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https://github.com/imjasonh/nescript
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Multi-tile sprites used to require one hand-written `draw` per tile,
e.g. the four-call sequence in `examples/platformer.ne`'s
`draw_player()`. The new `metasprite Name { ... }` declaration
collects parallel `dx`/`dy`/`frame` arrays plus a reference to the
underlying sprite, and `draw Name at: (x, y)` expands to one OAM
slot per tile in the IR lowering — the codegen sees N regular
DrawSprite ops, so the runtime OAM cursor allocator picks them up
without any metasprite-specific awareness.
The metasprite's `frame:` array is interpreted *relative to the
underlying sprite's base tile*: index 0 means "the first tile this
sprite owns", which is the natural reading for a 16×16 hero whose
pixel art the asset resolver split into four consecutive tiles.
The lowering walks `program.sprites` to compute base tile indices
the same way `assets::resolve_sprites` would, then folds the base
into each frame entry before storing the metasprite info. Sprites
sourced from external `@chr(...)` / `@binary(...)` files whose
bytes aren't available at parse time fall back to a one-tile
assumption — those programs are rare and can declare metasprites
against pixel-art sprites instead.
The new `examples/metasprite_demo.ne` declares a 16×16 hero sprite
and arranges its four tiles into a metasprite, then sweeps the
hero across the screen so the harness captures it mid-motion.
The new keyword is added to the lexer/token list, and the parser
accepts `sprite:` (the otherwise-keyword) as a property name in
metasprite bodies so the natural spelling parses.
https://claude.ai/code/session_01KEczoNUX3WmcFLfq6iAQxB
86 lines
2.5 KiB
Text
86 lines
2.5 KiB
Text
// Metasprite demo — declarative multi-tile sprite groups.
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//
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// The `metasprite` keyword bundles a list of (dx, dy, frame)
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// offsets into one named entity. `draw Hero at: (x, y)` then
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// expands to one OAM slot per tile, so user code stops having
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// to hand-write the four `draw Tileset at: (x+8, y+8) frame:
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// TILE_PLAYER_BR` calls that platformer.ne uses today. Each
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// tile inherits the OAM-cursor allocator from the runtime, so
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// metasprites compose with regular `draw` statements without
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// any extra wiring.
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//
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// Build: cargo run -- build examples/metasprite_demo.ne
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game "Metasprite Demo" {
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mapper: NROM
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}
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// 16×16 hero sprite drawn as ASCII pixel art. The parser splits
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// it into four 8×8 tiles in row-major order: tile 0 = top-left,
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// tile 1 = top-right, tile 2 = bottom-left, tile 3 = bottom-right.
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// We refer to those four tiles by base offset below.
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sprite Hero16 {
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pixels: [
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"..####....####..",
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".######..######.",
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"###@##....##@###",
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"###@##....##@###",
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"################",
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"################",
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".##############.",
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"..############..",
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"...##########...",
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"....########....",
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"....##....##....",
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"....##....##....",
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"....##....##....",
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"....##....##....",
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"...####..####...",
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"..######..######"
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]
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}
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// Arrange Hero16's four tiles into a 16×16 metasprite. Each
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// row in the metasprite block is logically one OAM slot; the
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// `dx` / `dy` arrays carry the per-tile offset from the
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// metasprite's anchor point and `frame` carries the tile index.
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//
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// `sprite: Hero16` resolves to the base tile index reserved by
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// the asset resolver; the four entries below pick consecutive
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// tiles starting at that base — i.e. the four 8×8 tiles the
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// pixel-art block was sliced into.
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metasprite Hero {
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sprite: Hero16
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dx: [0, 8, 0, 8]
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dy: [0, 0, 8, 8]
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frame: [0, 1, 2, 3]
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}
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var px: u8 = 120
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var py: u8 = 96
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var dir: u8 = 0 // 0 = right, 1 = left
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on frame {
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// Bounce horizontally between two rails so the harness
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// captures movement at frame 180 regardless of which
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// direction we started in.
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if dir == 0 {
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px += 1
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if px == 200 {
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dir = 1
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}
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} else {
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px -= 1
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if px == 32 {
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dir = 0
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}
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}
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// One `draw Hero` expands to four `draw Hero16` calls under
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// the hood. Compare with the four-line sequence in
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// platformer.ne's `draw_player()` — same OAM layout, much
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// less typing.
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draw Hero at: (px, py)
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}
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start Main
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