V10/man/man9/types.9

.TH TYPES 9.5
.CT 2 graphics
.SH NAME
Word, Point, Rectangle, Bitmap, Texture, Pt, Rect, Rpt, display, Drect, Jrect \- graphics data types
.SH SYNOPSIS
.B #include <jerq.h>
.PP
.B typedef int Word;
.br
.B typedef struct Point Point;
.br
.B typedef struct Rectangle Rectangle;
.br
.B typedef struct Bitmap Bitmap;
.br
.B typedef struct Texture Texture;
.PP
.B extern Bitmap display;
.br
.B extern Rectangle Drect, Jrect;
.PP
.B Point Pt(x, y)
.B int x, y;
.PP
.B Rectangle Rect(x0, y0, x1, y1)
.B int x0, y0, x1, y1;
.PP
.B Rectangle Rpt()
.B Point p0, p1;
.SH DESCRIPTION
A
.B Word
is a 32-bit integer, and is the unit of storage used in the graphics software.
.PP
A
.B Point
is a location in a Bitmap
(see below),
such as the display, and is defined as:
.IP
.EX
typedef struct Point {
	short x;
	short y;
} Point;
.EE
.PP
The coordinate system has
.I x
increasing to the right and
.I y
increasing down.
All objects and operators in the graphics world live in the same coordinate space\(emthat of the display bitmap.
.PP
A
.B Rectangle
is a rectangular area in a Bitmap.
.EX
.IP
typedef struct Rectangle {
	Point origin;	/* upper left */
	Point corner;	/* lower right */
} Rectangle;
.EE
.PP
By definition,
.B origin.x <= corner.x
and
.BR "origin.y <= corner.y" .
By convention, the right (maximum
.IR x )
and bottom (maximum
.IR y )
edges are
excluded from the represented rectangle, so abutting rectangles have no
points in common.
Thus,
.B corner
contains the coordinates of the first point beyond the rectangle.
The image on the display is contained in the Rectangle
.BR "{0, 0, XMAX, YMAX}" ,
where
.BR XMAX =800
and
.BR YMAX =1024.
.PP
A 
.B Bitmap
holds a rectangular image, stored in contiguous memory starting at
.IR base .
.EX
.IP
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;
.EE
.PP
Each
.B width
Words of memory form a scan-line of the image, and
.B rect
defines the coordinate system inside the
.BR Bitmap :
.B rect.origin
is the location in the Bitmap
of the upper-leftmost point in the image.
The coordinate system is arranged so
.I x
positions equal to 0 mod 32
are in the leftmost bit of a Word.
.PP
A
.B Texture
is a 16\(mu16 dot bit pattern.
.IP
.EX
typedef struct {
	Word bits[16];
} Texture;
.EE
.PP
Textures
are aligned to absolute display positions,
so adjacent areas colored with the same Texture
mesh smoothly.
.PP
The functions
.IR Pt ,
.I Rect
and
.I Rpt
construct geometrical data types from their components.
Since they are implemented as macros, they only work
in function argument lists.
.PP
The global
.I display
is a Bitmap
describing the display area of the process.
.I Drect
is a Rectangle defining, in screen coordinates,
the display area available to the program (inside the layer's border).
.I Jrect
is the Rectangle
.BR "{0, 0, XMAX, YMAX}" .