NAME

ODF::lpOD::Styles - Styles management

DESCRIPTION

A style controls the formatting and/or layout properties of a family of content objects. It's identified by its own name and its family. In the lpOD API, the family has a larger acception than in the OpenDocument specification. In the underlying XML, the family is indicated sometimes by the value of an explicit style:family attribute, and sometimes by the XML tag of the style element itself.

In order to hide the complexity of the ODF data structure, the level 1 API allows the user to handle any style as a high level odf_style object.

Common style features

Any style is created through a common odf_create_style() function with the family as its mandatory first argument. A name, that is the identifier of the style in the given family, is generally required. So, a typical style creation instruction looks like:

   $s = odf_create_style('text', name => 'MyTextStyleName');

The example above creates a named text style without any property. The properties are optionally passed as named parameters.

Additional named parameters can be required according to the family. An optional parent argument, whose value is the name of another common style of the same family (existing or to be created), can be provided, knowing that a style inherits (but can override) all the properties of its parent. A display name additional parameter may be provided; if set, this parameter designates a visible name that may differ from the internal name. It's possible to copy (instead of inherit) all the properties of an existing style of the same family, through a clone option, knowing that clone and parent are mutually exclusive options. The code example below produces two text styles whose properties are the same as "MyTextStyleName", but the first one will be affected by later changes of the base style while the second one is independant:

   odf_create_style('text', name => 'NewStyle1', parent => 'MyTextStyleName');
   $proto = doc->get_style('text', 'MyTextStyleName');
   odf_create_style('text', name => 'NewStyle2', clone => $proto);

An effective style name, unique for the family, is required as soon as the style is attached to a document, unless it's inserted as a default style. This name may be set or changed with set_name() after the style creation. When a style is used as a default style, its name and display name are meaningless and ignored. The family and the name constitute the absolute identifier of a style in a document.

The odf_create_style() function creates a free element, not included in a document. This element (or a clone of it) is available to be attached later to a document through a generic, document-based insert_style() method.

The insert_style() method requires a style object as its only one mandatory argument. An optional boolean parameter whose name is default is allowed; if provided and set to TRUE, this parameter means that the style is inserted as a default style. A default style is a style that automatically apply to elements whose style is not explicitly specified. A document can contain at most one default style for a style family, so any attachment of a default style replaces any existing default style of the same family.

All styles can't be used as default styles. Default styles are allowed for the following families: paragraph, text, section, table, table column, table row, table cell, table page, chart, drawing page, graphic, presentation, control and ruby.

Some styles may have a class property, that is an informative attribute, and that should not be confused with the family. A family is an application- defined property, used in order to identify a set of styles belonging to various families, for retrieval needs.

An existing style may be retrieved in a document using the get_style() document-based method. This method requires a family as its first argument and allows a style name as a second, optional argument. If the name is missing, this method tries to retrieve the default style for the given family, if any.

The following example extracts a paragraph style, so-called "MyParagraph", from a document and attaches a clone of this style as a default style of another document; the old default paragraph style of the target document (if any) is automatically replaced::

   $ps = $doc1->get_style('paragraph', 'MyParagraphStyle')->clone();
   $doc2->insert_style($ps, default => TRUE);

While a style is identified by name and family, it owns one or more sets of properties. A style property is a particular layout or formatting behaviour. The API provides a generic set_properties() method which allows the user to set these properties, while get_properties() returns the existing properties as an associative array.

However, some styles have more than one property set.

As an example, a paragraph style owns so-called "paragraph properties" and/or "text properties" (see below). In such a situation, an additional area parameter, whose value identifies the particular property set, with set_properties(). Of course, the same area parameter applies to get_properties().

Some styles allow the applications to specify a background. Such a background is sometimes characterized by the RGB, 3-bytes hexadecimal code of an arbitrary color, with a leading "#". However some styles allow the use of backround image instead of or in combination with a color. In order to deal with these possibilities, a set_background() is provided; this method (which works with some style objects only) is used with a color and/or a url named parameters. The color value range is #000000-#ffffff, while url should be set to the URL of the graphic resource. If url is set, some additional optional parameters may be provided, in order to control the way the image is displayed in the background, namely:

• position: a string that specifies the horizontal and vertical positions of the image, through one or two space-separated words (in any order) among center, left, right, top, bottom (default: center);

• repeat: specifies whether a background image is repeated or stretched, whose possible values are ``no-repeat`` meaning that the image should be displayed once, ``repeat`` to repeat the image in order to fill the whole background, and ``stretch`` to extend the image in order to fill the whole background;

• opacity: the percentage of opacity;

• filter: an application-specific filter to that is used to load and process the graphic file, according to the image format.

