Lua Cave Mapgen: Support flip_xy transform

data/lua/cave_map_generator.lua

@@ -151,8 +151,7 @@ function callbacks.generate_map(params)
 		if random(100) <= chance then
 			local transforms = {}
 			for t in params.transform:gmatch("[^%s,][^,]*") do
-				-- TODO: Possibly support other transformations, such as transpose, rotate_cw, rotate_ccw, etc
-				if t == 'flip_x' or t == 'flip_y' then
+				if MG.is_valid_transform(t) then
 					table.insert(transforms, t)
 				else
 					error("Unknown transformation '" .. t .. "'")

data/lua/mapgen_helper.lua

@@ -10,6 +10,16 @@ function mapgen_helper.create_map(width,height,default_terrain)
 	return map
 end
 
+local valid_transforms = {
+	flip_x = true,
+	flip_y = true,
+	flip_xy = true,
+}
+
+function mapgen_helper.is_valid_transform(t)
+	return valid_transforms[t]
+end
+
 local function loc_to_index(map,x,y)
 	return x + 1 + y * map.w
 end
@@ -65,6 +75,11 @@ function map_mt.__index.flip_y(map)
 	end
 end
 
+function map_mt.__index.flip_xy(map)
+	map:flip_x()
+	map:flip_y()
+end
+
 function map_mt.__tostring(map)
 	local map_builder = {}
 	-- The coordinates are 0-based to match the in-game coordinates