SIL Fonts - Using Font Features

Characters and Font Features

Each Unicode character supported by our fonts is typically represented by a single glyph, although that glyph may change depending on what other characters are in the sequence nearby, or may even be combined with other glyphs. There are, however, situations in which a different style or appearance of a glyph is preferred. For example:

These alternate glyphs can be controlled through the use of font features. These are user-selectable features applied to text, and often activated in applications through a font properties menu item, dialog, or style definition. They depend on either OpenType or Graphite technology. A font may include features for either technology—or both.

Features may be activated through:

Application support

There is no standard method used by all applications. Every application tends to have a unique way to control features. Applications also differ in which types of features they support. For example, Adobe InDesign supports stylistic set features (ss##) but offers no easy way to control character variant features (cv##).

The following sections describe how to activate particular features in individual applications and describe any limits on supported features. Examples of some features are given, but for details of which fonts support which features see the individual font project documentation.

Web browsers

See separate page about Using SIL Fonts on Web Pages.

Adobe InDesign (and similar Adobe apps)

Select the text and apply the feature as follows, either using the OpenType button (Properties palette, Character section) or the OpenType submenu of the Character palette. Some of these settings can also be applied in style definitions.

Alternate glyphs for individual characters can also be chosen by selecting the character and choosing the alternate from the set of choices that appear under the character.

LibreOffice

Both OpenType and Graphite font features have good support in LibreOffice. Note that if a font supports both OpenType and Graphite, LibreOffice will default to using the Graphite features.

There are two ways to activate stylistic sets and character variants, and the type and level of support has slight differences.

Using the LibreOffice UI

To activate one or more features select the text, go to Format / Character / Font, choose the Features button, then choose one or more features. These can also be applied when defining a style. Note, however, that there is no way to control multi-valued OpenType features through the UI. It needs to be set using the font description (see below). This limitation does not apply to Graphite features.

Editing the LibreOffice font description

Features can also be turned on by selecting the text, choosing the font, then adding the specific feature settings at the end of the font name in the font selection box using the feature ID, as in: fontname:feature=setting

For example, using the Charis SIL font, the Uppercase Eng alternate “Capital N with tail” would be specified as Charis SIL:cv43=2. If you wish to apply two (or more) features, you can separate them with &. Thus, Charis SIL:cv43=2&smcp=1 would apply “Capital N with tail” plus the “Small capitals” feature.

Microsoft Word

Support for font features is very limited in Microsoft Word. Even some OpenType behavior that is automatically activated in other apps requires special settings in Word. For example, to enable conjuncts or ligatures go to Format / Font / Advanced / OpenType features and change None to one of the other settings. It may also be necessary to choose Use Contextual Alternates.

XeTeX

Font features can be set in XeTeX font specifications in the source document or stylesheet.

If your application does not support font features

The only way to control features in applications that support neither OpenType nor Graphite is to create derivative fonts that have the desired behaviors (e.g. alternate glyphs) activated by default. For example, you could have a font called “Gentium Plus UCEng” that is just like Gentium Plus except it normally renders the Eng using the uppercase form. We have created a tool called TypeTuner Web which you can use to create derivative fonts like this based on many of our fonts.

Another good use of TypeTuner Web is to create a small capitals font for use in applications that do not support OpenType small caps (such as Microsoft Word). On TypeTuner Web select the font, choose “Select features”, change the Small Caps setting to “True”, then download and install the font. That will give you a special small capitals font for use in all applications.