Add 6d facedir rotation prediction routine

builtin/misc_helpers.lua

@@ -205,6 +205,84 @@ function tbl.formspec_escape(text)
 	return text
 end
 
+--------------------------------------------------------------------------------
+
+if minetest then
+	local dirs1 = { 9, 18, 7, 12 }
+	local dirs2 = { 20, 23, 22, 21 }
+
+	function minetest.rotate_and_place(itemstack, placer, pointed_thing, infinitestacks, orient_flags)
+
+		local node = minetest.get_node(pointed_thing.under)
+		if not minetest.registered_nodes[node.name]
+		   or not minetest.registered_nodes[node.name].on_rightclick then
+
+			local above = pointed_thing.above
+			local under = pointed_thing.under
+			local pitch = placer:get_look_pitch()
+			local pname = minetest.get_node(under).name
+			local node = minetest.get_node(above)
+			local fdir = minetest.dir_to_facedir(placer:get_look_dir())
+			local wield_name = itemstack:get_name()
+			local reg_node = minetest.registered_nodes[pname]
+
+			if not reg_node or not reg_node.on_rightclick then
+
+				local iswall = (above.x ~= under.x) or (above.z ~= under.z)
+				local isceiling = (above.x == under.x) and (above.z == under.z)
+								  and (pitch > 0)
+				local pos1 = above
+
+				if reg_node and reg_node.buildable_to then
+					pos1 = under
+					iswall = false
+				end
+
+				reg_node = minetest.registered_nodes[minetest.get_node(pos1).name]
+				if not reg_node or not reg_node.buildable_to then
+					return
+				end
+
+				if orient_flags.force_floor then
+					iswall = false
+					isceiling = false
+				elseif orient_flags.force_ceiling then 
+					iswall = false
+					isceiling = true
+				elseif orient_flags.force_wall then					
+					iswall = true
+					isceiling = false
+				elseif orient_flags.invert_wall then
+					iswall = not iswall
+				end
+
+				if iswall then
+					minetest.add_node(pos1, {name = wield_name, param2 = dirs1[fdir+1] })
+				elseif isceiling then
+					if orient_flags.force_facedir then
+						minetest.add_node(pos1, {name = wield_name, param2 = 20 })
+					else
+						minetest.add_node(pos1, {name = wield_name, param2 = dirs2[fdir+1] })
+					end
+				else -- place right side up
+					if orient_flags.force_facedir then
+						minetest.add_node(pos1, {name = wield_name, param2 = 0 })
+					else
+						minetest.add_node(pos1, {name = wield_name, param2 = fdir })
+					end
+				end
+
+				if not infinitestacks then
+					itemstack:take_item()
+					return itemstack
+				end
+			end
+		else
+			minetest.registered_nodes[node.name].on_rightclick(pointed_thing.under, node, placer, itemstack)
+		end
+	end
+end
+
 --------------------------------------------------------------------------------
 -- mainmenu only functions
 --------------------------------------------------------------------------------

doc/lua_api.txt

@@ -1543,6 +1543,23 @@ minetest.is_protected(pos, name) -> bool
 minetest.record_protection_violation(pos, name)
 ^ This function calls functions registered with
   minetest.register_on_protection_violation.
+minetest.rotate_and_place(itemstack, placer, pointed_thing, infinitestacks, orient_flags)
+^ Attempt to predict the desired orientation of the facedir-capable node
+  defined by itemstack, and place it accordingly (on-wall, on the floor, or
+  hanging from the ceiling). Stacks are handled normally if the infinitestacks
+  field is false or omitted (else, the itemstack is not changed). orient_flags
+  is an optional table containing extra tweaks to the placement code:
+  invert_wall:		if true, place wall-orientation on the ground and ground-
+					orientation on the wall.
+  force_wall:		if true, always place the node in wall orientation.
+  force_ceiling:	if true, always place on the ceiling.
+  force_floor:		if true, always place the node on the floor.
+
+  The above four options are mutually-exclusive; the last in the list takes
+  precedence over the first.
+
+  force_facedir:	if true, forcably reset the facedir to north when placing on
+					the floor or ceiling
 
 Global objects:
 minetest.env - EnvRef of the server environment and world.