TYPES(9.5)                                             TYPES(9.5)

          Word, Point, Rectangle, Bitmap, Texture, Pt, Rect, Rpt,
          display, Drect, Jrect - basic jerq graphics data types

          #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;

          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 coordinate space - that of the display bit-

          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 convention, the right (maximum x) and bottom (maximum y)
          edges are excluded from the represented rectangle, so abut-
          ting rectangles have no points in common.  Thus, corner is

     TYPES(9.5)                                             TYPES(9.5)

          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 starting 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 defines the coordinate system inside the Bitmap:
          rect.origin is the location in the Bitmap of the upper-
          leftmost point in the image.  The coordinate system is
          arranged so x positions equal to 0 mod 16 are in the left-
          most 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 adja-
          cent 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}.