[impression-x] network problem: document loaded twice

From: Jim Nagel <jim-imp@xxxxxxxxxxxxxxxx>
To: impression-x@xxxxxxxxxxxxx
Date: Sat, 25 May 2013 15:32:10 +0100
This follows from a thread I started in c.s.a.misc, called
"More than one copy of file open".

Now that I have several RiscOS machines on the home network, I find I 
need to be wary of having my working document open on two stations at 
the same time -- I could easily get into a muddle with edits from one 
copy overwriting edits done in the other copy.  It's especially 
Impression documents that concern me, but I guess this generalizes.

Interesting discussion ensued in c.s.a.misc.  It seems there is a 
distinction between a "file" being open (the term file "handle" would 
then apply) and a document being loaded -- most document processors do 
not keep a "file" open while the document is loaded.  Martin Würthner, 
for instance, said Techwriter normally behaves like this but in the 
case of a very large document where parts are not loaded till they are 
needed, the file might remain open.

Impression, like Fireworkz and other apps (surprisingly not including 
Artworks), won't let you load a second copy of the same doc on the 
same machine -- but unfortunately they don't notice a copy of the same 
doc already loaded elsewhere on the network.

So I began wondering about the possibility of a little standalone app 
or utility that could be invoked in the !Run file of Impression (or 
any document processor) so that trying to load a document would first 
check this app's scrapfile (which would have to be shared by all 
stations on the network) to see if it's already loaded.  If so, it 
would issue a warning.  Upon loading or closing the document, its 
pathname would be noted in this scrapfile, along with the ID of the 
station using it.
   Obviously the prefix "ADFS:" would apply to the filepath for one 
machine whereas other machines would have the prefix "ShareFS:", so 
the filesystem prefix would have to be ignored.

This led me to look inside Impression's !Run file to see what's 
already there.  This line caught my interest:
     Set DocumentManager$Scrap <Wimp$ScrapDir>.!Publisher
Hmm, now what's this about?  My scrap directory has no folder called 
!Impression; nor is there one called Impression or Publisher.

The RMstore folder inside Impression contains a module called Docman 
(Documentmanager, version 0.30, dated 1993).

I'm curious.  I wonder if Richard Keefe has any documentation to say 
what this is about, and whether it's relevant to my question.  Maybe 
it's a feature Computer Concepts never completed back in 1993, but 
you'd have thought there'd have been a need for such a mechanism back 
in the days of Impression on school networks.

-- 
Jim Nagel                        www.archivemag.co.uk
[impression-x] network problem: document loaded twice

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