Box should have an content Primitive

[delaneyj]

The Box primitive is used in many examples (especially Flex) but once you start using it adding contents inside the Box is not straight forward without generating custom Primitives and .Draw() functions. This is an initial bare minimum implementation to support Box having a .SetContents(p Primitive).

This does not change how b.draw works but long term it may mean the need for a DrawFunc is unnecessary and allows for more composability.

[rivo]

Thank you for your contribution. I'm not really sure I understand the motivation behind this PR. Box, while having functionality on its own, is the superclass of all other primitives. If you want to put content in a box, you don't start with Box but with one of the specialized other primitives (e.g. TextView).

I'm also not sure how your proposed changes make things easier for users of the package. If you want to put a border around a Table, you call table.SetBorders(true). No need to wrap a table in a box and then call box.SetBorders(true).

For most applications, it should not be necessary to write your own primitive. If tview is missing essential primitives in your opinion, I'd be very interested in knowing what those are.

Maybe you can describe the issues you're having (ideally with example code) so I have a better idea what you need.

[delaneyj]

Ah, I see now. Makes way more sense when you explain it like that. Sorry for the confusion.

[rivo]

No problem. Always happy to explain.