Re: [xsl] Images and XSL FO

Subject: Re: [xsl] Images and XSL FO
From: Paul Grosso <pgrosso@xxxxxxxxxxxxx>
Date: Fri, 19 Jan 2001 09:54:36 -0600
At 13:51 2001 01 19 +0000, Sebastian Rahtz wrote:
>David Tolpin writes:
> > Indeed. Floats (fo:float), floating horizontally are for
> > that. Unfortunately, in most implementations I'm aware of floats
> > either do not float at all, or float in the natural vertical
> > direction.
> > 

I happen to agree that it's unfortunate that XSL FOs use the
term "float" both for horizontal things (that I wouldn't call
floats, but CSS does, and the XSL WG felt constrainted by the
CSS use) and for vertical things (that I would really call floats).
Specifically, it was decided that the same FO, fo:float, would be
used to indicate both things.

>taking that as a challenge (:-}), I looked again at the spec. am I
>right in the following crude view?
> <fo:float float="none">...      stays exactly where it is
> <fo:float float="left">...      sits on the left side of the
>                                paragraph,  and text floats around it
> <fo:float float="right">...     sits on the right side of the
>                                paragraph,  and text floats around it
> <fo:float float="before">...    goes to top of this, or subsequent pages

Yes, you are basically correct.  So when fo:float's float property
is "before", you get what TeX would call a topfloat.

>this appears to exclude floats going to the *bottom* of the page, if I
>understand it right. surely this is unnaturely restrictive??? what if
>the float looked better at the bottom of the page?

Correct.  The theory of floats is complex (anyone familiar with the
details of TeX's inserts and such, as I know Sebastian is, can
appreciate this, and what TeX does with floats is less than half
of the actual complexity), and the XSL WG decided we'd never get
the XSL spec out if we didn't make some simplifying assumptions
in this area (the other alternative was to leave vertical floats
out of XSL 1.0 altogether, and we didn't want to do that).  So we
allowed for top floats only (and footnotes, but via the fo:footnote
FO) in XSL 1.0. 

>its also odd that "<fo:float>" defaults to float="none", and so does
>not float at all.....

The CSS default is none, and we just copied it.  Furthermore, since
the value of the float property could make for either a vertical
float (aka insert) or a horizontal "float" (aka wrap-around text)
which are very different things, it would be hard to have a default
that was useful and intuitive in the majority of cases.  Making the 
default none just means that, when you explicitly insert an fo:float, 
you also have to explicitly set the float property to something.


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