Allow both main thread & mapgen env execution

API.md

@@ -3,10 +3,27 @@
 This mod is built in a way to be easy to change the underground world.
 The API is written in a way to be very similar to the Minetest API.
 
+## Main thread vs. separate thread
+
+This mod can both run on the main thread or on the mapgen thread. Generally,
+the mapgen thread is recommended, but it isn't supported for Minetest versions
+5.8 and under. The main thread works for everyone but it is slower.
+
+This mod automatically determines whether a Minetest user is able to use the
+faster mapgen thread. As a result, you should use the function
+`ns_cavegen_init.register_cavegen_script`, with the input pointing to a file
+containing the script for the cave generator. This mod will ensure that your
+script is run on the appropriate thread.
+
+If you wish to decide for yourself which thread to run the cave generator on,
+you can use the `ns_cavegen_mapgen_environment` option in your settings file
+(usually `minetest.conf`) to tell the cave generator whether to run the cave
+generator in the separate thread or not.
+
 ## Shapes
 
 Underground caves have varying shapes, and the variable
-`noordstar.registered_shapes` contains all those definitions.
+`ns_cavegen.registered_shapes` contains all those definitions.
 
 For shapes, the following functions are available:
 

README.md

@@ -1,26 +1,14 @@
-# Noordstar caves
+# Noordstar cave generator
 
-The Noordstar caves mod helps add more caves to MineClone2 and Mineclonia.
+The Noordstar caves mod helps add more caves to Minetest games.
 
 For reference, see the [API documentation](API.md).
 
 This mod offers no new features to the player, but it allows programmers to add
 custom caves into the world and to lower the world depth.
 
-## Tested & supported on
+## Examples
 
-The mod has been tested on the following games:
+The following mods are known to use this cave generator mod:
 
-- [x] VoxeLibre
-- [ ] Mineclonia
-- [ ] MTG
-
-The mod has been tested on the following mapgens:
-
-- [x] v7
-- [ ] valleys
-- [ ] carpathian
-- [ ] v5
-- [ ] flat
-- [ ] fractal
-- [ ] singlenode
+- [ns_vl_caves](https://content.minetest.net/packages/Noordstar/ns_vl_caves/) for VoxeLibre & Mineclonia

init.lua

@@ -1,3 +1,28 @@
+ns_cavegen_init = {}
+
+-- Depending on the Minetest version, mapgen can be executed on the main thread
+-- or on the separate thread.
+
+-- Optionally, you can override this value.
+local execute_in_mapgen_environment = false
+
+function ns_cavegen_init.register_cavegen_script(file_name)
+    -- As of Minetest 5.9.0, a Minetest server can crash without notice when
+    -- a script is executed in the mapgen environment. This is likely related
+    -- to a memory leak error:
+    -- 
+    -- If you would like to override this setting, you can adjust the
+    -- "ns_cavegen_mapgen_environment" variable in your `minetest.conf` settings
+    -- file.
+    local use_mapgen_env = minetest.settings:get_bool("ns_cavegen_mapgen_environment", false)
+
+    if execute_in_mapgen_environment or use_mapgen_env then
+        minetest.register_mapgen_script(file_name)
+    else
+        dofile(file_name)
+    end
+end
+
 minetest.register_mapgen_script(
     minetest.get_modpath(minetest.get_current_modname()) .. "/script.lua"
 )

script.lua

@@ -33,6 +33,20 @@ local WORLD_DEPTH = -60
 
 local internal = {}
 
+function internal.init()
+    local uses_mapgen_env = minetest.save_gen_notify
+
+    if uses_mapgen_env then
+        minetest.register_on_generated(internal.mapgen)
+    else
+        minetest.register_on_generated(function(minp, maxp, blockseed)
+            local vm = minetest.get_mapgen_object("voxelmanip")
+            internal.mapgen(vm, minp, maxp, blockseed)
+            vm:write_to_map()
+        end)
+    end
+end
+
 -------------------------------------------------------------------------------
 -------------------------------------------------------------------------------
 -------------------------------- INTERNAL API ---------------------------------
@@ -653,7 +667,12 @@ function internal.write_classified_node(vm_data, va, used_biomes, classified_nod
 
             if ground_content_nodes[vm_node] == nil then
                 local name = minetest.get_name_from_content_id(content_id)
-                ground_content_nodes[vm_node] = minetest.registered_nodes[name].is_ground_content or true
+
+                if minetest.registered_nodes[name] == nil then
+                    ground_content_nodes[vm_node] = true
+                else
+                    ground_content_nodes[vm_node] = minetest.registered_nodes[name].is_ground_content or true
+                end
             end
 
             if ground_content_nodes[vm_node] then
@@ -887,7 +906,6 @@ end
 -------------------------------------------------------------------------------
 -------------------------------------------------------------------------------
 
-minetest.register_on_generated(internal.mapgen)
 
 ns_cavegen = {
     cave_vastness = function(pos)
@@ -923,4 +941,5 @@ ns_cavegen = {
     unregister_shape = internal.unregister_shape,
 }
 
+internal.init()
 -- dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/lua/register.lua")