diff --git a/include/wlr/types/wlr_compositor.h b/include/wlr/types/wlr_compositor.h
index eb870b7b..94262b4b 100644
--- a/include/wlr/types/wlr_compositor.h
+++ b/include/wlr/types/wlr_compositor.h
@@ -69,6 +69,9 @@ struct wlr_surface_state {
 	// Number of locks that prevent this surface state from being committed.
 	size_t cached_state_locks;
 	struct wl_list cached_state_link; // wlr_surface.cached
+
+	// Sync'ed object states, one per struct wlr_surface_synced
+	struct wl_array synced; // void *
 };
 
 struct wlr_surface_role {
@@ -222,6 +225,9 @@ struct wlr_surface {
 	int32_t preferred_buffer_scale;
 	bool preferred_buffer_transform_sent;
 	enum wl_output_transform preferred_buffer_transform;
+
+	struct wl_list synced; // wlr_surface_synced.link
+	size_t synced_len;
 };
 
 struct wlr_renderer;
@@ -430,6 +436,63 @@ void wlr_surface_set_preferred_buffer_scale(struct wlr_surface *surface,
 void wlr_surface_set_preferred_buffer_transform(struct wlr_surface *surface,
 	enum wl_output_transform transform);
 
+/**
+ * Implementation for struct wlr_surface_synced.
+ *
+ * struct wlr_surface takes care of allocating the sync'ed object state.
+ *
+ * The only mandatory field is state_size.
+ */
+struct wlr_surface_synced_impl {
+	// Size in bytes of the state struct.
+	size_t state_size;
+	// Initialize a state. If NULL, this is a no-op.
+	void (*init_state)(void *state);
+	// Finish a state. If NULL, this is a no-op.
+	void (*finish_state)(void *state);
+	// Move a state. If NULL, memcpy() is used.
+	void (*move_state)(void *dst, void *src);
+};
+
+/**
+ * An object synchronized with a surface.
+ *
+ * This is typically used by surface add-ons which integrate with the surface
+ * commit mechanism.
+ *
+ * A sync'ed object maintains state whose lifecycle is managed by
+ * struct wlr_surface_synced_impl. Clients make requests to mutate the pending
+ * state, then clients commit the pending state via wl_surface.commit. The
+ * pending state may become cached, then becomes current when it's applied.
+ */
+struct wlr_surface_synced {
+	struct wlr_surface *surface;
+	const struct wlr_surface_synced_impl *impl;
+	struct wl_list link; // wlr_surface.synced
+	size_t index;
+};
+
+/**
+ * Initialize a sync'ed object.
+ *
+ * pending and current must be pointers to the sync'ed object's state. This
+ * function will initialize them.
+ */
+bool wlr_surface_synced_init(struct wlr_surface_synced *synced,
+	struct wlr_surface *surface, const struct wlr_surface_synced_impl *impl,
+	void *pending, void *current);
+/**
+ * Finish a sync'ed object.
+ *
+ * This must be called before the struct wlr_surface is destroyed.
+ */
+void wlr_surface_synced_finish(struct wlr_surface_synced *synced);
+/**
+ * Obtain a sync'ed object state.
+ */
+void *wlr_surface_synced_get_state(struct wlr_surface_synced *synced,
+	const struct wlr_surface_state *state);
+
 /**
  * Get a Pixman region from a wl_region resource.
  */
diff --git a/types/wlr_compositor.c b/types/wlr_compositor.c
index 91996037..d9c7b3c1 100644
--- a/types/wlr_compositor.c
+++ b/types/wlr_compositor.c
@@ -12,6 +12,7 @@
 #include "types/wlr_buffer.h"
 #include "types/wlr_region.h"
 #include "types/wlr_subcompositor.h"
+#include "util/array.h"
 #include "util/time.h"
 
 #define COMPOSITOR_VERSION 6
@@ -272,11 +273,42 @@ static void surface_update_damage(pixman_region32_t *buffer_damage,
 	}
 }
 
