ref: 2c9b1c6b53c2a6573e286ce7cbd76ef316068a3a
dir: /sys/src/libdraw/debug.c/
#include <u.h> #include <libc.h> #include <draw.h> void drawsetdebug(int v) { uchar *a; a = bufimage(display, 1+1); if(a == 0){ fprint(2, "drawsetdebug: %r\n"); return; } a[0] = 'D'; a[1] = v; }