From fa76057e7f6811a8e7388a70d6fde7af61aa0bee Mon Sep 17 00:00:00 2001
From: PilzAdam <adam-k@outlook.com>
Date: Sat, 1 Dec 2012 13:32:32 +0100
Subject: Add the group attached_node Nodes in this group will be dropped as
 items if the node under them or the node in the wallmounted direction is not
 walkable.

---
 builtin/falling.lua | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 builtin/item.lua    |  7 +++++++
 2 files changed, 56 insertions(+)

(limited to 'builtin')

diff --git a/builtin/falling.lua b/builtin/falling.lua
index 3912727c3..903c5dfd0 100644
--- a/builtin/falling.lua
+++ b/builtin/falling.lua
@@ -91,6 +91,48 @@ function spawn_falling_node(p, nodename)
 	obj:get_luaentity():set_node(nodename)
 end
 
+function drop_attached_node(p)
+	local nn = minetest.env:get_node(p).name
+	minetest.env:remove_node(p)
+	for _,item in ipairs(minetest.get_node_drops(nn, "")) do
+		local pos = {
+			x = p.x + math.random(60)/60-0.3,
+			y = p.y + math.random(60)/60-0.3,
+			z = p.z + math.random(60)/60-0.3,
+		}
+		minetest.env:add_item(pos, item)
+	end
+end
+
+function check_attached_node(p, n)
+	local def = minetest.registered_nodes[n.name]
+	local d = {x=0, y=0, z=0}
+	if def.paramtype2 == "wallmounted" then
+		if n.param2 == 0 then
+			d.y = 1
+		elseif n.param2 == 1 then
+			d.y = -1
+		elseif n.param2 == 2 then
+			d.x = 1
+		elseif n.param2 == 3 then
+			d.x = -1
+		elseif n.param2 == 4 then
+			d.z = 1
+		elseif n.param2 == 5 then
+			d.z = -1
+		end
+	else
+		d.y = -1
+	end
+	local p2 = {x=p.x+d.x, y=p.y+d.y, z=p.z+d.z}
+	local nn = minetest.env:get_node(p2).name
+	local def2 = minetest.registered_nodes[nn]
+	if def2 and not def2.walkable then
+		return false
+	end
+	return true
+end
+
 --
 -- Some common functions
 --
@@ -108,6 +150,13 @@ function nodeupdate_single(p)
 			nodeupdate(p)
 		end
 	end
+	
+	if minetest.get_node_group(n.name, "attached_node") ~= 0 then
+		if not check_attached_node(p, n) then
+			drop_attached_node(p)
+			nodeupdate(p)
+		end
+	end
 end
 
 function nodeupdate(p)
diff --git a/builtin/item.lua b/builtin/item.lua
index 0f8dcff1f..9352a43fc 100644
--- a/builtin/item.lua
+++ b/builtin/item.lua
@@ -181,6 +181,13 @@ function minetest.item_place_node(itemstack, placer, pointed_thing)
 		end
 	end
 
+	-- Check if the node is attached and if it can be placed there
+	if not check_attached_node(place_to, newnode) then
+		minetest.log("action", "attached node " .. def.name ..
+			" can not be placed at " .. minetest.pos_to_string(place_to))
+		return
+	end
+
 	-- Add node and update
 	minetest.env:add_node(place_to, newnode)
 
-- 
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