initial commit

src/render/SpriteRenderer.lua

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+-- Overworld character sprites.  A 12-tile sheet (16x96 PNG) holds 6 16x16
+-- frames: stand down/up/left, walk down/up/left (data/sprites/facings.asm).
+-- Right-facing frames are horizontal flips of the left frames.
+-- Sprites draw 4px above their cell, like the GB engine.
+
+local SpriteRenderer = {}
+SpriteRenderer.__index = SpriteRenderer
+
+local imageCache = {}
+
+local function getImage(path)
+  if not imageCache[path] then
+    imageCache[path] = love.graphics.newImage(path)
+  end
+  return imageCache[path]
+end
+
+local STAND = { down = 0, up = 1, left = 2, right = 2 }
+local WALK = { down = 3, up = 4, left = 5, right = 5 }
+
+function SpriteRenderer.new(spriteDef)
+  local self = setmetatable({}, SpriteRenderer)
+  self.def = spriteDef
+  self.image = getImage(spriteDef.image)
+  local iw, ih = self.image:getDimensions()
+  self.frames = {}
+  for f = 0, spriteDef.frames - 1 do
+    self.frames[f] = love.graphics.newQuad(0, f * 16, 16, 16, iw, ih)
+  end
+  return self
+end
+
+-- facing: down/up/left/right; walkPhase: 0 stand, 1 walk; flip: alternate
+-- steps mirror the walk frame for up/down (GB uses OAM flip for this).
+function SpriteRenderer:draw(px, py, camX, camY, facing, walkPhase, stepFlip)
+  local x = math.floor(px - camX)
+  local y = math.floor(py - camY) - 4
+  -- single-frame sprites (item balls, fossils...) have one fixed pose;
+  -- still 3-frame sprites turn to face (the nurse at her machine,
+  -- facePlayer on STAY NPCs) but never show walk frames
+  if self.def.frames <= 1 then
+    love.graphics.draw(self.image, self.frames[0], x, y)
+    return
+  end
+  local frame = (self.def.walker and walkPhase == 1)
+                and WALK[facing] or STAND[facing]
+  local flip = false
+  if facing == "right" then
+    flip = true
+  elseif (facing == "down" or facing == "up") and walkPhase == 1 and stepFlip then
+    flip = true
+  end
+  local quad = self.frames[frame] or self.frames[0]
+  if flip then
+    love.graphics.draw(self.image, quad, x + 16, y, 0, -1, 1)
+  else
+    love.graphics.draw(self.image, quad, x, y)
+  end
+end
+
+return SpriteRenderer