Re: NSPasteboard on X, what to do?

[Pascal Bourguignon]

> From: Dan Pascu <dan@services.iiruc.ro>
> Date: Thu, 10 Jan 2002 07:48:53 +0200 (EET)
> 
> On  9 Jan, Richard Frith-Macdonald wrote:
> > 
> > On Wednesday, January 9, 2002, at 11:27 AM, Wim Oudshoorn wrote:
> > 
> >> You wrote:
> >>> Well, they are both displaying on the same screen of the same machine.
> >>> If I was controlling
> >>> the keyboard and mouse of the machine to which the screen was attached,
> >>> I'd expect to be
> >>> able to select text in the other persons app, cut it to the pasteboard,
> >>> move the mouse to
> >>> my app, and paste it in.
> >>
> >> Ok, I see.  But in my definition I view this as a really big screen.
> >> What I actually meant with screen was the X term Display.
> >> (You see I get really confused.)
> >>
> >> So to translate back.  My idea was to group by the X notion of Display.
> > 
> > OK ... that's pretty confusing then ... as the X concept of a Display is
> > pretty much what it sounded like you were referring to as a 'machine' ...
> > ie it's someones workstation,  while the X Screen is more like an
> > individual CRT or LCD device attached-to/part-of the machine.
> 
> I think some definitions are needed here for better understanding how X
> works:
> 
> 1. screen - physical CRT
> 2. display - an active X session (may manage multiple screens)
> 3. machine - a computer that can run multiple X sessions, each
>    associated with a unique display, but only one can be active at a
>    time, and they are completely isolated from each other (kind of
>    like virtual consoles).
> 
> since a DISPLAY (read X session) needs to have control of input (kbd
> and mouse) there is obvious that only one DISPLAY is active at a time.
> 
> so I think that what you should use as a unique identifier is the
> $DISPLAY. apps running inside a given display (even if it manages
> multiple screens (CRTs) can communicate and have access to the same
> resources the X server identified with that DISPLAY provides (including
> the cut/paste services). apps running on different DISPLAYs cannot see
> each other.

Right.
 
> to make things even more clear, a DISPLAY is associated with a running
> binary of the X server.
> you can start more X binaries, but cannot have all active at one time,
> because they need control of kbd and mouse. they also share no event
> space, so cannot communicate with each other.

1- A  X display does not  necessarily have any input  device. Then you
   can have several "active" X displays  at one time, at least in output
   mode.

2- You can have several "active"  X displays at the same time when you
   have several input  devices, each X display having  its own. Today,
   it's quite  easy to add  USB keyboards and  mice by the dozen  to a
   single PC.


> Hope this helps
> 
> -- 
> Dan



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