Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!SUN.COM!owen
From: owen@SUN.COM (Owen Densmore)
Newsgroups: comp.windows.news
Subject: Re:  Why doesn't the following simple NeWS example work?
Message-ID: <8804071639.AA15822@bigmac.sun.com>
Date: 7 Apr 88 22:30:09 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 70


    Below is the transcript from a psh session. Can someone tell me what the
    problem is (NeWS 1.1)?
    
	Welcome to NeWS Version 1.1
	/msg framebuffer /new DefaultWindow send def
	/reshapefromuser msg send
	/map msg send
	/destroy msg send
	***ERROR*** 
	Process: 0x24FF44   Error: killprocess
	Stack:
	Executing: `killprocessgroup'
	At: {FrameEventMgr *`killprocessgroup'}
	In: {FrameEventMgr 'null' 'ne' array{2} *'if'}
	In: {DestroyFrame *DestroyClient}
	In: Reading file(?,W,R)
	*****
	psh: NeWS server disconnected
    
	Process PostScript finished
    
    Thanks,
    
    Skip Montanaro (montanaro@sprite.steinmetz.ge.com, montanaro@ge-crd.arpa)

The problem is that the /destroy message executes a "killprocessgroup",
in which the psh is a member.  The message is innocous, but you can
avoid it by either subclassing the window to have the /destroy method
be a no-op, or you can launch the window in it's own processgroup.
Here's the former:

	/MyWindow DefaultWindow []
	classbegin
	    /destroy {/unmap self send} def
	classend def
	
	/msg framebuffer /new MyWindow send def
	/reshapefromuser msg send
	/map msg send
	/destroy msg send

[Note: I do a unmap so that the window will disappear rather than
waiting for garbage collection to take place when I re-define "msg".]

I also find it convenienent to launch windows, and simple clients, from a
psh.  My solution is a somewhat odd "runprogram" procedure which executes
a string as a psh script:

    /runprogram { % string => - (exececute the string as a psh program)
	(/tmp/pshscript) (w) file		% str file
	dup 3 -1 roll			% file file str
	writestring closefile		% -
	(psh /tmp/pshscript) forkunix
    } def

This survives the standard destroy just fine and really acts just like
a client:

	(
	    /msg framebuffer /new DefaultWindow send def
	    /reshapefromuser msg send
	    /map msg send
	) runprogram

..this window can be destroyed (zap menu) without the earlier message.
(You might have /msg put in system dict so that you can use it from
another interactive psh)

Owen Densmore
Sun Microsystems