CLOSES #1418

src/core/Game2.lua

@@ -1968,6 +1968,7 @@ function Game2:applyOptions()
   })
   require("src.core.VideoMode").applyOptions(options)
   require("src.core.FrameCap").applyOptions(options)
+  require("src.world.gen2.BorderFill").applyOptions(options)
   local GBCFX = require("src.render.GBCFX")
   if GBCFX.applyOptions(options) and self.save then
     -- applyOptions returns true when it had to clear an unsupported level.

src/core/gen2/Save.lua

@@ -274,6 +274,9 @@ Save.DEFAULT_OPTIONS = {
   color = "gbc",
   videoMode = "windowed",
   fpsCap = 60,
+  -- VOID FILL: fade | water | trees | black.  fade is each map header's own
+  -- border block with the dissolve across a boundary (#1418).
+  voidFill = "fade",
   musicVol = 7,             -- 0-7, like the GB's NR50 master volume
   sfxVol = 7,               -- 0-7
   musicFilter = 0,          -- low-pass steps, 0 = off

src/import/LauncherSettings.lua

@@ -529,9 +529,9 @@ end
 -- Gold reads NONE of the rows above.  Its OPTION screen writes a different
 -- set of names, several of which collide with Gen 1's at a different TYPE
 -- (battleStyle "SHIFT" vs "shift", textSpeed a label vs a frame delay), and
--- its renderer has no battle layout, no SGB palette packs and no void fill --
--- so a gear opened on the Gold tab used to offer a dozen controls that did
--- nothing and hide the seven that the cart itself has.
+-- its renderer has no battle layout and no SGB palette packs -- so a gear
+-- opened on the Gold tab used to offer a dozen controls that did nothing
+-- and hide the seven that the cart itself has.
 --
 -- The block lives in options.lua under `gold`, which is exactly where
 -- src/core/gen2/Save.lua loadOptions reads it, so an edit here is live on the
@@ -617,6 +617,21 @@ local function gen2Rows(opts, hooks)
       end)
   end
 
+  local okFill, BorderFill = pcall(require, "src.world.gen2.BorderFill")
+  if okFill and BorderFill.VOID_FILLS then
+    add(Strings("VOID FILL"),
+      function() return BorderFill.voidFillLabel(opts.voidFill) end,
+      function(dir)
+        local modes = BorderFill.VOID_FILLS
+        local cur, idx = opts.voidFill or "fade", 1
+        for i, m in ipairs(modes) do
+          if m == cur then idx = i break end
+        end
+        opts.voidFill = modes[wrapIndex(idx - 1 + dir, #modes) + 1]
+        return true
+      end)
+  end
+
   -- Same #136 gate as the Gen 1 row and the in-game one.
   local okFx, GBCFX = pcall(require, "src.render.GBCFX")
   if okFx and GBCFX.isSupported() then

src/ui/gen2/OptionsMenu.lua

@@ -134,6 +134,19 @@ local ROWS = {
     text = function(options)
       return require("src.render.Zoom").offsetLabel(options.zoom or 0)
     end },
+  -- VOID FILL: FADE is each map's own border block with the dissolve across
+  -- a boundary; WATER / TREES force one outdoor block; BLACK is a flat void.
+  -- #1418.  Same key the Gen 1 OPTION screen uses, different ladder (FADE
+  -- is Gold's default because that is already what the maps call for).
+  { label = "VOID FILL", key = "voidFill", port = true,
+    cycle = function(options, delta)
+      local BorderFill = require("src.world.gen2.BorderFill")
+      BorderFill.setVoidFill(options.voidFill or "fade")
+      options.voidFill = BorderFill.cycle(delta)
+    end,
+    text = function(options)
+      return require("src.world.gen2.BorderFill").voidFillLabel(options.voidFill)
+    end },
   { label = "TILT", key = "tilt", port = true,
     cycle = function(options, delta)
       local Tilt = require("src.render.Tilt")

src/world/gen2/BorderFill.lua

@@ -152,16 +152,95 @@ function BorderFill.bake(atlas, tileset, blockId, bgSet, waterFrame)
   return img
 end
 
