[Octave-bug-tracker] [bug #48175] "parse error" error message in GUI callbacks

[Rik]

Update of bug #48175 (project octave):

                Severity:              3 - Normal => 1 - Wish               
                Priority:              5 - Normal => 4                      
              Item Group:                    None => Feature Request        

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Follow-up Comment #3:

Changing this report to a Feature Request and lowering the Severity and
Priority.  Octave behaves equivalently to Matlab, except the error message is
less informative.

I don't know if it can be fixed, but the place to fix it will be in
libinterp/corefcn/graphics.cc.  The function in question is
gh_manager::do_execute_callback().  If the callback is a string, then
eval_string is called, if it is anything else then feval is called.

Interestingly, there are differences between eval_string and feval.  The
example in comment #0 used a string for the callback.  The following code uses
a function handle.



close all;
h = figure;
fcn = @() error ("My Error Msg");
uicontrol(h,'style','pushbutton','callback', fcn);


Just for grins, I put the feval in do_execute_callback inside a try/catch
block.  

if (fcn)
  {
    try
      {
        feval (fcn, args);
      }
    catch (...)
      {
        error ("Error executing callback\n");
      }
  }


And running now produces


tst_cb_err
error: My Error Msg
error: Error executing callback
error: parse error


It works to produce the new error message, but I also get a "parse error"
message.  This must be coming from the parser itself in
parse-tree/oct-parse.cc




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