fixed the mapgen v7 glitch via a horrible hack :(

README.md

@@ -16,4 +16,6 @@ Magma veins can be optionally be lined with a layer of obsidian. The density of
 
 ## Volcanoes
 
-Volcanoes are large cone-shaped mountains formed from lava that rises through a central pipe. This mod can scatter randomly sized and shaped volcanoes across the map, with configurable spacing and probability. Volcanoes come in "extinct", "dormant" and "active" forms, and tall volcanoes can have a mantle of snow clinging to their peaks.
+Volcanoes are large cone-shaped mountains formed from lava that rises through a central pipe. This mod can scatter randomly sized and shaped volcanoes across the map, with configurable spacing and probability. Volcanoes come in "extinct", "dormant" and "active" forms, and tall volcanoes can have a mantle of snow clinging to their peaks.
+
+If a player has the "findvolcano" priviledge he can use the "findvolcano" console command to locate nearby volcanoes.

volcanoes.lua

@@ -57,9 +57,16 @@ end
 local water_level = tonumber(minetest.get_mapgen_setting("water_level"))
 local mapgen_seed = tonumber(minetest.get_mapgen_setting("seed"))
 
+-- Mapgen v7 has a bizzare glitch where it will sometimes cut slices out of the generated volcano
+-- cone *after* mapgen is finished. The slices are taken at maxp.y or minp.y and resemble
+-- the curvy form of a vein or a cave that's one node tall.
+-- Some annoying hackery is needed to patch those slices back up
+-- again, and I only want to do that hackery if we're actually in mapgen v7.
+local mg_name = minetest.get_mapgen_setting("mg_name")
+
 -- derived values
 
-local radius_cone_max = (depth_maxpeak-depth_maxwidth)/(2*slope_min)
+local radius_cone_max = (depth_maxpeak-depth_maxwidth)/(2*slope_min) + radius_lining + 20
 local depth_maxwidth_dist = depth_maxwidth-depth_base
 local depth_maxpeak_dist = depth_maxpeak-depth_maxwidth
 
@@ -107,6 +114,40 @@ local nvals_perlin_buffer = {}
 local nobj_perlin = nil
 local data = {}
 
+-- Used as part of the post-mapgen hackery to fix the weird slices mapgen v7 sometimes takes out of volcano cones
+local patch_func = function(patch_area, patch_content)
+	local minp = patch_area.MinEdge
+	local maxp = patch_area.MaxEdge
+	
+	local map_vm = minetest.get_voxel_manip(minp, maxp)
+	local emin, emax = map_vm:get_emerged_area()
+	local patch_data = {}
+	map_vm:get_data(patch_data)
+	
+	local map_area = VoxelArea:new{MinEdge=emin, MaxEdge=emax}
+	local map_iterator = map_area:iterp(minp, maxp)
+	
+	changes_made = false
+	
+	for vi in patch_area:iterp(minp, maxp) do
+		local mi = map_iterator()
+		if patch_data[mi] == c_air and patch_content[vi] ~= nil then
+			patch_data[mi] = patch_content[vi]
+			changes_made = true
+		end	
+	end
+
+	if changes_made then	
+		--send data back to voxelmanip
+		map_vm:set_data(patch_data)
+		--calc lighting
+		map_vm:set_lighting({day = 0, night = 0})
+		map_vm:calc_lighting()
+		--write it to world
+		map_vm:write_to_map()
+	end
+end
+
 minetest.register_on_generated(function(minp, maxp, seed)
 	if minp.y > depth_maxpeak or maxp.y < depth_root then
 		return
@@ -132,6 +173,17 @@ minetest.register_on_generated(function(minp, maxp, seed)
 		return
 	end
 	
+	local patch_area_max
+	local patch_content_max	
+	local patch_area_min
+	local patch_content_min
+	if mg_name == "v7" then
+		patch_area_max = VoxelArea:new{MinEdge={x=minp.x, y=maxp.y, z=minp.z}, MaxEdge=maxp}
+		patch_content_max = {}
+		patch_area_min = VoxelArea:new{MinEdge=minp, MaxEdge={x=maxp.x, y=minp.y, z=maxp.z}}
+		patch_content_min = {}
+	end
+	
 	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
 	local area = VoxelArea:new{MinEdge=emin, MaxEdge=emax}
 	vm:get_data(data)
@@ -233,14 +285,24 @@ minetest.register_on_generated(function(minp, maxp, seed)
 					end
 				end
 			end
+			
+			-- Used as part of the post-mapgen hackery to fix the weird slices mapgen v7 sometimes takes out of volcano cones
+			if mg_name == "v7" then
+				if y == maxp.y then
+					patch_content_max[patch_area_max:index(x,y,z)] = data[vi]
+				elseif y == minp.y then
+					patch_content_min[patch_area_min:index(x,y,z)] = data[vi]
+				end
+			end
 		end
-	
+	end
+
+	-- Used as part of the post-mapgen hackery to fix the weird slices mapgen v7 sometimes takes out of volcano cones
+	if mg_name == "v7" then
+		minetest.after(2, patch_func, patch_area_max, patch_content_max)
+		minetest.after(2, patch_func, patch_area_min, patch_content_min)
 	end
 	
-	-- These don't seem to work?
-	--minetest.generate_decorations(vm, minp, maxp)
-	--minetest.generate_ores(vm, minp, maxp)
-		
 	--send data back to voxelmanip
 	vm:set_data(data)
 	--calc lighting