS_DISPLAY_DECL_NAME("XULTextBox", TYPE_XUL_TEXT_BOX)
+
+  virtual PRBool HasText() { return PR_TRUE; }
 };
 
 void