3monkeys

Overview

In my last article, OpenOffice .odt Opened Up – Part 2: Meta and Settings, I discussed two of the four top level subdocument elements, office:document-meta and office:document-settings. In this article, I will be taking a closer look at the office:document-styles element, in particular the office:font-face-decls sub-element. As before, my test cases where produced with the following software:

• SuSE Linux 10.1
• OpenOffice 2.0.2.7.1
• zip 2.31 (March 8th 2005)

The Relax-NG schema language is used to define elements of the specification. The original source document can be downloaded here oo_part1.odt, and in particular the subdocument under observation can be downloaded here styles.xml.

The office:document-styles element

The office:document-styles root element contains all font face declarations, named styles, automatic styles and master styles need for the document.

office:document-styles schema

Next let us explore the office:font-face-decls sub-element.

The office:font-face-decls element

This element is actually duplicated in the top-level office:document-content element. A few simple test indicate that, if differences exist in the two sub-elements, complete element omissions in one are populated by the other, and where two elements differ in content the definition in office:document-styles takes precedence, though this behavior is not defined explicately in the specification.

The office:font-face-decls element consist of style:font-face elements. If you remember, we generated our test document by selecting text from a pdf and pasting that text into an .odt. This generated such style:font-face elements as follows:

With the exception of the last element, this looks pretty ugly. The following is a sample of style:font-face elements taken from a newly created document.

The reason for this is that OpenDocument font face declarations directly correspond to the @font-face font description of CSS2 and the <font-face> element of SVG, but have two extensions.

1. OpenDocument font face declarations optionally may have an unique name. This name can be used inside styles as the value of the style:font-name attribute to immediately select a font face declaration. If a font face declaration is referenced this way, the steps described in CSS2 font matching algorithms for selecting a font declaration based on the font-family, font-style, font-variant, font-weight and font-size descriptors will not take place, but the referenced font face declaration is used directly.
2. Some additional font descriptor attributes may exist.

Which basically means svg:font-family="EIDQUI+CMSLTT10" uses the SVG font matching algorithm and not the named font. SVG is beyond the scope of this article. Reference material for SVG font declarations can be found here.

Back to the bigger picture. The benefit we can observe from this, is that a predefined set of fonts can be applied to an .odt. By doing this we can ensure that documents contain a consistent set of fonts and eliminate potential redundancy or functional overlap. Care must be taken that if a style:font-face is replaced, that all style:font-name, style:font-name-complex and style:font-name-asian attributes are examined and replaced as well. While potential size gains are arguably minimal, gains in consistent look and output are immeasurable.

One option Open Office gives the user to tackle this issue is the font replacement option. Simply choose Tools -> Options then OpenOffice.org -> Fonts. You should see a dialog similar to the following:

Click for full size image

The Open Office user can simply select which fonts to replace with which fonts on an Always or Screen only case. Though this is not always a complete solution. Amore complete solution will be provided in the final installment of OpenOffice .odt Opened Up – Part 3: Styles. I will provide an application that will indeed optimize all of the aspects of the office:document-style elements. Up next is the office:styles element.

Until next time,

-3monkeys

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This entry was posted on Wednesday, April 4th, 2007 at 6:06 am and is filed under ODF, Open Source, Software, Standards, XML. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.