[css-forms-1] The slider-orientation property might be missing a few things

[mfreed7]

I like that there's a slider-orientation proposal. (See #9832.) Some comments:

The spec draft says that auto is "defined by the writing mode and direction" but that needs more detail, and should hopefully be interoperable. It sounds straightforward, but interesting questions arise. E.g. should a slider that is slider-orientation:auto have "more" oriented toward the top or bottom, when writing-mode: vertical-lr? We spent some time looking into this a few years ago because it's not clear that "more" should be "down" just because text flows down. E.g. many folks expect "up" to always be "more". It's a quite-bad interop problem when sliders go different directions on different browsers.

Also, this is kind of implied by the text, but should be explicit: the slider-orientation property should "win" over writing-mode, direction, and even the orient=vertical attribute (though non-standard).

It might also be helpful to define what "more" means for things like <input type=checkbox switch>. It feels like "on" is "more", but that should be explicit.

Should there also be values of this property that are logical, e.g. slider-orientation: start-to-end or slider-orientation: block-start-to-block-end, etc.?