=head1	NAME

OpenOffice::OODoc::XPath - Low-level navigation in the documents

=head1	DESCRIPTION

This module is a low-level class which uses OODoc::File (without
inheriting anything from it) along with the classes defined in the
XML::Twig module. It's a common basis for the other, more user-
friendly, document-oriented modules. It uses XPath expressions in
order to retrieve any document element (but it doesn't provide a
full implementation of the XPath standard). In addition, while the
most part of the provided methods are OpenDocument-aware, this module
could be used against any other kind of XML documents, simply because
it benefits from all the features of XML::Twig. Such a possibility
may prove useful for applications that simultaneously process OpenDocument
and non-OpenDocument XML files.

The OpenOffice::OODoc::XPath class should not be explicitly used in the
applications, because all its features are available in more user-friendly
classes such as OODoc::Text, OODoc::Styles, OODoc::Image, OODoc::Document
and OODoc::Meta. The present manual page is provided to describe the
common methods and properties that are available with all these classes.

This chapter can be skipped by programmers who are only interested
in upper level methods provided by the OODoc::Text, ::Styles, ::Image and
::Meta modules. Understanding these modules is easier and using them
requires less Perl and XML expertise. However, calling OODoc::XPath methods
remains a good rescue option as it allows all kinds of operations on all types
of XML elements contained in any OpenDocument-compliant file.

OODoc::XPath is the common foundation of OODoc::Meta, OODoc::Text,
OODoc::Styles and OODoc::Image. It contains the lowest layer of
navigation services for XML documents and handles the link with
OODoc::File for file access. Its primary role is as an interface
with the XML::Twig API.

In the present manual chapter, you will see "elements" often mentioned.
When it says that a module expects a parameter or returns an element
(either singly or as a list), it is referring to an XML element.
It is important to distinguish elements from their content
(elements being simply references to XML data structures). To read
or modify the content of an element such as its text or XML
attributes, use the accessors also available within OODoc::XPath.

In most cases where XPath methods require a reference to an element
as an argument, there are two ways of proceeding:

- reference the element directly (obtained previously)

- or give an XPath expression and a position, being a string and an
integer respectively; for example, the pair ('//office:body/text:p', 12)
or ('//text:p', 12) represents the thirteenth occurrence of the 'text:p'
element, i.e. the 13th paragraph (occurrences are numbered starting from 0).

The second way requires the knowledge of an appropriate XPath
expression (according the OpenDocument XML format specification).
And a given XPath expression is not necessarily the same with an
OpenDocument as in an OpenOffice.org document. So you should
preferently use high level accessors (provided by derivative classes
such as OODoc::Document) and avoid XPath hardcoding. However, you
know you can at any time reach any element with XPath.

Of course, you will never need to use XPath expressions in order to
reach the most common text elements (such as paragraphs), because the
OODoc::Text module provides more friendly accessors (for example, you
will probably use the getParagraph() method and forget "//text:p").

Some methods accept both forms which means that if the first
parameter is recognised as an element reference, the position does
not need to be given. Therefore the number of arguments for certain
OODoc::XPath methods can vary.

For those who really want to access all areas there are also
OODoc::XPath methods which allow unrestricted access to every
element or XML attribute via an access path in XPath syntax. If you
are into this kind of thing, we recommend you obtain good syntax
reference manuals for XPath and OpenDocument and a supply of
aspirin.

Methods which may return several lines of text (e.g. getTextList) do
so either in the form of an unique character string containing "\n"
separators or in table form.

Unless otherwise stated, the word 'document' in this chapter only
refers to XML documents contained within OODoc::XPath objects and
not, say, OpenDocument files (as an end user would use).

Amongst the different methods which return elements, attributes or
text, some are called getXxx, others selectXxx or findXxx. Read
methods whose names start with "get" generally refer to an
unfiltered object or list, whereas others return an object or list
filtered according to a parameter value. In this latter case the
search parameter is treated as a standard expression and not an
exact value. This means that if the search criteria is "xyz", all
text containing "xyz" will be considered a match. To restrict the
search to text exactly equal to "xyz", use "^xyz$" as the search
criteria (following Perl regular expression syntax).

Several methods allow you to place copies of or references to
elements (from other documents or from other positions in the same
document) in any position in the current document. This offers
powerful manoeuvrability but only if these placements conform with
the destination position's context.

For example, you can easily copy a paragraph from one document
to another but only if you knowingly modify the paragraph's style
attribute if that style is not already defined in the destination
document. You can also copy the style but only if you are sure that
this style is not already defined by another unknown style in the
destination document (and so on).

For advanced users familiar with the XML::Twig API, it might be
interesting to know that all the objects called "elements" in the
following chapters are objects of the OpenOffice::OODoc::Element
class, which is an XML::Twig::Elt derivative. So all methods associated
with this class are directly applicable to these elements, on top of the
functionality described in this manual. However, the knowledge of XML::Twig
is not mandatory.

Important note: The applications should not explicitly work with this
class. We recommend using OODoc::Meta and OODoc::Document (which are both
OODoc::XPath derivatives). These two objects provide highest-level methods
which are neater and more productive. Explicit use of OODoc::XPath methods
(which sometimes require large numbers of parameters) should only be
considered as a last resort in unexpected circumstances for access to any
element or XML attribute not handled by more friendly methods. However,
the present manual chapter could prove helpful because all the common
features of OODoc::Meta and OODoc::Document are described here.

=head2	Methods

=head3	Constructor : OpenOffice::OODoc::XPath->new(<parameters>);

        Short Form: odfXPath(<parameters>)

	Returns a new OpenDocument connector, i.e. an interface which
	can be used for subsequent operations on a well-formed document.
	
	This constructor should not be called directly; it's implicitly
	triggered each time a Meta or Document object is created. So the
	following description apply to odfMeta() and odfDocument().

	The document is loaded and parsed according to various options.
	The most used option is 'file'; it simply allows the application
	to process an OpenDocument file selected by its path/name in the
	file system.
	
	Example:

		my $doc = odfXPath
				(
				file	=> "myfile.ods",
				part	=> "content"
				);
		# ... lot of processing ...
		$doc->save;

        Returns a new document connector. In the example above, the object
	is loaded from a regular OpenDocument file, that is the most current
	option, but there are other possibilities. It's possible to use
	flat XML (available as a string in memory, or loaded from a file).
	In addition, this constructor is able to create a new document
	from scratch.

        The value of the 'file' option may be an open IO::File object,
        that allows the application to use an application-provided file
        handle. However, you should prefer file paths/names when possible,
        and read the explanations about the constructor and the save() method
        in the OpenOffice::OODoc::File manual page before using open file
        handles. Remember that, as soon as the given file or handle is
        an ODF container, OODoc::XPath uses OODoc::File.

        Parameters are named (hash key => value). The constructor must get
        at least one parameter giving a means of obtaining the XML document
        that it will represent. Several options are available; each one is
	represented through the following examples:

	    # option 1 (using an existing flat XML document)
            my $doc = odfXPath(xml => $xml_string);

	    # option 2 (using a previously created ODF file interface)
	    my $oofile = odfContainer('source.odt');
            my $doc = odfXPath(container => $oofile, part => 'meta');

	    # option 3 (using a regular ODF file directly)
            my $doc = odfXPath(file => 'source.odt', part => 'content');
	
	    # option 4 (multiple instances against a single file)
	    my $content = odfXPath(file => 'source.odt', part => 'content');
	    my $meta = odfXPath(file => $content, part => 'meta');
	    my $styles = odfXPath(file => $content, part => 'styles');

	Remember "odfXPath()" represents "OpenOffice::OODoc::XPath->new()" 
	in the instructions above, and you can (and should) use this shortcut
	provided that you have loaded the main OpenOffice::OODoc module, and
	not only and explicitly the OpenOffice::OODoc::XPath module.

        The first form uses an XML string directly (previously loaded or
        created by the program). To be used for very specific applications
	working with flat XML documents exports and not with standard
	OOo/OpenDocument files.

        The second method links OODoc::XPath to an existing OODoc::File
        object (through the "container" option) and indicates which XML part it
	is to extract (metadata, content, styles, etc). The OODoc::File is an
	abstraction of an already open ODF container. It can be shared, i.e.
	several OODoc::XPath objects can be instantiated with the same
	OODoc::File object, and this possibility must be used when
	several OODoc::XPath objects have to bring consistent changes in
	a single file (see option 4 below). In order to create the
	required OODoc::File object, simply use odfFile() with a filename
	as argument (for advanced use, see OpenOffice::OODoc::File).

