G2 support

src/ui/gen2/TileSheet.lua

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+-- A screen's own tile sheet, addressed the way the cart addresses it.
+--
+-- The Gen 2 menus that are not built out of text boxes -- the #DEX, the
+-- POKeGEAR, the trainer card -- work by copying a sheet into VRAM at a known
+-- tile id and then writing tile ids into the tilemap.  Transcribing one of
+-- those screens means writing the same ids at the same hlcoords, so the only
+-- primitive needed is "draw sheet tile $NN at (tx, ty)".
+--
+-- `firstTile` is the VRAM id the sheet's tile 0 was loaded at (vTiles2 tile
+-- $31 for the dex, $00 for the town map), so a tile id maps to a sheet index
+-- by subtracting it.  A sheet is `wide` tiles across, which is how the
+-- extractor writes them.
+
+local Assets = require("src.render.Assets")
+local GbcPalette = require("src.render.GbcPalette")
+
+local TileSheet = {}
+TileSheet.__index = TileSheet
+
+-- opts: path, wide, firstTile, palette (a 4-colour table) or palettes + a
+-- paletteFor(tile, tx, ty) hook, transparent
+function TileSheet.new(opts)
+  local self = setmetatable({}, TileSheet)
+  self.path = opts and opts.path
+  self.wide = (opts and opts.wide) or 16
+  self.firstTile = (opts and opts.firstTile) or 0
+  self.palette = opts and opts.palette
+  self.paletteFor = opts and opts.paletteFor
+  self.quads = {}
+  return self
+end
+
+function TileSheet:image()
+  if self.loaded == nil then
+    self.loaded = false
+    if self.path then
+      -- `and` would truncate pcall's second return, so this cannot fold into
+      -- a one-liner.
+      local ok, image = pcall(Assets.image, self.path)
+      if ok and image then self.loaded = image end
+    end
+  end
+  return self.loaded or nil
+end
+
+function TileSheet:available()
+  return self:image() ~= nil
+end
+
+function TileSheet:quad(index)
+  local quad = self.quads[index]
+  if not quad then
+    local image = self:image()
+    if not image then return nil end
+    local w, h = image:getDimensions()
+    quad = love.graphics.newQuad(
+      (index % self.wide) * 8, math.floor(index / self.wide) * 8, 8, 8, w, h)
+    self.quads[index] = quad
+  end
+  return quad
+end
+
+-- Draws VRAM tile `tile` at tile coordinates (tx, ty).  A tile outside the
+-- sheet is silently skipped, which is what lets a screen name a tile that
+-- belongs to the font page instead.
+function TileSheet:draw(tile, tx, ty)
+  local image = self:image()
+  if not image then return false end
+  local index = tile - self.firstTile
+  if index < 0 then return false end
+  local quad = self:quad(index)
+  if not quad then return false end
+  local _, sy = quad:getViewport()
+  local _, ih = image:getDimensions()
+  if sy >= ih then return false end
+  local G = love.graphics
+  G.setColor(1, 1, 1, 1)
+  local colors = self.palette
+  if self.paletteFor then colors = self.paletteFor(tile, tx, ty) or colors end
+  local function body() G.draw(image, quad, tx * 8, ty * 8) end
+  if colors and GbcPalette.available() then
+    GbcPalette.with(colors, body)
+  else
+    body()
+  end
+  return true
+end
+
+-- A run of consecutive ids, left to right: the shape most of these routines
+-- use for a header strip or a caption.
+function TileSheet:run(first, count, tx, ty)
+  for i = 0, count - 1 do
+    self:draw(first + i, tx + i, ty)
+  end
+end
+
+-- A rectangle of consecutive ids, row-major.
+function TileSheet:block(first, wide, high, tx, ty)
+  for row = 0, high - 1 do
+    for col = 0, wide - 1 do
+      self:draw(first + row * wide + col, tx + col, ty + row)
+    end
+  end
+end
+
+return TileSheet