Rewrote the Moulder class for interactive 2D gravity modeling

[leouieda]

The fatiando.gui.simple.Moulder class created an interactive matplotlib window for drawing polygons and calculating their gravitational effect (using fatiando.gravmag.talwani). The functionality was very limited: could not edit polygons after they were drawn, orresume the app once the window was closed, or save the app state for loading later, etc.

I have rewritten the Moulder class to allow all of this. You can now:

• Move the polygon and its vertices
• Change the density
• Delete polygons and vertices
• Save the app state to a pickle file (Moulder.save)
• Save the predicted data to a text (XYZ) file (Moulder.save_predicted)
• Create a new instance of Moulder from the pickled state (Moulder.load)
• Insert a plot of the data and model into the IPython notebook (`Moulder.plot)

You can see this class in action in the 5th practical class of Geofísica 1: pratica5.ipynb. You'll to have this branch active on your local clone to run the notebook.

Here is a screenshot of the GUI window.

Problems and discussion

The new code breaks the BasinTri and BasinTrap classes that relied on the old Moulder.

I'm inclined to delete these classes (and the Lasagne class as well) because they can be easily replaced (and improved) by IPython widgets.

This raises the question: Should we even keep the fatiando.gui package? It is a tiny and virtually unused package. Things in it could easily be moved to other packages (Moulder could go into a fatiando.gravmag).

I think a better package structure would be to have interactive modules in the method packages (e.g., gravmag.interactive) where the GUIs and widgets could live.

I'd like some input on this, please, @birocoles, @eusoubrasileiro, @hbueno.

TODO

• There is a problem when resizing the window and then calling plot.
  Polygons get left out of the scene. Maybe make a "window close" callback that
  removes the animate flags and redraws the scene?
• Add IPython as a dependency

Checklist

• Make tests for new code (haven't figured out a way to test interactive code)
• Create/update docstrings
• Code follows PEP8 style conventions
• Code and docs have been spell-checked
• Changelog entry
• Documentation builds properly
• All tests pass
• Can be merged

[coveralls]

Coverage decreased (-2.87%) when pulling a71e20b on new-moulder into 3918e9d on master.

[coveralls]

Coverage decreased (-2.87%) when pulling 14fe7f3 on new-moulder into 32af5c0 on master.

[coveralls]

Coverage remained the same when pulling 14fe7f3 on new-moulder into 32af5c0 on master.

[coveralls]

Coverage remained the same when pulling fd00e0a on new-moulder into 32af5c0 on master.

[coveralls]

Coverage remained the same when pulling 8efe5e3 on new-moulder into 32af5c0 on master.

[leouieda]

I have made a tutorial notebook using the new Moulder class: http://nbviewer.ipython.org/github/fatiando/tutorials/blob/master/Interactive_gravmag_modeling.ipynb

[leouieda]

So in the end I've deleted the fatiando.gui package in favor of package specific interactive modules, like gravmag.interactive. The only class I've kept is Moulder. The others will be replaced by IPython widgets if the need arises.