[GRLUG] X overlay drawing app?

[Michael Mol]

Tricky to do, particularly with compositing window managers. I can
only think of three ways an app writer would do it:

1) Create a full screen window with backing store, draw the
annotations on top of it, and find a way to get X to refresh the
backing store periodically. (Will lead to either massive CPU overhead,
or the appearance of a very laggy system) Avoid capturing any input.
(I don't know enough to know how they'd do that part.)

2) Create a full screen window with an RGBA color space. (I don't even
know if X even supports this. It would require some compositing tricks
I'm not sure current compositing window managers do.) Avoid capturing
input. (I again don't know how to do that part.)

3) Create a *huge* number of windows, for each apparent block blit to
the screen; this would be incredibly hackish and wasteful, but *might*
work. If you can't avoid capturing the input, it would have the odd
side-effect of "erasing" underlying controls and buttons. Might make
an interesting prank app, that way.

If such an app does exist, I'd definitely be interested in poking at
it and seeing how it works!

On Mon, Apr 19, 2010 at 1:40 PM, Bill Littlejohn <billl at mtd-inc.com> wrote:
> I'm looking for an application to basically do annotations on the screen.
> (To be used with wii whiteboard)
> Gromit is the only thing I've found so far.
> http://www.home.unix-ag.org/simon/gromit/README
> Hasn't had a release since 2004 and drawing doesn't work properly on
> either of my test systems (Ubuntu 8.04, 9.10).
> Anyone know of an alternative?
>
> note: I use Shutter on my system, but I want 'live' drawing, not
> annotating a screenshot.
> -Bill
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