	The third method is the easiest, because the user just provide
	a filename and a member, and all the file interface is run silently
	(i.e. an invisible OODoc::File object is automatically created and
	used to get the content). It's probably the most used approach; its
	recommended when the user doesn't need to get more than one member
	in the same file.

	The 'part' option is a selector that tells what component is needed
	(content, styles, metadata, ...) knowing that an OODoc::XPath object
	can handle only one component. Its default value is 'content'.

	Note that the 'part' option replaces the deprecated 'member' option.
	However, for compatibility reasons, 'member' is supported yet (if
	both 'member' and 'part' are erroneously provided, 'member' prevails).
	
	If the application needs to process, say, the content and the styles
	in the same session, it must create two, or more, OODoc::XPath objects
	possibly associated with the same file interface. The appropriate way
	is shown in our last example above. The first instance is associated
	with a filename. Then the other instances are created with the first
	one, provided as the value of the 'file' option instead of a filename.
	The constructor tries to be user-friendly: if the 'file' value is
	a character string, it's regarded as a filename, but if this value,
	is an existing OpenOffice::OODoc::XPath object, the new object is
	automatically connected to the same file interface as the other one.
	The file interface is transparently provided by a common shared
	OpenOffice::OODoc::File object (you can safely ignore the features
	of this object, but a corresponding manual chapter is available for
	more details).
	
	Be careful: creating more than one OpenOffice::OODoc::XPath objects
	linked by their 'file' parameters to the same explicit filename (and
	not linked with each other) produces useless extra I/O operations and
	possible conflicts.
 
	Caution: being associated with a common interface via OODoc::File,
	none of these OODoc::XPath objects should be deleted before the final
	save() call for this archive. So by calling a save, the File object
	"calls up" all the XPath objects which were "connected" to it in order
	to "ask" each of them for the changes which were made to the XML
        (content, styles, meta, etc.). The results are unpredictable if any
        of them is absent when called.

	If the provided filename has a ".xml" or ".XML" suffix, or whatever
	the name if the 'flat_xml' option is set to 1, the file is processed
	as flat XML and not as a regular OOo file. No OODoc::File object is
	created, and the result of a subsequent call of the save() method
	produces a flat XML export (and not a regular OOo/OpenDocument file).

        You can pass the optional parameter 'element' in any case where the
        constructor is called without the 'xml' parameter. Bearing in mind
        that an OODoc::XPath object will not necessarily handle an entire
        XML document, this extra parameter indicates the name of the XML
        element to be loaded and handled. If the 'element' parameter is not
        given for an OpenDocument file, a default element will be chosen
	according to the following table:

            'meta'	=> 'office:document-meta'
            'content'	=> 'office:document-content'
            'styles'	=> 'office:document-styles'
            'settings'	=> 'office:document-settings'
	    'manifest'	=> 'manifest:manifest'

        Conversely, the 'element' parameter becomes mandatory if the chosen
        XML element is not listed above. Through OODoc::File, OODoc::XPath
        can actually access archives which are not necessarily in
        OpenDocument format and may be, for example, "databases" of
        presentation and content templates.

	If the application needs to create a new document, and not process
	an existing one, an additional option must be passed:

		create		=> "<class>"

	where "class" must be one of the following list: "text",
	"spreadsheet", "presentation" or "drawing", according to the needed
	content class. And, for very special needs, the user can pass an
	additional "template_path" to select an ad hoc directory of XML
	templates instead of the default one. This user-provided directory
	must have the same kind of structure and content as the "templates"
	subdirectory of the OpenOffice::OODoc installation.

	An additional 'opendocument' option can be provided and set to 'true'
	or 'false'. If this option is 'false', the new document is created
	according to the OpenOffice.org 1.0 format instead of the OASIS
	OpenDocument format. The default format is OpenDocument. The
	'opendocument' option works for new documents only and is ignored
	unless the 'create' option. This module can create and process either
	OpenOffice.org 1.0 documents or ODF documents but can't directly
	convert a document from one format to the other one.

	OODoc::XPath can process ODF documents provided through XML flat
	files as well as in the compressed (zip) format. The given file is
	automatically processed as flat XML if either it's name ends by ".xml"
	or the 'flat_xml' option is set to '1'. When processing a flat XML
	file, OODoc::XPath doesn't load the OODoc::File zip interface. So,
	a subsequent call of the save() method can only export the document
	as flat XML.

	An optional 'readable_XML' can be passed. If this option is provided
	and set to 'on' or 'true', the resulting XML will be smartly indented
	(and, of course, more space-consuming). This feature is intended for
	debugging purposes and should not be used in production.

	The 'local_encoding' option can be set with the appropriate value
	when a particular character set (and not the default one) must be
	used for a document.
	
	A 'read_only' can be provided and set to 'true' in order to prevent
	the current member from being written back to the physical ODF file
	when the save() method is called.

        Other optional parameters can also be passed to the constructor (see
        Properties below).

=head3	appendElement(path, position, name/xml, [options]);

=head3	appendElement(element, name/xml, [options]);

        Adds a new element or existing element to the list of child elements
        of an existing parent element given first (by [path, position] or by
        reference).

        The argument after the position argument can be an XML element name.

        Example:

            $content->appendElement
            	(
            	'//office:body', 0, 'text:p',
            	text => "New text"
            	);

        adds a paragraph containing the phrase "New text" to the end of the
        document body. (Remember that in the case of an OpenDocument text
	file (Writer), it would be better to use the appendParagraph method of
	OpenOffice::OODoc::Text as this requires fewer parameters.

        If the 'text' option is omitted, an empty element is created (in the
        above example it would be an empty paragraph or line feed).

        You can pass the 'attribute' or 'attributes' option which is a hash
	whose keys are the XML attribute names and whose values are the XML
        attribute values. Use of these options depends on the type of
        document and the type of element and requires knowledge of
        OpenDocument conventions.

        Example:

            $my_style	=
            	{
            	'style:name'	=> 'P1',
            	'style:family	=> 'paragraph'
            	};

            $content->appendElement
            	(
            	'//office:automatic-styles', 0, 'style:style',
            	attribute	=> $my_style
            	);

        creates a new paragraph style called 'P1' in the list of "automatic
        styles" ("automatic styles" are styles which are not explicitly
	indicated in the styles list as it appears to the end user).

        This method lets you add any kind of element into a document, even
        exotic ones. With the most common OpenDocument objects (e.g.
        paragraphs), though, it is easier to use the specialist methods
        contained in other modules.

        The 'name' argument can be replaced by an existing element in the
        same OODoc::XPath object or in another. In which case no element is
        created but the existing element is simply referenced with a new
        position even though it remains in its old position. Caution: any
        modification of an element which is referenced several times in one
        or more documents is made to all references. If you want to add a
        similar but separate element, you must use replicateElement which
        produces a new element from the content of an existing one.

        The 'name' argument can also be replaced by an XML string. This
        string must correspond to the correct XML description of a UTF-8
        encoded OpenDocument element. For example, it could be a
        string which had been previously exported using the exportXMLElement
        method of OODoc::XPath, or extracted from an OpenDocument file by
        some other application. If for any reason you absolutely have to
	use a non-UTF8 XML string which contains 8-bit characters (accented
	letters, etc.), you can always convert the string using the
	encode_text method before passing it to appendElement. Of course,
	the problem will not arise if you are absolutely sure that the string
	only contains ASCII (7 bit) characters. XML syntax is checked, but it
	is up to the user to verify that the element import conforms to
	OpenDocument XML grammar.

        The following piece of code produces the same result as the first
        example:

            $xml = '<text:p text:style-name="Standard">' .
            	'New text' .
            	'</text:p>';
            $content->appendElement
            	(
            	'//office:body', 0, $xml
            	);

        Using this method, after one or more element creations by direct
        importation of XML strings, it might be useful to call the
        reorganize method (but not absolutely necessary).
	
=head3	appendLineBreak(element)

	Appends a line break to a text element. This method allows the user
	to create a single text element (ex: a paragraph) including one or
	more breaks, instead of separate elements.
	
