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Gentium Plus — Documentation and Support

NRSI team, 2010-11-01; 11352 reads

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Table of Contents for this web page:

    System requirements
    Features of the font
        Advanced typographic capabilities
        User-selectable font features
        Known Issues
    Supported character ranges
        Private-use (PUA) characters
    WOFF Support
    Conversion
    Keyboarding
    Support

System requirements

The Gentium Plus font is designed to work on systems and with applications that provide support for TrueType fonts and for Unicode character encoding. This includes Microsoft Windows® 9x or greater, as well as recent versions of the Mac OS (version 9.0 and later), and also some implementations of Unix / Linux (TrueType font support on Unix and Linux may depend upon the particular applications in use). On some systems (true, at least, of 32-bit Windows), it can also be used with older applications that use legacy, industry-standard, 8-bit character encodings.

The preceding characterization of system requirements describes the minimum needed to display characters. Realizing the full capabilities of this font involves additional requirements. This font is designed to work with either of two advanced font technologies, Graphite or OpenType. To take advantage of the advanced typographic capabilities of this font, you must be using applications that provide an adequate level of support for Graphite and OpenType.

Features of the font

Gentium Plus contains near-complete coverage of all the characters defined in Unicode 5.1 for Latin and Cyrillic. In total, over 5,500 glyphs are included, providing support for over 2,500 characters as well as a large number of ligated character sequences (e.g., contour tone letters used in phonetic transcription of tonal languages) and alternately-designed glyphs. These are provided for a number of characters for use in particular contexts. The glyphs are accessible in applications that support advanced font technologies, specifically the Graphite or OpenType technologies. These technologies are also utilized to provide automatic positioning of diacritics relative to base characters in arbitrary base+diacritic combinations (including combinations involving multiple diacritics).

Some important issues with respect to Unicode need to be borne in mind. Unicode is a character encoding and not a glyph encoding. Thus you should endeavor to use the character that reflects your character needs rather than finding a glyph that looks right and using its character code. Thus, for example, there is only one code for CAPITAL ENG (U+014A), although there are 4 different glyph shapes for this character in use around the world. Therefore it is necessary to use other means, such as user-selectable font features, to ensure that your document displays the right glyph for the character that you are anticipating. The advanced typographic capabilities mentioned above provide this very capability.

See also “How do I use a feature?”

Advanced typographic capabilities

This font supports various advanced typographic capabilities using the Graphite or OpenType font technologies.

• Automatic conversion of sequences of pitch letters (U+02E5..U+02E9 and U+A712..U+A716) into ligatures.
• Automatic fi-type ligatures.
• Auto placement of diacritics to a sufficient level of stacking.
• Auto placement of double-width diacritics (U+035C..U+0362) according to heights and depths of adjacent clusters (in Graphite only)
• Vietnamese diacritic placement handling (enabled via a user-selectable font feature).

The automatic placement of diacritics is supported for data that may or may not be canonically ordered (as defined by the  Unicode Standard). This should normally be the responsibility of application software and text-processing resources (such as input methods), however, and not the user.

These capabilities are available in any application that supports the Graphite technology. They are also available via the OpenType technology, though this requires applications that provide a sufficient level of support for OpenType features. (See System Requirements.)

TypeTuner Support: Andika, Charis SIL, Doulos SIL and Gentium — a typeface for the nations all have SIL TypeTuner support. They are also all available through the online SIL TypeTuner Web.

User-selectable font features

The document below can be downloaded in order to see all the user-selectable font features that are available in the font. The feature names, feature ids, settings and examples are provided. The document was produced with Graphite OpenOffice.

Font Features for Gentium Plus 1.502 Lorna A. Priest, 2010-10-28 Download "GentiumPlus-features.pdf", Acrobat PDF document, 638KB [2633 downloads]

Because of the reduced character set, Gentium Basic Fonts included only some of the font features in Doulos SIL and Charis SIL. However, Gentium Plus has all of the font features found in Charis SIL and Doulos SIL. It also has a few features not found in those fonts.

These features are new to our Roman fonts:

Font features

TypeTuner legend: (All features are available for Graphite applications.)
R=glyphs are Reencoded (will work with dumb rendering); O=OpenType rules are activated; G=Graphite-only feature

