From dbb853f2051ca9af8b23bc68181ad45cfc529d5c Mon Sep 17 00:00:00 2001
From: Evgeni Spasov <evgeni.spasov@gmail.com>
Date: Fri, 26 Jul 2013 17:30:10 +0300
Subject: [PATCH] Fixed page jumb up/down when using arrow keys

When using the up and down arrow keys the page is scrolled repeatedly.
This fix checks if autocomplete selection is in browser viewport and
scrolls page only needed.
---
 vendor/assets/javascripts/controls.js | 35 ++++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/vendor/assets/javascripts/controls.js b/vendor/assets/javascripts/controls.js
index 7392fb6..8ac5bf6 100644
--- a/vendor/assets/javascripts/controls.js
+++ b/vendor/assets/javascripts/controls.js
@@ -211,15 +211,38 @@ Autocompleter.Base = Class.create({
   },
 
   markPrevious: function() {
-    if(this.index > 0) this.index--;
-      else this.index = this.entryCount-1;
-    this.getEntry(this.index).scrollIntoView(true);
+    if(this.index > 0) {
+      this.index--;
+    } else {
+      this.index = this.entryCount - 1;
+    }
+    
+    this.scrollIntoView();
   },
 
   markNext: function() {
-    if(this.index < this.entryCount-1) this.index++;
-      else this.index = 0;
-    this.getEntry(this.index).scrollIntoView(false);
+    if(this.index < this.entryCount-1) {
+      this.index++;
+    } else {
+      this.index = 0;
+    }
+    
+    this.scrollIntoView();
+  },
+
+  scrollIntoView: function() {
+    var selection_top = this.getEntry(this.index).viewportOffset().top;
+    var document_top = document.viewport.getScrollOffsets().top;
+    
+    // element is above scrolled height
+    if(selection_top < document_top) {
+      this.element.scrollIntoView(true);
+    }
+    
+    // element is below scrolled height
+    else if(selection_top > document_top + document.viewport.getDimensions().height) {
+      this.getEntry(this.entryCount - 1).scrollIntoView(false);
+    }
   },
 
   getEntry: function(index) {