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Re: Could someone please clarify the spec for alignment-adjust

From: Max Berger <max@berger.name>
Date: Sat, 7 Jul 2007 14:32:34 +0200
Message-Id: <8778F135-5AAC-44D7-91E3-87EC3E1417AC@berger.name>
Cc: www-xsl-fo@w3.org
To: Dave Pawson <dave.pawson@gmail.com>
Dear Dave,

I've received a reasonable explanation from a fop-developer:

> Well my interpretation is as follows: a positive (percentage or  
> length)
> value shifts the alignment point down *on the box*, which raises the
> box. This seems to be consistent.

Which means, the alignment adjust does indeed work the same way as  
baseline-shift and vertical-alignment, it is just written in a non- 
obvious way (double-negative). I've also tried with both FOP and XEP,  
and both exhibit this exact behavior.

>> However, the "graphic" I want to align in this case is a mathematical
>> formula, which does have an "internal textual structure".
>
> Unsure, but I guess the right question to ask is, does your formatter
> understand that 'internal text structure'.
> I.e. is it the font table information that your formatter understands,
> and from which it obtains the baseline?

Not really. So far this is only a cosmetic change.

>> For simplicity. Assume a "graphic" containing text: It does have the
>> baseline somewhere in there. If I would like to specify where the
>> real baseline is, i would find it natural to specify a percent value
>> between 0 and 100 (or a length between 0 and the height of the
>> object) rather than a negative value.
>
> "somewhere in there" isn't enough Max, IMHO.
> If it's a graphic, treat it as a block.
> If its a font entry it should be treated as a character?
>  I don't think you can assume 'somewhere in there' is enough?
> I'm on thin ground here so wait for a more informed opinion.

If its a character, it will most certainly contain a baseline which  
in most cases will lay within the bounds of the character itself  
(there may be exceptions, such as the - )

> regards

thank you for your help!


Max Berger
e-mail: max@berger.name

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Received on Saturday, 7 July 2007 12:32:47 GMT

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