	The example below appends a new text in a new line to the end of
	an existing paragraph:
	
	    my $p = $doc->getElement('//text:p', 5);
	    $doc->appendLineBreak($p);
	    $doc->extendText($p, 'A new line in the same paragraph');
	    
=head3	appendSpaces(element, length)

	Appends a sequence of multiple spaces to a text element, knowing that
	a string containing repeated spaces shouldn't be stored as is in a
	document (see setText() and spaces() for details about repeated
	spaces).
	
=head3	appendTabStop(element)

	Appends a tab stop ("\t") to a text element.

=head3	blankSpaces(length)

	See spaces().

=head3	cloneContent(oodoc_xpath_object)

        Cancels the entire document contents of the current instance and
        replaces it with a reference to the contents of another OODoc::XPath
        object.

        Example:

            $doc1	= OpenOffice::OODoc::XPath->new
            		(
            		file	=> 'template.ods',
            		member	=> 'styles'
            		);
            $doc2	= OpenOffice::OODoc::XPath->new
            		(
            		file	=> 'sheet.ods',
            		member	=> 'styles'
            		);
            $doc2->cloneContent($doc1);
            $doc2->save;

        This sequence replaces the styles and page layout of 'sheet.ods'
        with those of 'template.ods'.

        The above example could easily have been written without even using
        OODoc::XPath by acting directly on the files. For example, extract
        the 'styles.xml' member from 'template.ods' and insert it into
        'sheet.ods'. The use of OODoc::XPath and the cloneContent method
        guarantees that the transferred content corresponds to an
        OpenDocument document and allows reads/writes to it on the fly.

        Caution: the "cloned" content is not physically copied. Calling this
        method references one single physical content in two documents. Any
        modifications made to the content of either of these two documents
        applies equally to the other and vice-versa.

=head3	contentClass([class name])

	Accessor to get or set the class of the document content. If the
	current member is a document content, returns its class according
	to the OpenDocument terminology, i.e. one of the following values:
	"text", "spreadsheet", "presentation", or "drawing".

	Returns an empty string if the current member is not a document
	content (if it's, for example, the "meta" or "styles" member).

	This accessor is read-only.

=head3	createSpaces(length)

	See spaces().

=head3	createElement(name, text)

=head3	createElement(xml)

        Creates a new element without attributes which is not inserted in a
        document.

        Example:

            my $element =
            	$doc->createElement
            		('my_element', 'its content');

        creates a new XML element without attributes and returns its
        reference.

        Instead of a name, the first argument can be the full XML
        description of the element. Example:

            my $element = $doc->createElement
            		('<text:p>My text</text:p>');

        This new element is temporary: it is not linked to any document. It
        is destined to be used later by another method.

        The name can contain a namespace prefix which would look like this:
        'namespace:name'.

        In its second form, a well-formed XML string can be supplied as a
        single argument. The recognition criteria is the presence of the "<"
        character at the beginning of the argument. See appendElement for
        comments on the direct insertion of XML.

        Explicit calls to createElement should be rare. This method is
        normally called silently by higher-level methods which are capable
        of creating an element, inserting it in a document's XML tree and
        giving it attributes (see appendElement and insertElement).

=head3	createFrame(name => frame_name [, options])

	Creates an empty frame. A frame is an OpenDocument object which
	controls a rectangular area where a visible content is displayed.
	Possible contents for a frame are text boxes or images.
	
	This method works is not focused on a particular document class
	(for example, it works on text documents as well as on presentations),
	but the visible effects of some options are not always exactly the
	same.
	
	Possible options are:
	
		'name'		=> unique name
		
	The 'name' is an identifier; if provided, it should be unique for
	the document.
		
		'attachment'	=> existing container
		
	The value of this option, if provided, must be an existing element
	which can contain a text box according to the OpenDocument rules.
	Such an object may be, for example, a draw page if the current
	document class is 'presentation' or 'drawing', or a paragraph if
	this class is 'text'.
	
		'page'		=> page number or name
		
	The effects of the 'page' option depends on the content class of the
	current document. If this option is used, it indicates that the frame
	will be anchored to a page, and the given value is a page number.
	It does not matter if, when createFrame() is called, this number is
	beyond the end of the document or not. If the content class of the
	document is "presentation" (Impress) or "drawing" (Draw), then the
	page option must be either the visible name or the object reference
	of an existing draw page. Caution: the 'page' option is ignored if
	'attachment' is provided; in the other hand, either 'page' or
	'attachment' nust be provided in order to really include the new frame
	in the document.
	
		'position'	=> coordinates
		
	The coordinates are provided as a string. They go from left to right
	and top to bottom. Coordinates should be given here in the form of a
	string "x,y", and the default unit is centimeter. You can choose
	any other OpenDocument-supported unit instead by attaching the
	corresponding usual abbreviation, such as "12.5cm, 35mm" which is the
	same as "125mm, 3.5cm" or "12.5,3.5", etc. The point ("pt") unit is
	allowed as well. The default coordinates are "0, 0". By default,
	the coordinates are relative to the anchor point. So, the coordinates
	are directly page-related if a valid 'page' option is provided only,
	but if the box is attached to, say, a paragraph, the origin of the
	coordinates is the beginning of the paragraph. However, the real
	interpretation of the coordinates depends on the style. With some
	style definitions, the coordinates may just be ignored (ex: if the
	style says "the frame is centered", OpenOffice.org will center the
	frame whatever its stored coordinates). According to other possible
	style definitions, the coordinates could be counted from the right
	and/or from the bottom and not from the left/top.
	
		'size'		=> the size of the box

	Provided using as a string using the same syntax and units as the
	position, the 'size' option is strongly recommended knowing that a
	sizeless frame couldn't be properly displayed. The width comes
	first in the string. The height is sometimes ignored, according to
	the style of the frame: by default, the display height of a text box
	(which is a particular frame) is automatically adjusted to the
	content.
		
		'style'		=> style name
		
	The 'style' option allows the application to set the frame style.
	Caution, a text style can't be used as a frame style. A frame
	style controls the box properties only (border, background, shadow,
	and so on), and not the content properties. Reusing an existing frame
	style through this option is generally a good idea.
		
=head3	currentContext([context])

	Accessor allowing the application to change the context for some
	search methods (including getElement()).
	
	The default context is the root of the document. By setting the
	current context to a lower level object, the application can restrain
	the search to the descendants of this object.
	
	In the example below, the getElement() method retrieves a paragraph
	by order number in a previously selected section, and not in the whole
	document.
	
		my $section = $doc->getElement("//text:section", $s_number);
		$doc->currentContext($section);
		my $paragraph = $doc->getElement("//text:p", $p_number);
		
	Without argument, simply returns the previous current context.
	
	See also resetCurrentContext().

=head3	decode_text(utf8_string)

        Caution: this method is a non-exported class method. It must be used
        like this:

            OpenOffice::OODoc::XPath::decode_text($utf8_string);

        and not from an OODoc::XPath instance.

        Decodes a UTF-8 string and returns an 8 bit character translation
	of it out of the user's character set, as defined by the following
	variable:

            $OpenOffice::OODoc::XPath::LOCAL_CHARSET

        for which the default value is 'iso-8859-1'. See the Perl/Encode
	manual for the list of supported character sets.
	
	OpenDocument uses UTF-8 XML encoding.

        Explicit calls to this method should be rare. It is used internally
        by methods which return text extracted from document content (e.g.
        getText).

        Warning to contributors: any method which returns text extracted
        from ODF documents is based on decode_text; so any modification or
	improvement of the decoding logic should be made there.

=head3	encode_text(editable_string)

        Class method.

        Encodes "local" character strings (for writing to ODF documents).

        Example:

            $string = OpenOffice::OODoc::encode_text($local_string);

        The local character string is defined by the following global
        variable:

            $OpenOffice::OODoc::XPath::LOCAL_CHARSET

        for which the default value is 'iso-8859-1'.

        Explicit calls to this method should generally be avoided. It is
        used internally by methods which insert text or attribute values
        into documents (e.g. setText).

=head3	dispose()

	Deletes the calling document object. Recommended as soon as the
	object is no longer needed by the application, and sometimes
	mandatory to avoid memory leaks, especially in long-running processes.

=head3	exportXMLBody()

        Returns the XML string for use by another application representing
        the body of a document, without UTF8 decoding.

=head3	exportXMLContent()

	See getXMLContent()

=head3	exportXMLElement(path, position)

=head3	exportXMLElement(element)

        Returns the XML string which represents a particular document
        element (style definition, paragraph, table cell, object, etc.) for
        use by another application without UTF8 decoding.

