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Re: Emacs and Gnome Canvas

From: Jan Djärv
Subject: Re: Emacs and Gnome Canvas
Date: Fri, 16 Jul 2010 14:42:00 +0200
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; sv-SE; rv: Gecko/20100608 Thunderbird/3.1

Eli Zaretskii skrev 2010-07-16 12.39:
Date: Fri, 16 Jul 2010 19:15:25 +0900
From: YAMAMOTO Mitsuharu<address@hidden>

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?

There is an X extension for that, DAMAGE. But if that is not used, you would get just one rectangle. Since the extension exist and programs use it, I assume people found that it gave and advantage.

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

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?

If you for example have double buffer, you can split expose from update display. When an expose comes, you just copy the area from the backing store to the window. But for updating the display, you draw normally, but to the backing store. Then when you are done, you copy it to the window.

But I don't think optimizing for expose is worth it. Expose iis very rare compared to update.

        Jan D.

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