De-couple from original code

* `api.lua` create separate handler for listing registered nodes, leave the areas list clean
* `hud.lua` call second handler separately
* `api.md` extended and clarified documentaion

api.lua

@@ -18,10 +18,15 @@ local detect_extra_protection = function(pos,area_list)
 	return area_list
 end
 
+function areas:getRegisteredProtections(pos)
+	local res = {}
+	res = detect_extra_protection(pos,res)
+	return res
+end
+
 --- Returns a list of areas that include the provided position.
 function areas:getAreasAtPos(pos)
 	local res = {}
-	res = detect_extra_protection(pos,res)
 
 	if self.store then
 		local a = self.store:get_areas_for_pos(pos, false, true)

api.md

@@ -5,13 +5,38 @@ Adding your protections to the HUD
 
 If you are providing an extra protection mod to work in cunjunction with the
 HUD feature of `areas`, you can register a callback to add your mod's code to
-display your protection's existence. For example
+display your protection's existence.
 
-	local myhandler = function(pos,arealist)
+Registering a handler:
+
+* `areas.register_hud_handler(handler_name) --> nil`
+
+Handler specification:
+
+* `handler_name(pos,area_list) --> new_area_list`
+	* `pos` - the position at which to check for protection coverage by your mod
+	* `area_list` - the current list of protected areas
+	* `new_area_list` - the list of protected areas, updated with your entries
+
+Area list items:
+
+The area list item is a map table identified with an ID, and properties
+
+The ID should be in the format `modname:` and appended with an identifier for the protection.
+
+Each area list item should be a table with the following properties
+
+* `owner` - (required) the name of the protection owner
+* `name` - (optional) the name of the area
+
+Example
+-------
+
+	local myhandler = function(pos,area_list)
 		local areaowner = find_my_protections(pos)
 
 		if areaowner then
-			arealist["mymodname"] = {
+			arealist["mymodname:first"] = {
 				name = "Protection name",
 				owner = areaowner, 
 			}

hud.lua

@@ -7,11 +7,24 @@ minetest.register_globalstep(function(dtime)
 		local name = player:get_player_name()
 		local pos = vector.round(player:getpos())
 		local areaStrings = {}
+
 		for id, area in pairs(areas:getAreasAtPos(pos)) do
-			table.insert(areaStrings, ("%s [%s] (%s%s)")
+			table.insert(areaStrings, ("%s [%i] (%s%s)")
 					:format(area.name, id, area.owner,
 					area.open and ":open" or ""))
 		end
+
+		for id, area in pairs(areas:getRegisteredProtections(pos)) do
+			table.insert(
+				areaStrings, ("%s [%s] (%s)")
+				:format(
+					area.name or "",
+					id ,
+					area.owner
+				)
+			)
+		end
+
 		local areaString = "Areas:"
 		if #areaStrings > 0 then
 			areaString = areaString.."\n"..