From d6d6ff8cca476f3e7a53ebe1f596d0447c2d858f Mon Sep 17 00:00:00 2001
From: Kevin Sawicki & Nathan Sobo <kevin+nathan@github.com>
Date: Tue, 26 Feb 2013 15:08:33 -0800
Subject: [PATCH] :lipstick:

---
 src/app/display-buffer-marker.coffee | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/app/display-buffer-marker.coffee b/src/app/display-buffer-marker.coffee
index fdc641106..c8ed1648a 100644
--- a/src/app/display-buffer-marker.coffee
+++ b/src/app/display-buffer-marker.coffee
@@ -87,7 +87,9 @@ class DisplayBufferMarker
 
   notifyObservers: ({oldHeadBufferPosition, oldTailBufferPosition, bufferChanged, valid} = {}) ->
     oldHeadScreenPosition = @getHeadScreenPosition()
+    newHeadScreenPosition = oldHeadScreenPosition
     oldTailScreenPosition = @getTailScreenPosition()
+    newTailScreenPosition = oldTailScreenPosition
     valid ?= true
 
     if valid
@@ -95,11 +97,11 @@ class DisplayBufferMarker
       newHeadScreenPosition = @getHeadScreenPosition()
       @tailScreenPosition = null
       newTailScreenPosition = @getTailScreenPosition()
-    else
-      newHeadScreenPosition = oldHeadScreenPosition
-      newTailScreenPosition = oldTailScreenPosition
 
-    return if valid is @valid and _.isEqual(newHeadScreenPosition, oldHeadScreenPosition) and _.isEqual(newTailScreenPosition, oldTailScreenPosition)
+    validChanged = valid isnt @valid
+    headScreenPositionChanged = not _.isEqual(newHeadScreenPosition, oldHeadScreenPosition)
+    tailScreenPositionChanged = not _.isEqual(newTailScreenPosition, oldTailScreenPosition)
+    return unless validChanged or headScreenPositionChanged or tailScreenPositionChanged
 
     oldHeadBufferPosition ?= @getHeadBufferPosition()
     newHeadBufferPosition = @getHeadBufferPosition() ? oldHeadBufferPosition