[csswg-drafts] [css-values-4] `snap a length as a border width`: meaning of "Assert: len is non-negative." (#13795)

romainmenke has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-values-4] `snap a length as a border width`: meaning of "Assert: len is non-negative." ==
see: https://drafts.csswg.org/css-values-4/#snap-a-length-as-a-border-width

> Assert: len is non-negative.

What is the meaning/implication of `Assert` in this context?

Is the value invalid when negative?

Because step 2 explicitly has "do nothing" I am assuming it makes the value invalid, but this seems weird.

If the intention is to do nothing it might be better to write as:

```
1. If len is negative, do nothing.
2. If len is an integer number of device pixels, do nothing.
...
```

@tabatkins 

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13795 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Sunday, 12 April 2026 09:56:22 UTC