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Re: [CSS2.1][CSSOM] "Used Value" and "auto"

From: fantasai <fantasai.lists@inkedblade.net>
Date: Mon, 30 Jul 2012 14:32:07 -0700
Message-ID: <5016FD57.6040904@inkedblade.net>
To: Glenn Adams <glenn@skynav.com>
CC: www-style@w3.org
On 07/12/2012 12:46 PM, Glenn Adams wrote:
>
> This discussion also begs the same question about 'normal' with respect to:
>
> letter-spacing
> line-height
> word-spacing
>
> CSSOM Section 8 already lists line-height as using the 'used value' as the resolved value, but does not list
> {letter,word}-spacing, which, by symmetry, should get the same treatment.
>
> I notice that these last two have different specifications for "computed value" in CSS2.1 [1].
>
> for letter-spacing:
>
>     /Computed value:/ 	'normal' or absolute length
>
> for word-spacing:
>
>     /Computed value:/ 	for 'normal' the value 0; otherwise, the absolute length
>
> I wonder if this is an error, i.e., that letter-spacing should specify the same definition for computed value as for
> word-spacing. Does anyone know if this difference is intentional, and if so, then what is the rationale?
>
> [1] http://www.w3.org/TR/CSS2/text.html#spacing-props

I think the difference is that for 'letter-spacing', 'normal' and '0'
have different meanings when specified: zero means justification is
not allowed to change letter-spacing, whereas normal means it is allowed.

CSS3 Text tracks three different values for each of letter-spacing and
word-spacing, so we can have the "optimum" value compute to zero while
the minimum and maximum values compute to "normal", in order to capture
this difference in behavior.

~fantasai
Received on Monday, 30 July 2012 21:32:36 GMT

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