BUG: Add Figure.delcolorbar() to fully delete a colorbar

[KevKeating]

Closes #2688.

This creates a new Figure.delcolorbar() function, named to mimic Figure.delaxes(). The new function will delete a colorbar. If that colorbar was creating with use_gridspec=True, the function will also reset the gridspec. I added two tests to confirm that the function works as intended for colorbars creating with use_gridspec set to either True or False.

[tacaswell]

This probably does not need a image just, just ask the axes how big it is.

[tacaswell]

What happen in figures with out a colorbar? Sorry, being dumb.

[KevKeating]

The new diff switches from Figure.delcolorbar to Colorbar.remove_from_figure. Also, the tests now compare axes.figbox rather than using image comparison (based on @tacaswell's suggestion). I also added a note to the changelog.

[tacaswell]

Both tests need and @cleanup or we get strange effects with tests cross-talking.

[tacaswell]

Could you please squash this down to a single commit? (so we don't have the addition and removal in our repo forever)

[efiring]

Artists have a remove() method. The colorbar is not implemented as an Artist subclass, but wouldn't it still be better to give it a simply-named remove() method? And maybe Axes could also have a remove() method that would call self.get_figure().delaxes(self)? I don't like all this circularity, but it might be worth it for the sake of being able to invoke a remove method on just about anything that was added to a figure. The fewer method names a user needs to remember, the better.

[KevKeating]

I prefer remove to remove_from_figure since there shouldn't be any ambiguity about what the colorbar is going to be removed from, but I'm okay with either option.

[KevKeating]

I put up a new commit that should address all of the raised issues. I've changed the method name from remove_from_figure to remove, but I didn't add an Axes.remove method.

[efiring]

The Travis failure is unrelated.

[efiring]

Colorbar.colorbar_factory is normally used to make a colorbar (it is called by Figure.colorbar), and it performs two more operations that I think need to be undone when the colorbar is removed:

    mappable.callbacksSM.connect('changed', cb.on_mappable_changed)
    mappable.colorbar = cb

Also, when use_gridspec is False, it is still possible to undo the change that was made to the parent Axes. Something like this, where ax is the parent Axes:

pos = ax.get_position(original=True)
ax.set_position(pos)

[KevKeating]

With the new commit, the callback and colorbar attribute are reset, and get_position/set_position are called when use_gridspec was False.

[tacaswell]

This looks good to merge to me 👍

Thanks for fixing what was a very long standing bug.