XFA Specification
Chapter 7, Layout for Growable Objects
Flowing Layout for Containers
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Warning: Invalid Leader/Trailer Target
If a leader or trailer target is not valid (for example if it does not exist or is not an appropriate object), the
layout processor issues a warning message and continues processing without laying down the leader or
trailer.
Inheritance of Overflow Leaders and Trailers
When a subform does not specify an overflow leader or trailer, it inherits the overflow leader or trailer
specified by its containing subform. Along with the leader or trailer subform (or list of subforms) it inherits
the count(s) of maximum occurrences. In other words, the inherited leaders and trailers that are laid down
by the child subform count towards the maximum occurrence limits for the parent subform. On the other
hand, when a subform asserts a leader or trailer of its own, it acquires its own set of occurrence counts.
Even if the same leader or trailer subform is used by some other subform, the occurrence count(s) start at
zero for each asserting subform.
For example, a template includes the following declarations:
<template>
<subform "W" …>
<pageSet …>
<pageArea …>
<contentArea name="A" … />
<contentArea name="B" … />
<contentArea name="C" … />
<contentArea name="D" … />
</pageArea>
</pageSet>
<subform name="E" layout="tb" …>
<breakBefore
targetType="contentArea"
target="A"/>
<overflow trailer="#X_ID"/>
<field name="F" … > … </field>
<subform name="G" layout="tb" …>
<overflow trailer="#X_ID"/>
<field name="H" … > … </field>
</subform>
<field name="I" …> … </field>
</subform>
</subform>
<proto>
<subform name="X" ID="X_ID" …>
<occur max="1"/>
…
</subform>
</proto>
</template>