Popover: rework props around shift, filp and resize behavior

[ciampo]

What

Tracked in #42770

Currently, Popover exposes two props for tweaking its behavior when intersecting with the viewport's boundaries:

• __unstableForcePosition
• __unstableShift

However, it feels like these props don't offer the correct abstraction and actually limit the flexibility of the component.

Proposed next steps

We could look at removing __unstableForcePosition and replacing it with separate resize and flip props, in order to be more aligned with floating-ui's middleware options.

Bonus: we should also look at https://ariakit.org/examples/popover, and try to make a potential refactor of the component to ariakit as simple as possible

[talldan]

It turns out I didn't need this to fix the issue with legacy widgets (#43297).

But I can still push a PR that refactors this.

[talldan]

Bonus: we should also look at https://ariakit.org/examples/popover, and try to make a potential refactor of the component to ariakit as simple as possible

Nearly forgot, I looked at how ariakit's popover works.

It seems like that uses a fitViewport prop, which I guess is roughly the same as resize (though I don't know if 'viewport' is correct, but maybe that's just a nitpick):

• https://github.com/ariakit/ariakit/blob/main/packages/ariakit/src/popover/popover-state.ts#L480-L487

And there's a flip prop:

• https://github.com/ariakit/ariakit/blob/ece71049c13908c58a638c3f069375b7f9311ad6/packages/ariakit/src/popover/popover-state.ts#L445-L463

So that may be another reason to still change the props.

[ciampo]

Thank you for the exploration!

But I can still push a PR that refactors this.

That would be great!

[ciampo]

Reopening as the shift prop is still marked as __unstable — we should:

• add a new shift prop with the same default value of __unstableShift
• add a deprecation notice to __unstableShift

@talldan , would you be able to work on this? It should be a quick one.

[ciampo]

#43845