ref: a920c765f2b4130590fb5971a50690b21664957a
dir: /man/2/draw-font/
.TH DRAW-FONT 2
.SH NAME
Font \-
character images for Unicode text
.SH SYNOPSIS
.EX
include "draw.m";
draw := load Draw Draw->PATH;
Font: adt
{
name: string;
height: int;
ascent: int;
display: ref Display;
open: fn(d: ref Display, file: string): ref Font;
build: fn(d: ref Display, name, desc: string): ref Font;
width: fn(f: self ref Font, str: string): int;
};
.EE
.SH DESCRIPTION
The
.B Font
type defines the appearance of characters drawn with the
.B Image.text
primitive (see
.IR draw-image (2)).
.B Fonts
are usually read from files and are selected based on their
size, their style, the portion of Unicode space they represent,
and so on.
.PP
Fonts are built from a series of subfonts that define contiguous portions
of the Unicode character space, such as the ASCII or the
Greek alphabet.
Font files are textual descriptions of the allocation of characters in
the various regions of the Unicode space; see
.IR font (6)
for the format.
Subfonts are not visible from Limbo.
.PP
A default font, named
.BR *default* ,
is always available.
.PP
The type incorporates:
.TP 10
.BR ascent ", " height
These define the vertical sizes
of the font, in pixels.
The
.B ascent
is the distance from the font baseline to the top of
a line of text;
.B height
gives the interline spacing, that is, the distance from
one baseline to the next.
.TP
.B name
This field
identifies the font, either
the name of
the file from which the font was read, or
.B
"*default*"
for the default font.
.TP
.B display
Tells on which display the font resides.
.TP
.BI open( d\fP,\fP\ file\fP)
The
.B open
method creates a
.B Font
by reading the contents of the named
.IR file .
Fonts are cached, so an open request may return a pointer to an
existing
.BR Font ,
without rereading the file.
The name
.B
"*default*"
always describes a defined font.
Fonts are created for an instance of a
.B Display
object, even though the creation
functions are in type
.BR Font .
.TP
.BI build( d\fP,\fP\ name\fP,\fP\ desc )
.B Build
creates a
.B Font
object by reading the description from the string
.B desc
rather than a file.
.I Name
specifies the name of the font to be created.
.TP
\f2f\fP\f5.width(\fP \f2str\fP \f5)\fP
The
.B width
method returns the width in pixels that
.I str
would occupy if drawn by
.B Image.text
in the Font
.IR f .