[cairo] cairo and gdk/X11

[Kalle Vahlman]

2007/6/11, Tamas K Papp <tpapp at princeton.edu>:
> Hi Dan (and others),
>
> Thanks for the references, I found the thread and it was useful.  I
> will be using plain Xlib, not Gtk, since the latter is a mess with
> threads.

I don't think that's really true (depending on the definition of
"mess" of course), at least Andrew Cowie had an enlightening blog post
about this recently:

http://research.operationaldynamics.com/blogs/andrew/software/gnome-desktop/gtk-thread-awareness.html

My personal experiences with threaded Gdk software are limited though, so...

> I still have one question.  I refresh (copy from the pixmap to the
> drawable in the window) each time
>
> 1. X asks for it via an expose event,
> 2. cairo draws on the pixmap.
>
> I could call refresh explicitly each time (2) happens, but I wonder if
> there is a neater way, since my library supports various surfaces and
> I would have to handle one of them differently.
[...]
> b. a callback function that gets called each time the surface is
> modified.

With the X Damage extension you can receive events from the X server
whenever a pixmap (or a window) is "damaged", ie. it has been drawn
to. You can then clear the damage state and update the contents.

You can get hints on how to use it from this nice composite tutorial:

  http://ktown.kde.org/~fredrik/composite_howto.html

-- 
Kalle Vahlman, zuh at iki.fi
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