Known Issues

• The documentation (GentiumPlus-features.pdf) states the wrong values for the Low-profile diacritic feature. They should be 0=False and 1=True (instead of 0=High angle and 1=Low angle). This probably only has an effect on XeTeX usage (eg \font\test="Gentium Plus/GR:Low-profile diacritics=True).
• The font does not currently support the AAT capabilities that are in Doulos SIL and Charis SIL.
• There is no ligature substitution for U+0344 COMBINING GREEK DIALYTIKA TONOS from U+0308 COMBINING DIAERESIS followed by U+0301 COMBINING ACUTE ACCENT, but U+0344 can be obtained by entering the USV directly.
• On some systems tone contours have small spaces between each segment of a contour in OpenType support (this problem does not occur using Graphite).
• Greek support for NFD text is provided in Graphite by converting to NFC form. It has not had a lot of testing.
• There is some inconsistency in the use of low-profile diacritics between OpenType and Graphite and depending on whether you are using NFC or NFD data.
• U+1FBD GREEK KORONIS acts as a combining mark rather than as a spacing character (Graphite-only)
• The glyphs for U+1ECB LATIN SMALL LETTER I WITH DOT BELOW and U+1E2D LATIN SMALL LETTER I WITH TILDE BELOW use low profile forms of the lower case i, so they look slightly wrong. (They look identical to the low profile variants.)
• Kerning is supported in the OpenType but not yet in Graphite.
• When keyboarding Cyrillic texts the application may switch to another font. The workaround is to type the text and then apply Gentium Plus. We are working on a solution to this problem.
• The Graphite features in this font are not currently handled by the CSS support in Firefox 11.

Supported character ranges

This font supports over 2,500 characters from the Unicode 5.1 standard as well as over 229 Private Use Area (PUA) characters. In total, 5,500 glyphs are included, supporting stylistic alternates for a number of characters as well as a large number of ligated sequences (e.g., contour tone letters used in phonetic transcription of tonal languages). The following character ranges constitute the list of characters supported by this font:

Supported character ranges

Private-use (PUA) characters

There are 230 private-use characters that are supported in this font. These conform to SIL International’s corporate registry for usage of the Unicode private-use areas. Characters which are not yet in Unicode are shown below.

Specials

Combining Marks

Modifier Letters

Latin

Cyrillic

Deprecated SIL Corporate PUA characters Lorna A. Priest, 2012-02-07; 9541 reads

These PUA characters have been added to Unicode and are being deprecated. This page lists those PUA characters along with the appropriate Unicode codepoints. Please use the Unicode codepoint instead of the PUA codepoint. Our SIL Unicode Roman fonts will continue to support the PUA codepoint for backwards compatibility purposes.

WOFF Support

WOFF (Web Open Font Format) is a font 'wrapping' technology that is poised to become the standard for web fonts for the long-term future and has broad support, even in Internet Explorer 9. It compresses the font data, so is more efficient (and faster) than referring to hosted TrueType or OpenType fonts. It also is likely to have better long-term support. As of October 2010, WOFF fonts are supported in Firefox 3.6+, Chrome 6, Internet Explorer 9 preview versions and development versions of Safari.

We are working to provide standard WOFF versions of our fonts that you can download and host on your server. Gentium Plus is our first WOFF font made available to the public. See the download page.

Further information on using and testing are available here:

• Using SIL Fonts on Web Pages
• Demo page for using SIL fonts

Conversion

In order to use this font with existing data that was created for use with fonts developed using the Encore Fonts system, or with custom-encoded fonts created by other means, it is necessary to re-type or convert data to produce data that is encoded in conformance with the Unicode Standard. TECkit is one program that can be used for character encoding conversion. TECkit allows users to write their own custom conversion mappings.

The TECkit package is available for download from SIL’s TECkit Web site.

Some TECkit mapping files have already been created for some of the more widely used SIL legacy fonts.

The Unicode 4.1 standard included 139 characters that were previously allocated to codepoints in the Private Use Area by SIL's PUA committee. The Unicode 5.0 standard includes 45 characters that were previously allocated to codepoints in the Private Use Area by SIL's PUA committee. The Unicode 5.1 standard includes 17 characters that were previously allocated to codepoints in the Private Use Area by SIL's PUA committee.

All processes (input methods, mappings) that create Unicode data should be revised to generate the proper Unicode values instead of PUA codes.

If you have data that contains these PUA codes, it should be updated by replacing each PUA character with its official Unicode counterpart. This will facilitate data interchange and the use of standard fonts and software.
SIL PUA to Unicode 5.1 Mapping is provided for converting your data.

Keyboarding

The ability to obtain full benefits of this font is also dependent upon having means for Unicode character input. This package does not include keyboard input methods. Most current operating systems provide keyboard input methods for a number of different languages that have writing systems based on the Roman or Cyrillic scripts. Various means may be available for different operating-system platforms to create additional input methods for other languages. Some of these are listed here: Some tools and resources for character input.

Support

As this font is distributed at no cost, we are unable to provide a commercial level of personal technical support. We will, however, try to resolve problems that are reported to us.

Please note that this font is intended for use by experienced computer users. Installing and using this font is not a trivial matter. The most effective technical support is usually provided by an experienced computer user who can personally sit down with you at your computer to troubleshoot the problem.

Before requesting technical support, please:

• Carefully read all the documentation provided with the font.
• Check out all the links on this and the other SIL Unicode Roman fonts web pages, and read all the information and instructions the web pages contain.
• Review the list of Gentium — FAQ, SIL Unicode Roman Fonts – FAQ and Known Issues and the general Font FAQ page to see if your question has already been answered.

If that fails to answer your question, or for more information, contact:

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