Convenience API for unique apps

[Havoc Pennington]

On Wed, 2004-07-21 at 19:58, Mike Hearn wrote:
> Hi,
> 
> A common use case for activation systems is to make apps single
> instance.
> 
> It would be nice if libdbus had a simple API to automate this common
> task.
> For instance:
> 
> DBusConnection *connection =
> dbus_exit_if_not_unique("org.myprogram.myprogram");
> 
> Which connects to the bus, checks if the given service name has been
> acquired and disconnects + exit(0) if so, otherwise it's up to you to
> release the connection.

That isn't usually the right thing though, is it? Most single-instance
apps should open a new window in the existing instance, or at least
bring the current instance to the front, rather than exiting.

I do want a "KUniqueApplication" type of solution but it's pretty hard
to get right (see the mess in gnome-terminal...) mostly because of
command line options that can't be applied per-window or dynamically.
I guess strictly speaking we need to require that all command line
options make sense for a new window or for an already-running window in
desktop applications. In other words command line options should all
translate to parameters to a window_new() function.

Another complexity is per-display apps, somewhat different than single
instance (single instance really means "scope of the bus" e.g.
per-session). I wanted to do per-display by setting a globally unique
value in a property on each display, then including that value in the
service name. So making that convenient would have to be done in the GUI
toolkit.

Anyway, this is definitely a valuable area of hacking, I just wanted to
bring up some of the complexities. ;-)

Havoc