Bug 165149. Make children of a scrolled element inherit style directly from the element instead of via the scrolled frames. Add a new view property to indicate that the view is painted on a uniform background and use it to optimize scrolling, so that a scrolled element with a uniform background color can still be scrolled using bitblits. r+sr=dbaron

layout/base/nsCSSFrameConstructor.cpp

@@ -6617,6 +6617,15 @@ nsCSSFrameConstructor::ResolveStyleContext(nsIPresContext*   aPresContext,
   // Resolve the style context based on the content object and the parent
   // style context
   nsStyleContext* parentStyleContext = aParentFrame->GetStyleContext();
+
+  // skip past any parents that are scrolled-content. We want to inherit directly
+  // from the outer scroll frame.
+  nsCOMPtr<nsIAtom> pseudo;
+  while (parentStyleContext && (pseudo = parentStyleContext->GetPseudoType()) ==
+         nsCSSAnonBoxes::scrolledContent) {
+    parentStyleContext = parentStyleContext->GetParent();
+  }
+
   if (aContent->IsContentOfType(nsIContent::eELEMENT)) {
     return aPresContext->ResolveStyleContextFor(aContent, parentStyleContext);
   } else {

layout/generic/nsContainerFrame.cpp

@@ -548,11 +548,41 @@ SyncFrameViewGeometryDependentProperties(nsIPresContext*  aPresContext,
   // view's contents should be repainted and not bitblt'd
   vm->SetViewBitBltEnabled(aView, !fixedBackground);
 
+  nsCOMPtr<nsIAtom> pseudo = aFrame->GetStyleContext()->GetPseudoType();
+
+  // If the frame has a solid background color, 'background-clip:border',
+  // and it's a kind of frame that paints its background, and rounded borders aren't
+  // clipping the background, then it's opaque.
   PRBool  viewHasTransparentContent =
-    !hasBG ||
-    (bg->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) ||
-    !aFrame->CanPaintBackground() ||
-    HasNonZeroBorderRadius(aStyleContext);
+    !(hasBG && !(bg->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) &&
+      bg->mBackgroundClip == NS_STYLE_BG_CLIP_BORDER &&
+      aFrame->CanPaintBackground() &&
+      !HasNonZeroBorderRadius(aStyleContext));
+
+  PRBool drawnOnUniformField = PR_FALSE;
+  if (pseudo == nsCSSAnonBoxes::scrolledContent) {
+    // If the nsGfxScrollFrame draws a solid unclipped background
+    // color, and nothing else, then tell the view system that we're
+    // drawn on a uniform field. Note that it's OK if the background
+    // is clipped to the padding area, since the scrollport is within
+    // the borders.
+    nsIFrame* scrollFrame = aFrame->GetParent();
+    nsCOMPtr<nsIAtom> parentPseudo;
+    while ((parentPseudo = scrollFrame->GetStyleContext()->GetPseudoType())
+           == nsCSSAnonBoxes::scrolledContent) {
+      scrollFrame = scrollFrame->GetParent();
+    }
+    PRBool scrollFrameIsCanvas;
+    const nsStyleBackground* scrollFrameBG;
+    PRBool scrollFrameHasBG =
+      nsCSSRendering::FindBackground(aPresContext, scrollFrame, &scrollFrameBG,
+                                     &scrollFrameIsCanvas);
+    drawnOnUniformField = scrollFrameHasBG &&
+      !(scrollFrameBG->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) &&
+      (scrollFrameBG->mBackgroundFlags & NS_STYLE_BG_IMAGE_NONE) &&
+      !HasNonZeroBorderRadius(scrollFrame->GetStyleContext());
+  }
+  aView->SetHasUniformBackground(drawnOnUniformField);
 
   if (isCanvas) {
     nsIView* rootView;