        This method is principally designed to allow remote exchanges of
        elements between programs using any XML storage or transfer method.
        It acts as "sender" whilst the "receiver" can use appendElement or
        insertElement (for example) to insert any exported elements into a
        document. Example:

            # sender programme
            # ...
            open (EXPORT, "> transfer.xml");
            print EXPORT $doc->exportXMLElement('//text:p', 15);
            close EXPORT;

            # receiver programme
            # ...
            open (IMPORT, "< transfer.xml");
            $doc->appendElement('//office:body', 0, <IMPORT>);
            close (IMPORT);

        In this example, a paragraph is transferred but it could just as
        easily be any content, presentation or metadata element.

        Conversely, this method is not needed when transferring an element
        from one document to another in the same program (or from one
        document position to another). An element can be copied directly
        from within the same program by reference or replication without
        going via its XML (see appendElement(), insertElement() and
        replicateElement()).

=head3	extendText(path, position, text [, offset])

=head3	extendText(element, text [, offset])

	Appends the given text to the previous content of the given
	element. If the optional 'offset' element is provided, the
	new element is inserted at the given position.

	Example:

		$doc->setText($p, "Initial content");
		$doc->extendText($p, " extended");
	
	Assuming $p is a regular text element (ex: a paragraph), its
	content becomes "Initial content extended".
	
	If the second argument is an element itself, it's appended
	as is to the first element. This feature can be used, for
	example, in order to append sequences of repeated spaces:
	
		$doc->setText($p, "Begin");
		$spaces = $doc->spaces(6);
		$doc->extendText($p, $spaces);
		$doc->extendText($p, "End");
	
	After the code sequence above, the $p element contains:
	
		"Begin      End"
	
	knowing that a single string containing repeated spaces could
	not be properly processed by extendText(), even if the
	'multiple_spaces' property is set (this property affects the
	setText() method only).

	(See also setText()).

=head3	findElementList(element, filter [, replacement])

	Returns all the children of the given element whose content matches
        the given filter (regexp).

        If the third argument ('replacement') is given, every string which
        matches the filter in each child element will be replaced by this
        'replacement' value. This 'replacement' argument can be a character
        string or a function reference. (See replaceText() method below.)

        Filtering and possible replacement only affects an element's content
        and not its attributes.

        This method is mostly for internal use. We recommend using other
        methods for the selective extraction of elements.

=head3	flatten(element)

	Converts in place the content of the given element to a flat string,
	removing any structure. Same as $element->flatten() (see flatten()
	in the "Element methods" section below). If no element is provided,
	"flattens" the current context element, which is, by default, the
	root of the document (be careful !). 
	
=head3	getAttribute(path, position, name)

=head3	getAttribute(element, name)

        Returns the 'name' value of the chosen element (or undef if name is
        not defined or if the element does not exist).

        Example:

            my $style	=
             $doc->getAttribute('//text:p', 15, 'text:style-name');

        returns the style for paragraph 15.

=head3	getAttributes(path, position)

=head3	getAttributes(element)

        Returns a list of the element's attributes in the form of a hash
        whose keys are the attributes' XML names.

=head3	getBody()

	Returns the root of the document body. The document body is the
	main container of all the displayable content not including page
	headers, page footers, and page backgrounds.

=head3	getDescendants(tag [, context])

	Returns the list of the descendants of the given context element
	strictly matching the given tag. Example:
	
		my $section = $doc->getSection("SectionName");
		my @paragraphs = $doc->getDescendants('text:p', $section);
		
	Here, @paragraphs is the list of all the paragraphs which are the
	descendants (at every level) of a given section (the getSection()
	method is described in the OpenOffice::OODoc::Text chapter).
	
	If the second argument is not provided, the current context of the
	document is used (see currentContext()).
	
=head3	getElement(path [, position [, context]])

	This method is provided in order to allow the user to retrieve any
	element in any kind of XML document (ODF-compliant or not) using an
	application-provided XPath expression. It should be used with elements
	whose type is not explicitly supported by the more focused (and more
	user-friendly) methods, described in other manual chapters (::Text,
	::Styles, ::Meta, and ::Document).

	It returns an element's reference from an XPath path and a position
	(or undef if the given xpath does not indicate an existing element).
	
	The position argument is used to select a particular element, in the
	order of the document, knowing that the given xpath expression could
	select a set of elements. Without it, getElement() returns the first
	element matching the given xpath.
	
	The XPath expression applies in the current context, and not always
	in the whole document (see currentContext()). However, if the
	reference of a previously selected element is provided as a third
	argument, the given element is used as the context.

        Position indicators start at 0 just like in Perl tables (and some
	other programming languages).

        Example:

            my $p = $doc->getElement('//table:table', 0)

        indicates an element containing the first table of a text document
        or first sheet of a spreadsheet.

        Positions can also be counted backwards from the end by giving
        negative values, i.e. position -1 being the last element. Thus:

            my $h = $doc->getElement('//text:h', -2);

        indicates the second-last header of a text document.

	Note: None of the two examples above should be used in a real
	application, knowing that the ::Text module provides getTable() and
	getHeading() that do the job without XPath coding.
	
        When successful, this method ensures that the returned object is
        indeed an element and not another type of node (e.g. attribute,
        text, comment, etc.). Such an object is never a printable text; it's
	either a text container (whose content may be extracted using
	getText() or getFlatText()) or a non-text element (such as a style,
	a font declaration, a variable field, a document properties container,
	etc).
	
=head3	getElementList(path)

        Returns a list of all elements at a specified path.

        Example:

            my @ref_summary = $doc->getElementList('//text:h');

        The above example returns a table containing all header elements of
        a text document.

        The path can of course be a more complex XPath expression
        stipulating, for example, a selection of attribute values. In most
        cases, you should avoid complicating things unnecessarily
        (especially in Text, Image and Styles modules), as there are methods
        for searching by element type, attribute and content which are much
        easier to use and avoid the need to supply XPath expressions.

        Note: the returned list contains elements in the sense of getElement
        and not a list of element contents.

=head3	getFlatText(path, position)

=head3	getFlatText(element)

	Like getText() below, but without rendering of possible tab stops,
	line breaks, repeated spaces, or any other markup. The returned text
	is just a decoded flat string.
	
=head3	getFrameElement(name/number)

	Selects the frame identified by the given name, or by the given order
	number in the document context.
	
=head3	getNodeByXPath(xpath_expression)

=head3	getNodeByXPath(xpath_expression, context)

=head3	getNodeByXPath(context, xpath_expression)

        A low-level method which returns the node corresponding to the given
        XPath expression, if it exists in the document. This method (which
        gives unrestricted access to the entire content of a document) is
        designed for use with the unexpected. You will obviously need to be
        familiar with XPath syntax (not documented here) as well as
        OpenDocument structure. See also selectNodesByXPath().

=head3	getObjectCoordinates(object)

	Returns the coordinates (X, Y) of the target object, if any. This
	method makes sense with "positioned" objects, i.e. with frames and
	frame-like objects (images, text boxes).
	
	In an array context, the coordinates are returned as two distinct
	strings (horizontal, then vertical position). In a scalar context,
	the values are returned in a single string, and separated by a comma.
	
	See createFrameElement() for details about the coordinates and size
	units and notation.
	
=head3	getObjectDescription(object)

	Returns the litteral description of a visible object. This method
	makes sense for frames or frame-like objects (such as images or
	text boxes).
	
=head3	getObjectSize(object)

	Returns the size of the given object, if any. This method works with
	frames and other frame-based objects, such as images and text boxes.
	
	In the returned data, the width comes first, followed by the height.
	
	The size is returned in the same way as the coordinates with
	getObjectCoordinates().
	
=head3	getRoot()

	Returns the absolute root element of the document. The root element
	contains any other visible or non visible object, including the
	document body (see getBody) and style definitions.
	
=head3	getText(path, position)

=head3	getText(element)

        Returns text in the local character set, possibly UTF-8 decoded,
        contained in the element given as an argument (by path/position or
        by reference). See also getFlatText().

        Two equivalent examples:

        # version 1

        my $element	= $doc->getElement('//text:p', 4);

        my $text	= $doc->getText($element);

        # version 2

        my $text	= $doc->getText('//text:p', 4);

        Version 2 is better if the only aim is to get the text from
        paragraph 4. Version 1 is better, however, if during the course of
        the program you want to perform other operations on the same
        paragraph. Giving an element's reference will mean avoiding element
        handling methods having to recalculate a reference from the XPath
        path.

