Bug#534943: reportbug: python / GTK error about being unable to open display when used from console

[Sandro Tosi]

On Sun, Jun 28, 2009 at 18:47, Jakub Wilk<ubanus at users.sf.net> wrote:
> * Sandro Tosi <morph at debian.org>, 2009-06-28, 17:09:
>>>
>>> I find it perfectly reasonable that python-gtk2 issues a warning; in
>>> *most cases* the module has limited usefulness when $DISPLAY is not set to a
>>> valid value.
>>
>> ok, so this is informative for a user, but how can this be useful for a
>> program?
>
> The nice thing about warnings is that you can silence them or you can turn
> them into exceptions:

sure, so consider this situation:

- we silence the warning;
- a user really wants to use the Gtk+ gui, but has not set DISPLAY
(because messed up environment, or 1000s other reasons)
- no warning is issued but the gui won't start and we receive a bug
report because the Gtk+ gui doesn't work.

Should I silence the warning or not? I don't think so.

> Don't get me wrong: I don't claim that issuing a warning is an optimal
> solution for dealing with missing $DISPLAY. It's just *better* than raising
> an exception at import time.

To inform people using it, not programs importing the module. There
are 2 situations:

- the modules does not really work, so raise an exception
- the module can work, even if with limited functionalities, so don't
issue a warning

> Importing a module might be useful even if the module did not "work", as you
> could still:
> - Import it to ensure that it is *installed*. (And if it were not, instruct
> the user to install python-something.)
> - Import it to inspect the module contents (e.g. read docstrings).

Ok, so don't issue a warning at import time (because it still could be
interesting have a "limited functionalities" module loaded) but raise
an exception the very moment you're calling a method needing DISPLAY.

Programs will handle exception.

Regards,
-- 
Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi