Re: Emacs, QT and Cairo

[Eli Zaretskii]

> From: Chad Brown <address@hidden>
> Date: Tue, 13 Jul 2010 15:30:49 -0700
> Cc: Emacs development discussions <address@hidden>
> 
> 
> On Jul 13, 2010, at 1:48 PM, Jan Djärv wrote:
> > You would have to have a proper Cairo implementation of Emacs redisplay 
> > before that can be useful.  There was a patch for it here once.
> 
> It would be interesting to see an analysis of emacs' redisplay needs in light 
> of modern cpu/gpu/network usage, or even a list of needs for emacs' redisplay 
> priorities.  I recall the 18->19->20 discussions vaguely, but I'm willing to 
> wager that there are far fewer people using x-terminals over 14.4k modem 
> lines these days.  :-)

As Stephen wrote, the display optimizations are still relevant.  We
had at least 2 reminders of this lately:

  . Stefan's frustration with his nhexl mode, which somehow succeeds
    to bring the redisplay code to its knees, even on a local
    terminal.

  . Stefan's complaints about the slow-down related to the bidi
    reordering, when there are many frames simultaneously visible on
    the screen.

> A `truly excellent' effort in this space would almost certainly require a 
> huge amount of work from at least one of the already generous/overburdened 
> developers who truly understands the redisplay internals, and I would be 
> surprised to hear that any such feels that they have the free time to devote 
> to such a blue-sky project.

You are looking at the problem from the wrong angle.  For such an
effort to be worth our while, Someone(TM) should first present a
plausible and convincing case for reimplementing the Emacs display
engine.  At the very least, there should be an analysis of the
features we would like to have in Emacs, but cannot add without unduly
large effort, and which are available "for free" in Cairo or other
display engines, or would be available "for free" in the suggested new
implementation of our own.  And the number of these features should be
large enough to provide a "critical mass" sufficient to make the
redesign decision.  Then, and only then, the next step would be to
look for volunteers to do the job.

> I do wonder if anyone has concrete suggestions for a starting point for some 
> of us `younger' people, though.

The starting point is, of course, a thorough study of the current
display engine.