Re: Emacs and Gnome Canvas

[Eli Zaretskii]

> Date: Fri, 16 Jul 2010 19:15:25 +0900
> From: YAMAMOTO Mitsuharu <address@hidden>
> Cc: Jan Djärv <address@hidden>,       address@hidden,
>       address@hidden, address@hidden
> 
> >>>>> On Fri, 16 Jul 2010 12:52:12 +0300, Eli Zaretskii <address@hidden> said:
> 
> > Btw, I don't think I understand what Mitsuharu says in this Item #2.
> > Surely, we cannot "restrict the actual drawings to those in response
> > to exposure events"?  A completely exposed window does need to be
> > redrawn if the buffer text changes, right?  What am I missing?
> 
> The current code assumes that drawing is mainly done for updated area
> during redisplay, and expose_window is rather subsidiary.  So the
> latter is not so optimized for frequent use.

Is it really worth our while to optimize that?  What would be the
situation where we will get frequent expose events?

> For example, it does not accept multiple rectangles for exposed area
> that is necessary for minimal redrawing.

Don't we get a single expose event for each exposed rectangular area?
If we do, what would be the gain from processing multiple rectangles
at once?

> It also reuses functions primarily designed for drawing during
> redisplay and that does not necessarily efficient for exposure
> handing.

Are you talking about draw_glyphs?  If so, how is it biased in favor
of redisplay, and what would be a more efficient way of drawing glyphs
in a specified area of the display than what draw_glyphs does?