From ca79a32890f4040be7da7d4c1109c15661d50d2f Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sat, 20 Jun 2020 21:27:19 +0100
Subject: [PATCH] Scheduled dispatch: Fixup start dates when changing game date

---
 src/cheat_gui.cpp   | 2 ++
 src/date.cpp        | 1 +
 src/order_base.h    | 2 ++
 src/order_cmd.cpp   | 9 +++++++++
 src/toolbar_gui.cpp | 1 +
 5 files changed, 15 insertions(+)

diff --git a/src/cheat_gui.cpp b/src/cheat_gui.cpp
index bbfd2052eb..cbe1cd7e62 100644
--- a/src/cheat_gui.cpp
+++ b/src/cheat_gui.cpp
@@ -28,6 +28,7 @@
 #include "newgrf.h"
 #include "error.h"
 #include "network/network.h"
+#include "order_base.h"
 
 #include "widgets/cheat_widget.h"
 
@@ -108,6 +109,7 @@ static int32 ClickChangeDateCheat(int32 p1, int32 p2)
 
 	Date new_date = ConvertYMDToDate(p1, ymd.month, ymd.day);
 	LinkGraphSchedule::instance.ShiftDates(new_date - _date);
+	ShiftOrderDates(new_date - _date);
 	SetDate(new_date, _date_fract);
 	EnginesMonthlyLoop();
 	SetWindowDirty(WC_STATUS_BAR, 0);
diff --git a/src/date.cpp b/src/date.cpp
index 29c36dcb21..ef97a05289 100644
--- a/src/date.cpp
+++ b/src/date.cpp
@@ -231,6 +231,7 @@ static void OnNewYear()
 		_date -= days_this_year;
 		for (Vehicle *v : Vehicle::Iterate()) v->date_of_last_service -= days_this_year;
 		for (LinkGraph *lg : LinkGraph::Iterate()) lg->ShiftDates(-days_this_year);
+		ShiftOrderDates(-days_this_year);
 
 		/* Because the _date wraps here, and text-messages expire by game-days, we have to clean out
 		 *  all of them if the date is set back, else those messages will hang for ever */
diff --git a/src/order_base.h b/src/order_base.h
index 8e03a3f7d6..3fa8f3fffb 100644
--- a/src/order_base.h
+++ b/src/order_base.h
@@ -809,6 +809,8 @@ public:
 
 };
 
+void ShiftOrderDates(int interval);
+
 #define FOR_VEHICLE_ORDERS(v, order) for (order = (v->orders.list == nullptr) ? nullptr : v->orders.list->GetFirstOrder(); order != nullptr; order = order->next)
 
 #endif /* ORDER_BASE_H */
diff --git a/src/order_cmd.cpp b/src/order_cmd.cpp
index bfdee04b46..e895ca04b7 100644
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@@ -3004,3 +3004,12 @@ CommandCost CmdMassChangeOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 	}
 	return CommandCost();
 }
+
+void ShiftOrderDates(int interval)
+{
+	for (OrderList *orderlist : OrderList::Iterate()) {
+		if (orderlist->GetScheduledDispatchStartDatePart() >= 0) {
+			orderlist->SetScheduledDispatchStartDate(orderlist->GetScheduledDispatchStartDatePart() + interval, orderlist->GetScheduledDispatchStartDateFractPart());
+		}
+	}
+}
diff --git a/src/toolbar_gui.cpp b/src/toolbar_gui.cpp
index b32d14266b..ca0f3d8d74 100644
--- a/src/toolbar_gui.cpp
+++ b/src/toolbar_gui.cpp
@@ -1159,6 +1159,7 @@ void SetStartingYear(Year year)
 	Date new_date = ConvertYMDToDate(_settings_game.game_creation.starting_year, 0, 1);
 	/* If you open a savegame as scenario there may already be link graphs.*/
 	LinkGraphSchedule::instance.ShiftDates(new_date - _date);
+	ShiftOrderDates(new_date - _date);
 	SetDate(new_date, 0);
 }