=head3	getTextList(path)

        Returns text from all elements in the specified path.

        Example:

            my $summary = $doc->getTextList('//text:h');

            my $report = $doc->getTextList('//text:span');

        The $summary variable contains a concatenation of all headers.
        $report contains all the words or character strings that "stand out"
        which the user has designated by their context, e.g. words in
        italics in a non-italic paragraph.

        In a list context, the returned data is a table, each of whose
        elements contains the text of an XML element. In a scalar context
        (as in our two examples), the returned value is a unique piece of
        editable text and each element's content is separated from that of
        the following element by a line feed.

=head3	getXMLContent([filehandle])

        Without argument, returns a document's entire XML content.

	Exports the entire XML content of the current member to a flat file,
	if a file handle is provided.

	Note: the exported data are UTF8-encoded.

	Example:

		open my $fh, ">:utf8", "myfile.xml";
		$doc->getXMLContent($fh);
		close $fh;
	
	Synonym: exportXMLContent()

=head3	getXPathValue(xpath_expression)

=head3	getXPathValue(context, xpath_expression)

=head3	getXPathValue(xpath_expression, context)

        A low-level method which allows direct access to the value
        corresponding to the given XPath expression in a document. Character
        decoding is handled in the same way as with getText.

        Example:

            $expression =	'//office:automatic-styles'	.
            		'/style:style'			.
            		'[@style:style-name="P1"]'	.
            		'/@style:parent-style-name';

            print $doc->getXPathValue($expression);

        This sequence displays the name of the parent style of automatic
        style "P1" (if it exists within the document). Remember that more
        simple methods in Text and/or Styles modules would indeed produce
        the same result.

        The optional element reference "context" can be given as an argument
        either in first or second place. In this case, the search is limited
        to the section of the document tree below this given element. The
        default search area is the entire document.

        Just as with other methods which require XPath paths, this one is
        primarily for internal use. It should not be used by the majority of
        applications.

=head3	insertElement(path, position, name/xml [, options])

=head3	insertElement(element, name/xml [, options])

        Inserts a new element before or after the element specified by
        [path, position] or by reference.

        If the "name" argument is a literal, a new element with the name
        given is created and then inserted. If the same argument is a
        reference to an existing element, this element is then simply
        inserted at the position indicated. This method is useful either for
        adding new elements or for copying elements from one document to
        another or from one position to another within the same document.

        The position option allows you to choose the insertion point of the
	new element. Possible values are "before", "after" and "within" (the
	default is "before").
	
	If "position" is set to "within", the new element is inserted within
	the text of the target element, so an additional "offset" option (i.e.
	a numeric position in the string) is required. Caution: this feature
	is provided for a few special purposes only; inserting text elements
	within text strings is not the same as inserting text strings within
	text strings. 

	Other options are:

            text	=> "text of element"

            attribute	=> $attributes

        The "attribute" (or "attributes") option is itself a hash reference
	containing one or more attributes in the form [name => value] as in
	appendElement.

        When successful, this method returns the inserted element's
        reference (else undef).

        Example:

            my $attributes	=
            	{
            	'text:style-name'	=> 'Heading 2',
            	'text:level'		=> '2'
            	};
            $doc->insertElement
            	(
            	'//text:p', 4, 'text:h',
            	position	=> 'after',
            	text		=> 'New section',
            	attribute	=> $attributes
            	);

        This sequence (in a text document) inserts a level 2 header
	'New section' immediately after paragraph 4.

        The $name argument can be replaced by an existing element. In this
        case a new reference to the existing element is inserted, without
        creating a whole new element. In this way you can display an element
        at several locations or in several documents which is held in memory
        only once. See the appendElement section for the consequences of
        having multiple references to the same physical element. Better to
        use replicateElement to insert separate copies of an element.

        In the same conditions as in appendElement, the 'name' argument can
        be replaced by an XML string which describes the element.

        Note: to add an element to the end of a document, it would obviously
        be better to use appendElement.

=head3	isOpenDocument()

	Returns 1 (true) if the current document is an OASIS Open Document.
	To be used every time the application  needs to know the format of
	the document, knowing that some differences between the two formats
	can't be completely hidden by the API.

=head3	lineBreak

	Returns a special line break element, available for insertion within
	an existing text element (knowing that "\n" is not recognized as a
	line break if stored "as is"). The returned element is free, so it
	could/should be inserted later within a text element.

=head3	makeXPath(expression)

=head3	makeXPath(context, expression)

        Low-level method allowing the creation or direct modification
        without restriction (almost) of any document element. It allows
        "query" expressions in a language similar to XPath. If the given
        XPath expression crosses several levels of hierarchy, intermediate
        nodes can be created or modified "on the fly" by creating the
        necessary path which in turn creates the final node.

        Example:

            $doc->makeXPath
             (
             '//office:body/text:p[4 @text:style-name="Text body"]'
             );

        This "query" applies the "Text body" style to paragraph 4 in the
        body of the document. (In reality you will probably never use it
        because the setStyle method of the Text module would do the same
        thing much more simply.)

        If, as in the above example, a node is accompanied by a position
        indicator, it cannot be created but must simply act as a mandatory
        "passage". This method cannot therefore be used to create, for
        example, an Nth paragraph if there is already an N-1.

        The only restrictions apply to namespaces which are given as
        prefixes to element and attribute names. They must be defined in the
        document i.e. conform to OpenDocument specifications. For the rest,
	this method allows the creation of almost anything anywhere within a
	document. Its use is reserved for OpenDocument XML specialists.

        In its second form, a context node can be given as the first
        argument. If present, the path is sought (and if necessary created)
        starting from its position. By default, the path begins from the
        root.

        The returned value is the final node's reference (found or created).

        The full "query language" syntax used in this method is not
        documented here. makeXPath is designed to act more as a base for
        other OpenOffice::OODoc methods than to be used in applications.
	
=head3	moveElements(target_element, element_list)

	Moves a list of existing elements to a new attachment.
	
	One more elements are cut from their previous place and appended
	as children of the target element.
	
	This method can be used to move elements from one place to another
	place in the same document, as well as from one document to another
	one (caution, the elements are moved, not copied).

=head3	odfLocaltime()

	Class method.

	Converts the numeric time given in argument to an OpenOffice-compliant
	date (ISO-8601). The argument type is the same as for the standard
	Perl localtime() function, i.e. a number of seconds since the "epoch".
	It can be, for example, a value previously returned by a time() call.

	Without argument, returns the current local time in ISO-8601 format.

	The result of this function can be used as is in order to set the
	value of an ODF-compliant date-time element or attribute.

=head3	odfTimelocal()

	Class method.

	Translates an ODF-formatted date (ISO-8601) into a regular Perl
	numeric time format, i.e. a number of seconds since the "epoch". So,
	the returned value can be processed with any Perl date formatting or
	calculation function.

	Example:

		my $date_created = odfTimelocal($meta->creation_date());
		$lt = localtime($date_created);
		$elapsed = time() - $date_created;
		print "This document has been created $date_created\n";
		print "$elapsed seconds ago";
	
	This sequence prints the creation date of a document in local time
	string format, then prints the number of seconds between the creation
	date and now. Note that the creation_date() method used here works
	with the meta-data document part only (see OpenOffice::OODoc::Meta for
	details about this method).

	Note: This function requires the Time::Local Perl module.

=head3	odfVersion([new_version])

	See openDocumentVersion()

=head3	ooLocaltime([$time_value])

	Class method.

	See odfLocaltime()

=head3	ooTimelocal($oodate)

	Class method.

	See odfTimelocal()

=head3	openDocumentVersion([new_version])

	Returns the version of the Open Document Format (ODF) in use in the
	current document. If an argument is provided, it's used to set a
	new version identifier.

	Beware, this method doesn't really check the conformance of the
	document to any version of the ODF standard. It just retrieves the
	value of the version number attribute as it has been set by the
	application which created or modified the document.

	If openDocumentVersion() is used to set a new version number
	declaration, the given value is not checked. So, this value could
	be the number of a real or future ODF version (1.0, 1.1, 1.2, etc),
	as well as any other arbitrary value (ex: 99, -1, ...).

