interface/wlr_tablet_tool: rework destroy sequence

The destroy callback in wlr_tablet_tool_impl has been removed. The function
`wlr_tablet_tool_finish` has been introduced to clean up the resources owned by
a wlr_tablet_tool.

`wlr_input_device_destroy` no longer destroys the wlr_tablet_tool, attempting to
destroy a wlr_tablet_tool will result in a no-op.

The field `name` has been added to the wlr_tablet_tool_impl to be able to
identify a given wlr_tablet_tool device.

backend/libinput/events.c

@@ -27,7 +27,7 @@ void destroy_libinput_input_device(struct wlr_libinput_input_device *dev) {
 		wlr_touch_destroy(&dev->touch);
 	}
 	if (dev->tablet.impl) {
-		wlr_tablet_destroy(&dev->tablet);
+		finish_device_tablet(dev);
 	}
 	if (dev->tablet_pad.impl) {
 		finish_device_tablet_pad(dev);

backend/libinput/tablet_tool.c

@@ -14,24 +14,8 @@ struct tablet_tool {
 	struct wl_list link; // wlr_libinput_input_device::tablet_tools
 };
 
-static void tool_destroy(struct tablet_tool *tool) {
-	wlr_signal_emit_safe(&tool->wlr_tool.events.destroy, &tool->wlr_tool);
-	libinput_tablet_tool_unref(tool->handle);
-	libinput_tablet_tool_set_user_data(tool->handle, NULL);
-	wl_list_remove(&tool->link);
-	free(tool);
-}
-
-static void tablet_destroy(struct wlr_tablet *wlr_tablet) {
-	struct wlr_libinput_input_device *dev = device_from_tablet(wlr_tablet);
-	struct tablet_tool *tool, *tmp;
-	wl_list_for_each_safe(tool, tmp, &dev->tablet_tools, link) {
-		tool_destroy(tool);
-	}
-}
-
 const struct wlr_tablet_impl libinput_tablet_impl = {
-	.destroy = tablet_destroy,
+	.name = "libinput-tablet-tool",
 };
 
 void init_device_tablet(struct wlr_libinput_input_device *dev) {
@@ -48,6 +32,23 @@ void init_device_tablet(struct wlr_libinput_input_device *dev) {
 	wl_list_init(&dev->tablet_tools);
 }
 
+static void tool_destroy(struct tablet_tool *tool) {
+	wlr_signal_emit_safe(&tool->wlr_tool.events.destroy, &tool->wlr_tool);
+	libinput_tablet_tool_unref(tool->handle);
+	libinput_tablet_tool_set_user_data(tool->handle, NULL);
+	wl_list_remove(&tool->link);
+	free(tool);
+}
+
+void finish_device_tablet(struct wlr_libinput_input_device *dev) {
+	struct tablet_tool *tool, *tmp;
+	wl_list_for_each_safe(tool, tmp, &dev->tablet_tools, link) {
+		tool_destroy(tool);
+	}
+
+	wlr_tablet_finish(&dev->tablet);
+}
+
 struct wlr_libinput_input_device *device_from_tablet(
 		struct wlr_tablet *wlr_tablet) {
 	assert(wlr_tablet->impl == &libinput_tablet_impl);

backend/wayland/seat.c

@@ -563,6 +563,10 @@ void destroy_wl_input_device(struct wlr_wl_input_device *dev) {
 			wlr_tablet_pad_finish(wlr_dev->tablet_pad);
 			free(wlr_dev->tablet_pad);
 			break;
+		case WLR_INPUT_DEVICE_TABLET_TOOL:
+			wlr_tablet_finish(wlr_dev->tablet);
+			free(wlr_dev->tablet);
+			break;
 		default:
 			wlr_input_device_destroy(wlr_dev);
 			break;

backend/wayland/tablet_v2.c

@@ -867,13 +867,8 @@ static void handle_tablet_removed(void *data,
 		struct zwp_tablet_v2 *zwp_tablet_v2) {
 	struct wlr_wl_input_device *dev = data;
 
