This is in response to the request to split #2465 into several smaller PRs.

Goals

Main Goal

Separate the navigation state from the GUI (or physical) toolbar. Without touching any base class (as much as possible), to avoid forced refactor of other backends.

Secondary Goal

Add reconfiguration capabilities to the toolbar

Implementation

The following base classes were added

• NavigationBase: a derivate of NavigationToolbar2. This is the class that holds the state of the navigation.
• ToolbarBase: This is the physical or GUI toolbar. with the following new public methods
  • remove_tool
  • add_tool
  • move_tool

Includes Gtk3 implementation

• NavigationGTK3
• ToolbarGTK3
• Simple example of use examples/user_interfaces/reconfigurable_toolbar_gtk3.py

Future

If the functionality is worth the effort, and all the backends are ported to use this classes, it will be possible to merge NavigationBase and NavigationToolbar2.

Note

This is very similar to the idea of #1849 different implementation without touching the bases classes.