layout/generic/nsFrame.cpp

@@ -4437,6 +4437,9 @@ GetNextSiblingAcrossLines(nsIPresContext *aPresContext, nsIFrame *aFrame)
  *
  * Also correct for the frame tree mangling that happens when we create
  * wrappers for :before/:after.
+ *
+ * Also skip anonymous scrolled-content parents; inherit directly from the
+ * outer scroll frame.
  */
 static nsresult
 GetCorrectedParent(nsIPresContext* aPresContext, nsIFrame* aFrame,
@@ -4462,6 +4465,19 @@ GetCorrectedParent(nsIPresContext* aPresContext, nsIFrame* aFrame,
       } else {
         parent = parent->GetParent();
       }
+      parentPseudo = parent->GetStyleContext()->GetPseudoType();
+    }
+
+    // if this frame itself is not scrolled-content, then skip any scrolled-content
+    // parents since they're basically anonymous as far as the style system goes
+    if (parentPseudo == nsCSSAnonBoxes::scrolledContent) {
+      nsCOMPtr<nsIAtom> pseudo = aFrame->GetStyleContext()->GetPseudoType();
+      if (pseudo != nsCSSAnonBoxes::scrolledContent) {
+        do {
+          parent = parent->GetParent();
+          parentPseudo = parent->GetStyleContext()->GetPseudoType();
+        } while (parentPseudo == nsCSSAnonBoxes::scrolledContent);
+      }
     }
 
     if (parent->GetStateBits() & NS_FRAME_IS_SPECIAL) {

layout/html/base/src/nsContainerFrame.cpp

@@ -548,11 +548,41 @@ SyncFrameViewGeometryDependentProperties(nsIPresContext*  aPresContext,
   // view's contents should be repainted and not bitblt'd
   vm->SetViewBitBltEnabled(aView, !fixedBackground);
 
+  nsCOMPtr<nsIAtom> pseudo = aFrame->GetStyleContext()->GetPseudoType();
+
+  // If the frame has a solid background color, 'background-clip:border',
+  // and it's a kind of frame that paints its background, and rounded borders aren't
+  // clipping the background, then it's opaque.
   PRBool  viewHasTransparentContent =
-    !hasBG ||
-    (bg->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) ||
-    !aFrame->CanPaintBackground() ||
-    HasNonZeroBorderRadius(aStyleContext);
+    !(hasBG && !(bg->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) &&
+      bg->mBackgroundClip == NS_STYLE_BG_CLIP_BORDER &&
+      aFrame->CanPaintBackground() &&
+      !HasNonZeroBorderRadius(aStyleContext));
+
+  PRBool drawnOnUniformField = PR_FALSE;
+  if (pseudo == nsCSSAnonBoxes::scrolledContent) {
+    // If the nsGfxScrollFrame draws a solid unclipped background
+    // color, and nothing else, then tell the view system that we're
+    // drawn on a uniform field. Note that it's OK if the background
+    // is clipped to the padding area, since the scrollport is within
+    // the borders.
+    nsIFrame* scrollFrame = aFrame->GetParent();
+    nsCOMPtr<nsIAtom> parentPseudo;
+    while ((parentPseudo = scrollFrame->GetStyleContext()->GetPseudoType())
+           == nsCSSAnonBoxes::scrolledContent) {
+      scrollFrame = scrollFrame->GetParent();
+    }
+    PRBool scrollFrameIsCanvas;
+    const nsStyleBackground* scrollFrameBG;
+    PRBool scrollFrameHasBG =
+      nsCSSRendering::FindBackground(aPresContext, scrollFrame, &scrollFrameBG,
+                                     &scrollFrameIsCanvas);
+    drawnOnUniformField = scrollFrameHasBG &&
+      !(scrollFrameBG->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) &&
+      (scrollFrameBG->mBackgroundFlags & NS_STYLE_BG_IMAGE_NONE) &&
+      !HasNonZeroBorderRadius(scrollFrame->GetStyleContext());
+  }
+  aView->SetHasUniformBackground(drawnOnUniformField);
 
   if (isCanvas) {
     nsIView* rootView;

