term% cat index.txt FONT(9.5) FONT(9.5)
NAME
font - jerq font layouts
SYNOPSIS
#include <jerq.h>
#include <font.h>
typedef struct Fontchar Fontchar;
typedef struct Font Font;
extern Font defont;
DESCRIPTION
A Font is a character set, stored as a single Bitmap with the charac‐
ters placed side-by-side. It is described by the following data struc‐
tures.
typedef struct Fontchar {
short x; /* left edge of bits */
unsigned char top; /* first non-zero scan-line */
unsigned char bottom; /* last non-zero scan-line */
char left; /* offset of baseline */
unsigned char width; /* width of baseline */
} Fontchar;
typedef struct Font {
short n; /* number of chars in font */
char height; /* height of bitmap */
char ascent; /* top of bitmap to baseline */
long unused;
Bitmap *bits; /* where the characters are */
Fontchar info[n+1]; /* n+1 character descriptors */
} Font;
Characters in bits abut exactly, so the displayed width of the charac‐
ter c is Font.info[c+1].x-Font.info[c].x. The first left columns of
pixels in a character overlap the previous character. The upper left
corner of the nonempty columns appears at (x,0) in the bitmap. Width
is the distance to move horizontally after drawing a character. The
font bitmap has a fixed height; parameters top and bottom may be used
to optimize the copying of a character in some circumstances.
A character drawn at point p in an arbitrary Bitmap has its upper-left‐
most dot, including empty space above it in the Bitmap, at p.
To copy character c from font f to point p do
Fontchar *i = f->info + c;
bitblt(f->bits, Rect(i->x, i->top, (i+1)->x, i->bottom), Pt(p.x+i->left, p.y+i->top), fc);
p.x += i->width;
The above example is correct for XOR and OR mode. For STORE mode, the
bitblt call is different because all the scan lines must be drawn:
bitblt(f->bits, Rect(i->x, 0, (i+1)->x, f->height), Pt(p.x+left,
p.y), fc);
Fonts are stored on disk in binary with byte order that of the termi‐
nal. First in the file is the first eight bytes (up to unused) of the
Font strcture, then the array of Fontchar structures, then the data for
the bitmap Font.bits. The header for the bitmap must be inferred from
Font.height and Font.info[Font.n].x. See string(9.3) for a description
of how to read and write font files.
SEE ALSO
jf(9.1), string(9.3), infont(9.3)
FONT(9.5)