PDFlib 8 Windows COM/.NET Tutorial

8-bit encodings are discussed in detail in Section 4.2, »Single-Byte (8-Bit) Encodings«,
page 101. They can be pulled from various sources:
> A large number of predefined encodings according to Table 4.2. These cover the most
important encodings currently in use on a variety of systems, and in a variety of locales.
> User-defined encodings which can be supplied in an external file or constructed dynamically
at runtime with encoding_set_char( ). These encodings can be based on
glyph names or Unicode values.
> Encodings pulled from the operating system, also known as a system encoding. This
feature is available on Windows, IBM iSeries and zSeries.
The disadvantage of single-byte encodings is that only a limited set of characters and
glyphs is available. For this reason complex script shaping and OpenType layout features
are not supported for single-byte encodings.
Builtin encoding. Among other scenarios, you can specify encoding=builtin to use single-byte
codes for non-textual glyphs from symbolic fonts. The format of a font’s internal
encoding depends on the font type:
> TrueType: the encoding is created based on the font’s symbolic cmap, i.e. the (3, 0)
entry in the cmap table.
> OpenType fonts can contain an encoding in the CFF table.
> PostScript Type 1 fonts always contain an encoding.
> For Type 3 fonts the encoding is defined by the first 255 glyphs in the font.
If the font does not contain any builtin encoding font loading fails (e.g. OpenType CJK
fonts). You can use the symbolfont key in info_font( ) . If it returns false, the font is a text
font which can also be loaded with one of the common single-byte encodings. This is
not possible if the symbolfont key returns true. The glyphs in such symbolic fonts can
only be used if you know the corresponding code for each glyph (see Section 5.4.2, »Selecting
an Encoding for symbolic Fonts«, page 129).
The disadvantage of encoding=builtin is that in single-byte encoded text character
references cannot be used.
Multi-byte encodings. This encoding type is supported for CJK fonts, i.e. TrueType and
OpenType CID fonts with Chinese, Japanese, or Korean characters. A variety of encoding
schemes has been developed for use with these scripts, e.g. Shift-JIS and EUC for Japanese,
GB and Big5 for Chinese, and KSC for Korean. Multi-byte encodings are defined by
the Adobe CMaps or Windows codepages (see Section 4.3, »Chinese, Japanese, and Korean
Encodings«, page 105).
These traditional encodings are only supported in non-Unicode-aware language
bindings with the exception of Unicode CMaps which are equivalent to encoding=
unicode.
With multi-byte encodings the text will be written to the PDF output exactly as supplied
by the user if the keepnative option is true.
The disadvantage of multi-byte encodings is that PDFlib checks the input text only
for valid syntax, but does not check whether a glyph for the supplied text is available in
the font. Also, it is not possible to supply Unicode text since PDFlib cannot convert the
Unicode values to the corresponding multi-byte sequences. Finally, character references,
OpenType layout features and complex script shaping cannot be used.
128 Chapter 5: Font Handling (Edition for COM, .NET, and REALbasic)