Tab insertion via document.execCommand

app/assets/javascripts/app/frontend/controllers/editor.js

@@ -516,17 +516,22 @@ angular.module('app.frontend')
       var handleTab = function (event) {
         if (!event.shiftKey && event.which == 9) {
           event.preventDefault();
-          var start = this.selectionStart;
-          var end = this.selectionEnd;
-          var spaces = "    ";
 
-           // Insert 4 spaces
-          this.value = this.value.substring(0, start)
-            + spaces + this.value.substring(end);
+          // Using document.execCommand gives us undo support
+          if(!document.execCommand("insertText", false, "\t")) {
+            // document.execCommand works great on Chrome/Safari but not Firefox
+            var start = this.selectionStart;
+            var end = this.selectionEnd;
+            var spaces = "    ";
 
-          // Place cursor 4 spaces away from where
-          // the tab key was pressed
-          this.selectionStart = this.selectionEnd = start + 4;
+             // Insert 4 spaces
+            this.value = this.value.substring(0, start)
+              + spaces + this.value.substring(end);
+
+            // Place cursor 4 spaces away from where
+            // the tab key was pressed
+            this.selectionStart = this.selectionEnd = start + 4;
+          }
 
           parent.note.text = this.value;
           parent.changesMade();