Editing Complex text layout (section)

{{Short description|Neighbour-dependent grapheme positioning}}
{{Self-reference|For assistance with enabling complex text layout on your computer, see [[Help:Multilingual support]].}}
{{More footnotes|date=July 2013}}
[[File:JanaSanskritSans ddhrya.svg|thumb|The [[Devanagari]] ''{{IAST|ddhrya}}''-ligature, as displayed in the [https://web.archive.org/web/20110716160603/http://tdil.mit.gov.in/download/janasanskrit.htm JanaSanskritSans] font, which should be invoked by the layout engine to render the sequence द + ् + ध + ् + र + ् + य = द्ध्र्य.]]
[[File:Arabicrender.png|thumb|250px|The word {{lang|ar|العربية}} ''{{Transliteration|ar|al-arabiyyah}}'', "the Arabic [language]" in Arabic, in successive stages of rendering. The first line shows the letters in left-to-right order and unjoined, as they might appear in an application without complex text layout. In the second line, bidirectional display has been applied, and in the third the [[glyph]]-shaping mechanism has rendered the letters according to context.]]

'''Complex text layout''' ('''CTL''') or '''complex text rendering''' is the [[typesetting]] of [[writing system]]s in which the shape or positioning of a [[grapheme]] depends on its relation to other graphemes. The term is used in the field of software [[internationalization and localization|internationalization]], where each grapheme is a [[character (computing)|character]].

Scripts which require CTL for proper display may be known as '''complex scripts'''. Examples include the [[Arabic alphabet]] and scripts of the [[Brahmic scripts|Brahmic family]], such as [[Devanagari]], [[Khmer script]] or the [[Thai alphabet]]. Many scripts do not require CTL. For instance, the [[Latin alphabet]] or [[Chinese character]]s can be typeset by simply displaying each character one after another in straight rows or columns. However, even these scripts have alternate forms or optional features (such as [[cursive]] writing) which require CTL to produce on computers.