Live-blogging Marijn Haverbeke, creator of CodeMirror, at Full Frontal.
ACE – formerly Bespin – was faster and more portable, making CodeMirror look bad! So CodeMirror 2 is a rewrite based on some of those techniques.
Some performance tricks: * Indexes both by line number and by vertical offset. * Only renders the portion of the DOM you can see, plus a little on either side in case you scroll just a few lines. * Selections are passed back to the original text area.