ref: e1cd22504e26d0a732a4219d38d6e5fe3e03aa21
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; }