New trigger queue management.

No longer "merges" triggers to the same node.

Rate limits triggers. 16/s max. After that, exponentially decay
limit triggers for a while to each node. Tight loop circuits are
controlled well this way. Some larger loops will continue to
function.

mods/mech/init.lua

@@ -45,20 +45,45 @@ local function dehash_vector(s)
 end
 
 local defer_tbl = {}
+local rate_tbl = {}
+local rate_time = 1.0
 
 minetest.register_globalstep(function(dtime)
 	local t = table.copy(defer_tbl)
 	defer_tbl = {}
-	for pos, func in pairs(t) do
-		func(minetest.string_to_pos(pos))
+	for _, item in pairs(t) do
+		item.func(item.pos)
+	end
+
+	-- prune rate_tbl occasionally
+	rate_time = rate_time - dtime
+	if rate_time > 0 then
+		return
+	end
+	rate_time = 1.0
+
+	-- simple decay prune
+	local count = 0
+	for k, v in pairs(rate_tbl) do
+		count = count + 1
+		if v > 1 then
+			rate_tbl[k] = math.floor(v / 2)
+		else
+			rate_tbl[k] = nil
+		end
 	end
 end)
 
 local function defer(pos, func)
 	local p = minetest.pos_to_string(pos)
-	if not defer_tbl[p] then
-		defer_tbl[p] = func
+
+	local r = rate_tbl[p] or 1
+	rate_tbl[p] = r + 1
+	if r > 15 then
+		return
 	end
+
+	defer_tbl[#defer_tbl + 1] = {pos = pos, func = func}
 end
 
 function mech.trigger(pos)