In May of 2007, Red Hat announced its Liberation Fonts in response to "proprietary fonts present[ing] a barrier to truly open documents in that Microsoft will not license others to redistribute [their popular] fonts." These fonts are metric equivalents: "the fonts assume the identical horizontal spacing as the Microsoft fonts such that, when substituted for the Microsoft fonts, a line of text is identically displayed."

Why does it matter, are there alternatives fonts that really work, and how do you use them?

Why

The college class assignment is to type 10 pages. You type 10 and turn it in. A week later, the teacher returns your paper marked down for not following directions. The teacher says it was only 8 pages. The problem: you used Bitstream Vera Serif which has large leading (vertical space). The teacher didn't have Bitstream Vera Serif and the word processor substituted Times New Roman. The dimensions of each letter vary between fonts and can cause dramatic differences in layout.

Also, when your employer asks for an application in Microsoft Word .doc format, it isn't the time for gambling with document formats and fonts.

Recently there have been many debates about open document standards. Steven J. Vaughan-Nichols points out the problem is bigger than OOXML vs. OpenDocument. Within documents of any format, standards fonts are still necessary to reproduce the document faithfully.

Finding real metric equivalents

To find the best metric equivalent fonts for the ubiquitous Times New Roman and Arial, I ran some tests.

Against Times New Roman (a serif font) I tested Liberation Serif, Nimbus Roman No9 L, FreeSerif, Bitstream Vera Serif, and Linux Libertine, and the results were mixed. In the horizontal test, FreeSerif better matched Times New Roman than Liberation Serif by a small amount, but Liberation Serif did very well overall.

In the sans-serif fonts tests, Liberation Sans did an excellent job and was the only close match to Arial. See for yourself: the results are available as a PDF and, if you have the fonts installed, as an OpenDocument text .odt file.

Hinting

The Liberation Serif font behavior different according to font hinting. If you use Gnome and want a precise replacement with the Liberation fonts, disable font hinting. The problem is fixed in OpenOffice.org 2.4 (issue 77968).

To replace or to not replace

Should you use the Microsoft TrueType Core fonts or slightly-more-open-source alternatives? It depends.

When your documents are either distributed by PDF, internally within a company that uses the same fonts, or not at all, it's simply your preference.

When documents may be distributed, consider using open source fonts—surprise—by Microsoft. The Core Web fonts are Andale Mono, Arial, Comic Sans MS, Courier New, Georgia, Impact, Times New Roman, Trebuchet MS, Verdana, and Webdings. These de-facto standard fonts are available under an irrevocable open source license and hosted on SourceForge.net (which has strict policies on licenses).

The new Microsoft ClearType Font Collection (standard in Vista and Office 2007) is a different beast. Because of the restrictive license, I suggest not using these fonts for new documents. However, you will encounter them, so you must choose between installing them and font replacement.

Replacement method #1: Fully automatic font substitution

If a font is used in a document but does not exist on the system, the system will guess a substitute. Sometimes it works well and other times not.

OpenOffice.org since version 2.3.0 has automatic substitution rules for the Red Hat Liberation fonts (issue 77470).

Some information is stored in the document. The OpenDocument Specification section 15.4.15 defines 6 generic font families: Roman, Swiss, Modern, Decorative, Script, and System. The Word .doc format may do the same. This font family system does not allow much granularity, so the results are not so good.

I tested this feature with Word 2007. In OpenOffice.org 2.3.1 I created a document with Liberation Sans and Liberation Serif fonts. When transferred via .doc to an XP system with Word 2007, it successfully guessed the family of font (serif vs. non-serif). However, the actual typeface was different, so the number of pages changed significantly.

Basically, don't rely on automatic replacement.

Replacement Method #2: Font fallback within a document

For any range of text, you can specify multiple fonts by typing them in the font selection bar separated by a semicolon. If you work with HTML and CSS, this will feel familiar to you.

OpenOffice.org picks the first listed font. Though OpenOffice.org can store and retrieve this information in both OpenDocument Text and Microsoft Word .doc formats, Microsoft Word 2007 does not support this feature and only uses the first font.

Replacement method #3: Font replacement in OpenOffice.org

At the OpenOffice.org level, you can specify font replacement rules. That means whenever OpenOffice.org encounters font X, it will use font Y instead.

1. Open any OpenOffice.org application.
2. Click Tools > Options.
3. In the tree menu under OpenOffice.org, choose Fonts.
4. Check the box Apply replacement table.
5. Type the name of the Microsoft font in Font.
6. In Replace with, type the name of the non-Microsoft font.
7. Click the green checkmark.
8. Repeat steps 5-7 as needed
   

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