ref: 0d701b77592a7364529b300cbaad938326be1710
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; }