Re: [matplotlib-devel] propagation of error messages in matplotlib

[John H. <jdh...@ac...>]

>>>>> "Steve" == Steve Chaplin <ste...@ya...> writes:

    Steve> I've updated backend_gtk.py in cvs to use a default
    Steve> exception handler, and noticed a few things in the process:
    Steve> - sys.excepthook does not catch SystemExit, which is what
    Steve> we wanted anyway.

I think the full exception should be printed.  It makes debugging very
hard, otherwise.  In fact, while recently debugging some code, I
commented out the exception handler for this reason.  matplotlib.cbook
provides a method exception_to_str to convert a traceback to a string.

    Steve>  - for some errors I needed to display a matplotlib message
    Steve> rather than the default exception message, or to raise an
    Steve> exception where error_msg () was used with no exception. I
    Steve> added an 'MPLError' exception, its probably best to move it
    Steve> into a central file if other people need to use it also.

Perhaps in matplotlib.__init__ ?  

    Steve>  - changing from error_msg() to raise exception means the
    Steve> rest of the method will not execute, which I hadn't thought
    Steve> about. This is no good for 'get_filename_from_user()' where
    Steve> I want to loop until a file (or Cancel) is selected. So I
    Steve> think GTK still has a need to use of a popup message dialog
    Steve> occasionally.  And for print_figure() it means the section
    Steve> of code to restore figure settings will not get executed
    Steve> after an error.

I agree that a general facility to popup a message is useful How
abouts we follow Jochen's suggestion and make is a FigureManager
method?

As for your get_filename / restore figure problems, can't these be
addressed by try/catching the exceptions locally, and restoring the
figure state before forwarding the exception onwards?

JDH