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Arabic Script Unicode Fonts
for OpenType™ and AAT systems

Bob Hallissy, Jonathan Kew, 2007-06-22; 244792 reads

    Overview
        Character repertoire
        Language specific features
        Advanced features
    Software requirements
        Basic rendering
        Advanced features
    Downloads

Overview

Scheherazade and Lateef are extended Arabic script fonts designed by SIL International for modern Unicode-based systems using either OpenType or AAT (Apple Advanced Typography) for complex-script rendering. They support virtually all of the Unicode 4.1 Arabic character repertoire (excluding the Arabic Presentation Forms blocks, which are not recommended for normal use). Each typeface is currently available in Regular weight only.

Scheherazade, named after the heroine of the classic Arabian Nights tale, is designed in a similar style to traditional typefaces such as Monotype Naskh, extended to cover the full Unicode Arabic repertoire.

Lateef is named after Shah Abdul Lateef Bhitai, the famous Sindhi mystic and poet. It is intended to be an appropriate style for use in Sindhi and other languages of the South Asian region:

Both designs provide a “simplified” rendering of Arabic script, using basic connecting glyphs but not including a wide variety of additional ligatures or contextual alternates (only the required lam-alef ligatures). This simplified style is often preferred for clarity, especially in non-Arabic languages, but may be considered unattractive in more traditional and literate communities.

Character repertoire

Unicode block	Scheherazade	Lateef
Arabic		except for 0600..0603, 060B, 060E..0613, 0615
Arabic Supplement
Arabic Presentation Forms-A
Arabic Presentation Forms-B
Codepage 1252 (Western)1

A selection of characters from the General Punctuation block, such as various-sized spaces, are also supported; a utility such as SIL ViewGlyph can be used to examine the exact repertoire of each font.

Language specific features

Advanced features

Behavior	Scheherazade	Lateef
U+0600 ARABIC NUMBER SIGN	1-3 digits
U+0601 ARABIC SIGN SANAH	1-4 digits
U+0602 ARABIC FOOTNOTE MARKER	1-2 digits
U+0603 ARABIC SIGN SAFHA	1-3 digits
U+06DD ARABIC END OF AYAH	1-3 digits; stylistic alternates	1-3 digits

Software requirements

These fonts utilize OpenType and AAT technology to provide rendering information needed by application and system software. Usability of the features provided in these fonts will depend on the exact capabilities of your software.

Arabic script is a complex and difficult script, and this complexity is compounded by the fact that Arabic script is used for many different languages and cultures with variations in acceptable calligraphic style. From a computer perspective at least, the technologies used to implement Arabic script are not yet fully mature. The result is that while a given font might work for one set of languages on a given software platform, the same font might not work for other languages or on other platforms. This means that it is very difficult to give an accurate answer to the question of software requirements.

Basic rendering

These Arabic fonts are available in versions for two different rendering technologies, OpenType and AAT. The exact behavior varies slightly, because of the differing capabilities of these technologies.

OpenType

The fonts support the OpenType shaping features specified by  Microsoft. The result is that the fonts work pretty well in Microsoft Office XP (or later) as well as in most  Uniscribe-based applications such as  Paratext 6 and  Toolbox. At this time Uniscribe has not been updated for Unicode 4.1 and so does not support the Arabic Supplement characters (U+0750..U+077F), nor a few new characters in the 06xx block.

 International Components for Unicode (ICU) includes a shaping engine for Arabic text and thus applications such as XeTeX that use ICU Layout will be able to render text using SIL's Arabic fonts. The ICU Layout library used in XeTeX has been updated to support the Arabic Supplement characters added in Unicode 4.1.

 OpenOffice Writer on Windows is Uniscribe-based and on Linux is ICU-based. See preceding paragraphs regarding Uniscribe and ICU. Note that the character repertoire supported depends on the version of ICU Layout used, and may not yet include the latest additions to Unicode.

If you are aware of specific software environments where these fonts are known to work (or not work), we would like to hear from you.

Apple Advanced Typography (AAT)

The AAT-enabled versions of these fonts should automatically render with the proper contextual forms in applications that use the ATSUI (Apple Type Services for Unicode Imaging) text system on Mac OS X. This includes many standard OS X applications such as TextEdit, as well as software such as XeTeX (which can work with both the OpenType and AAT fonts). Note, however, that (like other Arabic fonts) they will not render properly in products such as Microsoft Word, Adobe InDesign, or other applications that use their own text-handling routines rather than relying on ATSUI.

Because of limitations of the AAT technology, diacritic positioning with the AAT-enabled fonts may be less accurate than the OpenType versions, and stacking of multiple diacritics is not well supported (except for a few commonly-used combinations).

Advanced features

Language-specific features in OpenType

For each supported script, an OpenType font provides a set of rules detailing the default shaping behavior. The font may optionally provide alternate shaping behavior to be used for specific languages.2 For example, the shape of U+0647  ARABIC LETTER HEH may need to be slightly different for the Sindhi language than for typical Arabic use.

However, the infrastructure needed to access the language-specific behavior is not yet present in a majority of applications. For example: with the exception of alternate digits, Uniscribe-based applications such as Microsoft Office do not benefit from language-specific behavior. Some ICU-based apps, e.g., XeTeX, can access language-specific behavior.

Optional font features in AAT

AAT fonts do not have the same model of “language systems” as OpenType, but the same glyph variants are accessible through “font features” that can be accessed via the Typography palette in many OS X applications (available from the “gear” icon in the Font panel, when this panel is large enough).

U+06DD ARABIC END OF AYAH and subtending marks (U+0600 ARABIC NUMBER SIGN..U+0603 ARABIC SIGN SAFHA)

These Arabic characters are intended to enclose or hold one or more digits. Uniscribe-based applications are likely to display these properly. Other applications may require the following hack: precede the entire sequence (subtending mark plus following digits) with either U+202D LEFT-TO-RIGHT OVERRIDE or U+202E RIGHT-TO-LEFT OVERRIDE and follow the entire sequence with U+202C POP DIRECTIONAL FORMATTING. Exactly which of these hacks might work depends on your application. (For typesetting with XeTeX, this can be automated using the “font mapping” feature to insert the directional controls needed.)

Additionally, Scheherazade includes two simplified alternates for U+06DD ARABIC END OF AYAH under the Stylistic Alternates (salt) feature, but at this time we know of no OpenType-based applications that can access these.

These characters, including the alternate U+06DD ARABIC END OF AYAH forms in Scheherazade, are also supported in the AAT versions of the fonts. However, at least in version 10.3 of Mac OS X, the Cocoa text system does not render them correctly, and so they will only work properly in applications such as WorldText or XeTeX that use ATSUI directly, not through the Cocoa text framework.

Downloads

Visit the Arabic Script Unicode Fonts — Downloads page for license details and downloadable packages.

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1	Inclusion of basic Latin repertoire is provided as a convenience, e.g., for use in menus or for displaying markup in text files; these fonts are not intended for extensive Latin script use.
2	For details see the Overview section of  OpenType Layout Common Table Formats.

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