+-- VOID FILL (#1418): the beyond-edge scenery under survey zoom.  FADE (the
+-- default) is each map header's own border block with the dissolve below;
+-- WATER / TREES force one block on outdoor tilesets that actually have that
+-- scenery; BLACK is a flat void.  Indoor and cave tilesets have no tree wall
+-- or water metatile, so water/trees fall through to the map's own border
+-- rather than painting a random block.
+--
+-- Canonical ids are the wMapBorderBlock values already used as those fills
+-- in data/maps/attributes.asm: New Bark / Route 30 $05 trees, Cherrygrove
+-- $35 water, Pallet $0f trees, Cinnabar $43 water, Ilex Forest $05 trees.
+BorderFill.VOID_FILLS = { "fade", "water", "trees", "black" }
+BorderFill.voidFill = "fade"
+
+local FILL_BLOCKS = {
+  TILESET_JOHTO = { trees = 0x05, water = 0x35 },
+  TILESET_JOHTO_MODERN = { trees = 0x05, water = 0x35 },
+  TILESET_KANTO = { trees = 0x0f, water = 0x43 },
+  TILESET_FOREST = { trees = 0x05 },
+}
+
+function BorderFill.setVoidFill(mode)
+  local ok = false
+  for _, name in ipairs(BorderFill.VOID_FILLS) do
+    if name == mode then ok = true; break end
+  end
+  BorderFill.voidFill = ok and mode or "fade"
+end
+
+function BorderFill.cycle(delta)
+  local cur = BorderFill.voidFill or "fade"
+  local at = 1
+  for i, name in ipairs(BorderFill.VOID_FILLS) do
+    if name == cur then at = i; break end
+  end
+  local n = #BorderFill.VOID_FILLS
+  at = (at - 1 + (delta or 1)) % n + 1
+  BorderFill.setVoidFill(BorderFill.VOID_FILLS[at])
+  return BorderFill.voidFill
+end
+
+function BorderFill.applyOptions(opts)
+  BorderFill.setVoidFill(opts and opts.voidFill or "fade")
+end
+
+function BorderFill.voidFillLabel(mode)
+  mode = mode or BorderFill.voidFill or "fade"
+  if mode == "water" then return "WATER" end
+  if mode == "trees" then return "TREES" end
+  if mode == "black" then return "BLACK" end
+  -- trailing space blanks the 5-char WATER/TREES/BLACK from the value column
+  return "FADE "
+end
+
+-- The metatile the void should bake, or false when BLACK skips tiling.
+function BorderFill.fillBlock(def)
+  local mode = BorderFill.voidFill or "fade"
+  if mode == "black" then return false end
+  if (mode == "water" or mode == "trees") and def then
+    local fills = FILL_BLOCKS[def.tileset]
+    local block = fills and fills[mode]
+    if block ~= nil then return block end
+  end
+  return def and def.borderBlock or 0
+end
+
+-- Crossfade identity: FADE dissolves per map (Cherrygrove water -> Route 30
+-- trees).  WATER/TREES dissolve only when the forced block itself changes
+-- (Johto water -> Kanto water), so walking two Johto routes does not fade
+-- identical water against itself.  BLACK is one sheet everywhere.
+function BorderFill.fillKey(def)
+  local mode = BorderFill.voidFill or "fade"
+  if mode == "black" then return "black" end
+  local block = BorderFill.fillBlock(def)
+  if mode == "water" or mode == "trees" then
+    return mode .. "|" .. tostring(def and def.tileset) .. "|" .. tostring(block)
+  end
+  return "fade|" .. tostring(def and def.id)
+end
+
 -- Each map header carries its OWN border block, so crossing a boundary swaps
 -- the whole void from one block to another: Cherrygrove's water becomes Route
 -- 30's trees between one frame and the next.  On a 20x18 viewport that is a few
 -- pixels at the screen edge and nobody sees it; under survey zoom the void is
 -- most of the window, and the swap reads as the background popping.
 --
--- So the swap is dissolved rather than cut.  `key` is the map the image belongs
--- to, not the image itself: the same block gets re-baked by the daytime
--- rollover, the COLOR option and the two-frame cave flicker, and a dissolve on
--- any of those would smear the flicker into mush.
+-- So the swap is dissolved rather than cut.  `key` is the fill identity
+-- (BorderFill.fillKey), not the image itself: the same block gets re-baked by
+-- the daytime rollover, the COLOR option and the two-frame cave flicker, and a
+-- dissolve on any of those would smear the flicker into mush.
 BorderFill.CROSSFADE_FRAMES = 20
 
