Complex text layout
Complex text layout (CTL) or complex text rendering is the typesetting of writing systems 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, where each grapheme is a character. Scripts which require CTL for proper display may be known as complex scripts. Examples include the Arabic alphabet and scripts of the Brahmic family, such as Devanagari, Khmer script or the Thai alphabet. Many scripts do not require CTL. For instance, the Latin alphabet or Chinese characters 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. Characteristics requiring CTL The main characteristics of CTL complexity are: Bi-directional text, where characters may be written from either right-to-left or left-to-right direction. Context-sensitive shaping and ligatures, where a character may change its shape, dependent on its location and/or the surrounding characters. For example, a character in Arabic script can have as many as four different shape-forms, depending on context. Ordering, where the displayed order of the characters is not