I am trying to find a good solution for tagging
poems in xsl-fo. The xsl-fo is then to be
converted into a PDF with XEP/RenderX.

Right now I am having problems avoiding widows
and orphans. It seems (but I am not sure about
that) that when there are empty fo:block tags
(serving as line breaks) within a parent
fo:block, then the widows and/or orphans settings don't apply.

A tagging of a poem might look like this:
<fo:block widows="5" orphans="5" hyphenate="false">
    Er folgte seinem Regiment<fo:block/>
    Ins Land, wo hoch die Palmen stehen,<fo:block/>
    Die Sonne hei_ herniederbrennt<fo:block/>
    Auf Bombays Tempel und Moscheen,<fo:block/>
    Wo tausend Scenen bunt und wild<fo:block/>
    Den Sinn berauschen und umfloren,<fo:block/>
    Allein der fernen Heimat Bild<fo:block/>
    Blieb seiner Seele unverloren.<fo:block/>
</fo:block>

But though widows and orphans are set to 5, my
experience is that sometimes less than 5 lines
are on the beginning or the end of a page.

<fo:block widows="5" orphans="5" hyphenate="false">
    <fo:block>Er folgte seinem Regiment</fo:block>
    <fo:block>Ins Land, wo hoch die Palmen stehen,</fo:block>
    <fo:block>Die Sonne hei_ herniederbrennt</fo:block>
    ... etc ...

would be more "normal" and might even work
better. But that is speculation on my part; I haven't tried it.

If I set keep-together to "always" another
problem comes up. Because if a verse is very
long and doesn't fit entirely on the current
page, the whole verse is shifted to the next
page, leaving a huge amount of white space on the current page.

My questions:
1. Is it true that settings for widows and
orphans are only working when there are no sub-blocks in a block?

1. What does the XSL-FO standard say should happen?
2. What actually happens in the engine you are using?

It is important that these are different because
they bear on what your choices are if things turn
out differently from the way you want.

That being said, however, I don't know the answer
to either question (sorry). I might be able to
determine question 1 by looking it up, but then so could you. :-)

I could also make an educated guess ... which
would go along with trying the code I've offered above ... but why guess?

2. What would be an appropriate tagging for
poems in order to achieve my goal (avoiding
widows and orphans but NOT placing verses that are too big on the next page)

I think that depends on the answers to the above.
First you need to determine whether there is a
correct way to do it that works in your tool. If
there isn't, you will need a workaround.

 * Consult the XSL Recommendation on widows, orphans and blocks
 * Try out your code and variations thereof in a
different engine to help determine any variance
in conformance or interpretation of the FO.

Beyond that, this is the kind of question that an
XSL-FO expert (not necessarily an XSLT expert)
*might* be able to answer off the top of their
head. And there's no harm in asking.

Good luck,
Wendell

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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
17 West Jefferson Street                    Direct Phone: 301/315-9635
Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
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