ref: f35d5ee5b036b7b4fa59b1839f52fca15b7f99f9
dir: /sys/src/cmd/plot/libplot/disk.c/
#include "mplot.h" void plotdisc(double xc, double yc, double r){ Point p; int rad; p.x=SCX(xc); p.y=SCY(yc); if (r < 0) rad=SCR(-r); else rad=SCR(r); fillellipse(screen, p, rad, rad, getcolor(e1->foregr), ZP); }