Complex Text Layout (CTL) refers to the typesetting of writing systems which require complex transformations between text input and text display for proper rendering on the screen or the printed page (also known as complex scripts). In other words, for these scripts the way text is stored is not mapped to the way it is displayed in a straightforward fashion. The term is used in the field of software internationalization. Writing Systems of the World today A Specimen of typeset fonts and languages, by William Caslon, letter founder; from the 1728 Cyclopaedia. ... Internationalization and localization are means of adapting products such as publications or software for non-native environments, especially other nations and cultures. ...

Examples of writing systems requiring CTL are the Arabic alphabet and scripts of the Brahmic family such as Devanagari or the Thai alphabet. The examples and perspective in this article or section may not represent a worldwide view. ... The Brahmic family is a family of abugidas (writing systems) used in South Asia, Southeast Asia, Tibet, Mongolia, Manchuria, and to an extent, Korea. ... Rigveda manuscript in Devanagari (early 19th century) Devanāgarī (देवनागरी — in English pronounced ) (ISCII – IS13194:1991) [1] is an abugida alphabet used to write several Indian languages, including Sanskrit, Hindi, Marathi, Kashmiri, Sindhi, Bihari, Bhili, Konkani, Bhojpuri and Nepali from Nepal. ... The Thai alphabet (ตัวอักษรไทย) is used to write the Thai language (ภาษาไทย) and other minority languages in Thailand. ...

CTL may be generalized under the concept of ligature: for the Latin alphabet, ligatures are usually considered a marginal aesthetic concern, but there is no fundamental difference between the ligatures required for acceptable typesetting of the Arabic script, and typesetting a Latin cursive.^[1] Conversely, most characters of the Chinese script are compositional and could be considered ligatures, but are usually encoded as so many individual characters, so that typesetting Chinese requires an enormous typeface rather than sophisticated layout. In writing and typography, a ligature occurs where two or more letterforms are written or printed as a unit. ... The Latin alphabet, also called the Roman alphabet, is the most widely used alphabetic writing system in the world today. ... Cursive is any style of handwriting in which all the letters in a word are connected, making a word one single (complicated) stroke. ... Technical note: Due to technical limitations, some web browsers may not display some special characters in this article. ...

The main characteristics of CTL language complexity are:

• Bi-directional text, where characters may be written from either right-to-left or left-to-right direction.
• Context-sensitive shaping (ligatures), where character may changes its shape, depends on its location and/or surrounding characters. For example, a character in Arabic script can have at least four different shape forms, depending on context.
• Ordering, the displayed order of the characters is not the same as the logical order. For example, in Devanagari, which is written from left to right, the grapheme for "short i" appears to the left ("before") the preceding vowels: in कि ki, the ि -i should render on the left, its bow reaching until above the क k- to the right.

Some writing systems of the world, such as Arabic and Hebrew, are written in a form known as right-to-left (RTL), in which writing begins at the right-hand side of a page and concludes at the left-hand side. ... The Arabic alphabet is the script used for writing the Arabic language, which is the language of the Quran, the holy book of Islam. ...

Notes

1. ^ indeed, historically, the Arabic alphabet is simply a cursive of the Nabatean alphabet, with context-dependent letter shapes that became mandatory from ca. the 4th century AD.

The Nabatean alphabet is a consonantal alphabet (abjad) that was used by the Nabateans in the 2nd century BC. Important inscriptions are found in Petra. ...

See also

• CJK
• Unicode
• Typography

CJK is a collective term for Chinese, Japanese, and Korean, which comprise the main East Asian languages. ... Because of technical limitations, some web browsers may not display some special characters in this article. ... This article or section is in need of attention from an expert on the subject. ...

External links

• Examples of complex rendering — SIL international's examples of complex writing systems around the world
• Complex Text Layout — The Open Group's Desktop Technologies
• Supporting Indic Scripts in Mozilla — also other CTL scripts
• Project SILA — Graphite and Mozilla integration project
• CTL Architecture in Solaris — Solaris Globalization Whitepapers
• Complex Scripts — Microsoft Global Development and Computing Portal
• Theppitak's Homepage — information about Thai language processing