Re: NSPasteboard on X, what to do?

[Jeremy Bettis]

I know this is probably hearcy on my part, but why not use the X clipboard?
I know it's not as rich as you're used to, but it does support multiple
formats and it is per-display just like it ought to be.
--
Jeremy Bettis
jeremy@bettis.org

----- Original Message -----
From: "Richard Frith-Macdonald" <richard@brainstorm.co.uk>
To: "Wim Oudshoorn" <woudshoo@sct.com>
Cc: <discuss-gnustep@gnu.org>
Sent: Wednesday, January 09, 2002 4:17 AM
Subject: Re: NSPasteboard on X, what to do?


>
> On Wednesday, January 9, 2002, at 08:58 AM, Wim Oudshoorn wrote:
> >> In MacOS-X (essentially OpenStep) I routinely perform a cut on one
> >> screen,
> >> move the mouse to an app on my other screen, and paste into the second
> >> app.
> >> Similarly, I drag stuff from an app on one screen to an app on the
> >> other.
> >
> > Hm, I see your point, but I do not understand how dragging is supposed
> > to work.
> > How do you drag from one screen to another?  (I have never
> > used a multi headed machine, so bear with me)
>
> The system is set up to 'know' where the screens are ... they are
> logically positioned
> adjacent to each other in some way (normally you will set this logical
> configuration to
> match the physical positioning on your desk).
> When you move the mouse pointer to the edge of a screen, and then
> continue to drag the
> mouse, the pointer appears on the adjacent screen.  It's really as if
> you had one big
> screen made out of smaller screens tiled together.  For most people,
> such setups are
> built with two video cards (or a dual port card) in their workstation,
> though I've seen
> a few graphic designers using three or more screens on the same machine!
> I have seen the same sort of setup linking multiple machines with X too,
> but I don't know
> if NeXTstep ever supported a multi-machine version - I've never seen a
> NeXTstep app display
> windows on more than one machine at a time, only on multiple screens of
> the same machine.
>
>
> >> Most copy and paste operations are performed on a single machine ...
> >> I'd
> >> venture
> >
> > Hm, still confused.  Suppose I log in to a server and set my Xdisplay
> > to my
> > local machine.  Some other person does the same,  what do these
> > processes in
> > common??
>
> 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.
>
> Additionally, if I had two screens on my workstation, and someone on a
> different machine set
> their app to display on one of my screens, I'd expect to be able to cut
> from that app and
> then paste into an app in my other screen.
>
> >>> 1. No DnD and copy/paste between different applications
> >>> running on different computers but on the same screen,
> >>> thereby going against the X philosophy.
> >>
> >> Not sure what you mean by this ... if you are receiving a drop from
> >> an app on another machine, the -draggingPasteboard method provided by
> >> the dragging info would return a pasteboard object connected to the
> >> pasteboard server on which the drag originated.
> >
> > This certainly can work for DnD, but what about the other pasteboards?
>
> I think they should be using the pasteboard server of the *machine* to
> which they are displaying.  So you could cut and paste between apps on
> any screen attached to that machine.  This model assumes that every
> screen
> is attached to a machine - I know that that is not 100% the case in X,
> where a screen may be a dumb X server, but I'd suggest that in such a
> situation it would be beast to designate some real server (where a
> pasteboard
> server process can run) as the owner of that screen.
>
> >> The aspect of this I've never been so happy about is the 'all'
> >> What about a multi-screened, multi-keyboarded machine with more than
> >> one user.  Do both users share the same pasteboard server?
> >> I think ideally not.  Each user would get their own server (to which
> >> they save data)
> >
> > Exactly! this is the problem.
>
> The problem with this is that simply having per-user pasteboard servers
> prohibits interaction between apps owned by different users.  This is
> as undesirable as having completely free interaction.  The existing
> mechanism
> of having a single pasteboard server per machine (rather than one per
> user)
> is about as secure/insecure as permitting aps to display on the screens
> of
> another machine in X.
>
> An ideal solution requires interaction but also some security control.
> The only control NeXTstep had was to deny/allow one machine to access
> anothers
> resources ... pretty much the same as the degree of control X permits.
>
> >> I completely disagree ... I hope I have shown above that the advantages
> >> you list for doing this do not actually exist, while the disadvantage
> >> you supply for grouping by computer does not exist.
> >
> > Well, I still think there are quite some problems with the grouping by
> > Computer.
>
> Any other than the security problem (which I think is not to do with the
> machine/screen issue anyway)?
>
> >>   How we cope with a cut and paste operation
> >> between two apps on different machines (either on the same screen or on
> >> two screens of one machine) I don't know.  I think this is the tricky
> >> case
> >> but it may be rare enough to ignore.
>
> I was being stupid because I allowed myself to be trapped into the model
> you presented where machines and screens are separate ...  the solution
> is trivial if you say that each screen is associated with a machine.
>
> > Actually, I do not think it is rare.  Maybe the following hypothetical
> > situation will show some problems.  (You probably are already aware
> > of them)
> >
> >
> > Two servers:  A, B
> > Two XDisplays: S, T  (one user behind S and one user behind T)
> > S is running two programs P1, P2
> > T is runnint two programs Q1, Q2
> >
> >         Server A,         Server B
> >
> >  S          P1                P2
> >  T          Q1                Q2
> >
> >
> > Now user S, selects something for the find panel, or
> > for copy/past in P1.  This ends up in the pasteboard of Server A.
> > Now S selects application P2, and reselects the find panel, or
> > pastes. NOTHING happens.   (note I am not talking DnD here)
> >
> > Afterwards user T opens the find panel or does a paste.
> > Voila, the content of what user S selected appears.
>
> If S is associated with A, then P1 and P2 should both use the
> pasteboard server on A ... and cut/paste should work as expected.
> The selection for P1 will appear in P2 and not in Q1 or Q2
>
>
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