backend/libinput: use NULL to indicate missing device name

libinput guarantees that the name is non-NULL, and an empty string
if unset. However wlroots uses NULL to indicate that an input device
name is unset.

backend/libinput/backend.c

@@ -233,3 +233,13 @@ struct libinput_device *wlr_libinput_get_device_handle(
 uint32_t usec_to_msec(uint64_t usec) {
 	return (uint32_t)(usec / 1000);
 }
+
+const char *get_libinput_device_name(struct libinput_device *device) {
+	// libinput guarantees that the name is non-NULL, and an empty string if
+	// unset. However wlroots uses NULL to indicate that the name is unset.
+	const char *name = libinput_device_get_name(device);
+	if (name[0] == '\0') {
+		return NULL;
+	}
+	return name;
+}

backend/libinput/keyboard.c

@@ -23,7 +23,7 @@ const struct wlr_keyboard_impl libinput_keyboard_impl = {
 };
 
 void init_device_keyboard(struct wlr_libinput_input_device *dev) {
-	const char *name = libinput_device_get_name(dev->handle);
+	const char *name = get_libinput_device_name(dev->handle);
 	struct wlr_keyboard *wlr_kb = &dev->keyboard;
 	wlr_keyboard_init(wlr_kb, &libinput_keyboard_impl, name);
 	wlr_kb->base.vendor = libinput_device_get_id_vendor(dev->handle);

backend/libinput/pointer.c

@@ -8,7 +8,7 @@ const struct wlr_pointer_impl libinput_pointer_impl = {
 };
 
 void init_device_pointer(struct wlr_libinput_input_device *dev) {
-	const char *name = libinput_device_get_name(dev->handle);
+	const char *name = get_libinput_device_name(dev->handle);
 	struct wlr_pointer *wlr_pointer = &dev->pointer;
 	wlr_pointer_init(wlr_pointer, &libinput_pointer_impl, name);
 	wlr_pointer->base.vendor = libinput_device_get_id_vendor(dev->handle);

backend/libinput/switch.c

@@ -8,7 +8,7 @@ const struct wlr_switch_impl libinput_switch_impl = {
 };
 
 void init_device_switch(struct wlr_libinput_input_device *dev) {
-	const char *name = libinput_device_get_name(dev->handle);
+	const char *name = get_libinput_device_name(dev->handle);
 	struct wlr_switch *wlr_switch = &dev->switch_device;
 	wlr_switch_init(wlr_switch, &libinput_switch_impl, name);
 	wlr_switch->base.vendor = libinput_device_get_id_vendor(dev->handle);

backend/libinput/tablet_pad.c

@@ -90,7 +90,7 @@ group_fail:
 
 void init_device_tablet_pad(struct wlr_libinput_input_device *dev) {
 	struct libinput_device *handle = dev->handle;
-	const char *name = libinput_device_get_name(handle);
+	const char *name = get_libinput_device_name(handle);
 	struct wlr_tablet_pad *wlr_tablet_pad = &dev->tablet_pad;
 	wlr_tablet_pad_init(wlr_tablet_pad, &libinput_tablet_pad_impl, name);
 	wlr_tablet_pad->base.vendor = libinput_device_get_id_vendor(handle);

backend/libinput/tablet_tool.c

@@ -17,7 +17,7 @@ const struct wlr_tablet_impl libinput_tablet_impl = {
 };
 
 void init_device_tablet(struct wlr_libinput_input_device *dev) {
-	const char *name = libinput_device_get_name(dev->handle);
+	const char *name = get_libinput_device_name(dev->handle);
 	struct wlr_tablet *wlr_tablet = &dev->tablet;
 	wlr_tablet_init(wlr_tablet, &libinput_tablet_impl, name);
 	wlr_tablet->base.vendor = libinput_device_get_id_vendor(dev->handle);

backend/libinput/touch.c

@@ -8,7 +8,7 @@ const struct wlr_touch_impl libinput_touch_impl = {
 };
 
 void init_device_touch(struct wlr_libinput_input_device *dev) {
-	const char *name = libinput_device_get_name(dev->handle);
+	const char *name = get_libinput_device_name(dev->handle);
 	struct wlr_touch *wlr_touch = &dev->touch;
 	wlr_touch_init(wlr_touch, &libinput_touch_impl, name);
 	wlr_touch->base.vendor = libinput_device_get_id_vendor(dev->handle);

include/backend/libinput.h

@@ -48,6 +48,7 @@ void handle_libinput_event(struct wlr_libinput_backend *state,
 		struct libinput_event *event);
 
 void destroy_libinput_input_device(struct wlr_libinput_input_device *dev);
+const char *get_libinput_device_name(struct libinput_device *device);
 
 extern const struct wlr_keyboard_impl libinput_keyboard_impl;
 extern const struct wlr_pointer_impl libinput_pointer_impl;