 -- The bookkeeping half, love-free so it can be checked without a canvas.

src/world/gen2/World.lua

@@ -7900,8 +7900,10 @@ function World:borderWaterFrame(def, tileset)
     end
   end
   if not tile then return nil end
+  local fill = BorderFill.fillBlock(def)
+  if fill == false then return nil end
   local block = tileset.blocks
-    and tileset.blocks[BorderFill.blockFor(0, def.borderBlock) + 1]
+    and tileset.blocks[BorderFill.blockFor(0, fill) + 1]
   if not block then return nil end
   local found = false
   for i = 1, 16 do
@@ -7933,11 +7935,19 @@ function World:borderImageFor(mapId)
   if not def then return nil end
   local tileset = self.tilesets and self.tilesets[def.tileset]
   if not tileset then return nil end
+  -- VOID FILL black skips the tiled bake; drawGround paints a flat void.
+  local fill = BorderFill.fillBlock(def)
+  if fill == false then return nil end
+  local blockId = BorderFill.blockFor(0, fill)
   -- A border block made of water animates with the rest of the map, so this
-  -- frame's row joins the key: four bakes per map instead of one.
+  -- frame's row joins the key: four bakes per map instead of one.  The VOID
+  -- FILL mode is in the key so switching FADE/WATER/TREES does not keep a
+  -- stale bake (#1418).
   local waterFrame = self:borderWaterFrame(def, tileset)
   local cacheKey = BorderFill.cacheKey(mapId .. "|" .. tostring(daytime)
     .. "|" .. tostring(GbcPalette.mode) .. "|" .. tostring(flicker)
+    .. "|" .. tostring(BorderFill.voidFill or "fade")
+    .. "|" .. tostring(blockId)
     .. "|" .. tostring(waterFrame and waterFrame.row or 0))
   local cached = self.mapImages[cacheKey]
   if cached ~= nil then return cached or nil end
@@ -7949,7 +7959,7 @@ function World:borderImageFor(mapId)
     bgSet = Palettes.withCaveFlicker(bgSet, flicker or 1)
   end
   local ok, img = pcall(BorderFill.bake, atlas, tileset,
-    BorderFill.blockFor(0, def.borderBlock), bgSet, waterFrame)
+    blockId, bgSet, waterFrame)
   -- `false` rather than nil: a bake that cannot be made (a headless run with
   -- no canvas support) must not be retried once per frame forever.
   self.mapImages[cacheKey] = (ok and img) or false
@@ -9719,8 +9729,16 @@ function World:drawGround(s)
     else
       bw, bh = GameViewport.dimensions()
     end
-    BorderFill.draw(self, self:borderImageFor(self.map.id),
-      cam.x, cam.y, bw, bh, s, self.map.id)
+    if BorderFill.fillBlock(self.map.def) == false then
+      -- BLACK: World:draw clears to a brown letterbox, so the void itself
+      -- has to be an actual black sheet or the map sits on that colour.
+      G.setColor(0, 0, 0, 1)
+      G.rectangle("fill", 0, 0, bw, bh)
+      G.setColor(1, 1, 1, 1)
+    else
+      BorderFill.draw(self, self:borderImageFor(self.map.id),
+        cam.x, cam.y, bw, bh, s, BorderFill.fillKey(self.map.def))
+    end
   end
   for _, nb in ipairs(self.neighbors) do
     G.draw(nb.image,