add recolor-on-place helper

if you add `after_place_node = unifieddyes.recolor_on_place,`
to your node def, UD will automatically colorize the node when
placed, using the last dye you colored that kind of node with.

If you switch to some other colorable node, or you run out of whatever
color dye you were using at the time, a warning message will be printed
and the autocolor will be reset back to neutral.

If a player signs off, autocolor for him/her is reset to neutral
(this also helps prevent a minor memory leak)

also get rid of one or two debug prints.

init.lua

@@ -30,6 +30,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 --=====================================================================
 
 unifieddyes = {}
+unifieddyes.last_used_dye = {}
+unifieddyes.last_dyed_node = {}
 
 local creative_mode = minetest.setting_getbool("creative_mode")
 
@@ -134,6 +136,72 @@ local default_dyes = {
 	"yellow"
 }
 
+-- automatically recolor a placed node to match the last-used dye
+-- should be called in the node's `after_place_node` callback.
+
+function unifieddyes.recolor_on_place(pos, placer, itemstack, pointed_thing)
+
+	local playername = placer:get_player_name()
+	local stackname = itemstack:get_name()
+
+	if unifieddyes.last_dyed_node[playername] ~= stackname then
+		if unifieddyes.last_used_dye[playername] then
+			minetest.chat_send_player(playername, "Switched to \""..stackname.."\" while auto-coloring, color reset to neutral.")
+		end
+		unifieddyes.last_used_dye[playername] = nil
+		unifieddyes.last_dyed_node[playername] = nil
+	end
+
+	unifieddyes.last_dyed_node[playername] = stackname
+
+	if unifieddyes.last_used_dye[playername] then
+		local lastdye = unifieddyes.last_used_dye[playername]
+
+		local inv = placer:get_inventory()
+		if (lastdye and lastdye ~= "" and inv:contains_item("main", lastdye.." 1")) or creative_mode then
+
+			local nodedef = minetest.registered_nodes[stackname]
+			local newname = nodedef.ud_replacement_node or stackname
+			local node = minetest.get_node(pos)
+
+			local palette_type = true -- default to 89-color split, because the others are easier to check for.
+			local oldfdir = node.param2 % 32
+
+			if nodedef.palette == "unifieddyes_palette.png" then
+				palette_type = false
+				oldfdir = 0
+			elseif nodedef.palette == "unifieddyes_palette_colorwallmounted.png" then
+				palette_type = "wallmounted"
+				oldfdir = node.param2 % 8
+			elseif nodedef.palette == "unifieddyes_palette_extended.png" then
+				palette_type = "extended"
+				oldfdir = 0
+			end
+
+			local paletteidx, hue = unifieddyes.getpaletteidx(lastdye, palette_type)
+			if palette_type == true then newname = string.gsub(newname, "_grey", "_"..unifieddyes.HUES[hue]) end
+
+			minetest.set_node(pos, { name = newname, param2 = oldfdir + paletteidx })
+
+			local meta = minetest.get_meta(pos)
+			meta:set_string("dye", lastdye)
+
+			if not creative_mode then
+				inv:remove_item("main", lastdye.." 1")
+			end
+		else
+			minetest.chat_send_player(playername, "Ran out of "..unifieddyes.last_used_dye[playername]..", resetting to neutral.")
+			unifieddyes.last_used_dye[playername] = nil
+		end
+	end
+end
+
+minetest.register_on_leaveplayer(function(player)
+	local playername = player:get_player_name()
+	unifieddyes.last_used_dye[playername] = nil
+	unifieddyes.last_dyed_node[playername] = nil
+end)
+
 -- code borrowed from homedecor
 -- call this function to reset the rotation of a "wallmounted" object on place
 
@@ -511,6 +579,7 @@ function unifieddyes.on_use(itemstack, player, pointed_thing)
 
 	local pos = minetest.get_pointed_thing_position(pointed_thing)
 	local node = minetest.get_node(pos)
+
 	local nodedef = minetest.registered_nodes[node.name]
 
 	if not nodedef then return end -- target was an unknown node, just bail out
@@ -542,8 +611,6 @@ function unifieddyes.on_use(itemstack, player, pointed_thing)
 		palette_type = "wallmounted"
 	end
 
-	print(palette_type)
-
 	if minetest.is_protected(pos, playername) and not minetest.check_player_privs(playername, {protection_bypass=true}) then
 		minetest.record_protection_violation(pos, playername)
 		return
@@ -555,6 +622,8 @@ function unifieddyes.on_use(itemstack, player, pointed_thing)
 
 	if paletteidx then
 
+		unifieddyes.last_used_dye[playername] = stackname
+
 		local meta = minetest.get_meta(pos)
 		local prevdye = meta:get_string("dye")
 		local inv = player:get_inventory()