(svn r132) -Fix: [1014278] TileAddWrap() gave wrong results. Fixed now.

functions.h

@@ -28,7 +28,7 @@ void ClickTile(uint tile);
 void GetTileDesc(uint tile, TileDesc *td);
 void DrawTile(TileInfo *ti);
 
-uint TileAddWrap(TileIndex tile, int add);
+uint TileAddWrap(TileIndex tile, int addx, int addy);
 enum {
 	TILE_WRAPPED = (uint)-1
 };

industry_cmd.c

@@ -969,7 +969,7 @@ static void MaybePlantFarmField(Industry *i)
 {
 	uint tile;
 	if (CHANCE16(1,8)) {
-		tile = TileAddWrap(i->xy, TILE_XY(i->width>>1, i->height>>1) + (Random()&TILE_XY(31,31))-TILE_XY(16,16));
+		tile = TileAddWrap(i->xy, ((i->width>>1) + Random() % 31 - 16), ((i->height>>1) + Random() % 31 - 16));
 		if (tile != TILE_WRAPPED)
 			PlantFarmField(tile);
 	}	
@@ -1473,10 +1473,10 @@ static void DoCreateNewIndustry(Industry *i, uint tile, int type, const Industry
 	if (i->type == IT_FARM || i->type == IT_FARM_2) {
 		tile = i->xy + TILE_XY((i->width >> 1), (i->height >> 1));
 		for(j=0; j!=50; j++) {
-			uint new_tile = TileAddWrap(tile, (Random() & TILE_XY(31,31)) - TILE_XY(16,16));
+			uint new_tile = TileAddWrap(tile, Random() % 31 - 16, Random() % 31 - 16);
 			if (new_tile != TILE_WRAPPED)
 				PlantFarmField(new_tile);
-		}	
+		}
 	}
 	_industry_sort_dirty = true;
 	InvalidateWindow(WC_INDUSTRY_DIRECTORY, 0);

landscape.c

@@ -742,11 +742,22 @@ TileIndex AdjustTileCoordRandomly(TileIndex a, byte rng)
 	);
 }
 
-uint TileAddWrap(TileIndex tile, int add)
+// This function checks if we add addx/addy to tile, if we
+//  do wrap around the edges. For example, tile = (10,2) and
+//  addx = +3 and addy = -4. This function will now return
+//  TILE_WRAPPED, because the y is wrapped. This is needed in
+//  for example, farmland. When the tile is not wrapped,
+//  the result will be tile + TILE_XY(addx, addy)
+uint TileAddWrap(TileIndex tile, int addx, int addy)
 {
-	uint t = tile + add;
-	if (t < TILES_X * TILE_Y_MAX && GET_TILE_X(t) != TILE_X_MAX)
-		return t;
+	int x, y;
+	x = GET_TILE_X(tile) + addx;
+	y = GET_TILE_Y(tile) + addy;
+	
+	// Are we about to wrap?
+	if (x > 0 && x < TILE_X_MAX && y > 0 && y < TILE_Y_MAX)
+		return tile + TILE_XY(addx, addy);
+
 	return TILE_WRAPPED;
 }