Re: remote hosting

[Tim McIntosh]

Hi Fred,

Sorry for the confusion.  The specific case that I want to work is as  
follows:  I have a machine running GNUstep (call it 'localhost').  I  
log into this machine from another non-GNUstep machine (call it  
'remotehost') using 'Xnest' (display ":1") to connect to the xdm on  
'localhost'.  Thus, DISPLAY is 'remotehost:1.0' and the GNUstep  
processes are running on 'localhost'.

This "sort of" works without the patch.  The initial processes that  
are launched _without_ the '-NSHost' argument will correctly display  
on 'remotehost:1.0', while printing the warning "NOTE: Only one  
display per host fully supported."  However, the 'NSHost' default  
will be (incorrectly) set to 'remotehost' by the code I've proposed  
deleting.  As I understand it, this default causes the programs to  
look for 'gdnc', 'gpbs', etc. on 'remotehost', instead of  
'localhost', where they are actually running.

The problem gets worse when one of those initial processes (e.g.  
GWorkspace) launches another GNUstep application via the NSWorkspace  
methods.  Since the parent process has the 'NSHost' default set, the  
new process will be launched with the '-NSHost' argument (see  
NSWorkspace.m).  When the -NSHost argument is specified, the code in  
the patched method (_initXContext) ignores the DISPLAY settings.   
Thus, the launched applications will use 'remotehost:0.0' for the  
display.  This leads to some surprising results when 'remotehost:0.0'  
is a valid display.

From looking at the code, I think you would also see a similar  
problem if you attempted to use display ":1" (or any nonzero display)  
on 'localhost', though I haven't tried this.

I think it makes sense for the '-NSHost' argument to override the  
DISPLAY setting, as it does today.  I think the problem is the  
assumption that the 'NSHost' default should be set according to  
DISPLAY if -NSHost was not explicitly specified.  As I see it, the '- 
NSHost' argument says that I want to connect to a remote GNUstep  
session.  If I don't specify -NSHost, I'm saying I want to run  
GNUstep on the local host and display according to the DISPLAY setting.

I realize that this is slightly less convenient in the case where you  
want to use a remote GNUstep session on 'remotehost:0.0' and would  
like to rely on the DISPLAY setting, but I'd rather have more control  
over the display.  Having to specify the -NSHost argument seems  
reasonable, especially considering that you had to do this under  
OPENSTEP and you'd have to do it anyway if you weren't using X11.

Tim


On Jan 30, 2006, at 4:30 AM, Fred Kiefer wrote:

> Hi Tim,
>
> I read through your mail and your patch, but still don't quite get the
> issue you have. It is a know problem that GNUstep will complain about
> multiple displays and it even may not work fully correctly in that  
> case,
> but what is causing you problems?
>
> What value are you using for DISPLAY? ":0.3" or ":1.0" or
> "localhost:1.0"? And in what way does it harm your application that
> NSHost gets automatically set? What value does it get set to?
> I would expect that having NSHost set to something like "localhost"
> would result in the same behaviour as not having it set at all. If  
> this
> is not the case, we need to look into that.
>
> I am not sure, if your solution, forcing people to set two environment
> variable to matching values, is a great idea. It most likely will  
> result
> in additional problems.
>
> Fred