=head3	raw_import(member, source)

        Physically imports an external file into an OpenDocument archive
        associated with an XPath object, if it exists i.e. if the object was
        created using file or archive parameters. This method only transmits
        the command to the OODoc::File's raw_import method. Caution: it must
        not be used with an "active" element i.e. an XML member to which the
        current XPath object or another XPath object is already associated.
        Remember too that the import is not actually carried out by
        OODoc::File until a save and the imported data is therefore not
        immediately available.

=head3	raw_export(member, target)

        Physically exports a member from an OpenDocument archive associated
	with an XPath object, if it exists i.e. if the object was created
	using file or archive parameters. This method only transmits the
	command to the OODoc::File's raw_import method.

=head3	removeAttribute(path, position, attribute)

=head3	removeAttribute(element, attribute)

        Deletes the "attribute" attribute (if found) of the given element by
        [path, position] or by reference and returns "true". Has no physical
        effect and returns undef if the attribute has not been defined or if
        the element does not exist.

=head3	removeElement(path, position)

=head3	removeElement(element)

        Deletes the given element (if found) by [path, position] or by
        reference and returns "true". Returns undef if the element does not
        exist.

=head3	replaceElement(path, position, replacement [, options])

=head3	replaceElement(old_element, new_element [, options])

        Deletes the given element by [path, position] or by reference and
        inserts another element in its place, either from another location
        in the same document or from another document.

        A new element can be supplied under the same conditions as for
        insertElement.

        By default or by using the mode => 'copy' option, it is a copy of
        the new element which is inserted. With the mode => 'reference'
        option, it is only a reference which is inserted. See the section on
        appendElement for comments on the subject of multiple references to
        a single physical element.

=head3	replaceText(path, position, filter, replacement)

=head3	replaceText(element, filter, replacement)

        Replaces all sub-strings which match "filter" with "replacement" in
        the text of an element (and its descendants) indicated by
	[path, position] or by reference and returns the modified text. The
	"filter" string can be an "exact" literal or a regular expression.

        Example:

            $doc->replaceText($p, "C(LIENT|USTOMER)", $contact);

        replaces each occurrence of "CLIENT" and "CUSTOMER" with the content
        of the $contact variable in the paragraph $p of document $doc.

        The "replacement" argument can be a function reference. In which
        case, the function is called each time the string is matched, and
        the value returned by the function is used as the replacement value.

        	sub action	{
        		my $arg = shift;
        		my $text = shift;
        		print "$arg : $text\n";
        		return "OK";
        		}
		$doc->replaceText($p, $expression, \&action, "Found");

        displays "Found: <text>" (where <text> is the text retrieved) each
        time a string matches $expression and replaces this string with
        "OK". If $expression contains an "exact" string (not a regexp), then
	clearly the text displayed will always be the same string. However,
	if it happens to be a regular expression, it is in effect the text
        retrieved which will be displayed.
	
        Generally speaking, if the replacement value is a function
        reference, the called function receives the remainder of the
        arguments which follow it, in this order:
	
	1) all the arguments following the function reference in the
	replaceText() call, in the same order;
	
	2) the string that matches the filter argument.
	
	See also substituteText(), which should be preferred in most
	situations.

=head3	replicateElement(original_element, position_object [, options]])

        Makes a copy of the first given element and inserts it into the
	current document at a position which depends on the second argument
	and an optional parameter.

	If the second argument is an existing object in the document, then
	the copy is inserted according to an optional 'position' parameter:
	
	- if no 'position' option is provided, then the copy is appended
	as the last child of the position object;
	
	- if 'position' => 'before' or 'after', then the copy is inserted at
	the same hierarchical level as the position object, according to the
	same logic as for insertElement().
		
	If the second argument is not an object, but simply 'end', then the
	new element is appended as the very last child of the physical root
	of the document. See getRoot(). This option should generally be
	avoided.

        If the second argument is given as 'body', then the new element
        is appended at the end of the document body (see getBody), as it was
	created through appendElement().

        Example:

            my $template = $doc_source->selectElementByAttribute
            		(
            		'//style::style',
            		'style:name',
            		'Text body'
            		);
            my $position = $doc_target->getElement
            		('//office:styles', 0);
            $doc_target->replicateElement($template, $position);

        This sequence adds a style 'Text body' to the style set of $doc_target
        which copies exactly the style of the same name in $doc_source.
	Obviously, the section of code dealing with the search for the element
	to copy and its position is the most laborious. (In a real application,
	thanks to OODoc::Styles, a more user-friendly coding would be allowed
	for style replication.)

        This method creates a new element which is an exact copy of the given
	element, but which is physically separate from it.

        This method is slower than simply modifying an existing element or
        inserting an element reference.

	If the user needs only a "free" copy of the element (out of the
	document structure, to be later attached), the XML::Twig::Elt copy()
	method should be preferred:
	
	    my $new_element = $old_element->copy;

=head3	resetCurrentContext()

	Resets the search context to its default value, which is the root of
	the document. See currentContext().

=head3	save([filename|filehandle])

	Saves the content of the current document through a physical
	output, that is either a regular file specified by path/name, or
	an open, application-provided IO::Handle. If no argument is
	provided, the document which had been used as the source (if any)
	is used as the default target.
	
	Technically, as soon as the document container is a regular ODF
	file, this method is a stub for the save() method of the associated
	OpenOffice::OODoc::File object, so all the related explanations and
	recommendations given in the OpenOffice::OODoc::File manual chapter
	apply. So, for example, be careful if the target is an open IO::Handle
	instead of a file path/name.

	The behaviour of this method depends on the way the current
	OpenOffice::OODoc::XPath object has been created.
	
	If the document is explicitly linked (through the 'file' option
	of it's constructor) to a regular OOo or OpenDocument file, the
	document is saved either in the source file, or (if a filename
	is provided as an argument) in a new file.
	
	If the document is linked to the same file interface as one or
	more other OpenOffice::OODoc::XPath objects, the behaviour is
	the same as in the previous case, but all the changes made by
	all the linked objects are automatically saved in the target
	file. Example:
	
		my $content	= odfXPath
				(
				file		=> 'source.odt',
				part		=> 'content'
				);
		my $styles	= odfXPath
				(
				container	=> $content,
				part		=> 'styles'
				)
		my $meta	= odfXPath
				(
				container	=> $content,
				part		=> 'meta'
				);
		# ... a lot of content processing
		# ... a lot of style processing
		# ... a lot of metadata processing
		$content->save('target.odt');
	
	At the end of the sequence above, all the changes made through
	the $content, $styles and $meta objects are saved in 'target.odt'
	because these objects share a common file interface. Note that
	in such a situation, the save() method can be issued from anyone
	of the objects sharing the file interface (i.e. $content->save
	could be replaced by $styles->save or $meta->save).
	
	However, any XML part (content, styles, meta, ...) whose
	'read_only' property is set to "true" is not saved. In the example
	above, if, say, the $meta object is created (through odfXPath())
	with a "read_only" option set to "true", only $content and $styles
	are really saved by the last instruction.
			
	If the document is not associated with a regular OpenDocument
	compressed file (used through an OODoc::File object), it's saved
	as "flat XML" to the given file. In such a situation, if the file name
	is not provided, the source XML file (if any) is used as the target.
	If the file is "flat XML", OODoc::XPath really effects the physical
	output, without using any OODoc::File connector.

	Note: if you need to save a document as flat XML while it's associated
	with an OpenDocument file, you should use exportXMLContent() with an
	application-provided file handle.

=head3	selectChildElementByName(path, position [, filter])

=head3	selectChildElementByName(element [, filter])

        Returns the first (or only) element whose name matches "filter" from
        within the child elements of the given element indicated by [path,
        position] or by reference.

        "filter" is taken to be a regular expression. If several values
        match the filter, the first of these is returned (in the XML's
        physical order which is not necessarily the logical order of the
        document). See the comments about selectElementByAttribute if
        wanting to select an exact name.

        Returns undef if no elements match the condition.

        Returns the first (or only) child (if there are more than one)
        without anything else if no filter is given or if the filter uses
        wildcards (".*").

=head3	selectChildElementsByName(path, position [, filter])

=head3	selectChildElementsByName(element [, filter])

        Like selectChildElementByName, but returns a list of all elements
        which match the condition.

