Provide public access to the toolbar state for widget interaction

[jlaura]

Currently the state of the MPL toolbar is not publicly available and must be accessed via fig.canvas.manager.toolbar._active. Accessing via _active is dangerous as it is private and could potentially be altered without notice [link].(http://stackoverflow.com/questions/20711148/ignore-matplotlib-cursor-widget-when-toolbar-widget-selected/20712813#20712813.)

Is it possible to provide public access to the toolbar state so that widgets can 'fire' only when a toolbar item is not selected. As an example, if a cursor widget is used to generate subplots, it currently generates a subplot based on the point of an initial pan or zoom request (toolbar item).

@tacaswell

[tacaswell]

@fariza Can you take a look at this?

[fariza]

This raises a very important point in the split of navigation and toolbar.

On the side of navigation there should be a public state. the api should allow to add/remove/disable/enable states.

On the toolbar side the buttons that respond to changes in the states should be converted to radio buttons. And again a new api to add/remove/etc... buttons.

Right after #2624 I will restart the discussion on this split, I will make sure this state handling is included.

[fariza]

@tacaswell Do you recommend doing the split based on a MEP? Or straight with a PR?

I am just asking to know what option have more chances of speedier review and approval.

[tacaswell]

I am not sure the best way to do it. You can see how well my major re-factor is going with a straight PR.

Given that you are blocked by #2624, I think writing out a MEP with all the api details would be good because the discussion on that can happen in parallel.

[fariza]

@tacaswell I am working on the MEP for the split, please checkit out

https://github.com/matplotlib/matplotlib/wiki/Mep22

[fariza]

@tacaswell please add MEP22 label

[fariza]

In MEP22 #2759 NavigationBase class, there is a new method get_active that returns a dictionnary with the currently toggled tool, and a list of the registered tool instances

[fariza]

MEP22 solved this problem. fig.canvas.manager.toolmanager.active_toggle returns the currently toggled tools
I'm closing this issue, please reopen if necessary