Malcolm J. Kudra wrote:
Andre van Zuydam wrote:
>Well - it could be any file. In my case its a text file (a php file). My
>programme is open and I want to know when windows wants to open another one
>so I can open it in my programme, it being the default
>editor. I hope this makes sense.

Andre, perhaps you could register the .PHP file extension with Windows
to be associated with (opened by default by your program) at
initialization time and return the .PHP association to its original
state as part of your application's finalization routine.

Would this achieve the effect you need?

That's not what he needs. He needs to know how to make his program
accept multiple files, instead of starting a new instance for each file.

This is his scenario: His program is already open, perhaps editing a PHP
file already, or perhaps without any files open. The user opens Explorer
and double-clicks a PHP file. With the usual file-association rules,
Windows will start a new instance of the application, passing the file
name as a command-line parameter. But instead of editing that file in
the new instance, which is what Andre's program already does, he wants
to edit that file in the instance that was already open before.

way to solve this is to change the file-association rules to use DDE
instead of just a command line. Andre's program can then use Delphi's
DDE components to accept commands from Windows to open another file.

The more common way to solve this is to have subsequent instances of the
program detect that they aren't the first, and instead of continuing
with their initialization sequence, they simply pass the file name along
to the already-open instance and terminate. Detecting multiple instances
is easy, and there are lots of examples in the newsgroup archives. There
are slightly fewer examples of sending the new instance's command line
to the old instance. I don't have time to explain it now, but I do it
this evening if necessary.

I think hijacking the file association while the program is running is a
bad idea. But I don't think it would affect anything in this case since
it sounds like Andre's program is already associated with PHP files, so
there's nothing to hijack.

Malcolm J. Kudra wrote:
Would you suggest that Andre implement your approach by using either the
TJvAppInstances component (from the JVCL) or the STFirst unit (from
SysTools), both available on SourceForge free of charge?

can you suggest other existing code that would work better than
either of these but still allow Andre to re-use rather than re-invent?

I'm not familiar with either of those; the one time I needed something
like this was long ago, and I just wrote my own thing that used a mutex
for detecting multiple instances and a thread with a mailslot to listen
for commands from new instances. , I think it was an elegant
solution, but I've never gotten around to generalizing it for others to
use.

I trust JEDI to get things right, though, so I'd recommend the JVCL
component.

http://jvcl.sourceforge.net/