Adjust indents for TOC entries

Determine the amount of space that second- (and third-, etc.) level TOC entries are indented below main entries.

Adjusting TOC indents is one of those thing that’s easy to do once you understand how it works, but understanding it is not exactly straightforward. So let’s untangle it a little bit.
  1. If the __toc__topic__content attribute set is not already in your copy of toc-attr.xsl, copy it from DITA-OT/plugins/org.dita.pdf2/cfg/fo/attrs/.
  2. Note the following attribute:
    <xsl:attribute name="text-indent">-<xsl:value-of select="$toc.text-indent"/></xsl:attribute>

    This attribute is not what you want to use to control indents. It actually shifts the entire TOC to the left or right, depending on the value ...