From help-octave-request at bevo dot che dot wisc dot edu  Sun Jan 30 21:14:04 2000
Subject: Re: perlTK
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Joao Cardoso <jcardoso at inescn dot pt>
Cc: "help-octave at bevo dot che dot wisc dot edu" <help-octave@bevo.che.wisc.edu>
Date: Sun, 30 Jan 2000 21:14:36 -0600 (CST)

On 31-Jan-2000, Joao Cardoso <jcardoso at inescn dot pt> wrote:

| Couldn't Octave have a function to do it? Something like
| 
|    on_idle("user function","user data")

Sure, I've appended a solution.

If your user function waits for and processes one GUI event at a
time, then you will also need something like

  void do_nothing (ClientData data, int i) { }

and

  Tk_CreateFileHandler (0, TK_READABLE, do_nothing, 0);

which sets up a function to be called whenever there is input waiting
on stdin.  By doing nothing, you force an event to happen and be
processed, then user function can return so that Octave (readline)
can process the next character(s) on the input stream.

I'm not really sure that the following function buys you much unless
you also write a DEFUN for your GUI's equivalent of

  Tcl_DoOneEvent (TCL_ALL_EVENTS);

so that it can be called from your user function.  In any case, it
would be more efficient to do it all in C/C++.

Also, my use of Tcl/Tk here should not be taken as an endorsement from
me for Tcl/Tk, or any indication that I plan to use Tcl/Tk with
Octave.  I just happened to have the Tcl/Tk and readline example
available.  You should be able to do similar things with other GUI
toolkits.

jwe



Index: input.cc
===================================================================
RCS file: /usr/local/cvsroot/octave/src/input.cc,v
retrieving revision 1.125
diff -c -r1.125 input.cc
*** input.cc	2000/01/27 23:30:46	1.125
--- input.cc	2000/01/31 03:06:06
***************
*** 880,885 ****
--- 880,956 ----
    return retval;
  }
  
+ static string hook_fcn;
+ static octave_value user_data;
+ 
+ static int
+ input_event_hook (...)
+ {
+   if (user_data.is_defined ())
+     feval (hook_fcn, user_data, 0);
+   else
+     feval (hook_fcn, octave_value_list (), 0);
+ 
+   return 0;
+ }
+ 
+ DEFUN (input_event_hook, args, ,
+   "-*- texinfo -*-\n\
+  at deftypefn {Built-in Function} {[@var{ofcn}, @var{odata}] =} input_event_hook (@var{fcn}, @var{data})\n\
+ Given the name of a function as a string and any Octave value object,\n\
+ install  at var{fcn} as a function to call periodically, when Octave is\n\
+ waiting for input.  The function should have the form\n\
+  at example\n\
+  at var{fcn} (@var{data})\n\
+  at end example\n\
+ \n\
+ If  at var{data} is omitted, Octave calls the function without any\n\
+ arguments.  If both  at var{fcn} and @var{data} are omitted, Octave\n\
+ clears the hook.  In all cases, the name of the previous hook function\n\
+ and the user data are returned.\n\
+  at end deftypefn")
+ {
+   octave_value_list retval;
+ 
+   int nargin = args.length ();
+ 
+   if (nargin > 2)
+     print_usage ("input_event_hook");
+   else
+     {
+       octave_value tmp_user_data;
+ 
+       string tmp_hook_fcn;
+ 
+       if (nargin > 1)
+ 	tmp_user_data = args(1);
+ 
+       if (nargin > 0)
+ 	{
+ 	  tmp_hook_fcn = args(0).string_value ();
+ 
+ 	  if (error_state)
+ 	    {
+ 	      error ("input_event_hook: expecting string as first arg");
+ 	      return retval;
+ 	    }
+ 
+ 	  command_editor::set_event_hook (input_event_hook);
+ 	}
+ 
+       if (nargin == 0)
+ 	command_editor::set_event_hook (0);
+ 
+       retval(1) = user_data;
+       retval(0) = hook_fcn;
+ 
+       hook_fcn = tmp_hook_fcn;
+       user_data = tmp_user_data;
+     }
+ 
+   return retval;
+ }
+ 
  static int
  ps1 (void)
  {



-----------------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.che.wisc.edu/octave/octave.html
How to fund new projects:  http://www.che.wisc.edu/octave/funding.html
Subscription information:  http://www.che.wisc.edu/octave/archive.html
-----------------------------------------------------------------------