mods/predict-rain: significant performance improvements

The latest beta introduces persistent global map icons throughout the
entirety of the rift's lifespan, which can be used to efficiently
simulate lunar hail level.

Currently, only a single rift is supported at this time, as there does
not seem to be a way to determine what global map icons originate from.
Thus, a moonlens brought to a rift could trick the implemented logic
into thinking it is the rift portal.

An array of rifts and periodic turf checks can be used to mitigate this,
at the cost of potential performance. However, this would still be
insignificant compared to the high cost of the previous method.

mods/predict-rain/modmain.lua

@@ -189,59 +189,25 @@ Modes: 0 for global chat, 1 for whisper chat, 2 for local chat.
 })
 
 if GetModConfigData("predicthail") then
+	local lunarrift = nil
+
+	AddPrefabPostInit("globalmapicon", function(inst)
+		inst:DoTaskInTime(0, function(inst)
+			if (lunarrift == nil or not lunarrift:IsValid()) and
+				_G.TheWorld:HasTag("forest") and
+				_G.TheWorld.Map:GetTileAtPoint(inst.Transform:GetWorldPosition()) then
+				lunarrift = inst
+			end
+		end)
+	end)
+
 	AddPrefabPostInit("world", function(inst)
-		inst:DoTaskInTime(1, function(inst)
-			if inst:HasTag("forest") then
-				local GOOD_ARENA_SQUARE_SIZE = 6
-				local w, h = inst.Map:GetSize()
-
-				w = w * _G.TILE_SCALE / 2
-				h = h * _G.TILE_SCALE / 2
-
-				local tiles = {}
-				local cache = false
-				local time = 0
-				local pt = nil
-
-				for x=-w,w,4 do
-					for y=-h,h,4 do
-						if inst.Map:IsAboveGroundInSquare(x, 0, y, GOOD_ARENA_SQUARE_SIZE, inst.Map.IsTileLandNoDocks) then
-							table.insert(tiles, _G.Vector3(x, 0, y))
-						end
-					end
+		inst:DoTaskInTime(0, function(inst)
+			inst.components.riftspawner = {
+				IsLunarPortalActive = function()
+					return lunarrift ~= nil and lunarrift:IsValid()
 				end
-
-				inst.components.riftspawner = {
-					IsLunarPortalActive = function()
-						if cache then
-							if inst.Map:GetTileAtPoint(pt:Get()) ~= _G.WORLD_TILES.RIFT_MOON then
-								cache = false
-								time = _G.GetTime()
-								pt = nil
-								return false
-							else
-								return true
-							end
-						else
-							if _G.GetTime() - time < 1 then
-								return false
-							end
-
-							for k, v in pairs(tiles) do
-								if inst.Map:GetTileAtPoint(v:Get()) == _G.WORLD_TILES.RIFT_MOON then
-									cache = true
-									time = _G.GetTime()
-									pt = v
-									return true
-								end
-							end
-
-							time = _G.GetTime()
-							return false
-						end
-					end
-				}
-			end
+			}
 		end)
 	end)