Allow to use Minetest's original flat mapgen again

mods/CORE/mcl_init/init.lua

@@ -11,7 +11,10 @@ mcl_vars.inventory_header = mcl_vars.gui_slots .. mcl_vars.gui_bg
 -- Mapgen variables
 local mg_name = minetest.get_mapgen_setting("mg_name")
 local minecraft_height_limit = 256
-if mg_name ~= "flat" then
+local superflat = mg_name == "flat" and minetest.get_mapgen_setting("mcl_superflat_classic") == "true"
+
+if not superflat then
+	-- Normal mode
 	--[[ Realm stacking (h is for height)
 	- Overworld (h>=256)
 	- Void (h>=1000)
@@ -32,17 +35,13 @@ if mg_name ~= "flat" then
 	mcl_vars.mg_bedrock_is_rough = true
 
 else
+	-- Classic superflat
 	local ground = minetest.get_mapgen_setting("mgflat_ground_level")
 	ground = tonumber(ground)
 	if not ground then
 		ground = 8
 	end
-	-- 1 perfectly flat bedrock layer
-	if minetest.get_mapgen_setting("mcl_superflat_classic") == "false" then
-		mcl_vars.mg_overworld_min = -30912
-	else
-		mcl_vars.mg_overworld_min = ground - 3
-	end
+	mcl_vars.mg_overworld_min = ground - 3
 	mcl_vars.mg_overworld_max_official = mcl_vars.mg_overworld_min + minecraft_height_limit
 	mcl_vars.mg_bedrock_overworld_min = mcl_vars.mg_overworld_min
 	mcl_vars.mg_bedrock_overworld_max = mcl_vars.mg_bedrock_overworld_min
@@ -58,14 +57,24 @@ mcl_vars.mg_nether_min = -29067 -- Carefully chosen to be at a mapchunk border
 mcl_vars.mg_nether_max = mcl_vars.mg_nether_min + 128
 mcl_vars.mg_bedrock_nether_bottom_min = mcl_vars.mg_nether_min
 mcl_vars.mg_bedrock_nether_top_max = mcl_vars.mg_nether_max
-mcl_vars.mg_lava_nether_max = mcl_vars.mg_nether_min + 31
-if mg_name ~= "flat" then
+if not superflat then
 	mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min + 4
 	mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max - 4
+	mcl_vars.mg_lava_nether_max = mcl_vars.mg_nether_min + 31
 else
-	-- Thin bedrock in flat mapgen
+	-- Thin bedrock in classic superflat mapgen
 	mcl_vars.mg_bedrock_nether_bottom_max = mcl_vars.mg_bedrock_nether_bottom_min
 	mcl_vars.mg_bedrock_nether_top_min = mcl_vars.mg_bedrock_nether_top_max
+	mcl_vars.mg_lava_nether_max = mcl_vars.mg_nether_min + 2
+end
+if mg_name == "flat" then
+	if superflat then
+		mcl_vars.mg_flat_nether_floor = mcl_vars.mg_bedrock_nether_bottom_max + 4
+		mcl_vars.mg_flat_nether_ceiling = mcl_vars.mg_bedrock_nether_bottom_max + 52
+	else
+		mcl_vars.mg_flat_nether_floor = mcl_vars.mg_lava_nether_max + 4
+		mcl_vars.mg_flat_nether_ceiling = mcl_vars.mg_lava_nether_max + 52
+	end
 end
 
 -- The End (surface at ca. Y = -27000)

mods/ITEMS/mcl_portals/portal_nether.lua

@@ -13,6 +13,7 @@ local TELEPORT_DELAY = 3 -- seconds before teleporting in Nether portal
 local TELEPORT_COOLOFF = 4 -- after object was teleported, for this many seconds it won't teleported again
 
 local mg_name = minetest.get_mapgen_setting("mg_name")
+local superflat = mg_name == "flat" and minetest.get_mapgen_setting("mcl_superflat_classic") == "true"
 
