use output layout for dirtomon

No need to track our own order; wlroots has a reasonable default for us
already.

config.def.h

@@ -32,8 +32,6 @@ static const MonitorRule monrules[] = {
 	/* example of a HiDPI laptop monitor:
 	{ "eDP-1",    0.5,  1,      2,    &layouts[0], WL_OUTPUT_TRANSFORM_NORMAL, 0, 0 },
 	*/
-	/* the order in which monitors are defined here affects the order in which
-	 * focusmon and tagmon cycle trough the monitors */
 	/* defaults */
 	{ NULL,       0.55, 1,      1,    &layouts[0], WL_OUTPUT_TRANSFORM_NORMAL, 0, 0 },
 };
@@ -87,10 +85,10 @@ static const Key keys[] = {
 	{ MODKEY, 					 XKB_KEY_e,    		togglefullscreen, {0} },
 	{ MODKEY,                    XKB_KEY_0,          view,           {.ui = ~0} },
 	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_parenright, tag,            {.ui = ~0} },
-	{ MODKEY,                    XKB_KEY_comma,      focusmon,       {.i = -1} },
-	{ MODKEY,                    XKB_KEY_period,     focusmon,       {.i = +1} },
-	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_less,       tagmon,         {.i = -1} },
-	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_greater,    tagmon,         {.i = +1} },
+	{ MODKEY,                    XKB_KEY_comma,      focusmon,       {.i = WLR_DIRECTION_LEFT} },
+	{ MODKEY,                    XKB_KEY_period,     focusmon,       {.i = WLR_DIRECTION_RIGHT} },
+	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_less,       tagmon,         {.i = WLR_DIRECTION_LEFT} },
+	{ MODKEY|WLR_MODIFIER_SHIFT, XKB_KEY_greater,    tagmon,         {.i = WLR_DIRECTION_RIGHT} },
 	TAGKEYS(          XKB_KEY_1, XKB_KEY_exclam,                     0),
 	TAGKEYS(          XKB_KEY_2, XKB_KEY_at,                         1),
 	TAGKEYS(          XKB_KEY_3, XKB_KEY_numbersign,                 2),

dwl.c

@@ -235,7 +235,7 @@ static void cursorframe(struct wl_listener *listener, void *data);
 static void destroylayersurfacenotify(struct wl_listener *listener, void *data);
 static void destroynotify(struct wl_listener *listener, void *data);
 static void destroyxdeco(struct wl_listener *listener, void *data);
-static Monitor *dirtomon(int dir);
+static Monitor *dirtomon(enum wlr_direction dir);
 static void focusclient(Client *c, int lift);
 static void focusmon(const Arg *arg);
 static void focusstack(const Arg *arg);
@@ -1096,19 +1096,17 @@ fullscreennotify(struct wl_listener *listener, void *data)
 }
 
 Monitor *
-dirtomon(int dir)
+dirtomon(enum wlr_direction dir)
 {
-	Monitor *m;
-
-	if (dir > 0) {
-		if (selmon->link.next == &mons)
-			return wl_container_of(mons.next, m, link);
-		return wl_container_of(selmon->link.next, m, link);
-	} else {
-		if (selmon->link.prev == &mons)
-			return wl_container_of(mons.prev, m, link);
-		return wl_container_of(selmon->link.prev, m, link);
-	}
+	struct wlr_output *next;
+	if ((next = wlr_output_layout_adjacent_output(output_layout,
+			dir, selmon->wlr_output, selmon->m.x, selmon->m.y)))
+		return next->data;
+	if ((next = wlr_output_layout_farthest_output(output_layout,
+			dir ^ (WLR_DIRECTION_LEFT|WLR_DIRECTION_RIGHT),
+			selmon->wlr_output, selmon->m.x, selmon->m.y)))
+		return next->data;
+	return selmon;
 }
 
 void