Overview of CTL Technology

Complex Text Layout (CTL) extensions enable Motif APIs to support writing systems that require complex transformations between logical and physical text representations, such as Arabic, Hebrew, and Thai. CTL Motif provides character shaping, such as ligatures, diacritics, and segment ordering, and supports the transformation of static and dynamic text widgets. It also supports right-to-left and left-to-right text orientation and tabbing for dynamic text widgets. Since text rendering is handled through the rendition layer, other widget libraries can be easily extended to support CTL.

To leverage the new features, users must have the Portable Layout Services (PLS) library and the appropriate language engine. CTL uses PLS as the interface to the language engine, and uses the language engine to transform text before it is rendered. Applications that support CTL must include additional resources as described in the CTL documentation.

Specifically, XmCTL supports the following complex language shaping and reordering features provided by underlying locale-dependent PLS module transformations:

• Positional variation

• Ligation (many-to-one) and character composition (one-to-many)

• Diacritics

• Bi-directionality

• Symmetrical swapping

• Numeral shaping

• String validation