This is a proposed addition to the protocol to fix a race condition.

References: https://gitlab.freedesktop.org/wlroots/wlr-protocols/-/merge_requests/114
---
 main.c                                        | 14 ++++--
 .../wlr-output-management-unstable-v1.xml     | 45 +++++++++++++------
 2 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/main.c b/main.c
index 349a214..87f94af 100644
--- a/main.c
+++ b/main.c
@@ -214,7 +214,11 @@ static void mode_handle_finished(void *data,
 		struct zwlr_output_mode_v1 *wlr_mode) {
 	struct randr_mode *mode = data;
 	wl_list_remove(&mode->link);
-	zwlr_output_mode_v1_destroy(mode->wlr_mode);
+	if (zwlr_output_mode_v1_get_version(mode->wlr_mode) >= 3) {
+		zwlr_output_mode_v1_release(mode->wlr_mode);
+	} else {
+		zwlr_output_mode_v1_destroy(mode->wlr_mode);
+	}
 	free(mode);
 }
 
@@ -304,7 +308,11 @@ static void head_handle_finished(void *data,
 		struct zwlr_output_head_v1 *wlr_head) {
 	struct randr_head *head = data;
 	wl_list_remove(&head->link);
-	zwlr_output_head_v1_destroy(head->wlr_head);
+	if (zwlr_output_head_v1_get_version(head->wlr_head) >= 3) {
+		zwlr_output_head_v1_release(head->wlr_head);
+	} else {
+		zwlr_output_head_v1_destroy(head->wlr_head);
+	}
 	free(head->name);
 	free(head->description);
 	free(head);
@@ -381,7 +389,7 @@ static void registry_handle_global(void *data, struct wl_registry *registry,
 	struct randr_state *state = data;
 
 	if (strcmp(interface, zwlr_output_manager_v1_interface.name) == 0) {
-		uint32_t version_to_bind = version <= 2 ? version : 2;
+		uint32_t version_to_bind = version <= 3 ? version : 3;
 		state->output_manager = wl_registry_bind(registry, name,
 			&zwlr_output_manager_v1_interface, version_to_bind);
 		zwlr_output_manager_v1_add_listener(state->output_manager,
diff --git a/protocol/wlr-output-management-unstable-v1.xml b/protocol/wlr-output-management-unstable-v1.xml
index bf0cc93..3568e04 100644
--- a/protocol/wlr-output-management-unstable-v1.xml
+++ b/protocol/wlr-output-management-unstable-v1.xml
@@ -39,7 +39,7 @@
     interface version number is reset.
   </description>
 
-  <interface name="zwlr_output_manager_v1" version="2">
+  <interface name="zwlr_output_manager_v1" version="3">
     <description summary="output device configuration manager">
       This interface is a manager that allows reading and writing the current
       output device configuration.
@@ -125,7 +125,7 @@
     </event>
   </interface>
 
-  <interface name="zwlr_output_head_v1" version="2">
+  <interface name="zwlr_output_head_v1" version="3">
     <description summary="output device">
       A head is an output device. The difference between a wl_output object and
       a head is that heads are advertised even if they are turned off. A head
@@ -251,14 +251,15 @@
     </event>
 
     <event name="finished">
-      <description summary="the head has been destroyed">
-        The compositor will destroy the object immediately after sending this
-        event, so it will become invalid and the client should release any
-        resources associated with it.
+      <description summary="the head has disappeared">
+        This event indicates that the head is no longer available. The head
+        object becomes inert. Clients should send a destroy request and release
+        any resources associated with it.
       </description>
     </event>
 
     <!-- Version 2 additions -->
+
     <event name="make" since="2">
       <description summary="head manufacturer">
         This event describes the manufacturer of the head.
@@ -328,9 +329,18 @@
       </description>
       <arg name="serial_number" type="string"/>
     </event>
+
+    <!-- Version 3 additions -->
+
+    <request name="release" type="destructor" since="3">
+      <description summary="destroy the head object">
+        This request indicates that the client will no longer use this head
+        object.
+      </description>
+    </request>
   </interface>
 
-  <interface name="zwlr_output_mode_v1" version="2">
+  <interface name="zwlr_output_mode_v1" version="3">
     <description summary="output mode">
       This object describes an output mode.
 
@@ -368,15 +378,24 @@
     </event>
 
     <event name="finished">
-      <description summary="the mode has been destroyed">
-        The compositor will destroy the object immediately after sending this
-        event, so it will become invalid and the client should release any
-        resources associated with it.
+      <description summary="the mode has disappeared">
+        This event indicates that the mode is no longer available. The mode
+        object becomes inert. Clients should send a destroy request and release
+        any resources associated with it.
       </description>
     </event>
+
+    <!-- Version 3 additions -->
+
+    <request name="release" type="destructor" since="3">
+      <description summary="destroy the mode object">
+        This request indicates that the client will no longer use this mode
+        object.
+      </description>
+    </request>
   </interface>
 
-  <interface name="zwlr_output_configuration_v1" version="2">
+  <interface name="zwlr_output_configuration_v1" version="3">
     <description summary="output configuration">
       This object is used by the client to describe a full output configuration.
 
@@ -494,7 +513,7 @@
     </request>
   </interface>
 
-  <interface name="zwlr_output_configuration_head_v1" version="2">
+  <interface name="zwlr_output_configuration_head_v1" version="3">
     <description summary="head configuration">
       This object is used by the client to update a single head's configuration.
 
-- 
2.36.1

LGTM