(svn r3032) -NewGRF, Feature: Add support for changing base prices.

economy.c

@@ -768,6 +768,33 @@ static const int32 _price_base[NUM_PRICES] = {
 	1000000, // build_industry
 };
 
+static byte price_base_multiplier[NUM_PRICES];
+
+/**
+ * Reset changes to the price base multipliers.
+ */
+void ResetPriceBaseMultipliers(void)
+{
+	int i;
+
+	// 8 means no multiplier.
+	for (i = 0; i < NUM_PRICES; i++)
+		price_base_multiplier[i] = 8;
+}
+
+/**
+ * Change a price base by the given factor.
+ * The price base is altered by factors of two, with an offset of 8.
+ * NewBaseCost = OldBaseCost * 2^(n-8)
+ * @param price Index of price base to change.
+ * @param factor Amount to change by.
+ */
+void SetPriceBaseMultiplier(int price, byte factor)
+{
+	if (price < NUM_PRICES)
+		price_base_multiplier[price] = factor;
+}
+
 void StartupEconomy(void)
 {
 	int i;
@@ -784,6 +811,11 @@ void StartupEconomy(void)
 				price = price * 9 >> 3;
 			}
 		}
+		if (price_base_multiplier[i] > 8) {
+			price <<= price_base_multiplier[i] - 8;
+		} else {
+			price >>= 8 - price_base_multiplier[i];
+		}
 		((int32*)&_price)[i] = price;
 		_price_frac[i] = 0;
 	}

economy.h

@@ -3,6 +3,9 @@
 #ifndef ECONOMY_H
 #define ECONOMY_H
 
+void ResetPriceBaseMultipliers(void);
+void SetPriceBaseMultiplier(int price, byte factor);
+
 typedef struct {
 	// Maximum possible loan
 	int32 max_loan;

newgrf.c

@@ -16,6 +16,7 @@
 #include "newgrf.h"
 #include "variables.h"
 #include "bridge.h"
+#include "economy.h"
 
 /* TTDPatch extended GRF format codec
  * (c) Petr Baudis 2004 (GPL'd)
@@ -51,6 +52,7 @@ typedef enum grfspec_feature {
 	GSF_CANAL,
 	GSF_BRIDGE,
 	GSF_TOWNHOUSE,
+	GSF_GLOBALVAR,
 } grfspec_feature;
 
 
@@ -1058,6 +1060,27 @@ static bool BridgeChangeInfo(uint brid, int numinfo, int prop, byte **bufp, int
 	return ret;
 }
 
+static bool GlobalVarChangeInfo(uint gvid, int numinfo, int prop, byte **bufp, int len)
+{
+	byte *buf = *bufp;
+	int i;
+	bool ret = false;
+
+	switch (prop) {
+		case 0x08: { /* Cost base factor */
+			FOR_EACH_OBJECT {
+				byte factor = grf_load_byte(&buf);
+
+				SetPriceBaseMultiplier(gvid + i, factor);
+			}
+		} break;
+		default:
+			ret = true;
+	}
+	*bufp = buf;
+	return ret;
+}
+
 /* Action 0x00 */
 static void VehicleChangeInfo(byte *buf, int len)
 {
@@ -1086,6 +1109,7 @@ static void VehicleChangeInfo(byte *buf, int len)
 		/* GSF_CANAL */    NULL,
 		/* GSF_BRIDGE */   BridgeChangeInfo,
 		/* GSF_TOWNHOUSE */NULL,
+		/* GSF_GLOBALVAR */GlobalVarChangeInfo,
 	};
 
 	uint8 feature;
@@ -2354,6 +2378,9 @@ static void ResetNewGRFData(void)
 	// Unload sprite group data
 	UnloadWagonOverrides();
 	UnloadCustomEngineSprites();
+
+	// Reset price base data
+	ResetPriceBaseMultipliers();
 }
 
 static void InitNewGRFFile(const char* filename, int sprite_offset)