From 17fa580ecd762024a3c854de4321d24bc9d6bc81 Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Wed, 2 Jul 2014 10:11:35 -0600
Subject: [PATCH] Ignore 'scroll' events when an update is pending

This prevents feedback loops where we handle stale 'scroll' events
for scrolls requested in the model layer. It prevents jitter when
autoscrolling with the cursor.
---
 spec/editor-component-spec.coffee | 2 +-
 src/editor-component.coffee       | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/spec/editor-component-spec.coffee b/spec/editor-component-spec.coffee
index 2b1e3c93e..0fbdb8858 100644
--- a/spec/editor-component-spec.coffee
+++ b/spec/editor-component-spec.coffee
@@ -724,11 +724,11 @@ describe "EditorComponent", ->
       # Add decorations that are out of range
       marker2 = editor.displayBuffer.markBufferRange([[9, 0], [9, 0]])
       editor.addDecorationForMarker(marker2, type: ['gutter', 'line'], class: 'b')
+      runSetImmediateCallbacks()
 
       # Scroll decorations into view
       verticalScrollbarNode.scrollTop = 2.5 * lineHeightInPixels
       verticalScrollbarNode.dispatchEvent(new UIEvent('scroll'))
-      runSetImmediateCallbacks()
       expect(lineAndLineNumberHaveClass(9, 'b')).toBe true
 
       # Fold a line to move the decorations
diff --git a/src/editor-component.coffee b/src/editor-component.coffee
index e101e00f4..714f72735 100644
--- a/src/editor-component.coffee
+++ b/src/editor-component.coffee
@@ -529,7 +529,7 @@ EditorComponent = React.createClass
   onVerticalScroll: (scrollTop) ->
     {editor} = @props
 
-    return if scrollTop is editor.getScrollTop()
+    return if @updateRequested or scrollTop is editor.getScrollTop()
 
     animationFramePending = @pendingScrollTop?
     @pendingScrollTop = scrollTop
@@ -542,7 +542,7 @@ EditorComponent = React.createClass
   onHorizontalScroll: (scrollLeft) ->
     {editor} = @props
 
-    return if scrollLeft is editor.getScrollLeft()
+    return if @updateRequested or scrollLeft is editor.getScrollLeft()
 
     animationFramePending = @pendingScrollLeft?
     @pendingScrollLeft = scrollLeft