Re: NSPasteboard on X, what to do?

[Dan Pascu]

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.

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.

Hope this helps

-- 
Dan