ref: 03d55733643f35d88a9df8bc62c410bcee9e37a6
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); m_disc(p, rad, e1->foregr); }