[mediaqueries] Improve definition of evaluating media features in boolean context

[cdoublev]

If I understand it correctly, the following is equivalent to the feature evaluates to false for any value that is the number 0, a <dimension> with the value 0, the keyword none, or a value explicitly defined by that media feature to evaluate as false in a boolean context, otherwise it evaluates to true.

If the feature would be true for any value other than the number 0, a <dimension> with the value 0, the keyword none, or a value explicitly defined by that media feature to evaluate as false in a boolean context, the media feature evaluates to true. Otherwise, it evaluates to false.

https://drafts.csswg.org/mediaqueries-5/#mq-boolean-context

I find the current wording a bit hard to read, especially to grasp the last condition, which requires to join these two parts with content in between:

• If the feature would be true for any value other than
• a value explicitly defined by that media feature to evaluate as false in a boolean context

[AtkinsSJ]

I'm also finding this difficult to get my head around.

I'd like to request that each media-feature definition gets an explicit explanation of what's true or false in a boolean context. The section in the spec that cdoublev quoted explains the general case, but it's not always true, and it's not clear why.

For example, @media (display-mode) is expected to evaluate to true (wpt). But @media (dynamic-range) evaluates to false (wpt). I can't see what's different about these two that that would make one true and the other false.

[AtkinsSJ]

After some discussion, I've concluded:

1. I misunderstood the spec completely before. (Please make it clearer! 😅)
2. The spec roughly means "True unless it's a falsey value like 0 or a defined false keyword.", like cdoublev says.
3. The dynamic-range test is wrong, and based on emilio misunderstanding the spec in the same way I did when updating it here @media (dynamic-range) should actually always evaluate to true.