Eliminate PDF doc build margin problem

[mwichmann]

This is an AI analysis of errors reported by Apache fop. The error looks like this (same for margin-right ):

[ERROR] FOUserAgent - Invalid property value encountered in margin-left="": org.apache.fop.fo.expr.PropertyException: file:/home/mats/github/scons/build/doc/user/scons-user.fo:3:6: No conversion defined ; property:'margin-left' (See position 147:8)

Some builds of fop report the error as SEVERE rather than ERROR.

The problem was identified as:

A. When $fop.extensions != 0, the <xsl:value-of> inside <xsl:attribute> elements produces whitespace-padded content that FOP can't parse as valid length values.
B. When $fop.extensions = 0, the <xsl:attribute> elements with empty content produce empty strings.

The solution is to use <xsl:choose> blocks that always produce valid length values:

• When $fop.extensions != 0: use 0pt (simple, valid FOP length)
• When $fop.extensions = 0: use the original dynamic variable values

To summarize the two-part fix across all four scons_title.xsl files:

1. (1 pair per file): Removed the redundant xsl:attribute elements from scons-titlepage-first that conflicted with the literal margin-left="0mm" margin-right="0mm"
2. (11 blocks per file): Replaced the broken content-mode xsl:attribute blocks that produced empty strings or malformed concat() values:

Note: we only build doc/man and doc/user, but the same fixes were applied to the two unused documents for consistency.

Note: three of the files had the old-style copyright header (with unexpanded __COPYRIGHT__ in them), changed to the short one that was already in use in the User Guide copy of the titlepage file.

Signed-off-by: Mats Wichmann mats@linux.com
Assisted-by: OpenCode 1.18.5 driving Qwen 3.8

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt and RELEASE.txt (and read the README.rst).
• I have updated the appropriate documentation