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[css-ui-3] handling unsupported cursor values

From: Florian Rivoal <florian@rivoal.net>
Date: Wed, 17 Jun 2015 14:45:19 +0200
Message-Id: <DB2A75EC-6C11-44A7-A043-4A2418ADC3C9@rivoal.net>
To: www-style list <www-style@w3.org>
I've been writing tests about css-ui-3's cursor, which made me review the spec prose closer than before.

The spec contains this sentence:

  "The UA may treat unsupported values as auto.
   E.g. on platforms that do not have a concept
   of a context-menu cursor, the UA may render
   default or whatever is appropriate."

I think this is bad:

a- as a general error handling mechanism in css, when you don't support a value, you should fail to parse it, so that authors can use the cascade for fallbacks.

b- "whatever is appropriate" is not something the UA can determine in this case. The only thing it know about the author's intent is that they want a context-menu cursor, and possibly which fallbacks they want if this value is not supported. 

c- regardless of whether the platform has a concept of a context menu, my web app may have one. I don't want the browser to second-guess what I want based on OS behavior.

I think we should either simply delete this sentence so that normal error handling applies, or if we want to be explicit (as we've been with outline-color), write this:

  "The UA must reject unsupported values at parse-time."

 - Florian
Received on Wednesday, 17 June 2015 12:45:52 UTC

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