Processing only works on chapter level

[stefan-jung]

This only works on <chapter> level. This might be insufficient, e.g. in multilanguage deliverables.

English <!-- Chapter level -->
  Chapter 1 <!-- Topic level -->
  Chapter 2 <!-- Topic level -->
  Chapter 3 <!-- Topic level -->
German <!-- Chapter level -->
  Chapter 1 <!-- Topic level -->
  Chapter 2 <!-- Topic level -->
  Chapter 3 <!-- Topic level -->

When trying to apply this on <topic> level, I get the following error:

org.apache.fop.apps.FOPException: net.sf.saxon.trans.XPathException: org.apache.fop.fo.ValidationException:
"fo:page-sequence" is not a valid child of "fo:block"! (See position 12:2606)
net.sf.saxon.trans.XPathException: org.apache.fop.fo.ValidationException: "fo:page-sequence" is not a valid child of 
"fo:block"! (See position 12:2606)

To trigger this, you can avoid triggering processTopicChapterInsideFlow by replacing

<xsl:apply-templates select="." mode="processTopicChapterInsideFlow"/>

with

<fo:page-sequence
	master-reference="{if (@outputclass) then (concat(@outputclass, '-sequence')) else 'body-sequence'}"
	xsl:use-attribute-sets="page-sequence.body">
	<xsl:call-template name="startPageNumbering"/>
	<xsl:call-template name="insertBodyStaticContents"/>
	<fo:flow flow-name="xsl-region-body">
		<fo:block xsl:use-attribute-sets="topic">
			<xsl:call-template name="commonattributes"/>
			<xsl:variable name="level" as="xs:integer">
				<xsl:apply-templates select="." mode="get-topic-level"/>
			</xsl:variable>
			<xsl:if test="$level eq 1">
				<fo:marker marker-class-name="current-topic-number">
					<xsl:variable name="topicref" select="key('map-id', ancestor-or-self::*[contains(@class, ' topic/topic ')][1]/@id)"/>
					<xsl:for-each select="$topicref">
						<xsl:apply-templates select="." mode="topicTitleNumber"/>
					</xsl:for-each>
				</fo:marker>
				<xsl:apply-templates select="." mode="insertTopicHeaderMarker"/>
			</xsl:if>
			
			<xsl:apply-templates select="*[contains(@class,' topic/prolog ')]"/>
			
			<xsl:apply-templates select="." mode="insertChapterFirstpageStaticContent">
				<xsl:with-param name="type" select="'chapter'"/>
			</xsl:apply-templates>
			
			<fo:block xsl:use-attribute-sets="topic.title">
				<xsl:call-template name="pullPrologIndexTerms"/>
				<xsl:for-each select="*[contains(@class,' topic/title ')]">
					<xsl:apply-templates select="." mode="getTitle"/>
				</xsl:for-each>
			</fo:block>
			
			<xsl:choose>
				<xsl:when test="$chapterLayout='BASIC'">
					<xsl:apply-templates select="*[not(contains(@class, ' topic/topic ') or contains(@class, ' topic/title ') or
						contains(@class, ' topic/prolog '))]"/>
				</xsl:when>
				<xsl:otherwise>
					<xsl:apply-templates select="." mode="createMiniToc"/>
				</xsl:otherwise>
			</xsl:choose>
			
			<xsl:apply-templates select="*[contains(@class,' topic/topic ')]"/>
			<xsl:call-template name="pullPrologIndexTerms.end-range"/>
		</fo:block>
	</fo:flow>
</fo:page-sequence>

[raducoravu]

Thanks @xephon2 we are not interested that much in XSL-FO based customizations any more having invested in CSS based PDF publishing which makes it very easy to change the layout on any DITA element.
But I will leave this issue opened, maybe others are interested in your fix details. Or you can open a pull request.