Markdown autoresize box quirky on enter

Start in models/Document.bones at the updateSize function and reproduce the autoresize behavior by pressing Enter in the markdown textarea in Chrome and Firefox. Compare the textarea and clone values during keydown; done means the textarea resizes without jumping up before the new line appears.

When hitting enter in a markdown autoresize textarea, the textarea is not resized until the enter key is released which leads to the text jumping up one line before it drops down again. I have observed this behavior in Chrome and FF. While the browser adds the new character to the textarea, it does not make it available via .val() until the key is released.

The following code is hideous, but addresses the issue. I wonder whether there are more elegante ways around this.

diff --git a/models/Document.bones b/models/Document.bones
index 23c2044..6f5bec9 100644
--- a/models/Document.bones
+++ b/models/Document.bones
@@ -202,9 +202,14 @@ model = Backbone.Model.extend({
                             letterSpacing: textarea.css('letterSpacing')
                         }).attr('tabIndex','-1').insertBefore(textarea);
                     })(),
-                    updateSize = function() {
+                    updateSize = function(ev) {
                         // Update clone.
-                        clone.val($(this).val()).scrollTop(10000);
+                        var val = $(this).val();
+                        On keydown, the newest character is not in .val().
+                        if (ev && ev.type == 'keydown') {
+                            val += String.fromCharCode(ev.keyCode);
+                        }
+                        clone.val(val).scrollTop(10000);
                         // Find scrolling height of text in clone and update
                         var height = clone.scrollTop();
                         if (!$.browser.msie) {