Re: [csswg-drafts] [css-values-4] Add vhc value (#4329)

I was talking in slack with someone, and they proposed an alternative idea.

What if the behavior of `vh` could be determined in a dynamic way, similar to `box-sizing`? For example

```css
.container {
  vh-sizing: collapsed-viewport-height;
  height: 100vh;
}
```

with `vh-sizing` options potentially being something like
* `collapsed-viewport-height` (the current behavior of `vh`)
* `expanded-viewport-height` (the desired behavior of a `vhc` unit)
* `exact-viewport-height` (a unit that would always match the viewport exactly, even with keyboards or other UA chrome)

(all of these are just placeholder names)

With this pattern, the developer has options for all three use cases as noted by @AmeliaBR [here](https://github.com/w3c/csswg-drafts/issues/4329#issuecomment-542427198), while also still being able to use `vh` in a backwards-compatible way with "progressive" enhancement (probably not the right word for it but I hope the idea comes across). 

I thought it was a novel enough idea, and the backwards and forwards compatibility aspect of it made it interesting enough for me to add here for feedback as well.

-- 
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Received on Thursday, 17 October 2019 20:17:28 UTC