add ability to add "measuring point" on sneak+punch

init.lua

@@ -8,6 +8,7 @@ local POINT_TO_LIQUIDS = true
 local COMPASS_RANGE = 180
 local WAYPOINT_ICON = "waypoint_compass_waypoint.png"
 local WAYPOINT_SCALE = {x=-1/16*9,y=-1}
+local COMPASS_MEASURE_TIMEOUT = 8 -- time until "measuring point" disappears
 
 local waypoint_lib = dofile(minetest.get_modpath("waypoint_compass") .. "/waypoint_lib.lua")
 
@@ -364,6 +365,49 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 end)
 
 
+local function compass_meausure_callback(itemstack, user, __pointed_thing)
+    if not user or not user:is_player() then
+	return
+    end
+
+    if not user:get_player_control()["sneak"] then
+	return
+    end
+    
+    local _, pointed_thing = waypoint_lib.get_pointed_position(user, COMPASS_RANGE, POINT_TO_OBJECTS, POINT_TO_LIQUIDS)
+    if not pointed_thing or pointed_thing.type == "nothing" then
+	return
+    end
+    local point_pos = nil
+    if pointed_thing.type == "node" then
+	point_pos = TARGET_ABOVE and pointed_thing.above or pointed_thing.under
+    else
+	return
+    end
+    local meta = itemstack:get_meta()
+    local compass_pos = get_compass_meta_pos(meta)
+    if not compass_pos then
+	return
+    end
+    local distance = vector.length(vector.subtract(compass_pos, point_pos))
+    local label = ("distance to waypoint: %.2fm"):format(distance)
+    local label_color = 0x00FF00
+    local icon = WAYPOINT_ICON
+    local icon_scale = WAYPOINT_SCALE
+    local icon_color = "#FFFFFF"
+    
+    local waypoint = waypoint_lib.IconWaypointHUD:new(point_pos, label, label_color, icon, icon_scale, icon_color)
+    waypoint:show(user)
+    local player_name = user:get_player_name()
+    minetest.after(COMPASS_MEASURE_TIMEOUT, function()
+		       local player = minetest.get_player_by_name(player_name)
+		       if player then
+			   waypoint:hide(player)
+		       end
+    end)
+end
+
+
 minetest.register_tool(
     "waypoint_compass:compass", {
         description = DEFAULT_DESCRIPTION,
@@ -373,6 +417,11 @@ minetest.register_tool(
 	color = "#f6d0a5",
         wield_scale = {x = 0.5, y = 0.5, z = 0.5},
         range = 2.0, -- TODO what's the good range?
+	on_use = function(itemstack, user, pointed_thing)
+	    compass_meausure_callback(itemstack, user, pointed_thing)
+	    -- return nil since compass in unchanged
+	    return nil
+	end,
         on_place = function(itemstack, placer, pointed_thing)
             return compass_use_callback(itemstack, placer, pointed_thing)
         end,