another approach

[xem]

Hi, nice project!

Here's an idea that is a bit dirty but could make a shorter code and a better compatibility (multiple checkboxes, firefox, ... which is not currently the case)

The textarea contains monospace characters. They are something like 10*18px each.

So when the user clicks the textarea, knowing the mouse position in the textarea, you can compute which character is clicked, and if this character is part of "[ ]", replace it with "[x]".

The only trap is to handle line breaks / line wraps correctly. But that's doable.

[subzey]

Uhh... I guess we'll have to deal with scrollTop/scrollWidth in that case. And glyph metrics may vary a lot depending on font face.