Complex text layout

However, even these scripts have alternate forms or optional features (such as cursive writing) which require CTL to produce on computers.

For example, the Greek alphabet has context-sensitive shaping of the letter sigma, which appears as ς at the end of a word and σ elsewhere.

Most text-rendering software that is capable of CTL will include information about specific scripts, and so will be able to render them correctly without font files needing to supply instructions on how to lay out characters.

Examples of this latter approach include Apple Advanced Typography (AAT) and Graphite.

The OpenType format is primarily intended for systems using the first approach (layout knowledge in the renderer, not the font), but it has a few features that assist with CTL, such as contextual ligatures.

The Devanagari ddhrya -ligature, as displayed in the JanaSanskritSans font, which should be invoked by the layout engine to render the sequence द + ् + ध + ् + र + ् + य = द्ध्र्य.
The word العربية 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.