From 9da4eab494402ae99180b21e4d3d58d6afe977b2 Mon Sep 17 00:00:00 2001
From: Botond Ballo <botond@mozilla.com>
Date: Fri, 28 Jul 2017 14:57:54 -0400
Subject: [PATCH] Bug 1105109 - Introduce a
 FrameMetrics::ClampAndSetScrollOffset() helper. r=kats

MozReview-Commit-ID: 6LCPKrdGM6M

--HG--
extra : rebase_source : 65f51ce5c40d9f1ac64c1f94055aa87d44a72cae
---
 gfx/layers/FrameMetrics.h                     |  6 ++++++
 gfx/layers/apz/src/AsyncPanZoomController.cpp | 11 ++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/gfx/layers/FrameMetrics.h b/gfx/layers/FrameMetrics.h
index 5fc0143f6f86..41c1ce6ec5bc 100644
--- a/gfx/layers/FrameMetrics.h
+++ b/gfx/layers/FrameMetrics.h
@@ -335,6 +335,12 @@ public:
     mScrollOffset = aScrollOffset;
   }
 
+  // Set scroll offset, first clamping to the scroll range.
+  void ClampAndSetScrollOffset(const CSSPoint& aScrollOffset)
+  {
+    SetScrollOffset(CalculateScrollRange().ClampPoint(aScrollOffset));
+  }
+
   const CSSPoint& GetScrollOffset() const
   {
     return mScrollOffset;
diff --git a/gfx/layers/apz/src/AsyncPanZoomController.cpp b/gfx/layers/apz/src/AsyncPanZoomController.cpp
index 90002ce5a3b0..ad563fd834d4 100644
--- a/gfx/layers/apz/src/AsyncPanZoomController.cpp
+++ b/gfx/layers/apz/src/AsyncPanZoomController.cpp
@@ -582,10 +582,9 @@ public:
       // offset to end up being a bit off from the destination, we can get
       // artefacts like "scroll to the next snap point in this direction"
       // scrolling to the snap point we're already supposed to be at.
-      aFrameMetrics.SetScrollOffset(
-          aFrameMetrics.CalculateScrollRange().ClampPoint(
-              CSSPoint::FromAppUnits(nsPoint(mXAxisModel.GetDestination(),
-                                             mYAxisModel.GetDestination()))));
+      aFrameMetrics.ClampAndSetScrollOffset(
+          CSSPoint::FromAppUnits(nsPoint(mXAxisModel.GetDestination(),
+                                         mYAxisModel.GetDestination())));
       return false;
     }
 
@@ -3789,9 +3788,7 @@ void AsyncPanZoomController::NotifyLayersUpdated(const ScrollMetadata& aScrollMe
       // Even if we didn't accept a new scroll offset from content, the
       // scrollable rect may have changed in a way that makes our local
       // scroll offset out of bounds, so re-clamp it.
-      mFrameMetrics.SetScrollOffset(
-          mFrameMetrics.CalculateScrollRange().ClampPoint(
-              mFrameMetrics.GetScrollOffset()));
+      mFrameMetrics.ClampAndSetScrollOffset(mFrameMetrics.GetScrollOffset());
     }
   }