diff --git a/lib/ace/css/editor.css b/lib/ace/css/editor.css
index 075c317e..45ca6d71 100644
--- a/lib/ace/css/editor.css
+++ b/lib/ace/css/editor.css
@@ -3,13 +3,13 @@
     overflow: hidden;
 
     font-family: "Menlo", "Monaco", "Courier New", monospace;
-    font-size: 12px;  
+    font-size: 12px;
 }
 
 .ace_scroller {
     position: absolute;
     overflow-x: scroll;
-    overflow-y: hidden;     
+    overflow-y: hidden;
 }
 
 .ace_content {
@@ -90,7 +90,7 @@
 .ace_layer {
     z-index: 1;
     position: absolute;
-    overflow: hidden;  
+    overflow: hidden;
     white-space: nowrap;
     height: 100%;
     width: 100%;
@@ -154,6 +154,10 @@
     -webkit-box-sizing: border-box;
 }
 
+.ace_line .ace_fold {
+    cursor: pointer;
+}
+
 .ace_dragging .ace_marker-layer, .ace_dragging .ace_text-layer {
   cursor: move;
 }
diff --git a/lib/ace/mouse_handler.js b/lib/ace/mouse_handler.js
index 8c722431..910a4ec0 100644
--- a/lib/ace/mouse_handler.js
+++ b/lib/ace/mouse_handler.js
@@ -58,7 +58,7 @@ var MouseHandler = function(editor) {
     event.addListener(editor.container, "selectstart", function(e) {
         return event.preventDefault(e);
     });
-    
+
     var mouseTarget = editor.renderer.getMouseEventTarget();
     event.addListener(mouseTarget, "mousedown", this.onMouseDown.bind(this));
     event.addMultiMouseDownListener(mouseTarget, 0, 2, 500, this.onMouseDoubleClick.bind(this));
@@ -73,7 +73,7 @@ var MouseHandler = function(editor) {
     this.setScrollSpeed = function(speed) {
         this.$scrollSpeed = speed;
     };
-    
+
     this.getScrollSpeed = function() {
         return this.$scrollSpeed;
     };
@@ -100,7 +100,7 @@ var MouseHandler = function(editor) {
         var selectionEmpty = selectionRange.isEmpty();
         var state = STATE_UNKNOWN;
         var inSelection = false;
-    
+
         var button = event.getButton(e);
         if (button !== 0) {
             if (selectionEmpty) {
@@ -112,6 +112,13 @@ var MouseHandler = function(editor) {
             }
             return;
         } else {
+            // Select the fold as the user clicks it.
+            var fold = editor.session.getFoldAt(pos.row, pos.column, 1);
+            if (fold) {
+                editor.selection.setSelectionRange(fold.range);
+                return;
+            }
+
             inSelection = !editor.getReadOnly()
                 && !selectionEmpty
                 && selectionRange.contains(pos.row, pos.column);
@@ -127,19 +134,19 @@ var MouseHandler = function(editor) {
         var overwrite = editor.getOverwrite();
         var mousedownTime = (new Date()).getTime();
         var dragCursor, dragRange;
-    
+
         var onMouseSelection = function(e) {
             mousePageX = event.getDocumentX(e);
             mousePageY = event.getDocumentY(e);
         };
-    
+
         var onMouseSelectionEnd = function() {
             clearInterval(timerId);
             if (state == STATE_UNKNOWN)
                 onStartSelect(pos);
             else if (state == STATE_DRAG)
                 onMouseDragSelectionEnd();
-                
+
             self.$clickSelection = null;
             state = STATE_UNKNOWN;
         };
@@ -172,7 +179,7 @@ var MouseHandler = function(editor) {
 
             editor.selection.setSelectionRange(newRange);
         };
-    
+
         var onSelectionInterval = function() {
             if (mousePageX === undefined || mousePageY === undefined)
                 return;
@@ -181,7 +188,7 @@ var MouseHandler = function(editor) {
                 var distance = self.$distance(pageX, pageY, mousePageX, mousePageY);
                 var time = (new Date()).getTime();
 
-                
+
                 if (distance > DRAG_OFFSET) {
                     state = STATE_SELECT;
                     var cursor = editor.renderer.screenToTextCoordinates(mousePageX, mousePageY);
@@ -197,13 +204,13 @@ var MouseHandler = function(editor) {
                 }
 
             }
-            
+
             if (state == STATE_DRAG)
                 onDragSelectionInterval();
             else if (state == STATE_SELECT)
                 onUpdateSelectionInterval();
         };
-    
+
         function onStartSelect(pos) {
             if (e.shiftKey)
                 editor.selection.selectToPosition(pos)
@@ -215,12 +222,12 @@ var MouseHandler = function(editor) {
             }
             state = STATE_SELECT;
         }
-        
+
         var onUpdateSelectionInterval = function() {
             var cursor = editor.renderer.screenToTextCoordinates(mousePageX, mousePageY);
             cursor.row = Math.max(0, Math.min(cursor.row, editor.session.getLength()-1));
-    
-            if (self.$clickSelection) {                
+
+            if (self.$clickSelection) {
                 if (self.$clickSelection.contains(cursor.row, cursor.column)) {
                     editor.selection.setSelectionRange(self.$clickSelection);
                 } else {
@@ -236,7 +243,7 @@ var MouseHandler = function(editor) {
             else {
                 editor.selection.selectToPosition(cursor);
             }
-    
+
             editor.renderer.scrollCursorIntoView();
         };
 
@@ -250,32 +257,40 @@ var MouseHandler = function(editor) {
 
         event.capture(editor.container, onMouseSelection, onMouseSelectionEnd);
         var timerId = setInterval(onSelectionInterval, 20);
-    
+
         return event.preventDefault(e);
     };
-    
+
     this.onMouseDoubleClick = function(e) {
+        var editor = this.editor;
         var pos = this.$getEventPosition(e);
-        this.editor.moveCursorToPosition(pos);
-        this.editor.selection.selectWord();
-        this.$clickSelection = this.editor.getSelectionRange();
+
+        // If the user dclicked on a fold, then expand it.
+        var fold = editor.session.getFoldAt(pos.row, pos.column, 1);
+        if (fold) {
+            editor.session.expandFold(fold);
+        } else {
+            editor.moveCursorToPosition(pos);
+            editor.selection.selectWord();
+            this.$clickSelection = editor.getSelectionRange();
+        }
     };
-    
+
     this.onMouseTripleClick = function(e) {
         var pos = this.$getEventPosition(e);
         this.editor.moveCursorToPosition(pos);
         this.editor.selection.selectLine();
         this.$clickSelection = this.editor.getSelectionRange();
     };
-    
+
     this.onMouseQuadClick = function(e) {
         this.editor.selectAll();
         this.$clickSelection = this.editor.getSelectionRange();
     };
-    
+
     this.onMouseWheel = function(e) {
         var speed = this.$scrollSpeed * 2;
-    
+
         this.editor.renderer.scrollBy(e.wheelX * speed, e.wheelY * speed);
         return event.preventDefault(e);
     };