NEWLAYER(9.2)                                       NEWLAYER(9.2)

          newlayer, dellayer, lbitblt, lpoint, lrectf, lsegment,
          ltexture, upfront - layer control and graphics

          #include <jerq.h>

          Layer *newlayer(r); Rectangle r;

          void dellayer(l) Layer *l;

          void lbitblt(sl, r, dl, p, f) Layer *sl, *dl; Rectangle r;
          Point p; Code f;

          void lpoint(l, p, f) Layer *l; Point p; Code f;

          void lrectf(l, r, f) Layer *l; Rectangle r; Code f;

          void segment(l, p, q, f) Layer *l; Point p, q; Code f;

          void ltexture(l, r, t, f) Layer *l; Rectangle r; Texture *t;
          Code f;

          Newlayer creates a layer in Rectangle r in the physical dis-
          play bitmap, and returns its address, or 0 on failure.
          Newproc(9.2) explains how to attach a process to a layer.

          Dellayer de-allocates a layer; the associated process must
          also be freed (see newproc(9.2)).

          The routines lbitblt, lpoint, lsegment and ltexture are
          equivalent to their bitblt(9.3) counterparts except that
          they never inhibit the mouse cursor, so they are mainly use-
          ful only for implementation of efficient composite graphics
          operations such as circle-drawing.  Because of the duality
          of Bitmaps and Layers, arguments of either type may be
          passed freely to any of the graphics primitives.

          bitblt(9.3), newproc(9.2)
          Graphics in Overlapping Bitmap Layers, Rob Pike, ACM Trans.
          on Graphics, April 1983.