variable-width/-height characters and glyphs

I've been thinking about how to extend the terminal model to handle variable-sized characters and more generally what I call "glyphs". There are some advantages beside the obvious.

I wrote up some preliminary notes and ideas. This issue is mainly a placeholder for related discussion and ideas. I make no commitment to followup up with either specification or implementation - though if I get positive feedback it might happen!

Note this isn't terribly difficult to implement - and it need not break the traditional model. DomTerm mostly already supports variable-size characters and lines, while still keeping very solid xterm compatibility. The main thing missing is to specify escape sequences to make it easier for an application to benefit from this model. I'm considering modifying fish shell to take advantage of such a mode (since I already did some work on fish redisplay). (The main changes to fish would be to treat the terminal as infinite-width, delegating line-breaking to the terminal; no special handling for double-width characters; ignore sigwinch.)