Combobox to choose Matplotlib backend

[Nodd]

Currently the matplotlib backend is set via a QLineEdit. Since the possible values are a few and well defined, a combobox is more appropriate.

Bonus points if only the available backends are shown (but it depends on the active interpreter ?).

[Nodd]

Same for ETS Toolkit, I guess.

[goanpeca]

Which are the valid options? and how to check from the valid options which ones are enabled?

[ccordoba12]

@goanpeca, we already have this for the IPython console. Check out its Graphics/Backend tab on Preferences to see what @Nodd wants. Right now we are only testing for available backends on the same interpreter that Spyder is running on, but that could be improved.

About ETS: I think there are only two possible options: qt and wx, so I don't think we need a combobox for that ;-)

[Nodd]

@ccordoba12 Exactly! I didn't notice that it was already used by IPython.

About ETS, having a QLineEdit for 2 options is more silly than having a combobox. 👅 Other options are a checkbox (which would be confusing) or 2 radio buttons, which would work well too. In any case it's not a big deal, only a minor improvement.

[goanpeca]

Even though I this is not terribly urgent, I do agree with @Nodd that even if only 2 options, we should change them to comboboxes.

[ccordoba12]

wx doesn't work on Python 3, so I don't think we need a combobox for that entry

[Nodd]

In that case this options should be hidden under python3, and use a combobox under python2. 😄

[ccordoba12]

As @goanpeca established: help-wanted. I really think the QLineEdit is just fine. Besides, I don't know if ETS is working on Python 3.

[Nodd]

👍

[ccordoba12]

I'm going to solve this one as part of solving #2471 (by limiting the number of backends we support).