+static void *surface_synced_create_state(struct wlr_surface_synced *synced) {
+	void *state = calloc(1, synced->impl->state_size);
+	if (state == NULL) {
+		return NULL;
+	}
+	if (synced->impl->init_state) {
+		synced->impl->init_state(state);
+	}
+	return state;
+}
+
+static void surface_synced_destroy_state(struct wlr_surface_synced *synced,
+		void *state) {
+	if (state == NULL) {
+		return;
+	}
+	if (synced->impl->finish_state) {
+		synced->impl->finish_state(state);
+	}
+	free(state);
+}
+
+static void surface_synced_move_state(struct wlr_surface_synced *synced,
+		void *dst, void *src) {
+	if (synced->impl->move_state) {
+		synced->impl->move_state(dst, src);
+	} else {
+		memcpy(dst, src, synced->impl->state_size);
+	}
+}
+
 /**
  * Overwrite state with a copy of the next state, then clear the next state.
  */
 static void surface_state_move(struct wlr_surface_state *state,
-		struct wlr_surface_state *next) {
+		struct wlr_surface_state *next, struct wlr_surface *surface) {
 	state->width = next->width;
 	state->height = next->height;
 	state->buffer_width = next->buffer_width;
@@ -331,6 +363,14 @@ static void surface_state_move(struct wlr_surface_state *state,
 		wl_list_init(&next->frame_callback_list);
 	}
 
+	void **state_synced = state->synced.data;
+	void **next_synced = next->synced.data;
+	struct wlr_surface_synced *synced;
+	wl_list_for_each(synced, &surface->synced, link) {
+		surface_synced_move_state(synced,
+			state_synced[synced->index], next_synced[synced->index]);
+	}
+
 	state->committed = next->committed;
 	next->committed = 0;
 
@@ -404,21 +444,44 @@ static void surface_update_input_region(struct wlr_surface *surface) {
 		0, 0, surface->current.width, surface->current.height);
 }
 
-static void surface_state_init(struct wlr_surface_state *state);
+static bool surface_state_init(struct wlr_surface_state *state,
+	struct wlr_surface *surface);
+static void surface_state_finish(struct wlr_surface_state *state);
 
 static void surface_cache_pending(struct wlr_surface *surface) {
 	struct wlr_surface_state *cached = calloc(1, sizeof(*cached));
 	if (!cached) {
-		wl_resource_post_no_memory(surface->resource);
-		return;
+		goto error;
+	}
+
+	if (!surface_state_init(cached, surface)) {
+		goto error_cached;
 	}
 
-	surface_state_init(cached);
-	surface_state_move(cached, &surface->pending);
+	void **cached_synced = cached->synced.data;
+	struct wlr_surface_synced *synced;
+	wl_list_for_each(synced, &surface->synced, link) {
+		void *synced_state = surface_synced_create_state(synced);
+		if (synced_state == NULL) {
+			goto error_state;
+		}
+		cached_synced[synced->index] = synced_state;
+	}
+
+	surface_state_move(cached, &surface->pending, surface);
 
 	wl_list_insert(surface->cached.prev, &cached->cached_state_link);
 
 	surface->pending.seq++;
+
+	return;
+
+error_state:
+	surface_state_finish(cached);
+error_cached:
+	free(cached);
+error:
+	wl_resource_post_no_memory(surface->resource);
 }
 
 static void surface_commit_state(struct wlr_surface *surface,
@@ -452,7 +515,7 @@ static void surface_commit_state(struct wlr_surface *surface,
 	surface->previous.buffer_width = surface->current.buffer_width;
 	surface->previous.buffer_height = surface->current.buffer_height;
 
-	surface_state_move(&surface->current, next);
+	surface_state_move(&surface->current, next, surface);
 
 	if (invalid_buffer) {
 		surface_apply_damage(surface);
@@ -579,7 +642,8 @@ struct wlr_surface *wlr_surface_from_resource(struct wl_resource *resource) {
 	return wl_resource_get_user_data(resource);
 }
 