layout/html/base/src/nsFrame.cpp

@@ -4437,6 +4437,9 @@ GetNextSiblingAcrossLines(nsIPresContext *aPresContext, nsIFrame *aFrame)
  *
  * Also correct for the frame tree mangling that happens when we create
  * wrappers for :before/:after.
+ *
+ * Also skip anonymous scrolled-content parents; inherit directly from the
+ * outer scroll frame.
  */
 static nsresult
 GetCorrectedParent(nsIPresContext* aPresContext, nsIFrame* aFrame,
@@ -4462,6 +4465,19 @@ GetCorrectedParent(nsIPresContext* aPresContext, nsIFrame* aFrame,
       } else {
         parent = parent->GetParent();
       }
+      parentPseudo = parent->GetStyleContext()->GetPseudoType();
+    }
+
+    // if this frame itself is not scrolled-content, then skip any scrolled-content
+    // parents since they're basically anonymous as far as the style system goes
+    if (parentPseudo == nsCSSAnonBoxes::scrolledContent) {
+      nsCOMPtr<nsIAtom> pseudo = aFrame->GetStyleContext()->GetPseudoType();
+      if (pseudo != nsCSSAnonBoxes::scrolledContent) {
+        do {
+          parent = parent->GetParent();
+          parentPseudo = parent->GetStyleContext()->GetPseudoType();
+        } while (parentPseudo == nsCSSAnonBoxes::scrolledContent);
+      }
     }
 
     if (parent->GetStateBits() & NS_FRAME_IS_SPECIAL) {

layout/html/document/src/ua.css

@@ -141,7 +141,6 @@
 
 *|*::-moz-scrolled-content { 
   /* e.g., text inputs, select boxes */
-  background: inherit;
   padding: inherit;
   display: inherit;
   -moz-box-orient: inherit;

layout/html/style/src/nsCSSFrameConstructor.cpp

@@ -6617,6 +6617,15 @@ nsCSSFrameConstructor::ResolveStyleContext(nsIPresContext*   aPresContext,
   // Resolve the style context based on the content object and the parent
   // style context
   nsStyleContext* parentStyleContext = aParentFrame->GetStyleContext();
+
+  // skip past any parents that are scrolled-content. We want to inherit directly
+  // from the outer scroll frame.
+  nsCOMPtr<nsIAtom> pseudo;
+  while (parentStyleContext && (pseudo = parentStyleContext->GetPseudoType()) ==
+         nsCSSAnonBoxes::scrolledContent) {
+    parentStyleContext = parentStyleContext->GetParent();
+  }
+
   if (aContent->IsContentOfType(nsIContent::eELEMENT)) {
     return aPresContext->ResolveStyleContextFor(aContent, parentStyleContext);
   } else {

layout/style/ua.css

@@ -141,7 +141,6 @@
 
 *|*::-moz-scrolled-content { 
   /* e.g., text inputs, select boxes */
-  background: inherit;
   padding: inherit;
   display: inherit;
   -moz-box-orient: inherit;

view/public/nsIView.h

@@ -74,6 +74,10 @@ enum nsViewVisibility {
 //the view is transparent
 #define NS_VIEW_FLAG_TRANSPARENT          0x0004
 
+// The view is always painted onto a background consisting
+// of a uniform field of opaque pixels.
+#define NS_VIEW_FLAG_UNIFORM_BACKGROUND   0x0008
+
 //indicates that the view should not be bitblt'd when moved
 //or scrolled and instead must be repainted
 #define NS_VIEW_FLAG_DONT_BITBLT          0x0010
@@ -244,6 +248,23 @@ public:
    */
   float GetOpacity() const { return mOpacity; }
 
+  /**
+   * Indicate that this view is always painted onto a uniform field of pixels. Thus,
+   * even if the view is transparent, it may still be bitblit scrollable because
+   * the background that shines through does not vary with position.
+   */
+  void SetHasUniformBackground(PRBool aUniform) {
+    if (aUniform) {
+      mVFlags |= NS_VIEW_FLAG_UNIFORM_BACKGROUND;
+    } else {
+      mVFlags &= ~NS_VIEW_FLAG_UNIFORM_BACKGROUND;
+    }
+  }
+
+  PRBool HasUniformBackground() {
+    return mVFlags & NS_VIEW_FLAG_UNIFORM_BACKGROUND;
+  }
+
   /**
    * Set the view's link to client owned data.
    * @param aData - data to associate with view. nsnull to disassociate

view/src/nsViewManager.cpp

@@ -1135,7 +1135,7 @@ void nsViewManager::RenderViews(nsView *aRootView, nsIRenderingContext& aRC,
   AddCoveringWidgetsToOpaqueRegion(opaqueRgn, mContext, aRootView);
 
   nsRect finalTransparentRect;
-  OptimizeDisplayList(&displayList, aRegion, finalTransparentRect, opaqueRgn);
+  OptimizeDisplayList(&displayList, aRegion, finalTransparentRect, opaqueRgn, PR_FALSE);
 
