From c58035b973225751962efb2a5500117b286ed0f4 Mon Sep 17 00:00:00 2001
From: Markus Stange <mstange@themasta.com>
Date: Tue, 3 Jun 2014 15:55:58 +0200
Subject: [PATCH] Bug 1018461 - Allow active scrolling inside SVG. Should give
 a big tscrollx win. r=roc

---
 layout/generic/nsGfxScrollFrame.cpp | 29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index 23ed8214ebf..a4d848e0a56 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -1798,22 +1798,9 @@ static void AdjustViews(nsIFrame* aFrame)
 }
 
 static bool
-CanScrollWithBlitting(nsIFrame* aFrame)
+NeedToInvalidateOnScroll(nsIFrame* aFrame)
 {
-  if (aFrame->GetStateBits() & NS_SCROLLFRAME_INVALIDATE_CONTENTS_ON_SCROLL)
-    return false;
-
-  for (nsIFrame* f = aFrame; f;
-       f = nsLayoutUtils::GetCrossDocParentFrame(f)) {
-    if (nsSVGIntegrationUtils::UsingEffectsForFrame(f) ||
-        f->IsFrameOfType(nsIFrame::eSVG) ||
-        f->GetStateBits() & NS_FRAME_NO_COMPONENT_ALPHA) {
-      return false;
-    }
-    if (nsLayoutUtils::IsPopup(f))
-      break;
-  }
-  return true;
+  return (aFrame->GetStateBits() & NS_SCROLLFRAME_INVALIDATE_CONTENTS_ON_SCROLL) != 0;
 }
 
 bool ScrollFrameHelper::IsIgnoringViewportClipping() const
@@ -1900,14 +1887,12 @@ void ScrollFrameHelper::ScrollVisual(nsPoint aOldScrolledFramePos)
   AdjustViews(mScrolledFrame);
   // We need to call this after fixing up the view positions
   // to be consistent with the frame hierarchy.
-  bool canScrollWithBlitting = CanScrollWithBlitting(mOuter);
+  bool needToInvalidateOnScroll = NeedToInvalidateOnScroll(mOuter);
   mOuter->RemoveStateBits(NS_SCROLLFRAME_INVALIDATE_CONTENTS_ON_SCROLL);
-  if (IsScrollingActive()) {
-    if (!canScrollWithBlitting) {
-      MarkInactive();
-    }
+  if (IsScrollingActive() && needToInvalidateOnScroll) {
+    MarkInactive();
   }
-  if (canScrollWithBlitting) {
+  if (!needToInvalidateOnScroll) {
     MarkActive();
   }
 
@@ -2422,7 +2407,7 @@ ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
 
   if (aBuilder->IsPaintingToWindow()) {
     mScrollPosAtLastPaint = GetScrollPosition();
-    if (IsScrollingActive() && !CanScrollWithBlitting(mOuter)) {
+    if (IsScrollingActive() && NeedToInvalidateOnScroll(mOuter)) {
       MarkInactive();
     }
     if (IsScrollingActive()) {