Re: Emacs and Gnome Canvas

[Chong Yidong <cyd@stupidchicken.com>]

Óscar Fuentes <ofv@wanadoo.es> writes:

> AFAIK the display system have evolved from the tty one by incremental
> updates

No, the redisplay system was redesigned during Emacs 21 specifically
with both tty and graphical terminals in mind.  It did not evolve
mindlessly; the design has a very specific logic behind it.  As long as
we support tty, there is no getting rid of the redisplay iterator.
Since we have the redisplay iterator, the same system might as well be
used for graphical displays; it would terribly problematic to switch
between completely different rendering schemes for tty and graphical
displays to render the same underlying content.

It is still not too clear to me what we would gain from a Canvas-type
revamp of redisplay, relative to the large costs involved.  It does not
seem like a promising avenue of development.

A more promising route is the one that Yamamoto Mitsuharu has explored,
mentioned earlier in this thread, which (IIUC) treats Cairo as a
graphical terminal to render onto, on the same footing as the
tty/X/Windows/NS terminals.  Here, I can see a reasonable path to real
improvement.  For example, it might allow us to use the GTK printing
infrastructure, which operates on Cairo contexts.  If you are interested
in redisplay development, that is the direction I'd suggest looking
into.