Re: Emacs canvas support

[David Engster]

> While right now svg.el seems to have more features, it isn't
> particularly well suited to displaying things quickly.
>
> In fact, my own bad experiences with using svg.el to draw rapidly
> changing information inspired me to begin working on this.
>
> In the future, I hope that canvases also become more flexible than
> svg.el.  A nice goal would be to have everything cairo has.

A while ago I played around with using Cairo primitives to draw in
Emacs. While it would be nice to have something like a 'canvas object'
to draw on, Eli is correct that you can achieve similar things already
with SVG - it may be slow, but that could be fixable.

IMHO, What would be much more exciting, is if you could draw directly
over normal text. This would enable a whole new set of
possibilities. For instance, I always liked visual diff tools like
'Meld' or 'Code Compare', but I don't see how you could do this with
Emacs. Or things like proper indentation guides, or widgets inside text
for code folding. Yes, those can be done in Emacs today, but it is very
difficult to get right and often not really satisfactory (weird
interactions between packages, too slow, etc.).

I know the tricky part is not the drawing, but redisplay. I would have
no idea how to handle this.

-David