Phantom types: background-size

[BrianHicks]

This adds backgroundSize and backgroundSize2 for #392. Commits for this start at 48733cd, and I'm happy to rebase onto phantom-types when/if #419 is merged.

I was going to add backgroundSizes to go along with backgroundImages, but I can't figure out a good way of doing the types. Essentially, we need to be able to have all these properties:

/* valid */
background-size: cover;
background-size: 100px;
background-size: 100px, cover;
background-size: 100px 20px, cover;

/* invalid */
backgrouns-size: cover cover;
background-size: 100px 20px, cover cover;

---

• Each Value is an open record with a single field. The field's name is the value's name, and its type is Supported. For example foo : Value { provides | foo : Supported }
• Each function returning Style accepts a closed record of Supported fields.
• If a function returning Style takes a single Value, that Value should always support inherit, initial, and unset because all CSS properties support those three values!
• If a function returning Style takes more than one Value, however, then none of its arguments should support inherit, initial, or unset, because these can never be used in conjunction with other values!
• Every exposed value has documentation which includes at least 1 code sample.
• Documentation links to to a CSS Tricks article if available, and MDN if not.
• Make a pull request against the phantom-types branch, not master!

[rtfeldman]

Just 2 quick documentation requests, and 👍 to rebasing on phantom-types now that #419 is merged!

[rtfeldman]

Nice, thanks for not including inherit et al 😄

[rtfeldman]

Can we get CSS Tricks (or, failing that, MDN) links for contain and cover?

[BrianHicks]

done. Ready for another review 😄

[rtfeldman]

Fantastic, thank you @BrianHicks!