<alt-Tab> for dwm

dwm.c

/* this implements <alt-Tab> for dwm, put it in config.h  */

static int alt_tab_count = 0;

/* focus and restack a client */
static void focus_restack(Client *c)
   { if (c) { focus(c); restack(selmon); } }

static void start_alt_tab(const Arg *arg)
   { alt_tab_count = 0; }

static Client *next_visible(Client *c)
{
   for(/* DO_NOTHING */; c && !ISVISIBLE(c); c=c->snext);
   return c;
}

static int count_visible(void)
{
   int count = 0;
   for (Client *c=next_visible(selmon->stack); c; c = next_visible(c->snext))
      count += 1;
   return count;
}

static Client *get_nth_client(int n)
{
   Client *c;
   for (c=next_visible(selmon->stack); c && n--; c = next_visible(c->snext));
   return c;
}

static void alt_tab(const Arg *arg)
{
   // put all of the windows back in their original focus/stack position */
   for (int i=0; i<alt_tab_count; i+=1)
      focus_restack(get_nth_client(alt_tab_count));

   // focus and restack the nth window */
   alt_tab_count = (alt_tab_count + 1) % count_visible();
   focus_restack(get_nth_client(alt_tab_count));
}

/*
static Key keys[] = {
   // ...
   { 0,       XK_Alt_L,   start_alt_tab,  {0} },
   { MODKEY,  XK_Tab,     alt_tab,        {0} },
   // ...
};
*/

Could this search clients throughout different tags aswell?