Auto separation: Add setting to scale vehicle lateness adjustments.

No longer set vehicle lateness to 0 if separation fails, instead
leave it as it was.

The setting defaults to 100% (full abruptness, old behaviour).
Reduce the setting if auto separation is too disruptive, e.g. causes
excessive waiting in stations.

Note that this is not savegame compatible.

src/lang/english.txt

@@ -1400,6 +1400,8 @@ STR_CONFIG_SETTING_TIMETABLE_IN_TICKS                           :Show timetable
 STR_CONFIG_SETTING_TIMETABLE_IN_TICKS_HELPTEXT                  :Show travel times in time tables in game ticks instead of days
 STR_CONFIG_SETTING_TIMETABLE_SEPARATION                         :Use timetable to ensure vehicle separation: {STRING2}
 STR_CONFIG_SETTING_TIMETABLE_SEPARATION_HELPTEXT                :Select whether to ensure separation of vehicles when using automatic timetables
+STR_CONFIG_SETTING_TIMETABLE_SEPARATION_RATE                    :Vehicle separation factor: {STRING2}
+STR_CONFIG_SETTING_TIMETABLE_SEPARATION_RATE_HELPTEXT           :How much of the vehicle separation timetable change to apply at each step
 STR_CONFIG_SETTING_TIMETABLE_SHOW_ARRIVAL_DEPARTURE             :Show arrival and departure in timetables: {STRING2}
 STR_CONFIG_SETTING_TIMETABLE_SHOW_ARRIVAL_DEPARTURE_HELPTEXT    :Display anticipated arrival and departure times in timetables
 STR_CONFIG_SETTING_QUICKGOTO                                    :Quick creation of vehicle orders: {STRING2}

src/settings_gui.cpp

@@ -1628,6 +1628,7 @@ static SettingsContainer &GetSettingsTree()
 			vehicles->Add(new SettingEntry("order.serviceathelipad"));
 			vehicles->Add(new SettingEntry("order.timetable_automated"));
 			vehicles->Add(new SettingEntry("order.timetable_separation"));
+			vehicles->Add(new SettingEntry("order.timetable_separation_rate"));
 		}
 
 		SettingsPage *limitations = main->Add(new SettingsPage(STR_CONFIG_SETTING_LIMITATIONS));

src/settings_type.h

@@ -440,6 +440,7 @@ struct OrderSettings {
 	bool   no_servicing_if_no_breakdowns;    ///< don't send vehicles to depot when breakdowns are disabled
 	bool   timetable_automated;              ///< whether to automatically manage timetables
 	bool   timetable_separation;             ///< whether to perform automatic separation based on timetable
+	uint8  timetable_separation_rate;        ///< percentage of timetable separation change to apply
 	bool   serviceathelipad;                 ///< service helicopters at helipads automatically (no need to send to depot)
 };
 

src/table/settings.ini

@@ -347,6 +347,20 @@ str      = STR_CONFIG_SETTING_TIMETABLE_SEPARATION
 strhelp  = STR_CONFIG_SETTING_TIMETABLE_SEPARATION_HELPTEXT
 cat      = SC_EXPERT
 
+[SDT_VAR]
+base     = GameSettings
+var      = order.timetable_separation_rate
+type     = SLE_UINT8
+from     = TIMESEP_SV
+def      = 100
+min      = 0
+max      = 100
+interval = 10
+str      = STR_CONFIG_SETTING_TIMETABLE_SEPARATION_RATE
+strhelp  = STR_CONFIG_SETTING_TIMETABLE_SEPARATION_RATE_HELPTEXT
+strval   = STR_CONFIG_SETTING_PERCENTAGE
+cat      = SC_EXPERT
+
 ; There are only 21 predefined town_name values (0-20), but you can have more with newgrf action F so allow
 ; these bigger values (21-255). Invalid values will fallback to english on use and (undefined string) in GUI.
 [SDT_OMANY]

src/timetable_cmd.cpp

@@ -548,8 +548,11 @@ void UpdateSeparationOrder(Vehicle *v_start)
 			}
 			int separation_ahead = SeparationBetween(v, v->AheadSeparation());
 			int separation_behind = SeparationBetween(v->BehindSeparation(), v);
-			v->lateness_counter = (separation_ahead - separation_behind) / 2;
+			if (separation_ahead != -1 && separation_behind != -1) {
-			if (separation_ahead == -1 || separation_behind == -1) v->lateness_counter = 0;
+				int new_lateness = (separation_ahead - separation_behind) / 2;
+				v->lateness_counter = (new_lateness * _settings_game.order.timetable_separation_rate +
+						v->lateness_counter * (100 - _settings_game.order.timetable_separation_rate)) / 100;
+			}
 			v = v->AheadSeparation();
 		} while (v != v_start);
 	}