ref: a0ba4c1f03a3f99fb17a9edf9b4448db49bb6c46
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); }