        Example:

            my @search_words =
            	$doc->selectChildElementsByName
            		('//text:p', 4, 'text:span');

        returns a list of elements from paragraph 4 which correspond to text
        which has particular attributes which distinguish it from the rest
        of the paragraph (colour, font, etc.)

=head3	selectElements([context,] path, filter)

=head3	selectElements([context,] path, filter, replacement)

=head3	selectElements([context,] path, filter, action [, arg1, ...])

        Returns a list of elements corresponding to a given XPath path and
        whose text matches the filter (regular expression). The "context"
        argument, if given, is an element reference which limits the search
        to its own child elements. The search is carried out in the entire
        document by default.

        An element is selected if the search string is found in its own text
        or in the text of any element descended from it. E.g. An image
        element (draw:image) can be selected from the value of its attached
        "description" field.

        You can replace all strings matching the search criteria with the
        'replacement' string, on the fly, if the latter is given as an
        argument after the filter.

        Lastly, instead of a replacement string, you can pass a subroutine's
        reference which will run (in call back mode) each time the search
        string is matched. If this subroutine returns a defined value, this
        value is used as the replacement string. The subroutine will
        automatically receive the rest of the arguments, in this order:

	Caution: this method can't retrieve a character string which is
	split into more than one text element or text span. So, for example,
	it will never retrieve "My String" as long as "My" and "String" are
	presented with different styles, even if the two parts of the string
	belong to the same paragraph.
	
        If, as is generally the case, you are working exclusively with text
        elements (paragraphs, headers, etc.), you would be better to use
        selectElementsByContent() of the Text module which is easier to use
        and does not require an XPath expression.

        Here is an example which returns the list of images whose
        descriptors contain the word "landscape" and displays the name of
        each selected image:

            sub	printMessage
        	{
        	my $doc		= shift;
        	my $element	= shift;
        	my $image = $element->parentNode;
        	print "Name: " . $image->find('@draw:name') . "\n";
        	}
            my @list = $doc->selectElements
            	(
            	'//draw:image/svg:desc',
            	'landscape',
            	\&printMessage,
            	$doc
            	);

        Never use this example of code in a real application as it is both
        purely for demonstration and unnecessarily complex. You can perform
        the same operation much more simply using the OODoc::Image module.

=head3	selectElementsByAttribute(path, attribute, filter)

        In a list context, returns a list of elements at the given path with
        the given attribute which contain a value matching the filter's
        regular expression.

        In a scalar context, returns the first (or only) element which
        matches the same condition.

        Returns undef if no elements match the condition.

        Example:

            my @paragraph_styles =
             $doc->selectElementsByAttribute
            	('style:style', 'style:family', 'paragraph');

        returns the list of elements which describe the paragraph styles of
        document $doc.

        Caution: the filter is treated as a regular expression and not as a
        classic string. This means that the above piece of code might not
        only return the elements whose "style:family" attribute equals
        "paragraph", but also all those in which the same attribute contains
        the word "paragraph". You must therefore use the appropriate syntax
        (in regexp language) if you want to select an exact value, which in
        this case would be "^paragraph$".

=head3	selectElementByAttribute(path, attribute, value)

        Like selectElementsByAttribute in a scalar context. Returns the
        first (or only) element at the given path which has the given
        attribute containing the given value.

        Returns undef if no element matches the condition.

=head3	selectNodesByXPath(xpath_expression)

        This low-level method returns a list of nodes (which are not
        necessarily elements) which match the give XPath expression. See
        getNodeByXPath() for options and comments.

=head3	setAttributes(path, position, attributes_table)

=head3	setAttributes(element, attributes_table)

        Modifies or adds one or more attributes to an element.

        The element is indicated by reference or by [path, position].

        The list of attributes is given in the form of a hash name => value.

        Example:

            my $h = $doc->getElement('//text:h', 12);
            my %attributes =
            	(
            	'text:style-name'	=> 'My Header',
            	'text:level		=> '3'
            	);
            $doc->setAttributes($h, %attributes);

        This sequence gives the 'My Header' style and level 3 to the 13th
        "header" element in the document.

=head3	setFlatText(path, position, text)

=head3	setFlatText(element, text)

	Like setText() described below, but without translation of "\t"
	and "\n".
	
	For exceptional use only. Allows, for example, the use of the OODoc
	API with non-OpenDocument XML files.

=head3	setObjectCoordinates(object, coordinates)

	Updates or creates the coordinates (X, Y) attributes of a visible
	object (ex: image, text box, frame). See createFrameElement() for the
	coordinates units and notation.
	
=head3	setObjectDescription(object, description)

	Updates or creates the litteral description of the given object.
	
	Should be used for frames, images or text boxes. Caution: the
	description is not the same as the printable content of a text
	box.
	
=head3	setObjectSize(object, size)

	Updates or creates the width and height attributes of a given object.
	
	This method makes sense for visible, rectangular objects only, such
	as the frames, images or text boxes.
	
	See createFrameElement() for details about the size units and
	notation. 
		
=head3	setText(path, position, text)

=head3	setText(element, text)

	Uses the given text as the content of the given element.

	Any previous content (including formatting markup, bookmarks,
	notes, references, etc) is replaced by the given text.
	
	If the given text includes tab stops ("\t") or line breaks ("\n"),
	they are replaced by the appropriate OpenDocument tags. If this
	translation must be avoided, use setFlatText() instead.
	
	Note: The strings containing repeated whitespaces are not properly
	processed by default. A sequence of repeated spaces, whatever its
	length, is replaced by a single space in the target document. So

		$doc->setText($p, "Begin        End");
	
	produces the same visible result as
	
		$doc->setText($p, "Begin End");

	It's possible to override this default behaviour using the
	'multiple_spaces' document property. If 'multiple_spaces' is
	set to 'on', the repeated spaces in the example above are properly
	recorded. However, this optional feature is a the price of some
	other features and, above all, it have a negative impact on the
	performances (due to an additional processing of *every* space).
	Of course, a temporary activation of the 'multiple_spaces'
	feature is allowed, like in the following example, which sets
	a content including multiples whitespaces:

		$doc->{'multiple_spaces'} = 'on';
		$doc->setText($p, "Begin        End");
		$doc->{'multiple_spaces'} = undef;

	See spaces() and extendText() for a workaround if you
	need to insert repeated spaces without using the 'multiple_spaces'
	property.
	
=head3	spaces(length)

	Returns a special element, available for insertion within a text
	element, representing repeated contiguous blank spaces (knowing
	that repeated spaces can't be properly displayed by an OpenDocument-
	compliant application if stored as a flat string). The returned
	element is free, so it could/should be inserted later within a text
	element. See extendText() for an example of use.

=head3	splitElement(element, offset)

	Splits a text element at a given offset. This method is a wrapper
	of the XML::Twig::Elt split_at() method, so, as said by Michel
	Rodriguez in his documentation, it splits "a text element in 2" at
	the given offset so "the original element now holds the first part
	of the string and a new element holds the right part".
	
	In addition, the new element is created with the same attributes (ex:
	the style or the heading level, if any) as the original one. 
	
	The method returns both the original and the new elements in a list
	context. In a scalar context, the new element only is returned.
	
	The new element is "free", i.e. it doesn't belong to the document.
	It's available for later use with any element attachment method,
	provided by OpenOffice::OODoc (appendElement(), insertElement()) or
	by XML::Twig (paste()). Example:
	
		my $new_elt = $doc->splitElement($para, 12);
		$doc->insertElement($para, $new_elt, position => 'after');
	
	This example splits the given paragraph in two consecutive paragraphs.

	Caution: splitElement() works properly on elements containing "flat
	text" only. It's a bit complicated to use and probably doesn't
	produce the right effects on elements containing line breaks, tab
	stops, "styled spans" or any kind of structure. So, it should be used
	on flat paragraphs or headings only.
	
=head3	substituteText(element, filter, replacement)

	Replaces any substring in a given element and its descendants,
	matching a given filter (regexp) by a given replacement string.
	
	It "replacement" is a string, this method produces the same result as
	replaceText(), and it should be preferred.
	
	If "replacement" is a function reference, the replacement value is the
	return value of the function. But, unlike replaceText(), any argument
	after "replacement" is ignored.
	
	This method is a wrapper for the subs_text() method provided by the
	XML::Twig::Elt class. See the XML::Twig documentation for advanced
	details.

