Add setting to control autosave interval mode

src/lang/extra/english.txt

@@ -437,6 +437,9 @@ STR_CONFIG_SETTING_VIEWPORT_MAP_DRAW_ROUTE_DASH_HELPTEXT        :How to draw the
 STR_CONFIG_SETTING_VIEWPORT_MAP_DRAW_ROUTE_DASH_VALUE           :dashed lines of {COMMA} pixel{P "" s}
 STR_CONFIG_SETTING_VIEWPORT_MAP_DRAW_ROUTE_DASH_DISABLED        :plain lines
 
+STR_CONFIG_SETTING_AUTOSAVE_REALTIME                            :Autosave interval uses real-time: {STRING2}
+STR_CONFIG_SETTING_AUTOSAVE_REALTIME_HELPTEXT                   :When enabled, autosave intervals uses real elapsed wall-clock time, (when paused autosaving will stop until you make any change to the game).{}When disabled, autosave intervals use elapsed game simulation time.
+
 STR_CONFIG_SETTING_AUTOSAVE_ON_NETWORK_DISCONNECT               :Autosave on network disconnection: {STRING2}
 STR_CONFIG_SETTING_AUTOSAVE_ON_NETWORK_DISCONNECT_HELPTEXT      :When enabled, multiplayer clients automatically save the game when disconnected from the server
 

src/openttd.cpp

@@ -2106,7 +2106,7 @@ void StateGameLoop()
 			_scaled_date_ticks++;   // This must update in lock-step with _tick_skip_counter, such that it always matches what SetScaledTickVariables would return.
 		}
 
-		if (!(_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP) &&
+		if (!(_game_mode == GM_MENU || _game_mode == GM_BOOTSTRAP) && !_settings_client.gui.autosave_realtime &&
 				(_scaled_date_ticks % (_settings_client.gui.autosave_interval * (_settings_game.economy.tick_rate == TRM_MODERN ? (60000 / 27) : (60000 / 30)))) == 0) {
 			_do_autosave = true;
 			_check_special_modes = true;
@@ -2228,7 +2228,8 @@ static IntervalTimer<TimerGameRealtime> _autosave_interval({std::chrono::millise
  */
 void ChangeAutosaveFrequency(bool reset)
 {
-	_autosave_interval.SetInterval({_settings_client.gui.autosave_realtime, TimerGameRealtime::AUTOSAVE}, reset);
+	std::chrono::minutes interval = _settings_client.gui.autosave_realtime ? std::chrono::minutes(_settings_client.gui.autosave_interval) : std::chrono::minutes::zero();
+	_autosave_interval.SetInterval({interval, TimerGameRealtime::AUTOSAVE}, reset);
 }
 
 /**

src/settings_gui.cpp

@@ -2001,6 +2001,7 @@ static SettingsContainer &GetSettingsTree()
 			SettingsPage *save = interface->Add(new SettingsPage(STR_CONFIG_SETTING_INTERFACE_SAVE));
 			{
 				save->Add(new SettingEntry("gui.autosave_interval"));
+				save->Add(new SettingEntry("gui.autosave_realtime"));
 				save->Add(new SettingEntry("gui.autosave_on_network_disconnect"));
 				save->Add(new SettingEntry("gui.savegame_overwrite_confirm"));
 			}

src/settings_type.h

@@ -177,6 +177,7 @@ struct GUISettings : public TimeSettings {
 	ZoomLevel zoom_max;                      ///< maximum zoom out level
 	ZoomLevel sprite_zoom_min;               ///< maximum zoom level at which higher-resolution alternative sprites will be used (if available) instead of scaling a lower resolution sprite
 	uint32 autosave_interval;                ///< how often should we do autosaves?
+	bool   autosave_realtime;                ///< autosaves based on real elapsed time (with pause handling)
 	bool   threaded_saves;                   ///< should we do threaded saves?
 	bool   keep_all_autosave;                ///< name the autosave in a different way
 	bool   autosave_on_exit;                 ///< save an autosave when you quit the game, but do not ask "Do you really want to quit?"

src/table/settings/settings.ini

@@ -4525,6 +4525,16 @@ strval   = STR_GAME_OPTIONS_AUTOSAVE_DROPDOWN_EVERY_MINUTES_CUSTOM
 post_cb  = AutosaveModeChanged
 cat      = SC_BASIC
 
+[SDTC_BOOL]
+var      = gui.autosave_realtime
+flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC
+def      = true
+str      = STR_CONFIG_SETTING_AUTOSAVE_REALTIME
+strhelp  = STR_CONFIG_SETTING_AUTOSAVE_REALTIME_HELPTEXT
+post_cb  = AutosaveModeChanged
+patchcat = SC_PATCH
+cat      = SC_EXPERT
+
 [SDTC_BOOL]
 var      = gui.threaded_saves
 flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC