From 8139b14e9c941433bce74e46a7330123cae4ae2b Mon Sep 17 00:00:00 2001
From: Eddi-z <43699911+Eddi-z@users.noreply.github.com>
Date: Sat, 2 Mar 2019 22:28:22 +0100
Subject: Change: Synchronize introduction date and reliability randomness
 across vehicles with the same base introduction date (#7147)

---
 src/engine.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/engine.cpp b/src/engine.cpp
index 9f500e1cd..d539a4852 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -652,7 +652,14 @@ void StartupOneEngine(Engine *e, Date aging_date)
 	/* Don't randomise the start-date in the first two years after gamestart to ensure availability
 	 * of engines in early starting games.
 	 * Note: TTDP uses fixed 1922 */
+	SavedRandomSeeds saved_seeds;
+	SaveRandomSeeds(&saved_seeds);
+	SetRandomSeed(_settings_game.game_creation.generation_seed ^
+	              ei->base_intro ^
+	              e->type ^
+	              e->GetGRFID());
 	uint32 r = Random();
+
 	e->intro_date = ei->base_intro <= ConvertYMDToDate(_settings_game.game_creation.starting_year + 2, 0, 1) ? ei->base_intro : (Date)GB(r, 0, 9) + ei->base_intro;
 	if (e->intro_date <= _date) {
 		e->age = (aging_date - e->intro_date) >> 5;
@@ -672,6 +679,7 @@ void StartupOneEngine(Engine *e, Date aging_date)
 
 	e->reliability_spd_dec = ei->decay_speed << 2;
 
+	RestoreRandomSeeds(saved_seeds);
 	CalcEngineReliability(e);
 
 	/* prevent certain engines from ever appearing. */
-- 
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