Re: [csswg-drafts] [mediaqueries] Non-positive value should be invalid for 'resolution' feature

The CSS Working Group just discussed `Non-positive value should be invalid for 'resolution' feature`, and agreed to the following resolutions:

* `RESOLVED: Spec should say resolution used to disallow negative numbers. It makes sense to allow negative with the boolean logic with some exmaples and that's for all MQ with a numberic value.`

<details><summary>The full IRC log of that discussion</summary>
&lt;dael> Topic:  Non-positive value should be invalid for 'resolution' feature<br>
&lt;dael> github topic: https://github.com/w3c/csswg-drafts/issues/1454<br>
&lt;dael> Florian: We found this about resolution, but it's more than that. There are a number of media features that take a range and for which negative value makes no sense. Resolution of -300 dpi makes no sense.<br>
&lt;dael> Florian: Old MQ it didn't really matter if we declared this as invalud don't parse or value evaluates to false. The difference it makes is in the OM. This has changed a bit in MQ4 because we have unknown values.<br>
&lt;dael> Florian: If we say it parses and is false there width -300 is false NOT width -300 is true.<br>
&lt;dael> Florian: I think it would be more useful to parse it and say it evaluates to false. If it doesn't parse we don't know if it is -300 or not.<br>
&lt;dael> Florian: We have, from the OM Po we have interop on the opposite. But the boolean logic isn't impl anywhere yet so it's not observable.<br>
&lt;dael> Florian: I don't feel like breaking the interop is a major issue, but maybe I'm wrong. What do you all think?<br>
&lt;dael> dino: I thinkw e should do as you said and break the interop.<br>
&lt;dael> Florian: If they're relying on media resolution -300dpi this will be fine. What this would break is very uncommon.<br>
&lt;dael> dbaron: Does the effect of the change...is it different on if the browser impl the unknown thing?<br>
&lt;dael> Florian: Yes. It's part of impl the logic for nested and/or/not. If you don't have that then it's undefined what this does, I guess.<br>
&lt;dael> dbaron: Maybe the spec should have a note saying that the previous version forbade negative values and that shouldn't be removed until you impl this stuff.<br>
&lt;dael> Florian: That's fair<br>
&lt;dael> astearns: Prop: have the spec say you should parrse - values if you implement this boolean stuff. Obj?<br>
&lt;dael> Florian: This is all media features with a range. width, heigth, aspect ratio, color I suppose.<br>
&lt;dael> astearns: Spec should say resolution used to disallow - numbers. It makes sense to allow - witht he boolean logic with some exmaples and that's for all MQ with a numberic value.<br>
&lt;dael> dbaron: There should be a note that it's a change and we're looking for feedback.<br>
&lt;dael> Florian: Fair.<br>
&lt;dbaron> s/change and we're looking for feedback/change from the previous version and we're looking for compat feedback/<br>
&lt;AmeliaBR> [Tangent] A reminder that this and many aspects of CSS parsing would have been easier define if there were CSS Values data types specifically for non-negative or strictly-positive values (https://github.com/w3c/csswg-drafts/issues/355).<br>
&lt;dael> RESOLVED: Spec should say resolution used to disallow negative numbers. It makes sense to allow negative with the boolean logic with some exmaples and that's for all MQ with a numberic value.<br>
</details>


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Received on Wednesday, 7 June 2017 23:52:52 UTC