@JonB , the overlay class is really nice. I would call it a palette, but each to there own. You have seen to specifically talk about MatplotLib here.
But was your intention that it could be just used as any other view in making a ui.
The below, I chopped up somethings quickly to see how it would work. Maybe I should have just used a ui.TableView instead of a custom ui.View class. But I think often it's a convenient programming container.
But the list appeared to work ok(I changed another setting in the code somewhere to receive events and hard coded the name)
But was not meant to be an exhaustive test, just wanted to see how I could use it.
In this case the bottom resizing arrow didn't work. But it's understandable, I didn't even try. Could be a simple thing