This page describes the complex scripts features of Apache™ FOP, which include:

• Support for languages written with right-to-left scripts, such as Arabic and Hebrew scripts.
• Support for languages written with South Asian and Southeast Asian scripts, such as Devanagari, Khmer, Tamil, Thai, and others.
• Support for advanced substitution, reordering, and positioning of glyphs according to language and script sensitive rules.
• Support for advanced number to string formatting.

Complex script features are enabled by default. If some application of FOP does not require this support, then it can be disabled in three ways:

1. Command line: The command line option -nocs turns off complex script features: fop -nocs -fo mydocument.fo -pdf mydocument.pdf
2. Embedding: userAgent.setComplexScriptFeaturesEnabled(false);
3. Optional setting in fop.xconf file:

   <fop version="1.0">
     <complex-scripts disabled="true"/>
     ...
   </fop>
             

When complex scripts features are enabled, additional information related to bidirectional level resolution, the association between characters and glyphs, and glyph position adjustments are added to the internal, parsed representation of the XSL-FO tree and its corresponding formatted area tree. This additional information will somewhat increase the memory requirements for processing documents that use these features.

In most circumstances, XSL-FO content does not need to change in order to make use of complex scripts features; however, in certain contexts, fully automatic processing is not sufficient. In these cases, an author may make use of the following XSL-FO constructs:

• The script property.
• The language property.
• The writing-mode property.
• The number to string conversion properties: format, grouping-separator, grouping-separator, grouping-size, letter-value, and fox:number-conversion-features.
• The fo:bidi-override element.
• Explicit bidirectional control characters: U+200E LRM, U+200F RLM, U+202A LRE, U+202B RLE, U+202C PDF, U+202D LRO, U+202E RLO.
• Explicit join control characters: U+200C ZWNJ and U+200D ZWJ.

The complex scripts related effects of the above enumerated XSL-FO constructs are more fully described in the following sub-sections.

Support for specific complex scripts is enumerated in the following table. Support for those marked as not being supported is expected to be added in future revisions.

Support for specific fonts is enumerated in the following sub-sections. If a given font is not listed, then it has not been tested with these complex scripts features.

Complex scripts support in Apache FOP is relatively new, so there are certain limitations. Please help us identify and close any gaps.

• Only the PDF output format fully supports complex scripts features at the present time.
• Shaping context does not extend across an element boundary. This limitation prevents the use of fo:character, fo:inline or fo:wrapper in order to colorize individual Arabic letters without affecting shaping behavior across the element boundary.

In addition to the XSL-FO specification, a number of external resources provide guidance about authoring documents that employ complex scripts and the features described above:

• The Unicode Standard
• OpenType Advanced Typographic Extensions
• Examples of Complex Rendering