Watch for local.org_kde_powerdevil dbus service to come online

Before we were just checking once at launch which meant if the service wasn't up by that time, we weren't able to control brightness on KDE.
Now we watch when it comes online and offline.

src/simple_dbus.cpp

@@ -36,10 +36,13 @@ bool registered_object_path = false;
  *
  *************************************************/
 
+static double max_kde_brightness = 0;
 
 void remove_service(const std::string &service) {
     for (int i = 0; i < running_dbus_services.size(); i++) {
         if (running_dbus_services[i] == service) {
+            if (running_dbus_services[i] == "local.org_kde_powerdevil")
+                max_kde_brightness = 0;
             running_dbus_services.erase(running_dbus_services.begin() + i);
             return;
         }
@@ -48,6 +51,8 @@ void remove_service(const std::string &service) {
 
 DBusHandlerResult handle_message_cb(DBusConnection *connection, DBusMessage *message, void *userdata);
 
+static bool dbus_kde_max_brightness();
+
 static DBusHandlerResult signal_handler(DBusConnection *connection,
                                         DBusMessage *message, void *user_data) {
     if (dbus_message_is_signal(message, "org.freedesktop.DBus",
@@ -67,6 +72,8 @@ static DBusHandlerResult signal_handler(DBusConnection *connection,
 
         if (strcmp(old_owner, "") == 0) {
             running_dbus_services.emplace_back(name);
+            if (std::string(name) == "local.org_kde_powerdevil")
+                dbus_kde_max_brightness();
         } else if (strcmp(new_owner, "") == 0) {
             remove_service(name);
         }
@@ -140,6 +147,8 @@ static void dbus_reply_to_list_names_request(DBusPendingCall *call, void *data)
     //
     for (char *name = *args; name; name = *++args) {
         running_dbus_services.emplace_back(name);
+        if (std::string(name) == "local.org_kde_powerdevil")
+            dbus_kde_max_brightness();
     }
 
     // Register some signals that we are interested in hearing about "NameOwnerChanged", "NameAcquired", "NameLost"
@@ -337,8 +346,6 @@ bool dbus_gnome_show_overview() {
     return true;
 }
 
-static double max_kde_brightness = 0;
-
 static void dbus_kde_max_brightness_response(DBusPendingCall *call, void *data) {
 #ifdef TRACY_ENABLE
     ZoneScoped;
@@ -355,7 +362,7 @@ static void dbus_kde_max_brightness_response(DBusPendingCall *call, void *data)
     }
 }
 
-bool dbus_kde_max_brightness() {
+static bool dbus_kde_max_brightness() {
     if (!dbus_connection) return false;
 
     DBusMessage *dbus_msg = dbus_message_new_method_call("local.org_kde_powerdevil", "/org/kde/Solid/PowerManagement/Actions/BrightnessControl",
@@ -385,7 +392,7 @@ double dbus_get_kde_max_brightness() {
 }
 
 double dbus_get_kde_current_brightness() {
-    if (!dbus_connection) return false;
+    if (!dbus_connection) return 0;
 
     DBusMessage *dbus_msg = dbus_message_new_method_call("local.org_kde_powerdevil", "/org/kde/Solid/PowerManagement/Actions/BrightnessControl",
                                                          "org.kde.Solid.PowerManagement.Actions.BrightnessControl",
@@ -750,8 +757,6 @@ void dbus_start() {
 
         dbus_poll_wakeup(nullptr, 0);
     }
-
-    dbus_kde_max_brightness();
 }
 
 void dbus_end() {