Feature: [NewGRF] Maximum curve speed modifier for rail vehicles (#9346)

1 files changed, 8 insertions, 0 deletions

diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 17e298c33..1498a5fad 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -115,6 +115,7 @@ void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
 	this->compatible_railtypes = RAILTYPES_NONE;
 
 	bool train_can_tilt = true;
+	int min_curve_speed_mod = INT_MAX;
 
 	for (Train *u = this; u != nullptr; u = u->Next()) {
 		const RailVehicleInfo *rvi_u = RailVehInfo(u->engine_type);
@@ -146,6 +147,7 @@ void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
 		const RailVehicleInfo *rvi_u = &e_u->u.rail;
 
 		if (!HasBit(e_u->info.misc_flags, EF_RAIL_TILTS)) train_can_tilt = false;
+		min_curve_speed_mod = std::min(min_curve_speed_mod, u->GetCurveSpeedModifier());
 
 		/* Cache wagon override sprite group. nullptr is returned if there is none */
 		u->tcache.cached_override = GetWagonOverrideSpriteSet(u->engine_type, u->cargo_type, u->gcache.first_engine);
@@ -229,6 +231,7 @@ void Train::ConsistChanged(ConsistChangeFlags allowed_changes)
 	/* store consist weight/max speed in cache */
 	this->vcache.cached_max_speed = max_speed;
 	this->tcache.cached_tilt = train_can_tilt;
+	this->tcache.cached_curve_speed_mod = min_curve_speed_mod;
 	this->tcache.cached_max_curve_speed = this->GetCurveSpeedLimit();
 
 	/* recalculate cached weights and power too (we do this *after* the rest, so it is known which wagons are powered and need extra weight added) */
@@ -357,6 +360,11 @@ int Train::GetCurveSpeedLimit() const
 			/* Apply max_speed bonus of 20% for a tilting train */
 			max_speed += max_speed / 5;
 		}
+
+		/* Apply max_speed modifier (cached value is fixed-point binary with 8 fractional bits)
+		 * and clamp the result to an acceptable range. */
+		max_speed += (max_speed * this->tcache.cached_curve_speed_mod) >> 8;
+		max_speed = Clamp(max_speed, 2, absolute_max_speed);
 	}
 
 	return max_speed;