backend/wayland: fix seat caps handling

Previously, each time a wl_seat.capabilities event was received the
Wayland backend created new input devices. It now only does so the first
time.

Input devices are now destroyed when the cap is removed.

Closes: https://github.com/swaywm/sway/issues/5055

backend/wayland/seat.c

@@ -289,8 +289,9 @@ static struct wlr_wl_input_device *get_wl_input_device_from_input_device(
 static void input_device_destroy(struct wlr_input_device *wlr_dev) {
 	struct wlr_wl_input_device *dev =
 		get_wl_input_device_from_input_device(wlr_dev);
-	if (dev->resource) {
-		wl_proxy_destroy(dev->resource);
+	if (dev->wlr_input_device.type == WLR_INPUT_DEVICE_KEYBOARD) {
+		wl_keyboard_release(dev->backend->keyboard);
+		dev->backend->keyboard = NULL;
 	}
 	wl_list_remove(&dev->wlr_input_device.link);
 	free(dev);
@@ -535,6 +536,7 @@ void create_wl_pointer(struct wl_pointer *wl_pointer, struct wlr_wl_output *outp
 			&relative_pointer_listener, dev);
 	}
 
+	wl_pointer_add_listener(wl_pointer, &pointer_listener, backend);
 	wlr_signal_emit_safe(&backend->backend.events.new_input, wlr_dev);
 }
 
@@ -556,7 +558,6 @@ void create_wl_keyboard(struct wl_keyboard *wl_keyboard, struct wlr_wl_backend *
 	wlr_keyboard_init(wlr_dev->keyboard, NULL);
 
 	wl_keyboard_add_listener(wl_keyboard, &keyboard_listener, wlr_dev);
-	dev->resource = wl_keyboard;
 	wlr_signal_emit_safe(&wl->backend.events.new_input, wlr_dev);
 }
 
@@ -565,7 +566,7 @@ static void seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
 	struct wlr_wl_backend *backend = data;
 	assert(backend->seat == wl_seat);
 
-	if ((caps & WL_SEAT_CAPABILITY_POINTER)) {
+	if ((caps & WL_SEAT_CAPABILITY_POINTER) && backend->pointer == NULL) {
 		wlr_log(WLR_DEBUG, "seat %p offered pointer", (void *)wl_seat);
 
 		struct wl_pointer *wl_pointer = wl_seat_get_pointer(wl_seat);
@@ -575,10 +576,22 @@ static void seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
 		wl_list_for_each(output, &backend->outputs, link) {
 			create_wl_pointer(wl_pointer, output);
 		}
+	}
+	if (!(caps & WL_SEAT_CAPABILITY_POINTER) && backend->pointer != NULL) {
+		wlr_log(WLR_DEBUG, "seat %p dropped pointer", (void *)wl_seat);
+
+		struct wlr_input_device *device, *tmp;
+		wl_list_for_each_safe(device, tmp, &backend->devices, link) {
+			if (device->type == WLR_INPUT_DEVICE_POINTER) {
+				wlr_input_device_destroy(device);
+			}
+		}
 
-		wl_pointer_add_listener(wl_pointer, &pointer_listener, backend);
+		wl_pointer_release(backend->pointer);
+		backend->pointer = NULL;
 	}
-	if ((caps & WL_SEAT_CAPABILITY_KEYBOARD)) {
+
+	if ((caps & WL_SEAT_CAPABILITY_KEYBOARD) && backend->keyboard == NULL) {
 		wlr_log(WLR_DEBUG, "seat %p offered keyboard", (void *)wl_seat);
 
 		struct wl_keyboard *wl_keyboard = wl_seat_get_keyboard(wl_seat);
@@ -588,6 +601,17 @@ static void seat_handle_capabilities(void *data, struct wl_seat *wl_seat,
 			create_wl_keyboard(wl_keyboard, backend);
 		}
 	}
+	if (!(caps & WL_SEAT_CAPABILITY_KEYBOARD) && backend->keyboard != NULL) {
+		wlr_log(WLR_DEBUG, "seat %p dropped keyboard", (void *)wl_seat);
+
+		struct wlr_input_device *device, *tmp;
+		wl_list_for_each_safe(device, tmp, &backend->devices, link) {
+			if (device->type == WLR_INPUT_DEVICE_KEYBOARD) {
+				wlr_input_device_destroy(device);
+			}
+		}
+		assert(backend->keyboard == NULL); // free'ed by input_device_destroy
+	}
 }
 
 static void seat_handle_name(void *data, struct wl_seat *wl_seat,