term% cat index.txt TYPES(9.5) TYPES(9.5)
NAME
Word, Point, Rectangle, Bitmap, Texture, Pt, Rect, Rpt, display, Drect,
Jrect - basic jerq graphics data types
SYNOPSIS
#include <jerq.h>
typedef int Word;
typedef struct Point Point;
typedef struct Rectangle Rectangle;
typedef struct Bitmap Bitmap;
typedef struct Texture Texture;
extern Bitmap display;
extern Rectangle Drect, Jrect;
Point Pt(x, y) int x, y;
Rectangle Rect(x0, y0, x1, y1) int x0, y0, x1, y1;
Rectangle Rpt() Point p0, p1;
DESCRIPTION
A Word is a 32-bit integer, and is the unit of storage used in the
graphics software.
A Point is a location in a Bitmap (see below), such as the display, and
is defined as:
typedef struct Point {
short x;
short y;
} Point;
The coordinate system has x increasing to the right and y increasing
down. All objects and operators in the graphics live in the same coor‐
dinate space — that of the display bitmap.
A Rectangle is a rectangular area in a Bitmap.
typedef struct Rectangle {
Point origin; /* upper left */
Point corner; /* lower right */
} Rectangle;
By definition, origin.x<=corner.x and origin.y<=corner.y. By conven‐
tion, the right (maximum x) and bottom (maximum y) edges are excluded
from the represented rectangle, so abutting rectangles have no points
in common. Thus, corner is the coordinates of the first point beyond
the rectangle. The image on the display is contained in the Rectangle
{0, 0, XMAX, YMAX}, where XMAX=800 and YMAX=1024.
A Bitmap holds a rectangular image, stored in contiguous memory start‐
ing at base.
typedef struct Bitmap {
Word *base; /* pointer to start of data */
unsigned width; /* width in Words of total data area */
Rectangle rect; /* rectangle in data area, screen coords */
} Bitmap;
Each width Words of memory form a scan-line of the image, and rect de‐
fines the coordinate system inside the Bitmap: rect.origin is the loca‐
tion in the Bitmap of the upper-leftmost point in the image. The coor‐
dinate system is arranged so x positions equal to 0 mod 16 are in the
leftmost bit of a Word.
A Texture is a 16×16 dot bit pattern.
typedef struct {
Word bits[16];
} Texture;
Textures are aligned to absolute display positions, so adjacent areas
colored with the same Texture mesh smoothly.
The functions Pt, Rect and Rpt construct geometrical data types from
their components. Since they are implemented as macros, they only work
in function argument lists.
The global display is a Bitmap describing the display area of the
process. Drect is a Rectangle defining, in screen coordinates, the
display area available to the program (inside the layer's border).
Jrect is the Rectangle {0, 0, XMAX, YMAX}.
TYPES(9.5)