An ICU OpenSource Library Supporting the Display of Complex Scripts
Eric Mader - IBM's Globalization Center of Competency
Some scripts require rendering behavior that is more complicated than the Latin script. We refer to these scripts as "complex scripts" and to text written in these scripts as "complex text." Examples of complex scripts are the Indic scripts (e.g. Devanagari, Tamil, Telugu and Gujarati), Thai and Arabic.
The ICU LayoutEngine is an OpenSource library that provides a uniform, easy to use interface for preparing complex text for display. The LayoutEngine code is independent of the underlying platform's font and rendering architecture. All access is through an abstract base class. A concrete instance of this base class must be implemented for each platform.
Complex text has four main complications:
Another complication is that in most cases, the contextual and ligature forms of characters have not been assigned Unicode code points and so cannot be displayed directly using code points.
The ICU LayoutEngine handles these complications in one of four ways:
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