[csswg-drafts] [css-fonts-4] Clearer rules for syntax error handling within @font-feature-values (#8131)

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

== [css-fonts-4] Clearer rules for syntax error handling within @font-feature-values  ==
For handling syntax errors within `@font-feature-value` the spec has the following:

From https://drafts.csswg.org/css-fonts-4/#font-feature-values-syntax

> A syntax error within a [font feature value declaration](https://drafts.csswg.org/css-fonts-4/#font-feature-value-declaration) makes the declaration invalid and ignored, but does not invalidate the font feature value block it occurs in. An unknown at-rule within a [@font-feature-values](https://drafts.csswg.org/css-fonts-4/#at-ruledef-font-feature-values) block (not using one of the predefined list of allowed at-keywords) makes that at-rule invalid and ignored, but does not invalidate the @font-feature-values rule.

There are two issues:
* Example 62 (ending on "redrum") does not illustrate a syntax error within a font feature value declaration, but inside the font feature value bock.
* Syntax error handling for the font feature block is described only to the extent of handling unknown at-rules. 

There's a mismatch between the example and the spec text. 
To improve that, we can strip or change the example to demonstrate a syntax error within a font feature value declaration, 
or we elaborate on syntax error handling for the font feature value block. 

One possible and IMO implementable option is to say something like:
"While encountering unknown declarations within the font feature value block seek forward until either a closing bracket or an @-keyword-token is found and continue regular parsing for block end or at-rules from there. "




Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/8131 using your GitHub account


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Received on Thursday, 24 November 2022 12:23:22 UTC