ref: ca9d65e40b3f78d2580fff9ff1844bad1be08673
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 == nil){ fprint(2, "drawsetdebug: %r\n"); return; } a[0] = 'D'; a[1] = v; }