Double-clicking a document in Windows

[Graham Samuel]

On Sun, 23 Feb 2003 18:29:22 -0600 "Chipp Walters" <chipp at chipp.com> wrote:
>
>Hi Graham,
>
>You can't easily open a doc in an already opened application by
>double-clicking on the document, because it will launch another instance of
>the application. What you need it 'intra-application communication' for
>instance: when the app launches, it checks a temp txt file to see if an
>instance of itself is already opened, if it is, then it sends a message to
>the other app (via the same text file and/or some sort of polling mechanism)
>to open the newly requested file.
>
>There's actually a RunRev user group setup to try and build an OpenSource
>implementation of the 'intra-application' protocol and libray...but there's
>not much done on it yet.
>
>So, the short answer is it's currently very difficult to do this in Windows.
>
>Here's a tip on "Creating a custom icon for Windows"
>
>http://www.altuit.com/webs/altuit2/RunRev/Tutorials.htm
>
Chipp, thanks very much for the link. I feel so ignorant about so 
many things I'm suddenly having to learn about (don't get me started 
on QT movies!).

I am surprised that a second double-click will create another 
instance of an application in Windows, because IMHO this behaviour 
would be counterintuitive for most non-technical PC users, who after 
all are Msoft's most numerous customers. Indeed, grabbing the first 
PC I could find (running Office 2000 under Windows 95), I find that 
Microsoft Word works the way I expected, i.e. double-click on a 
document will open the app, double-click on a second document, the 
app acts like you did File/Open from a menu. Of course in MS Office 
applications, it's legit to have several documents/files open at the 
same time.

I had no idea that there was an 'intra-application' issue, which I 
suppose MS Office itself has had to grapple with.

I suppose then my fallback is to design the app to deal with only one 
document (double-clickable file) at a time - but even with this 
restriction published to my users, how can I tell if the user has in 
fact done a second 'unauthorised' double-click and somehow reject it?

Incidentally, since Mac OSX is based on Unix, it seems worth asking 
if this problem also exists there - I sense that this 
multiple-instantiation thing is more 'classical' in some sense than 
the original MacOS solution and therefore likely to exist in Unix too.

TIA for any further info.

Graham
-- 
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          Graham Samuel / The Living Fossil Co. / UK & France