graphics and stutters part 1

src/world/MapLoader.lua

@@ -2,6 +2,13 @@
 -- data, cached by map id.  The cache is keyed so a mod that patches one
 -- map record after boot (or the dev-mode hot reload) can drop just that
 -- entry instead of every map's SpriteBatches.
+--
+-- The resident set is trimmed LRU (trim) so exploring a large world never
+-- holds every visited map's GPU objects at once.  Maps are built on demand
+-- and cheaply: a map's tile layer draws windowed to the camera (see
+-- TileRenderer), so there is no per-map batch to construct up front and thus
+-- nothing to stream -- OverworldState:rebuildNeighbors just loads each
+-- neighbor directly.
 
 local Assets = require("src.render.Assets")
 local Map = require("src.world.Map")
@@ -10,9 +17,20 @@ local TileRenderer = require("src.render.TileRenderer")
 local MapLoader = {}
 
 local cache = {}
+-- mapId -> monotonic access stamp, for LRU eviction
+local lru = {}
+local accessSeq = 0
+-- max map renderers kept resident.  Comfortably above the largest
+-- current+neighbor set (~15 in dense overworld), so protected maps are
+-- never the ones evicted; this only caps the lingering trail behind you.
+local RESIDENT_CAP = 32
 
-function MapLoader.load(data, mapId)
-  if cache[mapId] then return cache[mapId] end
+local function touch(mapId)
+  accessSeq = accessSeq + 1
+  lru[mapId] = accessSeq
+end
+
+local function build(data, mapId)
   local def = data.maps[mapId]
   assert(def, "unknown map: " .. tostring(mapId) ..
          " (not in the maps registry)")
@@ -25,26 +43,75 @@ function MapLoader.load(data, mapId)
   local map = Map.new(def, tilesetDef)
   map.renderer = TileRenderer.new(map, data)
   cache[mapId] = map
+  touch(mapId)
   return map
 end
 
+function MapLoader.load(data, mapId)
+  local m = cache[mapId]
+  if m then touch(mapId); return m end
+  return build(data, mapId)
+end
+
 -- the live instance for a map id, or nil when it has not been loaded;
 -- callers that must not build a map (invalidation, tests) use this
 function MapLoader.cached(mapId)
-  return cache[mapId]
+  local m = cache[mapId]
+  if m then touch(mapId) end
+  return m
+end
+
+-- evict one resident map, releasing its renderer's GPU objects.  Callers
+-- must ensure the map is not the current map and not drawn as a connected
+-- strip (nothing live may hold its renderer) -- MapLoader.trim guarantees
+-- this via its `protected` set.
+function MapLoader.evict(mapId)
+  local m = cache[mapId]
+  if not m then return false end
+  cache[mapId] = nil
+  lru[mapId] = nil
+  local r = m.renderer
+  if r and r.release then pcall(r.release, r) end
+  return true
+end
+
+-- keep the resident renderer set bounded.  `protected` (mapId -> true) is
+-- never evicted (the current map and everything drawn as a connected
+-- strip); the rest is trimmed least-recently-used down to RESIDENT_CAP.
+function MapLoader.trim(protected)
+  local n = 0
+  for _ in pairs(cache) do n = n + 1 end
+  if n <= RESIDENT_CAP then return end
+  local ids = {}
+  for id in pairs(cache) do
+    if not (protected and protected[id]) then ids[#ids + 1] = id end
+  end
+  table.sort(ids, function(a, b) return (lru[a] or 0) < (lru[b] or 0) end)
+  local over = n - RESIDENT_CAP
+  for _, id in ipairs(ids) do
+    if over <= 0 then break end
+    MapLoader.evict(id)
+    over = over - 1
+  end
 end
 
 -- drop one map so the next load re-reads its record and rebuilds its
--- renderer.  Callers holding the old instance keep it -- OverworldState
--- re-points self.map itself (WorldAPI:invalidateMap).
+-- renderer.  Deliberately does NOT release the old renderer: callers
+-- holding the old instance keep drawing it until they re-point themselves
+-- (OverworldState re-points self.map / self.neighbors via setMap /
+-- rebuildNeighbors), so releasing here would free a batch still in use.
+-- The orphaned instance is reclaimed by GC; MapLoader.evict is the path
+-- that releases eagerly, and it only runs on maps nothing live holds.
 function MapLoader.invalidate(mapId)
   local had = cache[mapId] ~= nil
   cache[mapId] = nil
+  lru[mapId] = nil
   return had
 end
 
 function MapLoader.invalidateAll()
   cache = {}
+  lru = {}
 end
 
 -- kept as the pre-v2 name