diff --git a/src/core/state.c b/src/core/state.c
index d8faebc..40da138 100644
--- a/src/core/state.c
+++ b/src/core/state.c
@@ -1,6 +1,7 @@
 #include "core/state.h"
 
 #include <stddef.h>
+#include <stdint.h>
 #include <string.h>
 #include <zdwm/types.h>
 
@@ -267,6 +268,14 @@ bool state_output_valid(const state_t *state, output_id_t id) {
 #endif
 }
 
+void state_cycle_current_output(state_t *state, int delta) {
+  int64_t count = (int64_t)state->output_count;
+  int64_t current = (int64_t)state->current_output_index;
+  int64_t next = (current + (int64_t)delta) % count;
+  if (next < 0) next += count;
+  state->current_output_index = (size_t)next;
+}
+
 static inline void window_set_geometry_mode(
   window_t *window, window_geometry_mode_t geometry_mode) {
   window->geometry_mode = geometry_mode;
diff --git a/src/core/state.h b/src/core/state.h
index d8c43a1..ee156af 100644
--- a/src/core/state.h
+++ b/src/core/state.h
@@ -65,6 +65,7 @@ typedef struct state_t {
 
   output_t *outputs;
   size_t output_count;
+  size_t current_output_index;
 
   window_t *windows;
   size_t window_count;
@@ -129,6 +130,7 @@ void state_output_set_current_workspace(state_t *state, output_id_t output_id,
                                         workspace_id_t workspace_id);
 size_t state_output_count(const state_t *state);
 bool state_output_valid(const state_t *state, output_id_t id);
+void state_cycle_current_output(state_t *state, int delta);
 
 /*
  * state 持有的 window 集合接口