 -- 3D noise
 local np_cave = {
@@ -187,7 +188,7 @@ end
 
 local function find_nether_target_y(target_x, target_z)
 	if mg_name == "flat" then
-		return mcl_vars.mg_bedrock_nether_bottom_max + 5
+		return mcl_vars.mg_flat_nether_floor + 1
 	end
 	local start_y = math.random(mcl_vars.mg_lava_nether_max + 1, mcl_vars.mg_bedrock_nether_top_min - 5) -- Search start
 	if not nobj_cave then
@@ -330,8 +331,15 @@ function mcl_portals.light_nether_portal(pos)
 	local target = {x = p1.x, y = p1.y, z = p1.z}
 	target.x = target.x + 1
 	if target.y < mcl_vars.mg_nether_max and target.y > mcl_vars.mg_nether_min then
-		if mg_name == "flat" then
+		if superflat then
 			target.y = mcl_vars.mg_bedrock_overworld_max + 5
+		elseif mg_name == "flat" then
+			local ground = minetest.get_mapgen_setting("mgflat_ground_level")
+			ground = tonumber(ground)
+			if not ground then
+				ground = 8
+			end
+			target.y = ground + 2
 		else
 			target.y = math.random(mcl_vars.mg_overworld_min + 40, mcl_vars.mg_overworld_min + 96)
 		end

mods/MAPGEN/mcl_biomes/init.lua

@@ -2,6 +2,7 @@ local mg_name = minetest.get_mapgen_setting("mg_name")
 
 -- Some mapgen settings
 local imitate = minetest.settings:get("mcl_imitation_mode")
+local superflat = mg_name == "flat" and minetest.get_mapgen_setting("mcl_superflat_classic") == "true"
 
 local generate_fallen_logs = false
 
@@ -3209,7 +3210,7 @@ end
 -- Detect mapgen to select functions
 --
 if mg_name ~= "singlenode" then
-	if mg_name ~= "flat" then
+	if not superflat then
 		if mg_name ~= "v6" then
 			register_biomes()
 			register_biomelike_ores()
@@ -3219,7 +3220,9 @@ if mg_name ~= "singlenode" then
 			register_decorations()
 		end
 	else
-		-- Implementation of Minecraft's Superflat mapgen, classic style
+		-- Implementation of Minecraft's Superflat mapgen, classic style:
+		-- * Perfectly flat land, 1 grass biome, no decorations, no caves
+		-- * 4 layers, from top to bottom: grass block, dirt, dirt, bedrock
 		minetest.clear_registered_biomes()
 		minetest.clear_registered_decorations()
 		minetest.clear_registered_schematics()

mods/MAPGEN/mcl_mapgen_core/init.lua

@@ -44,6 +44,7 @@ minetest.register_alias("mapgen_stair_sandstone_block", "mcl_stairs:stair_sandst
 minetest.register_alias("mapgen_stair_desert_stone", "mcl_stairs:stair_sandstone")
 
 local mg_name = minetest.get_mapgen_setting("mg_name")
+local superflat = mg_name == "flat" and minetest.get_mapgen_setting("mcl_superflat_classic") == "true"
 
 local WITCH_HUT_HEIGHT = 3 -- Exact Y level to spawn witch huts at. This height refers to the height of the floor
 
@@ -550,8 +551,7 @@ minetest.register_ore({
 	y_max          = mcl_worlds.layer_to_y(32),
 })
 
-if mg_name ~= "flat" then
-
+if not superflat then
 -- Water and lava springs (single blocks of lava/water source)
 -- Water appears at nearly every height, but not near the bottom
 minetest.register_ore({
@@ -622,13 +622,8 @@ minetest.register_ore({
 	y_min          = mcl_worlds.layer_to_y(62),
 	y_max          = mcl_worlds.layer_to_y(127),
 })
-
 end
 
-
-
-
-
 local function register_mgv6_decorations()
 
