.TH LIBPARSEPCF_GET_ENCODING 3 LIBPARSEPCF
.SH NAME
libparsepcf_get_encoding \- Get glyph index
.SH SYNOPSIS
.nf
#include <libparsepcf.h>
#define LIBPARSEPCF_BDF_ENCODINGS /* value omitted */
#define LIBPARSEPCF_NOT_ENCODED ((size_t)0xFFFF)
struct libparsepcf_encoding {
uint16_t \fImin_byte2\fP;
uint16_t \fImax_byte2\fP;
uint16_t \fImin_byte1\fP;
uint16_t \fImax_byte1\fP;
uint16_t \fIdefault_glyph\fP;
size_t \fIchar_count\fP;
};
int libparsepcf_get_encoding(const void *\fIdata\fP, size_t \fIsize\fP,
const struct libparsepcf_table *\fItable\fP,
struct libparsepcf_encoding *\fImeta_out\fP);
int libparsepcf_get_glyph_indices(const void *\fIdata\fP, size_t \fIsize\fP,
const struct libparsepcf_table *\fItable\fP,
const struct libparsepcf_encoding *\fImeta\fP,
size_t *\fIindices_out\fP,
size_t \fIfirst\fP, size_t \fIcount\fP);
.fi
.PP
Link with
.IR -lparsepcf .
.SH DESCRIPTION
PCF fonts file are encoded for specific for characters
sets and encodings do not encode glyphs by codepoints
but rather by how characters are encoded. To get the
appropriate glyph for a character, the
.BR libparsepcf_get_properties (3)
function must first be used to determine the encoding,
and if it does not match the expeced encoding translate
the text into the encoding used by the font (it may
also be possible to load a version of the font the
uses the expected encoding). Second, the
.BR libparsepcf_get_tables (3)
function is used to find the table with the type
.BR LIBPARSEPCF_BDF_ENCODINGS ,
which is then passed into the
.BR libparsepcf_get_encoding (3)
function as it's third argument
.RI ( table ),
along with the font file contents in the
.I data
argument and size, in bytes, of the file in the
.I size
argument to get the coverage of the font, encoding
information, and the default glyph to use when the
font does not have the glyph for a character.
If the encoding uses one byte for each character,
.I meta_out->min_byte1
and
.I meta_out->max_byte1
are both set to 0, otherwise, the encoding uses
two bytes for each character.
The index of the default glyph will be stored in
.IR meta_out->default_glyph .
The fields
.IR meta_out->min_byte1 ,
.IR meta_out->max_byte1 ,
.IR meta_out->min_byte2 ,
and
.I meta_out->max_byte2
are used to translate an encoded character into
a character index which can then be mapped into
a glyph index using the
.BR libparsepcf_get_glyph_indices ()
function.
.PP
When calling the
.BR libparsepcf_get_glyph_indices ()
function, the first four arguments shall be
the same as passed into the
.BR libparsepcf_get_encoding ()
function.
.I first
shall be the index of the character with the lowest index
of the character the function shall get the glyph index
for, and
.I count
shall be the number of consecutive characters
(including the first character) to get this information
for. For each queried character with index
.IR i ,
the glyph index will be stored in
.IR indices_out[i-first] ,
however if character is not encoded (does not have
a glyph), it the value
.I LIBPARSEPCF_NOT_ENCODED
will be stored instead.
.PP
The application shall ensure that
.IR "first + count <= meta->char_count" .
.PP
For single-byte encodings, the character index
is calculated by subtracting
.I meta_out->min_byte2
from the character byte, however the application
must make sure that the value of the character
byte is at least
.I meta_out->min_byte2
but no greater than
.IR meta_out->max_byte2 .
.PP
For dual-bute encodings, the application must
first ensure that there are two bytes available,
and ensure that the value of the first byte is
at least
.I meta_out->min_byte1
but no greater than
.IR meta_out->max_byte1 ,
and that the value of the second byte is at least
.I meta_out->min_byte2
but no greater than
.IR meta_out->max_byte2 .
The application can then subtract
.I meta_out->min_byte1
from the value of the first byte, and call the
difference
.IR a ,
and subtract
.I meta_out->min_byte2
from the value of the second byte, and call the
difference
.IR b .
If the application has already calculated the
font-constant value
.IR ".max_byte2 - .min_byte2 + 1" ,
called
.IR k .
The character's index is than calculated by
.IR "a * k + b" .
(This is the simplest description of the
formula but it can be optimised for the
application to use one less subtract.)
.SH RETURN VALUE
The
.BR libparsepcf_get_encoding ()
and
.BR libparsepcf_get_glyph_indices ()
functions return 0 upon successful completion.
On failure, -1 is returned and
.I errno
is set appropriately to indicate the error.
.SH ERRORS
The
.BR libparsepcf_get_encoding ()
and
.BR libparsepcf_get_glyph_indices ()
functions fail if:
.TP
.B EBFONT
The font file is corrupt or unsupported.
.SH SEE ALSO
.BR libparsepcf (7),
.BR libparsepcf_preparse_font (3)
