(svn r22849) -Codechange: Add ShipVehicleInfo::ApplyWaterClassSpeedFrac() to apply ocean/canal speed fractions to velocities.

src/engine_type.h

@@ -74,6 +74,13 @@ struct ShipVehicleInfo {
 	byte visual_effect;    ///< Bitstuffed NewGRF visual effect data
 	byte ocean_speed_frac; ///< Fraction of maximum speed for ocean tiles.
 	byte canal_speed_frac; ///< Fraction of maximum speed for canal/river tiles.
+
+	/** Apply ocean/canal speed fraction to a velocity */
+	uint ApplyWaterClassSpeedFrac(uint raw_speed, bool is_ocean) const
+	{
+		/* speed_frac == 0 means no reduction while 0xFF means reduction to 1/256. */
+		return raw_speed * (256 - (is_ocean ? this->ocean_speed_frac : this->canal_speed_frac)) / 256;
+	}
 };
 
 /**

src/ship_cmd.cpp

@@ -178,9 +178,9 @@ void Ship::UpdateCache()
 	const ShipVehicleInfo *svi = ShipVehInfo(this->engine_type);
 
 	/* Get speed fraction for the current water type. Aqueducts are always canals. */
-	byte speed_frac = (GetEffectiveWaterClass(this->tile) == WATER_CLASS_SEA) ? svi->ocean_speed_frac : svi->canal_speed_frac;
-	/* speed_frac == 0 means no reduction while 0xFF means reduction to 1/256. */
-	this->vcache.cached_max_speed = GetVehicleProperty(this, PROP_SHIP_SPEED, svi->max_speed) * (256 - speed_frac) / 256;
+	bool is_ocean = GetEffectiveWaterClass(this->tile) == WATER_CLASS_SEA;
+	uint raw_speed = GetVehicleProperty(this, PROP_SHIP_SPEED, svi->max_speed);
+	this->vcache.cached_max_speed = svi->ApplyWaterClassSpeedFrac(raw_speed, is_ocean);
 
 	/* Update cargo aging period. */
 	this->vcache.cached_cargo_age_period = GetVehicleProperty(this, PROP_SHIP_CARGO_AGE_PERIOD, EngInfo(this->engine_type)->cargo_age_period);