For a long time I thought the Provider classes were kinda mysterious. As
soon as I started using them, their mystery disappeared.
This post will tell document these Provider classes in more detail. This
post will be pre-writing for a dev info issue.
*Overview*
Terry created the Provider classes as part of his free_layout project, in
plugins/free_layout.py This project also contains the nested splitter Gui
code, in plugins/nested_splitter.py. The nested splitter code creates the
so-called Easter Egg interface, which appears if you right-click the
divider between any two panes.
*The Provider interface*
The Provider classes implement an interface, partially described in the
docstring for the FreeLayoutController class in free_layout.py and more
fully described in the docstring for NestedSplitter.register_provider.
The interface works like an extended factory method. Provider classes *must
*contain the following methods:
*ns_provides*: Return a list of tuples ('Item name', '__item_id') that
describe the panes returned by the factory.
*ns_provide(id_)*: This is the factory itself. It returns the Qt pane for
id's that the Provider provides, and None otherwise.
The following methods are optional:
*ns_provider_id()*: return the id string for the Qt pane provided by the
provider.
*ns_title(_id)*: Return the desired window title for the Qt pane with the
given id string.
And that's probably all you need to know.
*Examples in the viewrendered plugins*
The VR plugin provides a *different *Qt pane for each outline (commander).
There is a separate Provider for each commander, and each Provider has a
distinct id from all other VR providers.
At present, the same is true for the VR3 plugin, but #1683
<https://github.com/leo-editor/leo-editor/issues/1685> suggests using a
global Qt pane. To do this, the Provider would simply use a single id for
global Qt pane. Like this:
- ns_provides: return ('VR3 pane', '_vr3')
- ns_provide: return a singleton, global, Qt dock.
- ns_provider_id(): return '_vr3'
*- *ns_title(_id): return 'VR3 pane'
*Summary*
Terry's Provider interface provides a framework for creating various kinds
of factory methods.
The VR and VR3 plugins use this interface to create and describe the Qt
panes that they create.
All comments, questions and corrections are welcome.
Edward
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