Default: Prevent placing sapling if grown tree intersects protection

Add a global 'intersects protection' function to functions.lua for
checking if a specified volume intersects with a protected volume.
A 3D lattice of points are checked with an adjustable interval.
Add a global 'sapling on place' function to avoid duplicated code in
nodes.lua.

mods/default/nodes.lua

@@ -500,9 +500,6 @@ minetest.register_node("default:sapling", {
 	sunlight_propagates = true,
 	walkable = false,
 	on_timer = default.grow_sapling,
-	on_construct = function(pos)
-		minetest.get_node_timer(pos):start(math.random(2400,4800))
-	end,
 	selection_box = {
 		type = "fixed",
 		fixed = {-0.3, -0.5, -0.3, 0.3, 0.35, 0.3}
@@ -510,6 +507,23 @@ minetest.register_node("default:sapling", {
 	groups = {snappy = 2, dig_immediate = 3, flammable = 2,
 		attached_node = 1, sapling = 1},
 	sounds = default.node_sound_leaves_defaults(),
+
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(math.random(2400,4800))
+	end,
+
+	on_place = function(itemstack, placer, pointed_thing)
+		itemstack = default.sapling_on_place(itemstack, placer, pointed_thing,
+			"default:sapling",
+			-- minp, maxp to be checked, relative to sapling pos
+			-- minp_relative.y = 1 because sapling pos has been checked
+			{x = -2, y = 1, z = -2},
+			{x = 2, y = 6, z = 2},
+			-- maximum interval of interior volume check
+			4)
+
+		return itemstack
+	end,
 })
 
 minetest.register_node("default:leaves", {
@@ -624,9 +638,6 @@ minetest.register_node("default:junglesapling", {
 	sunlight_propagates = true,
 	walkable = false,
 	on_timer = default.grow_sapling,
-	on_construct = function(pos)
-		minetest.get_node_timer(pos):start(math.random(2400,4800))
-	end,
 	selection_box = {
 		type = "fixed",
 		fixed = {-0.3, -0.5, -0.3, 0.3, 0.35, 0.3}
@@ -634,6 +645,23 @@ minetest.register_node("default:junglesapling", {
 	groups = {snappy = 2, dig_immediate = 3, flammable = 2,
 		attached_node = 1, sapling = 1},
 	sounds = default.node_sound_leaves_defaults(),
+
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(math.random(2400,4800))
+	end,
+
+	on_place = function(itemstack, placer, pointed_thing)
+		itemstack = default.sapling_on_place(itemstack, placer, pointed_thing,
+			"default:junglesapling",
+			-- minp, maxp to be checked, relative to sapling pos
+			-- minp_relative.y = 1 because sapling pos has been checked
+			{x = -2, y = 1, z = -2},
+			{x = 2, y = 15, z = 2},
+			-- maximum interval of interior volume check
+			4)
+
+		return itemstack
+	end,
 })
 
 
@@ -691,9 +719,6 @@ minetest.register_node("default:pine_sapling", {
 	sunlight_propagates = true,
 	walkable = false,
 	on_timer = default.grow_sapling,
-	on_construct = function(pos)
-		minetest.get_node_timer(pos):start(math.random(2400,4800))
-	end,
 	selection_box = {
 		type = "fixed",
 		fixed = {-0.3, -0.5, -0.3, 0.3, 0.35, 0.3}
@@ -701,6 +726,23 @@ minetest.register_node("default:pine_sapling", {
 	groups = {snappy = 2, dig_immediate = 3, flammable = 2,
 		attached_node = 1, sapling = 1},
 	sounds = default.node_sound_leaves_defaults(),
+
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(math.random(2400,4800))
+	end,
+
+	on_place = function(itemstack, placer, pointed_thing)
+		itemstack = default.sapling_on_place(itemstack, placer, pointed_thing,
+			"default:pine_sapling",
+			-- minp, maxp to be checked, relative to sapling pos
+			-- minp_relative.y = 1 because sapling pos has been checked
+			{x = -2, y = 1, z = -2},
+			{x = 2, y = 12, z = 2},
+			-- maximum interval of interior volume check
+			4)
+
+		return itemstack
+	end,
 })
 
 
@@ -758,9 +800,6 @@ minetest.register_node("default:acacia_sapling", {
 	sunlight_propagates = true,
 	walkable = false,
 	on_timer = default.grow_sapling,
-	on_construct = function(pos)
-		minetest.get_node_timer(pos):start(math.random(2400,4800))
-	end,
 	selection_box = {
 		type = "fixed",
 		fixed = {-0.3, -0.5, -0.3, 0.3, 0.35, 0.3}
@@ -768,6 +807,23 @@ minetest.register_node("default:acacia_sapling", {
 	groups = {snappy = 2, dig_immediate = 3, flammable = 2,
 		attached_node = 1, sapling = 1},
 	sounds = default.node_sound_leaves_defaults(),
+
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(math.random(2400,4800))
+	end,
+
+	on_place = function(itemstack, placer, pointed_thing)
+		itemstack = default.sapling_on_place(itemstack, placer, pointed_thing,
+			"default:acacia_sapling",
+			-- minp, maxp to be checked, relative to sapling pos
+			-- minp_relative.y = 1 because sapling pos has been checked
+			{x = -4, y = 1, z = -4},
+			{x = 4, y = 6, z = 4},
+			-- maximum interval of interior volume check
+			4)
+
+		return itemstack
+	end,
 })
 
 minetest.register_node("default:aspen_tree", {
@@ -824,9 +880,6 @@ minetest.register_node("default:aspen_sapling", {
 	sunlight_propagates = true,
 	walkable = false,
 	on_timer = default.grow_sapling,
-	on_construct = function(pos)
-		minetest.get_node_timer(pos):start(math.random(2400,4800))
-	end,
 	selection_box = {
 		type = "fixed",
 		fixed = {-0.3, -0.5, -0.3, 0.3, 0.35, 0.3}
@@ -834,7 +887,25 @@ minetest.register_node("default:aspen_sapling", {
 	groups = {snappy = 2, dig_immediate = 3, flammable = 2,
 		attached_node = 1, sapling = 1},
 	sounds = default.node_sound_leaves_defaults(),
+
+	on_construct = function(pos)
+		minetest.get_node_timer(pos):start(math.random(2400,4800))
+	end,
+
+	on_place = function(itemstack, placer, pointed_thing)
+		itemstack = default.sapling_on_place(itemstack, placer, pointed_thing,
+			"default:aspen_sapling",
+			-- minp, maxp to be checked, relative to sapling pos
+			-- minp_relative.y = 1 because sapling pos has been checked
+			{x = -2, y = 1, z = -2},
+			{x = 2, y = 12, z = 2},
+			-- maximum interval of interior volume check
+			4)
+
+		return itemstack
+	end,
 })
+
 --
 -- Ores
 --