[gtkada] Addressing external data in a GUI

[Michael Bode]

Rick Duley schrieb:

>My GUI has two features to inform the User of progress:
>(1)  A Gtk.GEntry which displays the name of the file being processed;
>(2)  A Gtk.Progress_Bar (in Pulse mode) to show that work continues.
>
>My problem is adressing these widgets from the Engine, i.e. from outside the
>GUI.  I have devised a task which does this.  It's a brutal way to do the job
>but it's the only way I could devise.  Trouble is, to get the effects to
>display properly on-screen I need the Interrupts created by moving the cursor
>over the GUI - otherwise I get (at best) intermittent, jumpy movement of the
>Progressbar.  (I don't want the User to have to sit all day moving the cursor
>over the GUI. ;}  )  I've tried 'Grab_Focus', 'Show_All' and 'Show_Now' but I
>just can't get the thing to update without the Cursor Interrupts.  This is the
>task I devised:
>  
>

I do things like that using a protected type and a timer or idle procedure.
In the worker package:

type status_record is
  -- status information
end record;

protected Status is
    procedure set (S: status_record);
    function get return status_record;
end Status;

and in the GUI package:

function Display_Status return Boolean
is
  S : Status_Record;
begin
   Gdk.Threads.Enter;  -- timeout callback must call this
   S := Some_Instance_of_Status.Get;
   ...
  Gdk.Threads.Leave; -- timeout callback must call this
   return True;
end Display_Status;

ID :=  Gtk.Main.Timeout_Add (500, Display_Status'access); -- call it 
every 500ms

Code not compiled, likely contains bugs.

-- 
Michael Bode
Laserline GmbH
Fraunhoferstr.
56218 Mülheim-Kärlich
Phone:     +49 2630 964-2200
Fax:       +49 2630 964-2209