Prevent placing most plants on mycelium

mods/CORE/mcl_util/init.lua

@@ -228,3 +228,48 @@ end
 function mcl_util.layer_to_y(layer, minecraft_dimension)
 	return layer + mcl_vars.mg_overworld_min
 end
+
+-- on_place function for plants which can't grow on mycelium
+
+function mcl_util.on_place_non_mycelium_plant(itemstack, placer, pointed_thing)
+	if pointed_thing.type ~= "node" then
+		-- no interaction possible with entities
+		return itemstack
+	end
+
+	-- Call on_rightclick if the pointed node defines it
+	local node = minetest.get_node(pointed_thing.under)
+	if placer and not placer:get_player_control().sneak then
+		if minetest.registered_nodes[node.name] and minetest.registered_nodes[node.name].on_rightclick then
+			return minetest.registered_nodes[node.name].on_rightclick(pointed_thing.under, node, placer, itemstack) or itemstack
+		end
+	end
+
+	local place_pos, soil_node
+	local def_under = minetest.registered_nodes[minetest.get_node(pointed_thing.under).name]
+	local def_above = minetest.registered_nodes[minetest.get_node(pointed_thing.above).name]
+	if def_under.buildable_to then
+		place_pos = pointed_thing.under
+	elseif def_above.buildable_to then
+		place_pos = pointed_thing.above
+	else
+		return itemstack
+	end
+	soil_node = minetest.get_node({x=place_pos.x, y=place_pos.y-1, z=place_pos.z})
+
+	-- Placement rules:
+	-- * Allowed on everything except mycelium
+	if soil_node.name ~= "mcl_core:mycelium" then
+		local idef = itemstack:get_definition()
+		local new_itemstack, success = minetest.item_place_node(itemstack, placer, pointed_thing)
+
+		if success then
+			if idef.sounds and idef.sounds.place then
+				minetest.sound_play(idef.sounds.place, {pos=above, gain=1})
+			end
+		end
+		itemstack = new_itemstack
+	end
+
+	return itemstack
+end

mods/ITEMS/mcl_core/nodes.lua

@@ -712,6 +712,8 @@ minetest.register_node("mcl_core:sapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -796,6 +798,8 @@ minetest.register_node("mcl_core:darksapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -938,6 +942,8 @@ minetest.register_node("mcl_core:junglesapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -1013,6 +1019,8 @@ minetest.register_node("mcl_core:acaciasapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	stack_max = 64,
 	groups = {dig_immediate=3, sapling=1,non_mycelium_plant=1,non_mycelium_plant=1,attached_node=1,dig_by_water=1,deco_block=1},
 	sounds = mcl_sounds.node_sound_leaves_defaults(),
@@ -1099,6 +1107,8 @@ minetest.register_node("mcl_core:sprucesapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -1177,6 +1187,8 @@ minetest.register_node("mcl_core:birchsapling", {
 		local meta = minetest.get_meta(pos)
 		meta:set_int("stage", 0)
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -1280,6 +1292,8 @@ minetest.register_node("mcl_core:reeds", {
 	stack_max = 64,
 	groups = {dig_immediate=3, craftitem=1, non_mycelium_plant=1, dig_by_piston=1},
 	sounds = mcl_sounds.node_sound_leaves_defaults(),
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -1813,6 +1827,8 @@ minetest.register_node("mcl_core:deadbush", {
 		type = "fixed",
 		fixed = {-6/16, -8/16, -6/16, 6/16, 8/16, 6/16},
 	},
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })

mods/ITEMS/mcl_flowers/depends.txt

@@ -1,3 +1,4 @@
 mcl_core
+mcl_util
 mcl_sounds
 doc?

mods/ITEMS/mcl_flowers/init.lua

@@ -20,6 +20,8 @@ local function add_simple_flower(name, desc, image, simple_selection_box)
 		stack_max = 64,
 		groups = {dig_immediate=3,flammable=2,flower=1,non_mycelium_plant=1,attached_node=1,dig_by_water=1,dig_by_piston=1,deco_block=1},
 		sounds = mcl_sounds.node_sound_leaves_defaults(),
+		node_placement_prediction = "",
+		on_place = mcl_util.on_place_non_mycelium_plant,
 		selection_box = {
 			type = "fixed",
 			fixed = simple_selection_box,
@@ -75,6 +77,8 @@ minetest.register_node("mcl_flowers:tallgrass", {
 			minetest.add_item(pos, oldnode.name)
 		end
 	end,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	_mcl_blast_resistance = 0,
 	_mcl_hardness = 0,
 })
@@ -102,6 +106,8 @@ minetest.register_node("mcl_flowers:fern", {
 		end
 	end,
 	drop = wheat_seed_drop,
+	node_placement_prediction = "",
+	on_place = mcl_util.on_place_non_mycelium_plant,
 	selection_box = {
 		type = "fixed",
 		fixed = { -4/16, -0.5, -4/16, 4/16, 7/16, 4/16 },
@@ -151,7 +157,7 @@ local function add_large_plant(name, desc, longdesc, bottom_img, top_img, inv_im
 			local bottom_buildable = minetest.registered_nodes[minetest.get_node(bottom).name].buildable_to
 			local top_buildable = minetest.registered_nodes[minetest.get_node(top).name].buildable_to
 			local floorname = minetest.get_node({x=bottom.x, y=bottom.y-1, z=bottom.z}).name
-			if minetest.registered_nodes[floorname].walkable and bottom_buildable and top_buildable then
+			if floorname ~= "mcl_core:mycelium" and minetest.registered_nodes[floorname].walkable and bottom_buildable and top_buildable then
 				-- Success! We can now place the flower
 				minetest.sound_play(minetest.registered_nodes["mcl_flowers:"..name].sounds.place, {pos = bottom, gain=1})
 				minetest.set_node(bottom, {name="mcl_flowers:"..name})