-	/* This doesn't free anything, but emits the destroy signal */
-	wlr_input_device_destroy(&dev->wlr_input_device);
-	/* This is a bit ugly, but we need to remove it from our list */
-	wl_list_remove(&dev->link);
-
 	zwp_tablet_v2_destroy(dev->resource);
-	free(dev);
+	destroy_wl_input_device(dev);
 }
 
 static const struct zwp_tablet_v2_listener tablet_listener = {
@@ -884,7 +879,9 @@ static const struct zwp_tablet_v2_listener tablet_listener = {
 	.removed = handle_tablet_removed,
 };
 
-const struct wlr_tablet_impl tablet_impl = {0};
+const struct wlr_tablet_impl tablet_impl = {
+	.name = "wl-tablet-tool",
+};
 
 static void handle_tab_added(void *data,
 		struct zwp_tablet_seat_v2 *zwp_tablet_seat_v2,
@@ -908,7 +905,7 @@ static void handle_tab_added(void *data,
 		return;
 	}
 	zwp_tablet_v2_set_user_data(id, wlr_dev->tablet);
-	wlr_tablet_init(wlr_dev->tablet, &tablet_impl, wlr_dev->name);
+	wlr_tablet_init(wlr_dev->tablet, &tablet_impl, "wlr_tablet_v2");
 	zwp_tablet_v2_add_listener(id, &tablet_listener, dev);
 }
 

include/backend/libinput.h

@@ -108,6 +108,7 @@ void handle_touch_frame(struct libinput_event *event,
 	struct wlr_touch *touch);
 
 void init_device_tablet(struct wlr_libinput_input_device *dev);
+void finish_device_tablet(struct wlr_libinput_input_device *dev);
 struct wlr_libinput_input_device *device_from_tablet(
 	struct wlr_tablet *tablet);
 void handle_tablet_tool_axis(struct libinput_event *event,

include/wlr/interfaces/wlr_tablet_tool.h

@@ -12,11 +12,11 @@
 #include <wlr/types/wlr_tablet_tool.h>
 
 struct wlr_tablet_impl {
-	void (*destroy)(struct wlr_tablet *tablet);
+	const char *name;
 };
 
 void wlr_tablet_init(struct wlr_tablet *tablet,
 	const struct wlr_tablet_impl *impl, const char *name);
-void wlr_tablet_destroy(struct wlr_tablet *tablet);
+void wlr_tablet_finish(struct wlr_tablet *tablet);
 
 #endif

types/wlr_input_device.c

@@ -2,7 +2,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <wayland-server-core.h>
-#include <wlr/interfaces/wlr_tablet_tool.h>
 #include <wlr/interfaces/wlr_touch.h>
 #include <wlr/types/wlr_input_device.h>
 #include <wlr/util/log.h>
@@ -49,7 +48,7 @@ void wlr_input_device_destroy(struct wlr_input_device *dev) {
 			wlr_touch_destroy(dev->touch);
 			break;
 		case WLR_INPUT_DEVICE_TABLET_TOOL:
-			wlr_tablet_destroy(dev->tablet);
+			wlr_log(WLR_ERROR, "wlr_tablet_tool will not be destroyed");
 			break;
 		case WLR_INPUT_DEVICE_TABLET_PAD:
 			wlr_log(WLR_ERROR, "wlr_tablet_pad will not be destroyed");

types/wlr_tablet_tool.c

@@ -17,21 +17,12 @@ void wlr_tablet_init(struct wlr_tablet *tablet,
 	wl_array_init(&tablet->paths);
 }
 
-void wlr_tablet_destroy(struct wlr_tablet *tablet) {
+void wlr_tablet_finish(struct wlr_tablet *tablet) {
-	if (!tablet) {
+	wlr_input_device_finish(&tablet->base);
-		return;
-	}
 
 	char **path_ptr;
 	wl_array_for_each(path_ptr, &tablet->paths) {
 		free(*path_ptr);
 	}
 	wl_array_release(&tablet->paths);
-
-	wlr_input_device_finish(&tablet->base);
-	if (tablet->impl && tablet->impl->destroy) {
-		tablet->impl->destroy(tablet);
-	} else {
-		free(tablet);
-	}
 }