PDFlib 8 Windows COM/.NET Tutorial

Requirements for shaping. A font for use with complex script shaping must meet the
following requirements in addition to containing glyphs for the target script:
> It must be a TrueType or OpenType font with GDEF, GSUB, and GPOS feature tables
and correct Unicode mappings appropriate for the target script. As an alternative to
the OpenType tables, for the Arabic and Hebrew scripts, the font may contain glyphs
for the Unicode presentation forms (e.g. Arabic Apple fonts are constructed this
way). In this case internal tables will be used for the shaping process. For Thai text
the font must contain contextual forms according to Microsoft, Apple, or Monotype
Worldtype (e.g. used in some IBM products) conventions for Thai.
> If standard CJK fonts are to be used, the corresponding font file must be available.
> The font must be loaded with encoding=unicode or glyphid.
> The monospace and vertical options of load_font( ) must not be used, and the
readshaping option must not be set to false.
> If the fallbackfonts option of load_font( ) was used, text in a single text run must not
contain glyphs from a fallback font.
6.4.2 Script and Language
Script and language settings play a role the functional aspects listed below. They can be
controlled with the following options:
> The script text option identifies the target script (writing system). It supports the
four-letter keywords listed in Table 6.2. Examples:
script=latn
script=cyrl
script=arab
script=hebr
script=deva
script={lao }
With script=_auto PDFlib automatically assigns that script to which the majority of
characters in the text belong. Since Latin text doesn’t require shaping it will not be
counted when determining the script automatically.
You can query the scripts used for some text with the scriptlist keyword of info_
textline( ).
> The language option specifies the natural language in which the text is written. It
supports the three-character keywords listed in Table 6.3. Examples:
language=ARA
language=URD
language=ZHS
language=HIN
Complex script processing. Complex script processing (option shaping) requires the
script option. The language option can additionally be supplied. It controls languagespecific
aspects of shaping, e.g. different figures for Arabic vs. Urdu. However, only few
fonts contain language-specific script shaping tables, so in most cases specifying the
script option will be sufficient, and shaping cannot be improved with the language option.
OpenType layout features. Fonts can implement OpenType layout features in a language-specific
manner (see »Script- and language-specific OpenType layout features«,
6.4 Complex Script Output 165