 	-- Cacti
@@ -951,20 +946,10 @@ end
 if mg_name == "v6" then
 	register_mgv6_decorations()
 	minetest.set_mapgen_setting("mg_flags", "caves,nodungeons,decorations,light", true)
-elseif mg_name == "flat" then
-	local classic = minetest.get_mapgen_setting("mcl_superflat_classic")
-	if classic == nil then
-		classic = minetest.settings:get_bool("mcl_superflat_classic")
-		minetest.set_mapgen_setting("mcl_superflat_classic", "true", true)
-	end
-	if classic ~= "false" then
-		-- Enforce superflat-like mapgen: No hills, lakes or caves
-		minetest.set_mapgen_setting("mg_flags", "nocaves,nodungeons,nodecorations,light", true)
-		minetest.set_mapgen_setting("mgflat_spflags", "nolakes,nohills", true)
-	else
-		-- If superflat mode is disabled, mapgen is way more liberal
-		minetest.set_mapgen_setting("mg_flags", "caves,nodungeons,nodecorations,light", true)
-	end
+elseif superflat then
+	-- Enforce superflat-like mapgen: No hills, lakes or caves
+	minetest.set_mapgen_setting("mg_flags", "nocaves,nodungeons,nodecorations,light", true)
+	minetest.set_mapgen_setting("mgflat_spflags", "nolakes,nohills", true)
 else
 	minetest.set_mapgen_setting("mg_flags", "caves,nodungeons,decorations,light", true)
 end
@@ -1731,7 +1716,7 @@ minetest.register_on_generated(function(minp, maxp, seed)
 
 		-- Flat Nether
 		if mg_name == "flat" then
-			lvm_used = set_layers(c_air, nil, mcl_vars.mg_bedrock_nether_bottom_max + 4, mcl_vars.mg_bedrock_nether_bottom_max + 52, minp, maxp, lvm_used)
+			lvm_used = set_layers(c_air, nil, mcl_vars.mg_flat_nether_floor, mcl_vars.mg_flat_nether_ceiling, minp, maxp, lvm_used)
 		end
 
 		-- Big lava seas by replacing air below a certain height

settingtypes.txt

@@ -95,17 +95,24 @@ flame_sound (Flame sound) bool true
 # Feedback is appreciated.
 craftguide_progressive_mode (Enable recipe book progressive mode) bool false
 
-# If enabled, the “flat” map generator generates a “classic” superflat map:
-# Completely flat, 1 layer of grass blocks on top of 2 layers of dirt on
-# top of a final layer of bedrock.
-# Note if this is enabled, the setting “mgflat_flags” is ignored. To
-# customize the “flat” map generator, you must disable this setting.
-# Warning: Disabling this setting is currently EXPERIMENTAL! The generated map
-# may not be that pretty.
-mcl_superflat_classic (Classic superflat map generation) bool true
-
 # Mobs difficulty. This is a number that will affect the initial and maximum
 # health and the amount of damage that mobs deal. Health and damage will
 # be multiplied with this number.
 # This feature is not finished yet!
 mob_difficulty (Mob difficulty factor) float 1.0 0.0
+
+# If enabled, the “flat” map generator generates a Classic Superflat world:
+# Completely flat, 1 layer of grass blocks on top of 2 layers of dirt on
+# top of a final layer of bedrock. No caves, trees or plants.
+# Also, if enabled, the setting “mgflat_flags” is ignored.
+# If disabled, Minetest's default flat map generator is used, that is, trees,
+# caves, and a deeper underground can be generated.
+#
+# Caution: Change this setting with care!
+# If you change this setting, then play on an existing flat world
+# that started with a different setting (e.g. you changed from superflat
+# from “enabled” to “disabled”), there will be continuity errors when players
+# reach new areas. Most importantly, the void is much higher in Superflat than
+# in “normal” Flat.
+# But creating new flat worlds after changing this setting should be safe.
+mcl_superflat_classic (Classic superflat map generation) bool true