Interesting concept, well done for shipping. Just a couple of points:
- You id="mask" element has a higher z-order than your formatting popup making it impossible to select styles in the demo.
- The blink from the original to the edited content is kind of jarring. Not sure where your servers are, but here from AUS the lag was very noticable.
- This is a peeve I have with all editors: When you select a H1,2,3 etc style the entire block is styled. This is the opposite of what users expect. Instead you should break that fragment out and run your execCommand on it. This way only the selected text receives the style and your users aren't left scratching their heads :)
- Consider adding an in-line editor for in-line images. Popping over a modal editor onmouseup is not intuitive for your average Joe.
Copybar cofounder here, thanks for the great feedback. We'll take a look at the mask issue asap. Delivery will continue to be optimized and I dig your ideas on the styling and image editing, look for those enhancements soon.