Watch changes of WM_CLASS

There may be some interesting information in there.
Sometimes it may be hard to identify applications by their title.

wdmtg.c

@@ -86,6 +86,7 @@ latin1_to_utf8(const gchar *latin1, gsize len)
 struct event {
 	gint64 timestamp;                   // When the event happened
 	gchar *title;                       // Current title at the time
+	gchar *class;                       // Current class at the time
 	gboolean idle;                      // Whether the user is idle
 };
 
@@ -93,6 +94,7 @@ static void
 event_free(struct event *self)
 {
 	g_free(self->title);
+	g_free(self->class);
 	g_slice_free(struct event, self);
 }
 
@@ -117,6 +119,7 @@ struct {
 	// Window title tracking
 
 	gchar *current_title;               // Current window title or NULL
+	gchar *current_class;               // Current window class or NULL
 	xcb_window_t current_window;        // Current window
 	gboolean current_idle;              // Current idle status
 
@@ -286,6 +289,7 @@ push_event(void) {
 	struct event *event = g_slice_new0(struct event);
 	event->timestamp = g_get_real_time();
 	event->title = g_strdup(gen.current_title);
+	event->class = g_strdup(gen.current_class);
 	event->idle = gen.current_idle;
 	g_async_queue_push(g.queue, event);
 
@@ -313,6 +317,33 @@ update_window_title(char *new_title)
 	return changed;
 }
 
+static char *
+x_window_class(xcb_window_t window)
+{
+	GString *title;
+	if (!(title = x_text_property(window, XCB_ATOM_WM_CLASS)))
+		return NULL;
+
+	// First is an "instance name", followed by a NUL and a "class name".
+	// Strongly prefer Firefox/Thunderbird over Navigator/Mail.
+	size_t skip = strlen(title->str);
+	if (++skip >= title->len)
+		return g_string_free(title, true);
+
+	g_string_erase(title, 0, skip);
+	return g_string_free(title, false);
+}
+
+static bool
+update_window_class(char *new_class)
+{
+	bool changed = !gen.current_class != !new_class
+		|| (new_class && strcmp(gen.current_class, new_class));
+	free(gen.current_class);
+	gen.current_class = new_class;
+	return changed;
+}
+
 static void
 update_current_window(void)
 {
@@ -322,14 +353,8 @@ update_current_window(void)
 	if (!gpr)
 		return;
 
-	// TODO: also consider watching XCB_ATOM_WM_CLASS
-	//  - the first one is an "Instance name", the second one a "Class name"
-	//  - don't know which one to pick, though probably the second one,
-	//    since the instance name is Navigator/Mail for Firefox/Thunderbird
-	//     - they are separated by a NUL character
-	//  - it's not worth to watch for changes of this property
-
 	char *new_title = NULL;
+	char *new_class = NULL;
 	if (xcb_get_property_value_length(gpr)) {
 		xcb_window_t active_window =
 			*(xcb_window_t *) xcb_get_property_value(gpr);
@@ -344,11 +369,14 @@ update_current_window(void)
 			active_window, XCB_CW_EVENT_MASK, enable);
 
 		new_title = x_window_title(active_window);
+		new_class = x_window_class(active_window);
 		gen.current_window = active_window;
 	}
-
 	free(gpr);
-	if (update_window_title(new_title))
+
+	// We need to absorb both pointers, so we need a bitwise OR
+	if (update_window_title(new_title) |
+		update_window_class(new_class))
 		push_event();
 }
 
@@ -555,14 +583,18 @@ on_queue_incoming(G_GNUC_UNUSED gpointer user_data)
 	// in a transaction at once (the amount of dequeues here)
 	struct event *event = NULL;
 	while ((event = g_async_queue_try_pop(g.queue))) {
-		printf("Event: ts: %ld, title: %s, idle: %d\n",
-			event->timestamp, event->title ?: "(none)", event->idle);
+		printf("Event: ts: %ld, title: %s, class: %s, idle: %d\n",
+			event->timestamp, event->title ?: "(none)",
+			event->class ?: "(none)", event->idle);
 
 		if ((rc = sqlite3_bind_int64(g.add_event, 1, event->timestamp)) ||
 			// FIXME: it will fail on NULL titles
 			(rc = sqlite3_bind_text(g.add_event, 2, event->title, -1,
 				SQLITE_STATIC)) ||
-			(rc = sqlite3_bind_int(g.add_event, 3, event->idle)))
+			// FIXME: it will fail on NULL classes
+			(rc = sqlite3_bind_text(g.add_event, 3, event->class, -1,
+				SQLITE_STATIC)) ||
+			(rc = sqlite3_bind_int(g.add_event, 4, event->idle)))
 			g_printerr("DB bind error: %s\n", sqlite3_errmsg(g.db));
 
 		if (((rc = sqlite3_step(g.add_event)) && rc != SQLITE_DONE) ||
@@ -612,6 +644,7 @@ database_init(const gchar *db_path)
 			"id INTEGER PRIMARY KEY AUTOINCREMENT, "
 			"timestamp INTEGER, "
 			"title TEXT, "
+			"class TEXT, "
 			"idle BOOLEAN)", NULL, NULL, &errmsg)))
 			exit_fatal("%s: %s", db_path, errmsg);
 		if ((rc = sqlite3_exec(db, "PRAGMA user_version = 1", NULL, NULL,
@@ -624,8 +657,8 @@ database_init(const gchar *db_path)
 		exit_fatal("%s: %s", db_path, errmsg);
 
 	if ((rc = sqlite3_prepare_v2(db,
-		"INSERT INTO events (timestamp, title, idle) VALUES (?, ?, ?)", -1,
-		&g.add_event, NULL)))
+		"INSERT INTO events (timestamp, title, class, idle) "
+		"VALUES (?, ?, ?, ?)", -1, &g.add_event, NULL)))
 		exit_fatal("%s: %s", db_path, sqlite3_errmsg(db));
 	return db;
 }