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[CSS3-color] Errata

From: Anton Prowse <prowse@moonhenge.net>
Date: Sun, 03 Jul 2011 12:09:10 +0200
Message-ID: <4E103FC6.4040805@moonhenge.net>
To: "www-style@w3.org" <www-style@w3.org>
Congratulations on getting CSS Color 3 to Rec!  I have a couple of 
comments which perhaps could be addressed as errata where appropriate.


Comment 1

   # 1. Introduction

   # The specification is the result of the merging of relevant parts of
   # the following Recommendations and Working Drafts, and the addition
   # of some new features.
   #
   #     * HTML 4.01 [HTML401]
   #     * CSS 2.0 [CSS2]
   #     * SVG 1.0 [SVG10]
   #     * User Interface for CSS3 (16 February 2000) [CSS3UI]

This section references CSS2 rather than CSS21, yet CSS21 is what's 
actually cited throughout the spec.  (CSS2 is listed as an informative 
reference.)  As a result, I found this section confusing.  I think it's 
trying to explain the origins of the spec, but I would find it clearer 
if there were a note at the end of the sentence explaining which 
versions of the listed specs are subsequently cited as normative 
references in the current spec.


Comment 2

   # 3.2. Transparency: the ‘opacity’ property

   # <alphavalue>
   #     Syntactically a <number>. The uniform opacity setting to be
   #     applied across an entire object. Any values outside the range
   #     0.0 (fully transparent) to 1.0 (fully opaque) will be clamped
   #     to this range. If the object is a container element, then the
   #     effect is as if the contents of the container element were
   #     blended against the current background using a mask where the
   #     value of each pixel of the mask is <alphavalue>.

"Container element" appears to be SVG terminology.  What does it mean in 
the context of CSS?


Comment 3

   # 3.2. Transparency: the ‘opacity’ property

   # If an element with opacity less than 1 is not positioned,
   # implementations must paint the layer it creates, within its parent
   # stacking context, at the same stacking order that would be used if
   # it were a positioned element with ‘z-index: 0’ and ‘opacity: 1’. If
   # an element with opacity less than 1 is positioned, the ‘z-index’
   # property applies as described in [CSS21], except that ‘auto’ is
   # treated as ‘0’ since a new stacking context is always created.

It's not clear what "treated" means in the phrase "‘auto’ is treated as 
‘0’"; is the computed value of 'z-index' affected here?

Assuming that "treated" is just sloppy language, then under the new 
terminology established for CSS21, the above sentences could be replaced 
by something more succinct:

   | If an element with opacity less than 1 is not positioned
   | then it is painted on the same layer, within its parent stacking
   | context, as positioned elements with stack level 0. Otherwise, its
   | stack level is determined according to its 'z-index' property as
   | described in [CSS21].

(The second sentence might well be regarded as superfluous.)


Cheers,
Anton Prowse
http://dev.moonhenge.net
Received on Sunday, 3 July 2011 10:10:10 GMT

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