[Telepathy] Vino-telepathy for a single window?

[Daniel Stone]

Hi,

On Thu, Aug 13, 2009 at 02:04:54PM +0100, Robert McQueen wrote:
> I believe libvncserver (inside Vino) already uses damage and composite
> internally, to get a pixbuf for the root window. So I think its not too
> hard to modify it to look at one particular window, but the devil is in
> the details. There are a lot of them. :(
> 
> [...]
> 
> * Input delivery is also... fun. Because currently, X input doesn't
>   support co-ordinate redirection, so input events are absolute. You get
>   the problem that if an application's window is covered by another at
>   that absolute screen position, you can't deliver remotely-originated
>   events to the right application.

This is pretty much the kicker.  There's XSendEvent, but pretty much
every toolkit/app ever goes out of its way to ignore it.  Don't ask why
it exists.

> * If an application is minimised, usually the window manager unmaps it,
>   which means it stops being rendered by the application. If an
>   application is locally minimised, but remotely still visible, the
>   window manager needs to keep it mapped even if it's not being
>   composited onto the screen.

I think most compositing WMs just move them offscreen these days.

> So because of these issues, and partly for efficiency's sake, then I
> think this kind of single-app-sharing functionality would need to be
> done with the collusion of a compositing window manager, to track which
> windows belong to which application, map them off-screen so they
> actually render, make sure the user is aware what is being shared, and
> arrange them off-screen in an appropriate non-overlapping way so you can
> transform and deliver input events.

If they're offscreen, then it's entirely possible with new enough X
servers to create another cursor and just warp that around to your
heart's content.  This would need minor hackery to allow offscreen
input, however (cough).

> We thought about having a row of hackergotchies/avatars in the title bar
> to show who was using a certain application would be pretty cool. Bonus
> points if you then use MPX and have one pointer belonging to each user
> who is using the application. Lose points for the application being
> utterly confused at that at the moment however. :)

Actually, apps are shockingly robust against this kind of thing, mostly,
kind of, until you open a menu.

Cheers,
Daniel
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