PDFlib Text Extraction Toolkit (TET) Manual

Composite characters and sequences. Some glyphs map to a sequence of multiple
characters. For example, ligatures will be mapped to multiple characters according to
their constituent characters. However, composite characters (such as the Roman numeral
in Figure 7.1) may or may not be split, subject to information in the font and PDF
as well as the decompose document option (see Section 7.3, »Unicode Postprocessing«,
page 97).
If appropriate, TET will split composite characters into a sequence of constituent
characters. The corresponding sequence will be part of the text returned by TET_get_
text( ). For each character, details of the underlying glyph(s) can be obtained via TET_get_
char_info( ), including the information whether the character is the start or continuation
of a sequence. Position information will only be returned for the first character of a
sequence. Subsequent characters of a sequence will not have any associated position or
width information, but must be processed in combination with the first character.
Characters without any corresponding glyph. Although every glyph on the page will
be mapped to one or more corresponding Unicode characters, not all characters delivered
by TET actually correspond to a glyph. Characters which correspond to a glyph are
called real characters, others are called artificial characters. There are several classes of
artificial characters which will be delivered although a directly corresponding glyph is
not available:
> A composite character (see above) will map to a sequence of multiple Unicode characters.
While the first character in the sequence corresponds to the actual glyph, the
remaining characters do not correspond to any glyph.
> Separator characters inserted via the lineseparator/wordseparator options are artifacts
without any corresponding glyph.
7.1 Important Unicode Concepts 93