Re: Timers and GTK

["Bobby D. Bryant" <bdbryant@mail.utexas.edu>]

GUILLOU Jacques wrote:

> Can anyone help me using GTK timer functions ? (callback function that
> is called every 100 ms for example) ?
> thanx

By chance I just worked that out a couple of days ago.  The following
example uses the GtkAda bindings; I'm picking out lines that are widely
separated among my files, so here's hoping I haven't forgotten anything.

-----
Instantiate the "Timeout" package:

   -- Package for handling timeout callbacks:
   package Timeout_Callback is
      new Gtk.Main.Timeout( Data_Type => Integer );

[Use whatever data type you happen to need in your callback function.]

-----
Declare a variable to recieve the timeout's identifier:

      Timeout_Handle : Glib.Guint;

and a variable to define the interval (or just use a constant):

   Migration_Interval    : Glib.Guint := 1000; -- ms.

-----
Declare a function to be invoked by the timer:

   function Migrate( Number_To_Move : in Integer )
      return Boolean;

   function Migrate( Number_To_Move : in Integer ) return Boolean is
...
   begin
...
      return True; -- "false" will disable further timeouts on this.
   end Migrate;

[Notice that the integer argument matches the data type in the package I
instantiated above.]

-----
Set up the callback:

      Timeout_Handle
        := Timeout_Callback.Add( Interval => Migration_Interval,
                                           Func     => Migrate'Access,
                                           D        => 1000 ); -- # to
move.

[ The "D" value is passed to Migrate whenever it is invoked.]

-----
Works like a charm.  Good luck!

Bobby Bryant
Austin, Texas