Set param2 to 1 if player places leaves

game_api.txt

@@ -206,5 +206,9 @@ the node can be without decaying.
 If param2 of the node is ~= 0, the node will always be preserved. Thus, if
 the player places a node of that kind, you will want to set param2=1 or so.
 
+The function default.after_place_leaves can be set as after_place_node of a node
+to set param2 to 1 if the player places the node (should not be used for nodes
+that use param2 otherwise (e.g. facedir)).
+
 If the node is in the leafdecay_drop group then it will always be dropped as an
 item.

mods/default/functions.lua

@@ -244,6 +244,12 @@ minetest.register_globalstep(function(dtime)
 			math.floor(dtime * finds_per_second)
 end)
 
+default.after_place_leaves = function(pos, placer, itemstack, pointed_thing)
+	local node = minetest.get_node(pos)
+	node.param2 = 1
+	minetest.set_node(pos, node)
+end
+
 minetest.register_abm({
 	nodenames = {"group:leafdecay"},
 	neighbors = {"air", "group:liquid"},

mods/default/nodes.lua

@@ -277,6 +277,7 @@ minetest.register_node("default:jungleleaves", {
 		}
 	},
 	sounds = default.node_sound_leaves_defaults(),
+	after_place_node = default.after_place_leaves,
 })
 
 minetest.register_node("default:junglesapling", {
@@ -341,6 +342,7 @@ minetest.register_node("default:leaves", {
 		}
 	},
 	sounds = default.node_sound_leaves_defaults(),
+	after_place_node = default.after_place_leaves,
 })
 
 minetest.register_node("default:cactus", {
@@ -1505,6 +1507,7 @@ minetest.register_node("default:pine_needles",{
 		}
 	},
 	sounds = default.node_sound_leaves_defaults(),
+	after_place_node = default.after_place_leaves,
 })
 
 minetest.register_node("default:pine_sapling", {