diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index e3cbcbee..8af5f169 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -318,18 +318,18 @@ var EditSession = function(text, mode) {
     };
 
     this.getWidth = function() {
-        this.$computeWidth(!this.width);
+        this.$computeWidth();
         return this.width;
     };
 
     this.getScreenWidth = function() {
-        this.$computeWidth(!this.screenWidth);
+        this.$computeWidth();
         return this.screenWidth;
     };
 
     this.$computeWidth = function(force) {
-        if (this.modified || force) {
-            this.modified = false;
+        if (this.$modified || force) {
+            this.$modified = false;
 
             var lines = this.doc.getAllLines();
             var longestLine = 0;
@@ -340,7 +340,7 @@ var EditSession = function(text, mode) {
                 var len = lines[i].length;
                 longestLine = Math.max(longestLine, len);
 
-                lines[i].replace("\t", function(m) {
+                lines[i].replace(/\t/g, function(m) {
                     len += tabSize-1;
                     return m;
                 });
diff --git a/lib/ace/keyboard/textinput.js b/lib/ace/keyboard/textinput.js
index 459f9e0e..b6faa25f 100644
--- a/lib/ace/keyboard/textinput.js
+++ b/lib/ace/keyboard/textinput.js
@@ -56,15 +56,17 @@ var TextInput = function(parentNode, host) {
     style.opacity = 0;
     style.width = "10px";
     style.height = "30px";
-    
+
     var changeCursor = function() {
+        if (host.renderer.isMockRenderer) return;
+
         var cursor = host.getCursorPosition();
         var pos = host.renderer.textToScreenCoordinates(cursor.row, cursor.column);
         var epos = parentNode.getBoundingClientRect();
         style.left = (pos.pageX - epos.left - 6) + "px";
         style.top = (pos.pageY - epos.top + 52) + "px";
     };
-    
+
     host.addEventListener("changeSession", function(e) {
         if (e.oldSession)
             e.oldSession.getSelection().removeEventListener("changeCursor", changeCursor);
diff --git a/lib/ace/test/document_test.js b/lib/ace/test/document_test.js
index 4a33dcb0..b2705f4e 100644
--- a/lib/ace/test/document_test.js
+++ b/lib/ace/test/document_test.js
@@ -285,7 +285,7 @@ var Test = {
         var splits;
         var tabSize = 4;
         var wrapLimit = 12;
-        var computeWrapSplits = Document.prototype.$computeWrapSplits;
+        var computeWrapSplits = EditSession.prototype.$computeWrapSplits;
         var c = 0;
 
         function computeAndAssert(line, assertEqual) {
diff --git a/lib/ace/test/edit_session_test.js b/lib/ace/test/edit_session_test.js
index 967783cb..6ef7e4d7 100644
--- a/lib/ace/test/edit_session_test.js
+++ b/lib/ace/test/edit_session_test.js
@@ -257,6 +257,7 @@ var Test = {
 
         session.doc.insertNewLine(0);
         session.doc.insertLines(1, ["\t\t"]);
+
         assert.equal(session.getWidth(), 3);
         assert.equal(session.getScreenWidth(), 8);
 
diff --git a/lib/ace/test/mockrenderer.js b/lib/ace/test/mockrenderer.js
index 412a418a..b076cc78 100644
--- a/lib/ace/test/mockrenderer.js
+++ b/lib/ace/test/mockrenderer.js
@@ -50,6 +50,8 @@ MockRenderer = function(visibleRowCount) {
         firstVisibleRow : 0,
         lastVisibleRow : this.visibleRowCount
     };
+
+    this.isMockRenderer = true;
 };
 
 
@@ -117,10 +119,10 @@ MockRenderer.prototype.addMarker = function() {
 MockRenderer.prototype.setBreakpoints = function() {
 };
 
-MockRenderer.prototype.updateFull = function() {  
+MockRenderer.prototype.updateFull = function() {
 };
 
-MockRenderer.prototype.updateText = function() {  
+MockRenderer.prototype.updateText = function() {
 };
 
 MockRenderer.prototype.showCursor = function() {
@@ -132,5 +134,12 @@ MockRenderer.prototype.visualizeFocus = function() {
 MockRenderer.prototype.setAnnotations = function() {
 };
 
+MockRenderer.prototype.textToScreenCoordinates = function() {
+    return {
+        pageX: 0,
+        pageY: 0
+    }
+};
+
 return MockRenderer;
 });