Description
Callouts, such as numbered bullets, are an annotation mechanism. In an
online system, these bullets are frequently "hot," and clicking on
them sends you to the corresponding annotation.
A ProgramListingCO is a wrapper around an AreaSpec and
a ProgramListing. An AreaSpec identifies the locations
(coordinates)
in the ProgramListing where the callouts occur.
The ProgramListingCO may also contain the list of annotations in
a CalloutList, although the CalloutList may also
occur outside of the wrapper, elsewhere in the document.
It is also possible to embed CO elements directly in the
verbatim text, in order to avoid having to calculate the
correct coordinates. If you decided to go this route, use a
ProgramListing and a CalloutList without the
ProgramListingCO wrapper. A ProgramListingCO
must specify at least one coordinate.
For a complete description of callouts, see Callout.
Processing expectations
Formatted as a displayed block. This element is displayed "verbatim";
whitespace and linebreaks within this element are significant.
The mandatory processing expectations of a ProgramListingCO are
minimal: a system is expected to render the program listing and the
callout list, if present.
If explicit CO elements are embedded in a
ProgramListing, they must generate appropriate
callout marks.
In online environments, the processing system may be able to instantiate
the linking relationships between the callout marks in the program listing and
the annotations.
Some systems may even be able to go a step further and generate
the callout marks automatically from the coordinate information,
but this level of sophistication is not mandatory.
Parents
These elements contain ProgramListingCO:
Answer, Appendix, Article, BiblioDiv, Bibliography, BlockQuote, Callout, Caption, Caution, Chapter, Colophon, Dedication, entry, Example, Figure, Footnote, Glossary, GlossDef, GlossDiv, Important, Index, IndexDiv, InformalExample, InformalFigure, LegalNotice, ListItem, MsgExplan, MsgText, Note, Para, PartIntro, Preface, Procedure, QandADiv, QandASet, Question, RefSect1, RefSect2, RefSect3, RefSynopsisDiv, Sect1, Sect2, Sect3, Sect4, Sect5, Section, SetIndex, Sidebar, SimpleSect, Step, TextObject, Tip, Warning.
Examples
<!DOCTYPE programlistingco PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
<programlistingco>
<areaspec>
<areaset id="ex.plco.const" coords="">
<area id="ex.plco.c1" coords=4>
<area id="ex.plco.c2" coords=8>
</areaset>
<area id="ex.plco.ret" coords=12>
<area id="ex.plco.dest" coords=12>
</areaspec>
<programlisting>
sub do_nothing_useful {
my($a, $b, $c);
$a = new A;
$a->does_nothing_either();
$b = new B;
$c = "frog";
return ($a, $c);
}
</programlisting>
<calloutlist>
<callout arearefs="ex.plco.const">
<para>
These are calls to the constructor <function>new</function> in the object
classes.
</para>
</callout>
<callout arearefs="ex.plco.ret">
<para>
This function returns a two-element list.
</para>
</callout>
<callout arearefs="ex.plco.dest">
<para>
The <emphasis>destructor</emphasis> (<function>DESTROY</function>) for
the object <literal>$b</literal> will be called automatically for this
object since there can be no other references to it outside this function.
</para>
</callout>
</calloutlist>
</programlistingco>sub do_nothing_useful {
my($a, $b, $c);
$a = new A; 
$a->does_nothing_either();
$b = new B;
$c = "frog";
return ($a, $c); 
}- These are calls to the constructor new in the object
classes.
- This function returns a two-element list.
- The destructor (DESTROY) for
the object $b will be called automatically for this
object since there can be no other references to it outside this function.