-static void surface_state_init(struct wlr_surface_state *state) {
+static bool surface_state_init(struct wlr_surface_state *state,
+		struct wlr_surface *surface) {
 	*state = (struct wlr_surface_state){
 		.scale = 1,
 		.transform = WL_OUTPUT_TRANSFORM_NORMAL,
@@ -595,6 +659,10 @@ static void surface_state_init(struct wlr_surface_state *state) {
 	pixman_region32_init(&state->opaque);
 	pixman_region32_init_rect(&state->input,
 		INT32_MIN, INT32_MIN, UINT32_MAX, UINT32_MAX);
+
+	wl_array_init(&state->synced);
+	void *ptr = wl_array_add(&state->synced, surface->synced_len * sizeof(void *));
+	return ptr != NULL;
 }
 
 static void surface_state_finish(struct wlr_surface_state *state) {
@@ -609,9 +677,18 @@ static void surface_state_finish(struct wlr_surface_state *state) {
 	pixman_region32_fini(&state->buffer_damage);
 	pixman_region32_fini(&state->opaque);
 	pixman_region32_fini(&state->input);
+
+	wl_array_release(&state->synced);
 }
 
-static void surface_state_destroy_cached(struct wlr_surface_state *state) {
+static void surface_state_destroy_cached(struct wlr_surface_state *state,
+		struct wlr_surface *surface) {
+	void **synced_states = state->synced.data;
+	struct wlr_surface_synced *synced;
+	wl_list_for_each(synced, &surface->synced, link) {
+		surface_synced_destroy_state(synced, synced_states[synced->index]);
+	}
+
 	surface_state_finish(state);
 	wl_list_remove(&state->cached_state_link);
 	free(state);
@@ -634,10 +711,11 @@ static void surface_handle_resource_destroy(struct wl_resource *resource) {
 	wl_signal_emit_mutable(&surface->events.destroy, surface);
 
 	wlr_addon_set_finish(&surface->addons);
+	assert(wl_list_empty(&surface->synced));
 
 	struct wlr_surface_state *cached, *cached_tmp;
 	wl_list_for_each_safe(cached, cached_tmp, &surface->cached, cached_state_link) {
-		surface_state_destroy_cached(cached);
+		surface_state_destroy_cached(cached, surface);
 	}
 
 	wl_list_remove(&surface->renderer_destroy.link);
@@ -682,8 +760,8 @@ static struct wlr_surface *surface_create(struct wl_client *client,
 
 	surface->renderer = renderer;
 
-	surface_state_init(&surface->current);
-	surface_state_init(&surface->pending);
+	surface_state_init(&surface->current, surface);
+	surface_state_init(&surface->pending, surface);
 	surface->pending.seq = 1;
 
 	wl_signal_init(&surface->events.client_commit);
@@ -699,6 +777,7 @@ static struct wlr_surface *surface_create(struct wl_client *client,
 	pixman_region32_init(&surface->opaque_region);
 	pixman_region32_init(&surface->input_region);
 	wlr_addon_set_init(&surface->addons);
+	wl_list_init(&surface->synced);
 
 	if (renderer != NULL) {
 		wl_signal_add(&renderer->events.destroy, &surface->renderer_destroy);
@@ -860,7 +939,7 @@ void wlr_surface_unlock_cached(struct wlr_surface *surface, uint32_t seq) {
 		}
 
 		surface_commit_state(surface, next);
-		surface_state_destroy_cached(next);
+		surface_state_destroy_cached(next, surface);
 	}
 }
 
