Set more sensible defaults in BoxAnnotation

[mattpap]

fixes #13432

[codecov]

Codecov Report

Merging #13468 (462d4d7) into branch-3.4 (8072a9a) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

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  Misses           1520     1520           

[bryevdv]

Is this for demonstration, or required? I don't think having to explicitly specify this is an improvement, or what users would normally want to have to do to have the box be "unbounded" in a direction.

[mattpap]

It's now required. Note that BoxAnnotation doesn't imply that it's bound to frame in any capacity (it's just a historical artifact), so unspecified positioning properties don't give a clue what the behavior will be (i.e. will it span, will it show at all?). It should be possible to attach it to anything like canvas or a panel or another box annotation. The syntax is indeed verbose, but at least the behavior is clear. BoxAnnotation wasn't ever a truly unbounded annotation, because it always draws lines on all sides and doesn't hit test at infinity, two things that {H,V}Strip glyphs do.

[bryevdv]

Note that BoxAnnotation doesn't imply that it's bound to frame in any capacity (it's just a historical artifact)

I'm not sure where this is coming from, but it is not correct. "missing bound = extend to plot edge" was an explicit design criteria of the original BoxAnnotation and is also what is and has been officially documented:

To define the bounds of these boxes, use the left/right or top/ bottom properties. If you provide only one bound (for example, a left value but no right value), the box will extend to the edge of the available plot area for the dimension you did not specify.

I'm pretty sure I am 👎 on this change as-is in general, but I am defintely 👎 on backporting such a breaking change to a point release.

[bryevdv]

Attempting to regain some movement on this PR. @mattpap is the plan to deprecate BoxAnnotation entirely in favor of glyph alternatives? If so, then I would support these changes provided that the deprecation happens at the same time.

[mattpap]

I reverted the defaults, so that they are not required anymore and point to symbolic nodes of the frame.

[github-actions]

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