NAME

       XML::Filter::Reindent - Reformats whitespace for pretty printing XML

SYNOPSIS

        use XML::Handler::Composer;
        use XML::Filter::Reindent;

        my $composer = new XML::Handler::Composer (%OPTIONS);
        my $indent = new XML::Filter::Reindent (Handler => $composer, %OPTIONS);

DESCRIPTION

       XML::Filter::Reindent is a sub class of XML::Filter::DetectWS.

       XML::Filter::Reindent can be used as a PerlSAX filter to reformat an XML document before
       sending it to a PerlSAX handler that prints it (like XML::Handler::Composer.)

       Like XML::Filter::DetectWS, it detects ignorable whitespace and blocks of whitespace
       characters in certain places. It uses this information and information supplied by the
       user to determine where whitespace may be modified, deleted or inserted.  Based on the
       indent settings, it then modifies, inserts and deletes characters and ignorable_whitespace
       events accordingly.

       This is just a first stab at the implementation.  It may be buggy and may change
       completely!

Constructor Options

       •   Handler

           The PerlSAX handler (or filter) that will receive the PerlSAX events from this filter.

       •   Tab (Default: one space)

           The number of spaces per indent level for elements etc. in document content.

       •   Newline (Default: "\x0A")

           The newline to use when re-indenting.  The default is the internal newline used by
           XML::Parser, XML::DOM etc., and should be fine when used in combination with
           XML::Handler::Composer.

$self->indent_children ($start_element_event)

       This method determines whether children of a certain element may be reformatted.  The
       default implementation checks the PreserveWS parameter of the specified start_element
       event and returns 0 if it is set or MAYBE otherwise.  The value MAYBE (2) indicates that
       further investigation is needed, e.g.  by examining the element contents. A value of 1
       means yes, indent the child nodes, no further investigation is needed.

       NOTE: the PreserveWS parameter is set by the parent class, XML::Filter::DetectWS, when the
       element or one of its ancestors has the attribute xml:space="preserve".

       Override this method to tweak the behavior of this class.

$self->indent_element ($start_element_event, $parent_says_indent)

       This method determines whether a certain element may be re-indented.  The default
       implementation returns the value of the $parent_says_indent parameter, which was set to
       the value returned by indent_children for the parent element. In other words, the element
       will be re-indented if the parent element allows it.

       Override this method to tweak the behavior of this class.  I'm not sure how useful this
       hook is. Please provide feedback!

Current Implementation

       The current implementation puts all incoming Perl SAX events in a queue for further
       processing. When determining which nodes should be re-indented, it sometimes needs
       information from previous events, hence the use of the queue.

       The parameter (Compress => 1) is added to matching start_element and end_element events
       with no events in between This indicates to an XML printer that a compressed notation can
       be used, e.g <foo/>.

       If an element allows reformatting of its contents (xml:space="preserve" was not active and
       indent_children returned MAYBE), the element contents will be reformatted unless it only
       has one child node and that child is a regular text node (characters event.)  In that
       case, the element will be printed as <foo>text contents</foo>.

       If you want element nodes with just one text child to be reindented as well, simply
       override indent_children to return 1 instead of MAYBE (2.)

       This behavior may be changed or extended in the future.

CAVEATS

       This code is highly experimental!  It has not been tested well and the API may change.

       The code that detects blocks of whitespace at potential indent positions may need some
       work.

AUTHOR

       Original Author is Enno Derksen.

       Send bug reports, hints, tips, suggestions to T.J. Mather at <tjmather@tjmather.com>.