To remove the background color or image (i.e. to set the background to the default, that is transparent), the user just have to call set_background() with color and url set to undef.

A style that apply in some way to a rectangular area (ex: shape, frame, paragraph) other than a page may have visible borders and a shadow. Borders are specified using border xxx attributes where xxx is either left, right, top or bottom; if all the borders are the same, a single border property is convenient. The value of a border property is a 3-part string that describes the thickness, the line style and the line color (according to the XSL/FO grammar), like "0.1cm solid #000000" for a one millimeter solid black line. The shadow is specified through a shadow property whose value is a 3-part string describing the color and the size, like "#808080 0.18cm 0.18cm".

A style can be inserted as either common (or named and visible for the user of a typical office application) or automatic, according to a boolean automatic option, whose default value is FALSE. A common style may have a secondary unique name which is its display name, which can be set through an additional option. With the exception of this optional property, and a few other ones, there is no difference between automatic and common styles.

Defaults styles and common styles are automatically inserted in the STYLES document part. But automatic styles may be inserted, at the user's choice, in CONTENT or STYLES. The default is CONTENT but STYLES may be specified through a part optional parameter of insert_style(). The user must check that any automatic style is inserted in the same document part as the element that uses it (so, an automatic style must be inserted in STYLES if it's used by another style defined in this part).

Of course, a style is really in use when one or more content objects explicitly reference it through its style property.

The API allows the user to retrieve and select an existing style by name and family. The display name, if set, may be used as a replacement of the name for retrieval.

Once selected, a style could be removed from the document through a standard level 0 element deletion method.

Text styles

A text style can be defined either to control the layout of a text container, i.e. a paragraph, or to control a text range inside a paragraph. So the API allows the user to handle two families of text styles, so called text and paragraph. For any style in the text or paragraph families, the text class is recommended.

Text family

A text style (i.e. a style whose family is text, whatever its optional class) is a style which directly applies to characters (whatever the layout of the containing paragraph). So, it can bear any property directly related to the font and its representation. The most used properties are the font name, the font size, the font style (ex: normal, oblique, etc), the text color, the text background color (which may differ from the common background color of the paragraph).

A text style may apply to any text span in any text paragraph. However some ODF editing or viewing applications don't fully support them in some situations. For example, OpenOffice.org doesn't currently allow the use of common text styles with spreadsheets, while it allows common and automatic text styles in text documents.

A text style can apply to one or more text spans; see the "Text spans" section. It can be used as the default text style of a document. In addition, an existing text style may be reused to set the text properties of a paragraph style (see below).

The example hereafter creates a text style, so called "My Colored Text", using Times New Roman, 14-sized navy blue bold italic characters with a yellow background::

   $s = odf_create_style('text',
                        name            => 'MyColoredText',
                        'display name'  => 'My Colored Text',
                        font            => 'Times New Roman',
                        size            => '14pt',
                        weight          => 'bold',
                        style           => 'italic',
                        color           => '#000080'
                        );
   $s->set_background(color => '#ffff00')

This new style could be inserted using insert_style() then retrieved and changed later using get_style() then the set_properties() method of the style object. For example, the following code modifies an existing text style definition so the font size is increased to 16pt and the color turns green:

   $s = $document->get_style('text', 'MyColoredText');
   $s->set_properties(size => '16pt', color => '#00ff00');

The set_properties() method may be used in order to delete a property, without replacement; to do so, the target property must be set to undef.

Note that set_properties() can't change any identifying attribute such as name, family or display name.

The lpOD level 1 API allows the applications to set any property without ODF compliance checking. The compliant property set for text styles is described in the section §15.4 of the OASIS ODF specification. Beware, some of them are not supported by any ODF text processor or viewer.

