Re: How can I find out if a program is already running

[Zoltan Boszormenyi <zboszor freemail hu>]

Thanks for the answer, although I still have problems with this.

Mark Leisher írta:

> Zoltan Boszormenyi wrote:
>
> > Hi,
> >
> > I need to find out whether an instance of a program is already running
> > and possibly unminimize it or bring it above any other windows, so
> > I can prevent an application started again.
> > Is is possible using GTK-1.2, or GTK-2.x, and how?
>
> The following procedure is an old X11 trick. It will not work on Windows.
>
> 0. Add code to your program to handle GDK_SELECTION_CLEAR events. See 
> 5 below for what this code should do.
>
> 1. At startup of the program, create an atom with gdk_intern_atom().
>
> 2. Use gdk_selection_owner_get() on the atom.
>
> 3. If the selection owner is NULL, then call gdk_selection_owner_set() 
> with the time_ parameter set to GDK_CURRENT_TIME and the send_event 
> parameter set to FALSE.


My problem is, the owner this call returns is always NULL.
This has something to do with the fact that the actual owner is a window 
in another process.
There is this call:  GdkWindow *gdk_window_foreign_new(GdkNativeWindow anid)
This GdkNativeWindow is a native X Window ID or HWND on Windows.
I seem to have to call this, wrap a foreign window into a GdkWindow before
gdk_selection_owner_set() can give me sensible return value.

But how can I tell the XID of  a window created from another process?
Sorry, I don't know too much about low level Xlib programming...

> 4. Else, there is a valid owner of the atom, so the program is already 
> running. Assert ownership of the selection with 
> gdk_selection_owner_set() again. This causes the running application 
> to lose ownership and call the code to handle GDK_SELECTION_CLEAR 
> events. Then exit.
>
> 5. The code to handle GDK_SELECTION_CLEAR events should do 2 things:
>   A. If minimized, unminimize.
>   B. Assert ownership of the selection again.
>
> This doesn't work on Windows because the GDK selection API apparently 
> only works within applications and not globally like they do in X11.