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Another batch from the cc65/nesdoug gap catalogue. All six items
gated on marker labels (or default-false attributes) so existing
programs produce byte-identical ROMs — every pre-existing .nes
file round-trips unchanged.
**Language / runtime additions:**
- `mapper: GNROM` (iNES 66). Combines AxROM's 32 KB PRG pages with
CNROM's 8 KB CHR banks in a single `$8000` register. Linker
pads single-page ROMs to 32 KB to match mapper-66 expectations.
- `game { debug_port: fceux | mesen | 0xXXXX }`. `debug.log`,
`debug.assert`, and the `__debug_halt` sentinel now target a
user-selected address. `fceux` (default, $4800) and `mesen`
($4018) are named aliases; custom hex addresses are accepted
for unusual debuggers.
- `game { sprite_flicker: true }`. IR lowerer injects an
`IrOp::CycleSprites` at the top of every `on frame` handler,
which flips on the rotating-OAM NMI variant with no per-site
boilerplate. Default false so existing ROMs keep their layout.
- `fade_out(step_frames)` / `fade_in(step_frames)` builtins.
Blocking helpers that walk brightness 4 → 0 or 0 → 4 with
`step_frames` frames between each step. Runtime splices
`__fade_out`, `__fade_in`, and a callable `__wait_frame_rt`
helper when the builtin is used. Zero-guard on step_frames
prevents a pathological 256-frame spin when the caller
accidentally passes 0.
- `sprite_0_split(scroll_x, scroll_y)` intrinsic. Emits a
two-phase busy-wait on `$2002` bit 6 (wait-for-clear,
wait-for-set) then writes the new scroll values to `$2005`.
Works on any mapper — unlike `on_scanline(N)` which requires
MMC3. Enables HUD-over-playfield scrolling on NROM/UxROM/MMC1.
**Docs:**
- New paragraph in the language guide explaining the no-recursion
design choice and the explicit-stack workaround pattern.
- `future-work.md` updated to mark the shipped items out of the
catalogue; remaining items reshuffled in the priority ranking.
- README + examples/README updated with the new mapper and
builtins.
**Tests:**
- 12 new integration tests covering: GNROM header emission,
debug-port targeting (fceux/mesen/custom), unknown-alias
rejection, sprite_flicker on/off/bad-value, fade_out JSR + marker
coupling, fade omitted-when-unused, fade-in-expression rejected,
sprite_0_split byte-level busy-wait verification, sprite_0_split
arity enforcement, sprite_0_split omitted-when-unused, and an
extended void-intrinsic-in-expression-position test covering the
three new void builtins.
- `nes2_mapper_high_nibble_in_byte_8_is_zero_for_small_mappers`
extended to include GNROM.
- Four new examples with committed .nes ROMs + pixel/audio
goldens: `gnrom_simple`, `auto_sprite_flicker`, `fade_demo`,
`sprite_0_split_demo`.
All 752 tests pass. Clippy clean. 44/44 emulator goldens match.
25 lines
573 B
Text
25 lines
573 B
Text
// GNROM (mapper 66) demo — 32 KB PRG page + 8 KB CHR bank in a
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// single write to `$8000-$FFFF`. Bits 4-5 select the PRG page,
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// bits 0-1 select the CHR bank. Single-page GNROM is functionally
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// equivalent to AxROM at the PRG level; this example just exercises
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// the reset-time init and iNES header emission.
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game "GNROM Demo" {
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mapper: GNROM
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}
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var px: u8 = 120
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var dx: u8 = 1
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on frame {
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if dx == 1 {
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px += 1
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if px >= 240 { dx = 0 }
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} else {
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px -= 1
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if px == 0 { dx = 1 }
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}
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draw Ball at: (px, 100)
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}
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start Main
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