The
Font
type defines the appearance of characters drawn with the
Image.text
primitive (see
draw-image(2)).
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.
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
font(6)
for the format.
Subfonts are not visible from Limbo.
A default font, named
*default*,
is always available.
The type incorporates:
- ascent, height
- These define the vertical sizes
of the font, in pixels.
The
ascent
is the distance from the font baseline to the top of
a line of text;
height
gives the interline spacing, that is, the distance from
one baseline to the next.
- name
- This field
identifies the font, either
the name of
the file from which the font was read, or
"*default*"
for the default font.
- display
- Tells on which display the font resides.
- open(d, file)
- The
open
method creates a
Font
by reading the contents of the named
file.
Fonts are cached, so an open request may return a pointer to an
existing
Font,
without rereading the file.
The name
"*default*"
always describes a defined font.
Fonts are created for an instance of a
Display
object, even though the creation
functions are in type
Font.
- build(d, name, desc)
- Build
creates a
Font
object by reading the description from the string
desc
rather than a file.
Name
specifies the name of the font to be created.
- f.width( str )
- The
width
method returns the width in pixels that
str
would occupy if drawn by
Image.text
in the Font
f.