Re: Emacs and Gnome Canvas

["Jan Djärv" <jan.h.d@swipnet.se>]

And besides this, you would have to have a GnomeCanvas per Emacs window.

	Jan D.

Jan Djärv skrev 2010-07-15 09.46:
>
>
> Eli Zaretskii skrev 2010-07-15 08.55:
>>
>> . Canvas seems to need GTK+. What does this mean for platforms where
>> GTK+ is unavailable or not maintained? What about supporting the
>> TTY? Do these issues mean we will need to keep the existing
>> display engine in parallel with the Canvas-based one?
>
> Gtk+ is required, you would have to have a parallel display engine for all
> non-Gtk+ cases.
>>
>> . The Canvas redisplay runs from the GTK+ idle handlers. In Emacs,
>> the idle loop, in addition to triggering redisplay, also checks for
>> input from the keyboard and from subprocesses. Does this mean that
>> part of the input handling will need to be run by GTK+?
>
> Yes. Now we run the Gtk+ event loop (or actually not the loop, just a step)
> only when we know there is events pending. Again, parallel implementation for
> non-Gtk+. But normal redisplay for Gtk+ also happens in idle handlers. We are
> in the Gtk+ event loop often enough for this to happen often enough. Sometimes
> though (scroll bars mainly) we force redisplay in Gtk+. I assume you can do
> that for the Canvas also.
>
>>
>> . Canvas redisplay is caused by requests from the application to
>> update some "canvas item" when the underlying application's objects
>> are modified; these requests are then served when GTK+ idle
>> handlers are run. Emacs display engine works differently: changes
>> that require redisplay are not considered until redisplay is
>> entered; the "requests" to update the display are implicitly
>> recorded in the buffers and in the various related data structures
>> (text properties and overlays, display strings, etc.), but not
>> explicitly translated to display terms until redisplay time, and as
>> an inherent part of redisplay itself. These two very different
>> models will need to be reconciled in some reasonably efficient way.
>
> The changes that require redisplay would have to notify the Canvas that things
> changed. I think this style is more efficient.
>
> But I'm not sure it is the right way to go for Emacs unless Gtk+ can run on
> all platforms now. Even if it can, do we want Gtk+ look and feel on W32, OSX,
> Nextstep etc.? TTY is still a separate issue though.
>
> Jan D.