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From Jeremias Maerki <...@jeremias-maerki.ch>
Subject Re: letter-spacing
Date Wed, 01 Mar 2006 16:11:05 GMT

On 01.03.2006 16:44:39 Luca Furini wrote:
> Jeremias Maerki wrote:
> 
> > > The recommendation states that "The algorithm for resolving the adjusted 
> > > values between word spacing and letter spacing is User Agent dependent." 
> > > (7.17.2 in the candidate recommendation), so I think this is not a wrong 
> > > behaviour: it just assumes that word spaces have a higher precedence than 
> > > letter spaces.
> > 
> > No, actually in both cases the precedence is "force" so all spaces
> > survive the resolution process.
> 
> So, just to check I understood:
> 
> - according to the pdf specifications between two words there is
>    1 word space + 2 letter spaces

1 ls + 1 ws + 1 ls, yes.

> - according to the xsl recommendation there is
>    1 word space + 1 letter space (or better, two half letter spaces)

yes, more or less. Even the word space is separated into two halves.

> - fop currently puts just a word space

yes

> Is this correct?
> 
> But I still don't understand what the words concerning "adjusted values 
> between word spacing and letter spacing" are supposed to mean ...

I've been wondering about that, too. The user agent has some freedom
about choosing default letter and word spacing. The letter- and
word-spacing properties specify spaces in addition to the default spaces.
Maybe this applies to the default spacing. If you just take the space
traits generated by the spacing properties, then it's clear that the
normal space-resolution rules apply. Hmm.

> > However, while I was out for a few hours I was thinking about this and I 
> > came to the conclusion that it may make sense to keep an array of 
> > character offsets as an attribute of a WordArea in the area tree.
> 
> It would probably be the best way to deal with kerning too.

That's one of my next topics. It's actually another reason why I thought
about this. Just forgot to list it.

> My only concern is about the resulting pdf size: if we specify an offset 
> for each character, wouldn't it become (at least) twice as big as before?

I don't think it gets twice as big, but yes, we could not use the more
space-efficient commands anymore in that case. But it's only plain text
which is easily compressed with the Flate algorithm.

Jeremias Maerki


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