 #ifdef DEBUG_roc
   // ShowDisplayList(&displayList);
@@ -2867,13 +2867,22 @@ PRBool nsViewManager::CanScrollWithBitBlt(nsView* aView)
     }
   }
 
-  // We DO need to use OptimizeDisplayList here to eliminate views that are covered by views we know
-  // are opaque. Typically aView itself is opaque and we want to eliminate views behind aView, such as
-  // aView's parent, that aren't being scrolled and would otherwise cause us to decide not to blit.
+  // We DO need to use OptimizeDisplayList here to eliminate views
+  // that are covered by views we know are opaque. Typically aView's
+  // scrolled view is opaque and we want to eliminate views behind it,
+  // such as aView itself, that aren't being moved and would otherwise
+  // cause us to decide not to blit.  Note that if for some view,
+  // view->HasUniformBackground(), that's also sufficient to ignore
+  // views behind 'view'; we've been promised that they produce only a
+  // uniform background, which is still blittable. So we can treat
+  // 'view' as opaque.
 
-  // (Of course it's possible that aView's parent is actually in front of aView (if aView has a negative
-  // z-index) but if so, this code still does the right thing. Yay for the display list based approach!)
-  OptimizeDisplayList(&displayList, nsRegion(r), finalTransparentRect, opaqueRegion);
+  // (Note that it's possible for aView's parent to actually be in
+  // front of aView (if aView has a negative z-index) but if so, this
+  // code still does the right thing. Yay for the display list based
+  // approach!)
+
+  OptimizeDisplayList(&displayList, nsRegion(r), finalTransparentRect, opaqueRegion, PR_TRUE);
 
   PRBool anyUnscrolledViews = PR_FALSE;
   PRBool anyUnblittableViews = PR_FALSE;
@@ -3613,7 +3622,7 @@ PRBool nsViewManager::AddToDisplayList(nsView *aView,
 */
 void nsViewManager::OptimizeDisplayList(nsAutoVoidArray* aDisplayList, const nsRegion& aDamageRegion,
                                         nsRect& aFinalTransparentRect,
-                                        nsRegion &aOpaqueRegion)
+                                        nsRegion &aOpaqueRegion, PRBool aTreatUniformAsOpaque)
 {
   for (PRInt32 i = aDisplayList->Count() - 1; i >= 0; i--) {
     DisplayListElement2* element = NS_STATIC_CAST(DisplayListElement2*, aDisplayList->ElementAt(i));
@@ -3628,7 +3637,8 @@ void nsViewManager::OptimizeDisplayList(nsAutoVoidArray* aDisplayList, const nsR
         element->mBounds = tmpRgn.GetBounds();
 
         // a view is opaque if it is neither transparent nor transluscent
-        if (!(element->mFlags & (VIEW_TRANSPARENT | VIEW_TRANSLUCENT))) {
+        if (!(element->mFlags & (VIEW_TRANSPARENT | VIEW_TRANSLUCENT))
+            || (element->mView->HasUniformBackground() && aTreatUniformAsOpaque)) {
           aOpaqueRegion.Or(aOpaqueRegion, element->mBounds);
         }
       }

view/src/nsViewManager.h

@@ -282,7 +282,8 @@ private:
                           nsRect& aDirtyRect, PRUint32 aFlags, nscoord aAbsX, nscoord aAbsY,
                           PRBool aAssumeIntersection);
   void OptimizeDisplayList(nsAutoVoidArray* aDisplayList, const nsRegion& aDirtyRegion,
-                           nsRect& aFinalTransparentRect, nsRegion& aOpaqueRgn);
+                           nsRect& aFinalTransparentRect, nsRegion& aOpaqueRgn,
+                           PRBool aTreatUniformAsOpaque);
     // Remove redundant PUSH/POP_CLIP pairs.
   void ComputeViewOffset(nsView *aView, nsPoint *aOrigin);