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Re: [css3-colors] Comments on Last Call

From: Tantek «elik <tantek@cs.stanford.edu>
Date: Mon, 14 Apr 2003 10:22:41 -0700
To: Christoph Pšper <christoph@paeper.de>, <www-style@w3.org>
Message-ID: <BAC03C6B.2606B%tantek@cs.stanford.edu>

Hi Christoph,

Thanks for your feedback.  I would like to respond to a few of your
questions/points.

On 2/16/03 4:57 AM, "Christoph Pšper" <christoph.paeper@tu-clausthal.de>
wrote:

> 
> ∑ <alphavalue>, rgba, hsla etc.
> 
> I don't understand, why alpha values are noted as a number between 0 and 1,
> while for colors percentages are used. They're pretty much the same, except
> percentages are 100 times the value and sufficed by '%'.
> HSL is the strangest: RGB allows you to decide, whether you use values
> between 0 and 255 or percentages. HSL OTOH requires a mixture of these.
> HSLA, as RGBA, even adds 0..1 for the alpha value--three different notations
> in one color definition.

<alpha> values were introduced as values between 0 and 1 in the SVG 1.0
specification.  CSS3 Color continues with that convention.  Similarly, the
rgb() color value format which takes percentages or integers 0..255 was
introduced in CSS1 and CSS3 Color continues with that as well.  HSL was
chosen to be consistent with the proposal made by Steven Pemberton.


> 3.1. Foreground color: the 'color' property
> 
> | The computed value for HTML4 keywords, RGB hex values
> | and SVG color keywords is the equivalent six digit hex value.
> | The computed value of the keyword 'transparent' is rgba(0,0,0,0).
> 
> Am I the only one to whom this looks a bit strange (always hex, but for
> 'transparent')? Not that there was an alternative, except introducing 4 and
> 8 digit hex values with transparency.

Actually, "equivalent six digit hex value" could be represented as an rgb()
value internally as well.  CSS3 Color does not require a particular internal
representation.  To clarify this, I have changed the wording in the text to
say "equivalent triplet of numerical RGB values".


> 3.4. The 'rendering-intent' property
> 
> Hm, all the other baby-blue tables have more details than just the property
> name.

I have double checked the property description table for 'rendering-intent'
and it seems to show the values, initial value, media etc. just like the
other properties.  Perhaps a problem with the W3C working draft style sheet
and your browser?


> 4.1. HTML4 color keywords
> 
> The table should look like the one in 4.3.

The table was taken from HTML4.01:
 
 http://www.w3.org/TR/html401/types.html#h-6.5

and kept that way to make it clear that it was the same table.


> 4.2.4. HSL color values
> 
> | By definition red=0=360, and the other colors are
> | spread around the circle, so green=120, glue=240,
> 
> :-D
> 
> I've never heard of the ABC programming language before, as may others, and
> would prefer to see the algorithms expressed in English, although ABC is
> somehow close to that.

Since it sounds like ABC is acceptable to you, I prefer leaving it like
that, since it is precisely defined as currently written, and I have
received feedback from implementers that confirms that.


> 4.2.4.1. HSL Examples
> 
> I haven't checked why, but the color charts are all placed next to each
> other horizontally in my Opera 6.05.

That is a bug in Opera 6.05. According to CSS1 (and latter versions) floats
don't fit horizontally next to other floats inside their containing block
are supposed to be placed below (essentially, wrapped to the next "line")
where they will fit.  I believe this may be fixed in a newer versions.


> 4.3. SVG color keywords
> 
> Just wanted to express my objection against the /official/ inclusion of the
> mad X11 color names, again. I'd have rather seen CNS or the suggestion from
> <http://lists.w3.org/Archives/Public/www-style/2002May/0201.html>, which are
> more user friendly and memorable.
>
> Please adjust the case in the table header cells and use uppercase
> hexadecimal digits.


The /official/ inclusion of the X11 color names occurred quite some time ago
in the SVG 1.0 specification which is a W3C Recommendation, and was
reiterated in the SVG 1.1 specification which is also a W3C Recommendation.

 http://www.w3.org/TR/2001/REC-SVG-20010904/
 http://www.w3.org/TR/2003/REC-SVG11-20030114/

I have adjusted the case in the table header cells and hexadecimal digits as
you suggested.



> 4.4. 'currentColor' color keyword
> 
> Nothing against it, but camelCase isn't something CSS used to use, is it?
> System colors use it, but with the starting letter being capital =>
> 'CurrentColor'.

Values in CSS are case-insensitive, thus you may use any of the following:
 currentColor
 CurrentColor
 currentcolor

The particular capitalization 'currentColor' is used in the spec simply
because that is the same capitalization that is used for that value in the
SVG specifications.



> 4.5. CSS System Colors
> 
> If I have
>   body {background: AppWorkspace;}
> and the browser has a wallpaper for the MDI background (e.g. Opera allows
> that), should/may this image be shown as page background or definitely just
> the color?
> This is of course a bit out of scope of the Color Module.

The wallpaper should probably not be shown because that would be a system
background-image, rather than a system background-color.

However, you have revealed the problem with the system colors, and that is
that they are an extreme oversimplification of the problem of default system
appearance.  Even with "loosely" interpretation allowing a named "color" to
represent a fill or a pattern, there are many aspects of the user interface
which a simple color value is unable to represent.

Thus we are deprecating the system colors in preference to the upcoming CSS3
Basic UI appearance property.


> 5. Sample style sheet for HTML 4.0
> 
> Why "HTML 4.0" and not "XHTML 1", "XHTML 1.1", "XHTML 1.0", "HTML 4.01" or
> "HTML 4"? Well, for XHTML the first selector should presumably read "html,
> body".
> More generally: Why is HTML4 used as normative source, e.g. for color names,
> instead of XHTML1?

In reverse order - you are right, HTML4 should NOT be used as a normative
source, e.g. for color names, as this specification itself serves to define
the color names and values.

XHTML1 cannot be used as a normative source for color names because it has
no definition of color names.  XHTML1 itself actually has very little
defined meaning, and instead relies upon HTML4 for (nearly) all of its
semantics.

I have updated the sample style sheet to note that it can be used for XHTML
as well as you suggested.



> Christoph Pšper
> 
> --
> <http://webdesign.crissov.de/Farbsysteme/Ben>
> <http://webdesign.crissov.de/Farbsysteme/CNS>


Thanks for all your suggestions - the specification has certainly benefited
from your feedback.


Tantek (co-editor of the CSS3 Color module).
Received on Monday, 14 April 2003 13:21:19 GMT

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