@@ -1258,3 +1337,125 @@ struct wlr_compositor *wlr_compositor_create(struct wl_display *display,
 
 	return compositor;
 }
+
+static bool surface_state_add_synced(struct wlr_surface_state *state, void *value) {
+	void **ptr = wl_array_add(&state->synced, sizeof(void *));
+	if (ptr == NULL) {
+		return false;
+	}
+	*ptr = value;
+	return true;
+}
+
+static void *surface_state_remove_synced(struct wlr_surface_state *state,
+		struct wlr_surface_synced *synced) {
+	void **synced_states = state->synced.data;
+	void *synced_state = synced_states[synced->index];
+	array_remove_at(&state->synced, synced->index * sizeof(void *), sizeof(void *));
+	return synced_state;
+}
+
+static void surface_state_remove_and_destroy_synced(struct wlr_surface_state *state,
+		struct wlr_surface_synced *synced) {
+	void *synced_state = surface_state_remove_synced(state, synced);
+	surface_synced_destroy_state(synced, synced_state);
+}
+
+bool wlr_surface_synced_init(struct wlr_surface_synced *synced,
+		struct wlr_surface *surface, const struct wlr_surface_synced_impl *impl,
+		void *pending, void *current) {
+	assert(impl->state_size > 0);
+
+	struct wlr_surface_synced *other;
+	wl_list_for_each(other, &surface->synced, link) {
+		assert(synced != other);
+	}
+
+	memset(pending, 0, impl->state_size);
+	memset(current, 0, impl->state_size);
+	if (impl->init_state) {
+		impl->init_state(pending);
+		impl->init_state(current);
+	}
+	if (!surface_state_add_synced(&surface->pending, pending)) {
+		goto error_init;
+	}
+	if (!surface_state_add_synced(&surface->current, current)) {
+		goto error_pending;
+	}
+
+	*synced = (struct wlr_surface_synced){
+		.surface = surface,
+		.impl = impl,
+		.index = surface->synced_len,
+	};
+
+	struct wlr_surface_state *cached;
+	wl_list_for_each(cached, &surface->cached, cached_state_link) {
+		void *synced_state = surface_synced_create_state(synced);
+		if (synced_state == NULL ||
+				!surface_state_add_synced(cached, synced_state)) {
+			surface_synced_destroy_state(synced, synced_state);
+			goto error_cached;
+		}
+	}
+
+	wl_list_insert(&surface->synced, &synced->link);
+	surface->synced_len++;
+
+	return true;
+
+error_cached:;
+	struct wlr_surface_state *failed_at = cached;
+	wl_list_for_each(cached, &surface->cached, cached_state_link) {
+		if (cached == failed_at) {
+			break;
+		}
+		surface_state_remove_and_destroy_synced(cached, synced);
+	}
+	surface_state_remove_synced(&surface->current, synced);
+error_pending:
+	surface_state_remove_synced(&surface->pending, synced);
+error_init:
+	if (synced->impl->finish_state) {
+		synced->impl->finish_state(pending);
+		synced->impl->finish_state(current);
+	}
+	return false;
+}
+
+void wlr_surface_synced_finish(struct wlr_surface_synced *synced) {
+	struct wlr_surface *surface = synced->surface;
+
+	bool found = false;
+	struct wlr_surface_synced *other;
+	wl_list_for_each(other, &surface->synced, link) {
+		if (other == synced) {
+			found = true;
+		} else if (other->index > synced->index) {
+			other->index--;
+		}
+	}
+	assert(found);
+
+	struct wlr_surface_state *cached;
+	wl_list_for_each(cached, &surface->cached, cached_state_link) {
+		surface_state_remove_and_destroy_synced(cached, synced);
+	}
+
+	void *pending = surface_state_remove_synced(&surface->pending, synced);
+	void *current = surface_state_remove_synced(&surface->current, synced);
+	if (synced->impl->finish_state) {
+		synced->impl->finish_state(pending);
+		synced->impl->finish_state(current);
+	}
+
+	wl_list_remove(&synced->link);
+	synced->surface->synced_len--;
+}
+
+void *wlr_surface_synced_get_state(struct wlr_surface_synced *synced,
+		const struct wlr_surface_state *state) {
+	void **synced_states = state->synced.data;
+	return synced_states[synced->index];
+}