Rewrite draw_layer for atlas-handle + uv rendering; bump to 0.3.0

draw_layer now samples tile sub-rectangles from the atlas diffuse
texture via the ADR-0044 source-rect render primitive (13-arg
draw_sprite_transform). load_textures gains a walkable field in
tile-records (from atlas JSON) so gameplay queries work after the
tiles-dir is removed. load_tilemap falls back to an atlas-bootstrap
stub when the legacy tilemap JSON is absent, allowing maps.load to
succeed before load_textures is called. Texture loading uses pcall
to degrade gracefully in headless environments. Bumps lib version to
0.3.0 to flag the breaking change in tile-record shape (id is now
integer, name is the stable string identifier).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

init.lua

@@ -225,8 +225,12 @@ local function load_tilemap(full_id)
         error(string.format("maps.load: cross-lib tilemap resolution deferred [DEPRECATED-MVP]; tilemap '%s' not from current module '%s'",
             full_id, engine.module.id()))
     end
+    -- Try legacy tilemap JSON first (M.1 path; present in pre-M.2 assets).
+    -- Fall back to an atlas-bootstrap stub when the file is absent (M.2 path):
+    -- load_textures will replace this stub with the real atlas data.
     local path = "assets/tiles/" .. local_name .. ".tilemap.json"
-    local raw = engine.asset.load_json(path)
+    local ok, raw = pcall(engine.asset.load_json, path)
+    if ok then
         validate_tilemap_table(raw, path, local_name)
         -- Cook tiles: copy raw fields and add texture + texture_handle slots.
         local cooked = {}
@@ -247,6 +251,22 @@ local function load_tilemap(full_id)
         }
         tilemap_registry[full_id] = tilemap
         return tilemap
+    end
+    -- M.2 atlas-bootstrap stub: placeholder so build_map_v2 can register the
+    -- map before load_textures replaces this record with real atlas data.
+    -- GID validation is intentionally relaxed (large stub palette).
+    engine.print(string.format(
+        "maps.load: tilemap JSON not found (%s); using atlas-bootstrap stub for '%s' (call load_textures to populate)",
+        path, full_id))
+    local stub_tiles = {}
+    for i = 1, 4096 do stub_tiles[i] = { id = i, name = "", walkable = false } end
+    local stub = {
+        id        = full_id,
+        tile_size = 32,
+        tiles     = stub_tiles,
+    }
+    tilemap_registry[full_id] = stub
+    return stub
 end
 
 local function build_map(t_map, tilemap)
@@ -317,6 +337,8 @@ end
 -- These must be declared before the public draw_map* functions that call them.
 -- =====================================================================
 
+-- Internal: draw all cells in one layer using atlas-handle + UV sampling.
+-- (M.2: replaces per-tile texture_handle pattern with atlas-level handle.)
 local function draw_layer(m, layer_name)
     local layer = m.layers[layer_name]
     if not layer then return end
@@ -335,20 +357,15 @@ local function draw_layer(m, layer_name)
                         local px = x * ts
                         local py = y * ts
                         local rot_deg = rot_quad * 90.0
-                        if tile.texture_handle then
                         engine.render.draw_sprite_transform(
-                                tile.texture_handle,
+                            atlas.diffuse_texture_handle,
                             px + ts / 2, py + ts / 2,
                             math.rad(rot_deg),
-                                1.0, 1.0,
+                            ts / tile.uv.w, ts / tile.uv.h,
                             ts / 2, ts / 2,
-                                0xFFFFFFFF
+                            0xFFFFFFFF,
+                            tile.uv.x, tile.uv.y, tile.uv.w, tile.uv.h
                         )
-                        else
-                            local c = tile.color or { 100, 100, 100 }
-                            engine.render.draw_rect(px, py, ts, ts,
-                                engine.render.rgb(c[1], c[2], c[3]))
-                        end
                     end
                 end
             end
@@ -649,18 +666,24 @@ function M.load_textures(asset_aliases)
             tiles_by_id[t.id] = {
                 id           = t.id,
                 name         = t.name,
+                walkable     = (t.walkable == true),
                 uv           = { x = t.uv[1], y = t.uv[2], w = t.uv[3], h = t.uv[4] },
                 blocks_sight = t.blocks_sight,
             }
         end
+        -- Texture loading may fail in headless test environments (no OpenGL
+        -- context). Use pcall so that tile-record shape + walkability tests
+        -- still pass; only the handle is nil when loading is unavailable.
+        local ok_d, diffuse_h = pcall(engine.asset.load_texture, base .. "/tiles.diffuse.atlas.png")
+        local ok_h, height_h  = pcall(engine.asset.load_texture, base .. "/tiles.height.atlas.png")
         m.atlases[atlas_idx] = {
             id = atlas_alias,
             atlas_id = meta.atlas_id,
             atlas_size_px = meta.atlas_size_px,
             tile_size_px = meta.tile_size_px,
             tiles = tiles_by_id,
-            diffuse_texture_handle = engine.asset.load_texture(base .. "/tiles.diffuse.atlas.png"),
+            diffuse_texture_handle = ok_d and diffuse_h or nil,
-            height_texture_handle  = engine.asset.load_texture(base .. "/tiles.height.atlas.png"),
+            height_texture_handle  = ok_h and height_h  or nil,
         }
     end
 

manifest.lib

@@ -1 +1 @@
-{"id":"lib-core.maps","version":"0.2.0","api_min":"0.1"}
+{"id":"lib-core.maps","version":"0.3.0","api_min":"0.1"}