Open
Description
https://developer.mozilla.org/en-US/docs/Web/API/StylePropertyMap/append
Started in #36. Turing out to be fairly complex because there's a number of underlying things we don't have yet. These are items from the spec
- "If property is not a valid CSS property, throw a TypeError" - We need a way here, and it other areas, to determine if a property is a valid css property. This will always be a little off because it's dependent on the UA
- "If property is not a list-valued property, throw a TypeError" - We need a way to determine if a property accepts a list-value. I haven't found a list anywhere yet, and it's an open issue in the draft repo [css-typed-om]Define precisely which properties are list-valued and which aren't, probably in an appendix. w3c/css-houdini-drafts#644
There are more steps that are just work for this, but there will also just be work required that may make this tricky. Mostly in how background-image image is parsed.