Re: FLTK initialization bug?

[John W. Eaton]

On 13-Sep-2010, Jordi Gutiérrez Hermoso wrote:

| On 13 September 2010 20:12, Ben Abbott <address@hidden> wrote:
| > This looks like a timing problem to me.
| >
| >        octave:1> backend ("fltk") ; __go_figure__ (1, "__backend__", "fltk")
| >        warning: implicit conversion from matrix to sq_string
| >        error: fltk_backend: could not recognize fltk index
| >        octave:1> backend ("fltk")
| >        octave:2> __go_figure__ (1, "__backend__", "fltk")
| >        ans =  1
| 
| I can't reproduce this. The warning and error happen here even if
| they're on separate lines. Regardless, if you're seeing it, it's
| doubtless a race condition... I wonder if we need to start bothering
| with semaphores and mutexes...

Maybe the change is as simple as the following?  But since I don't
really know how the fltk backend is supposed to work I'm not sure.  It
just makes sense to me that if the __plot_stream__ object is an empty
matrix, it is probably not initialized ([] is the default value of
__plot_stream__ when a new figure is created, isn't it?) so we
shouldn't need to delete it.

diff --git a/src/DLD-FUNCTIONS/fltk_backend.cc 
b/src/DLD-FUNCTIONS/fltk_backend.cc
--- a/src/DLD-FUNCTIONS/fltk_backend.cc
+++ b/src/DLD-FUNCTIONS/fltk_backend.cc
@@ -1186,7 +1186,9 @@
     if (go.isa ("figure"))
       {
         octave_value ov = go.get (caseless_str ("__plot_stream__"));
-        figure_manager::delete_window (ov.string_value ());
+
+        if (! ov.is_empty ())
+          figure_manager::delete_window (ov.string_value ());
       }
   }
 

BTW, I think we could improve the names of the following functions in
the graphics backend classes:

  // Called when graphics object using this backend changes it's property.
  virtual void property_changed (const graphics_object&, int)

  // Called when new object using this backend is created.
  virtual void object_created (const graphics_object&)

  // Called when object using this backend is destroyed.
  virtual void object_destroyed (const graphics_object&)

I think

  // Callback function executed when the given graphics object
  // changes.  This allows the grahpics backend to act on property
  // changes if needed.
  virtual void update (const graphics_object&, int);

  // Callback function executed when the given graphics object is
  // created.  This allows the graphics backend to do backend-specific
  // initializations for a newly created object.
  virtual void initialize (const_graphics_object&)

  // Callback function executed just prior to deleting the given
  // graphics object.  This allows the graphics backend to perform
  // backend-specific cleanup operations before an object is deleted.
  virtual void finalize (const_graphics_object&)

would be better (assuming the comments are correct).

Any objection to making this change?

jwe