Waffles can overflow the frame

[mbostock]

As noted in https://github.com/observablehq/plot/pull/2132#issuecomment-2489891444:

Plot.waffleY([0.5, 2, 4], {x: null, fill: Plot.indexOf}).plot({color: {type: "categorical"}})

Above, the y-scale only extends from [0, 6.5], but the waffle visually extends to y = 7.5… that’s because here each cell of the waffle is 3 y-units tall, as there are three columns. We’d need the waffle mark to provide a hint to the y scale that the domain needs to be taller than the apparent value from the y1 and y2 channels.

[Fil]

This is a difficult one conceptually 🤔

Do we want 7.5 in this case (the top y2 of all the points generated by the waffle geometry), or do we want 9 (meaning, we derive our unit height (multiple = 3) and just want to round it up to make enough room for the top row—even if it's not filling up entirely?

(Also, when you look at the current order of operations, the waffle geometry is computed in an initializer, after the y scale has already been derived, so something that says 7.5 or 9 doesn't seem easy to implement.)

There is a similar issue with circles — we're not accounting for their radius and they can get clipped if on an edge. We currently expect the user to add an insetTop or something.

Quite often I'd like the default style to be overflow:visible — it would solve many issues of this kind (and create different issues! yay).

[mbostock]

the waffle geometry is computed in an initializer, after the y scale has already been derived, so something that says 7.5 or 9 doesn't seem easy to implement

Hmm, yes, perhaps this means this isn’t solvable. We’d either have to allow initializers to redefine position scales (potentially running the initializer again until it coalesces?) or we’d only be able to solve this when the multiple option is fixed ahead of time.