=head3	tabStop

	Returns a special tabulation mark element, available for insertion
	within an existing text element (knowing that "\t" is not recognized
	as a tab stop if stored "as is"). The returned element is free, so
	it could/should be inserted later within a text element.
	
=head2	Element methods

	Every document element is an OpenOffice::OODoc::Element object,
	and OpenOffice::OODoc::Element inherits all the rich features of
	XML::Twig::Elt, including the very powerful copy(), cut(), paste(),
	move() and replace() methods (look at the XML::Twig documentation
	for details). Some additional methods, provided in the ::Element
	package, are described below.
	
	The "element methods" should be regarded as reserved for advanced
	uses, possibly in combination with native XML::Twig::Elt methods
	(not documented here, but the XML::Twig package itself is well
	documented).
	
	Remember these methods belong to the element and not to the
	document...!
	
=head3	appendChild(newnode)

	Appends a node as the last child of the calling node.
	
	If the argument is an existing node, it's appended as is.
	If the argument is a string, a new node is created, with the
	given string as the XML tag name.

=head3	appendTextChild(text)

	Appends a text node (PCDATA) as the last child of the calling
	element.

=head3	flatten()

	Converts in place the content of the calling element to a flat string,
	removing any structure. All the children of the calling element are
	removed and their text content is concatenated. The resulting string
	becomes the only content of the element. For example, if the calling
	element is a table, the tabular structure disappears and is replaced
	by the concatenated contents of all the cells. Any possible internal
	tab stop or line break element is removed, as well as any "styled"
	text span (see setSpan() and removeSpan() is the OODoc::Text chapter
	for information about styled text spans).
	
	Be careful, a lot of elements are not displayed by the OpenDocument
	compliant software. For example, a section element becomes invisible
	if it directly contains its text, without structure elements such as
	paragraphs, headings, tables, and so on. In order to make visible the
	"flattened" content of a previously complex element, the XML tag
	should be replaced by the tag of a "displayable" element. In the
	following example, a section is flattened, then tagged as a
	paragraph, so its content remains visible:
	
		my $s = $doc->getSection("AnySection");
		$s->flatten;
		$s->set_tag('text:p');
		
	Note: getSection() belongs to OpenOffice::OODoc::Text and set_tag()
	is provided by the underlying XML::Twig::Elt package.
	
	The text flattening is sometimes required in order to allow the
	applications to retrieve strings which are split into more than one
	text container. For example, a string such as "OpenDocument" can't
	be retrieved using selectElements() or any other string search method
	of the API if, say, "Open" and "Office" don't belong to the same text
	span (i.e. if they have different styles; look at setSpan() in
	OpenOffice::OODoc::Text to know more about text spans). In such a
	situation, flatten() removes any text span markup, so the whole text
	content of the element can be processed as a regular character string.
	
	Caution, this method can produce terrific results when misused.
	
=head3	getLocalPosition([regexp])

	Returns	the position of the current element in the list of all
	the children of the same parent with the same type.

	Example:

		$cell->getLocalPosition();

	Assuming $cell is a table cell, this example returns the position
	of the cell in the row without counting the covered cells (if any).

	If a regular expression is provided as the optional argument, all
	the siblings matching the expression are counted; but the method
	returns zero if the calling element itself doesn't match the
	expression.

	Example:

		$cell->getLocalPosition(qr'table:(covered-|)table-cell');

	returns the position of the cell among all the cells (covered or not)
	in the row.

	Note: This method is a wrapper of the pos() method of XML::Twig::Elt,
	but the returned values are zero-based in order to be consistent
	with the other element addressing features of OpenOffice::OODoc.

=head3	insertNewNode(xml_tag, position_flag [, offset])

	Creates a new XML element, whose tag is passed as the 1st argument,
	before, after or within the calling element. The 2nd argument
	must be set to 'before', 'after', 'within', or any other value
	accepted by the paste() method of XML::Twig. If the 2nd argument
	is 'within', a 3rd one must be provided and indicate the offset.
	
=head3	replicateNode(count, position)

	Produces one or more copies of the calling element and inserts
	the copies before or after it. The position argument should be
	'before' or 'after'; its default is 'after'. Technically, the
	position argument could be anyone of the position options of
	the XML::Twig::Elt->paste method, including 'first_child',
	'last_child' or 'within'; but any other than 'before' and 'after'
	probably don't make sense in an OpenDocument-compliant data
	structure.

	Without any argument, the calling element is replicated once.
	But if the count argument is provided and set to zero or a
	negative value, nothing is done.
	
	Example :
	
		my $row = $doc->getTableRow("Table1", -1);
		$row->replicateNode(5);
		
	This sequence appends 5 more rows to a table; each new row is a
	copy of the last original row, including each individual cell
	and its content.
	
=head3	selectChildElement(filter)

	Like selectChildElements() below, but returns only the first node
	matching the filter.
	
	Note: the first_child() method of XML::Twig::Elt should be preferred
	when the filter is the exact tag name of the needed element.
	
=head3	selectChildElements(filter)

	Selects the children with XML tag names matching a given filter.
	The filter is processed as a regexp.
	
	Note: the children() method of XML::Twig::Elt should be preferred
	if the filter is the exact tag name of the needed elements.

=head3	selectFrameElementByName(name)

	Selects the first frame element whose name is exactly the given
	argument. A frame is an OpenDocument container which can host a
	rectangular object, such as an image or a text box.
			
=head2	Properties

        No class variables are exported; the applications, if needed,
	must access them using their full name ($OpenOffice::OODoc::XPath:XXX)

        The following names should be prefixed explicitly with
	"$OpenOffice::OODoc::XPath::"

            CHARS_TO_ESCAPE

        contains the list of reserved characters which, in XML, should be
        replaced by escape sequences.

            OO_CHARSET

        indicates the character set used for OpenDocument document
        encoding and whose default value is 'utf8' (it should not be changed).

            LOCAL_CHARSET

        indicates the user's character set, by default 'iso-8859-1'; it must
	be changed according to the real user's needs (warning: there is no
	kind of automatic adaptation to the user's locales, so the application
	must explicitly load the right value in this variable); it should be
	done using the odfLocalEncoding() accessor (see the OpenOffice::OODoc
	man page and, for the list of supported character sets, the Encode
	module's documentation).

        The content of these three variables should not normally be directly
        modified by the applications.

        Instance hash variables are :

            'container'		=> <oodoc_file_object>
            'file'		=> <OpenDocument file>
            'part'		=> <name of the XML part in the ODF package>
	    'readable_XML'	=> <'true' or 'false'>
	    'local_encoding'	=> <user's output encoding>
	    'multiple_spaces'	=> <'on' or undef, see setText()>
            'element'		=> <name of loaded XML element>
	    'xpath'		=> <XML::Twig, XPath-capable object>
	    'twig_options'	=> <XML::Twig options as a hash reference>
	    'opendocument'	=> <'true' or 'false'>

        However, the 'xml' variable is cleared almost immediately after a
        successful constructor call, in order to save memory. As soon as the
        corresponding XPath object has been created, the XML source is no
        longer required.

        The 'xpath' variable of an OODoc::XPath object contains a reference
        to the document structure as it's made available through XML::Twig
	(see CPAN documentation). This object encompasses the entire current
	XML tree. Each access to XML using OODoc::XPath objects is done via
	XML::Twig. So, after having run the following command:

            my $xp = $doc->{'xpath'};

        the experienced programmer will be able to use $xp to access all the
        functionality of the XML::Twig API, bearing in mind that all
        operations using this interface will have a direct effect on the
        content of the $doc object.
	
	'twig_options' allows the user to provide a hash reference of
	additional options to XML::Twig. These options can modify the way the
	document is parsed during the execution of odfXPath(). For special
	applications only (see the XML::Twig reference manual).

	The 'opendocument' property, if true, means that the document is
	declared as an OASIS Open Document. If this property is false or
	undef, the document format is OpenOffice.org version 1. This property
	should not be changed (as long as OpenOffice::OODoc can't change the
	format of an existing document).

=head1	AUTHOR/COPYRIGHT

Developer/Maintainer: Jean-Marie Gouarne L<http://jean.marie.gouarne.online.fr>

Contact: jmgdoc@cpan.org

Copyright 2004-2010 by Genicorp, S.A. L<http://www.genicorp.com>

Initial English version of the reference manual by Graeme A. Hunter
(graeme.hunter@zen.co.uk).

License: GNU Lesser General Public License v2.1

=cut
