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Questions about <space> compound type

From: Peter B. West <pbwest@powerup.com.au>
Date: Wed, 26 Sep 2001 23:53:35 -0400 (EDT)
Message-ID: <3BB2A2AC.7070200@powerup.com.au>
To: xsl-editors <xsl-editors@w3.org>
CC: fop-dev <fop-dev@xml.apache.org>
The editors,

The following sections contain references to start-space and end-space. 
  I assume that these references should be to space-start and space-end.

5.5.1 Word spacing and Letter spacing Properties
These properties may set values for the start-space and end-space 
traits, as described in the property definitions."

7.16.2 "letter-spacing"
'For an fo:character that in the Unicode database is classified as 
"Alphabetic", unless the treat-as-word-space trait has the value "true", 
the start-space and end-space traits are each set to a value as follows:'

7.16.8 "word-spacing"
'For fo:character whose treat-as-word-space trait has the value "true", 
the start-space and end-space traits are each set to a value as follows:'

The quote from 7.16.2 continues:

'For "normal": .optimum = "the normal spacing for the current font" / 2, 
.maximum = auto, .minimum = auto, .precedence = force, and 
.conditionality = discard. A value of auto for a component implies that 
the limits are User Agent specific.'

That is, it allows the .maximum and .minimum sub-properties of a <space> 
to take on values of "auto".  "Auto" is not mentioned as a valid 
assignment to these properties in wither the general discussion of 
<space> in 5.11, where .maximum, .optimum and .minimum are defined as 
<length>s, nor in the discussions of space-start and space-end in 7.11.1 
& 7.11.2.  Further, in 7.14.1 "block-progression-dimension" and 7.14.5 
"inline-progression-dimension", a value of "auto" is defined to set the 
three <length> sub-properties to "auto".

Am I right in assuming that, where a compound property is one of the 
possible assignments to a property, any specified value imples some 
computed setting of each of the compound components?  That is, that 
there are no circumstances in which a property which may take a compound 
"datatype" will have undefined computed values for the components?

In that case, what are the default values of .precedence and 
.conditionality for 7.16.2 "letter-spacing" and 7.16.8 "word-spacing"? 
7.16.2 and 7.16.8 do not discuss conditionality at all, and only 
indirectly mention precedence.  7.16.2 has:

'If it is desired that the letter space combine with other spaces that 
have less than forcing precedence, then the value of the "letter-space" 
should be specified as a <space> with precedence less than force which 
implies that space combines according to the space resolution rules 
described in [4.3 Spaces and Conditionality].'

However, in the absence of any specific default setting, the other 
indications from the discussion in 5.11 and in sections where the 
default values of precedence are spelled out would indicate a default 
value of 0.  Likewise, the default value for conditionality would seem 
to be "discard".

Yours faithfully,
Peter West
Peter B. West  pbwest@powerup.com.au  http://powerup.com.au/~pbwest
"Lord, to whom shall we go?"
Received on Thursday, 27 September 2001 06:41:15 UTC

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