The API allows the user to set any attribute using its official name according to the ODF specification (§15.4). For example, the properties which control the character name and size are respectively fo:font-name and fo:font-size. However, the API allows the use of mnemonic shortcuts for a few, frequently required properties, namely:

• font: font name;

• size: font size (absolute with unit or percentage with '%');

• weight: font weight, which may be normal, bold, or one of the official nine numeric values from 100 to 900 (§15.4.32);

• style: to specify whether to use normal or italic font face; the legal values are normal, italic and oblique;

• color: the color of the characters (i.e. foreground color), provided as a RGB, 6-digit hexadecimal string with a leading '#';

• underline: to specify if and how text is underlined; possible values are solid (for a continuous line), dotted, dash, long dash, dot dash, dot dot dash, wave, and none;

• display: to specify if the text should by displayed or hidden; possible values are true (meaning visible) none (meaning hidden) or condition (meaning that the text is to be visible or hidden according to a condition defined elsewhere).

A text style may have a background color, but not a background image.

Paragraph family

A paragraph style apply to paragraphs at large, i.e. to ODF paragraphs and headings, which are the common text containers. It controls the layout of both the text content and the container, so its definition is made of two distinct parts, the text part and the paragraph part.

The text part of a paragraph style definition may have exactly the same properties as a regular text style. The rules are defined by the §15.4 of the OASIS 1.1 ODF specification, and the API provides the same property shortcuts as for a text style creation. Practically, this text part defines the default text style that apply to the text content of the paragraph; any property in this part may be overriden as soon as one or more text spans with explicit styles are defined inside the paragraphs.

The creation of a full-featured paragraph style takes two steps. The first one is a regular odf_create_style() instruction, with paragraph as the value of the family mandatory argument, a name parameter (unless the user just wants to create a default style) and any number of named paragraph properties. The second (optional) step consists of appending a text part to the new paragraph style; it can be accomplished, at the user's choice, either by specifying a previously defined text style element, or by explicitly defining new text properties, through the set_properties() method with the area option set to text. In the second case, the prototype text style is provided through the clone parameter.

Assuming that a "MyColoredText" text style has been defined according to the text style creation example above, the following sequence creates a new paragraph style whose text part is a clone of "MyColoredText", and whose paragraph part features are the text justification, a first line 5mm indent, a black, continuous, half-millimiter border line with a bottom-right, one millimeter grey shadow, with other possible properties inherited from a "Standard" style:

   $ps = odf_create_style(
                        'paragraph',
                        name            => 'BorderedShadowed',
                        'display name'  => 'Strange Boxed Paragraph',
                        parent          => 'Standard',
                        align           => 'justify',
                        indent          => '5mm',
                        border          => '0.5mm solid #000000',
                        shadow          => '#808080 1mm 1mm'
                        );
   $ts = $document->get_style('text', 'MyColoredText');
   $ps->set_properties(area => 'text', clone => $ts);

Note that "MyColoredText" is reused by copy, not by reference; so the new paragraph style will not be affected if "MyColoredText" is changed or deleted later.

The value of the clone parameter, if any, may be a paragraph style element instead of a text style element, provided that the given paragraph style contains a text part; so the text part of the given paragraph style (and this part only) is used as the prototype.

The API allows the user to set any attribute using its official name according to the ODF specification related to the paragraph formatting properties (§15.5). However, the API allows the use of mnemonic shortcuts for a few, frequently required properties, namely:

• align: text alignment, whose legal values are start, end, left, right, center, or justify;

• align-last: to specify how to align the last line of a justified paragraph, legal values are start, end, center;

• indent: to specify the size of the first line indent, if any;

• widows: to specify the minimum number of lines allowed at the top of a page to avoid paragraph widows;

• orphans: to specify the minimum number of lines required at the bottom of a page to avoid paragraph orphans;

• together: to control whether the lines of a paragraph should be kept together on the same page or column, possible values being always or auto;

• margin: to control all the margins of the paragraph;

• margin xxx (where xxx is left, right, top or bottom): to control the margins of the paragraph separately;

• border: a 3-part string to specify the thickness, the line style and the line color (according to the XSL/FO grammar);

• border xxx (where xxx is left, right, top or bottom): the same as border but to specify a particular border for one side;

• shadow: a 3-part string to specify the color and the size of the shadow;

• padding: the space around the paragraph;

• padding xxx (where xxx is left, right, top or bottom): to specify the space around the paragraph side by side;

• keep with next: to specify whether or not to keep the paragraph and the next paragraph together on a page or in a column, possible values are always or auto;

• break xxx (where xxx is before or after): to specify if a page or column break must be inserted before or after any paragraph using the style, legal values are page, column, auto.

A pararaph style may have a background color or image.

cpanm ODF::lpOD

perl -MCPAN -e shell
install ODF::lpOD