From 05fec77aa1354e5d78a4f90aa8bb0c5a3d04095d Mon Sep 17 00:00:00 2001
From: Robert O'Callahan <robert@ocallahan.org>
Date: Fri, 8 Apr 2011 12:06:36 -0700
Subject: [PATCH] Bug 279629. Allow scrolling to anchors to use smooth
 scrolling. r=mats

---
 layout/base/nsIPresShell.h  |  7 ++++---
 layout/base/nsPresShell.cpp | 12 ++++++++----
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/layout/base/nsIPresShell.h b/layout/base/nsIPresShell.h
index 7a90912e51b..3b49d50f84c 100644
--- a/layout/base/nsIPresShell.h
+++ b/layout/base/nsIPresShell.h
@@ -139,8 +139,8 @@ typedef struct CapturingContentInfo {
 } CapturingContentInfo;
 
 #define NS_IPRESSHELL_IID     \
- { 0x3a8030b5, 0x8d2c, 0x4cb3, \
-    { 0xb5, 0xae, 0xb2, 0x43, 0xa9, 0x28, 0x02, 0x82 } }
+  { 0xfd4ba6e3, 0x921c, 0x4058, \
+    { 0xa6, 0x1b, 0xc7, 0x14, 0x5e, 0x80, 0x50, 0x1f } }
 
 // Constants for ScrollContentIntoView() function
 #define NS_PRESSHELL_SCROLL_TOP      0
@@ -573,7 +573,8 @@ public:
   enum {
     SCROLL_FIRST_ANCESTOR_ONLY = 0x01,
     SCROLL_OVERFLOW_HIDDEN = 0x02,
-    SCROLL_NO_PARENT_FRAMES = 0x04
+    SCROLL_NO_PARENT_FRAMES = 0x04,
+    SCROLL_ALLOW_SMOOTH = 0x08
   };
   /**
    * Scrolls the view of the document so that the given area of a frame
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 789c376f288..a954fab4173 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -224,7 +224,8 @@
 #define NS_TIME_FUNCTION_WITH_DOCURL do{} while(0)
 #endif
 
-#define ANCHOR_SCROLL_FLAGS (SCROLL_OVERFLOW_HIDDEN | SCROLL_NO_PARENT_FRAMES)
+static const PRUint32 ANCHOR_SCROLL_FLAGS =
+    SCROLL_OVERFLOW_HIDDEN | SCROLL_NO_PARENT_FRAMES | SCROLL_ALLOW_SMOOTH;
 
 #include "nsContentCID.h"
 static NS_DEFINE_IID(kRangeCID,     NS_RANGE_CID);
@@ -1194,8 +1195,9 @@ protected:
   // Information needed to properly handle scrolling content into view if the
   // pre-scroll reflow flush can be interrupted.  mContentToScrollTo is
   // non-null between the initial scroll attempt and the first time we finish
-  // processing all our dirty roots.  mContentScrollVPosition and
-  // mContentScrollHPosition are only used when it's non-null.
+  // processing all our dirty roots.  mContentScrollVPosition,
+  // mContentScrollHPosition and mContentToScrollToFlags are only used when
+  // it's non-null.
   nsCOMPtr<nsIContent> mContentToScrollTo;
   PRIntn mContentScrollVPosition;
   PRIntn mContentScrollHPosition;
@@ -4149,7 +4151,9 @@ static void ScrollToShowRect(nsIScrollableFrame* aScrollFrame,
     }
   }
 
-  aScrollFrame->ScrollTo(scrollPt, nsIScrollableFrame::INSTANT);
+  aScrollFrame->ScrollTo(scrollPt,
+      (aFlags & nsIPresShell::SCROLL_ALLOW_SMOOTH) ? nsIScrollableFrame::SMOOTH :
+                                                     nsIScrollableFrame::INSTANT);
 }
 
 nsresult