# TODO

## Internal consistency

Findings from a sweep of `src/` and `include/`. These are consistency and
convention problems, not new functional defects — where one has a functional
consequence it is called out. Ordered roughly by blast radius. Items that
overlap the existing **Defects** list are cross-referenced rather than repeated.

### 1. Public naming conventions

1. **Include guards use three different schemes.** `_AKGL_ACTOR_H_`,
   `_AKGL_CHARACTER_H_`, `_AKGL_GAME_H_`, `_AKGL_HEAP_H_`, `_AKGL_ITERATOR_H_`,
   `_AKGL_SPRITE_H_`, and `_AKGL_TYPES_H_` carry the project prefix; `_ASSETS_H_`,
   `_CONTROLLER_H_`, `_DRAW_H_`, `_ERROR_H_`, `_JSON_HELPERS_H_`, `_PHYSICS_H_`,
   `_REGISTRY_H_`, `_RENDERER_H_`, `_TEXT_H_`, `_TILEMAP_H_`, and `_UTIL_H_` do
   not. Pick `_AKGL_<FILE>_H_` everywhere.

   The worst case is `include/akgl/staticstring.h:6`, which guards with
   `_STRING_H_` — a name several libc implementations use for their own
   `<string.h>`. The same file then does `#include "string.h"` (line 9) with
   quotes, which is a relative-first lookup that only reaches the system header
   by accident. Rename the guard to `_AKGL_STATICSTRING_H_` and use
   `#include <string.h>`.

2. **Function names contradict the stated convention.** `AGENTS.md` says public
   symbols use `akgl_` and types use `akgl_TypeName`. Exceptions:
   - `akgl_Actor_cmhf_left_on` and its seven siblings (`include/akgl/actor.h:196-252`)
     embed the *type* name in a *function* name, unlike every other actor entry
     point (`akgl_actor_*`). Rename to `akgl_actor_cmhf_*`.
   - `akgl_game_updateFPS` (`include/akgl/game.h:104`) is camelCase; every other
     function is snake_case.
   - `akgl_render_init2d` (`include/akgl/renderer.h:83`) puts the `2d` at the end
     while the six functions it installs are `akgl_render_2d_*`. Make it
     `akgl_render_2d_init`.
   - `akgl_sprite_sheet_coords_for_frame` (`include/akgl/sprite.h:86`) spells it
     `sprite_sheet`; `akgl_spritesheet_initialize` and `akgl_heap_next_spritesheet`
     spell it `spritesheet`.

3. **Two public types have no prefix at all.** `point` and `RectanglePoints`
   (`include/akgl/util.h:13-25`) are unprefixed, and `RectanglePoints` is
   PascalCase with no namespace. Both are dumped into every translation unit
   that includes `util.h`. Rename to `akgl_Point` / `akgl_RectanglePoints`.

4. **Global variables use four different conventions.** `window`, `bgm`, `game`,
   `gamemap`, `renderer`, `physics`, and `camera` (`src/game.c:26-43`) are
   unprefixed single common words exported from a shared library — `renderer`
   and `camera` in particular are very likely to collide with a consuming game.
   Alongside them the same file exports `akgl_mixer` and `akgl_tracks` (prefixed),
   `_akgl_renderer` / `_akgl_camera` / `_akgl_physics` / `_akgl_gamemap`
   (underscore-prefixed, which is reserved at file scope), and elsewhere
   `HEAP_ACTOR`…`HEAP_STRING` (`src/heap.c:17-21`) and `GAME_ControlMaps`
   (`src/controller.c:13`) are SCREAMING_SNAKE, which the convention reserves for
   constants and macros. Settle on `akgl_` for all exported objects.

5. **`AKGL_SPRITE_MAX_CHARACTER_NAME_LENGTH`** (`include/akgl/character.h:13`) is a
   character constant carrying the `SPRITE` prefix, and lives in `character.h`.
   Rename to `AKGL_CHARACTER_MAX_NAME_LENGTH`.

6. **`AKGL_TIME_ONESEC_MS` is misnamed and the error is live.**
   `include/akgl/game.h:22` defines it as `1000000`. One second in milliseconds
   is `1000`; `1000000` is the number of nanoseconds in a *millisecond*. The name
   says "one second" but the value means "one millisecond", so:
   - `src/character.c:209` and `src/sprite.c:141` use it correctly as a
     milliseconds-to-nanoseconds scale factor.
   - `src/game.c:136` uses it as documented — a one-second budget for the state
     lock — in a loop that advances `totaltime += 100` alongside `SDL_Delay(100)`.
     The loop therefore runs 10,000 iterations of 100 ms, so `akgl_game_state_lock`
     blocks for roughly 16 minutes rather than 1 second before reporting failure.

   Rename to `AKGL_TIME_ONEMS_NS` to match `AKGL_TIME_ONESEC_NS`, and give
   `akgl_game_state_lock` a real one-second budget.

### 2. Header/implementation surface drift

7. **Nineteen non-static functions are defined in `src/` but declared in no
   header.** They have external linkage and public-looking names, so they are
   part of the ABI whether intended or not, and no consumer can call them:

   `akgl_game_load_objectnamemap`, `akgl_game_load_versioncmp`,
   `akgl_game_save_actors`, `akgl_game_save_actorname_iterator`,
   `akgl_game_save_charactername_iterator`, `akgl_game_save_spritename_iterator`,
   `akgl_game_save_spritesheetname_iterator` (`src/game.c`);
   `akgl_get_json_properties_double`, `akgl_get_json_properties_float`,
   `akgl_get_json_properties_number`, `akgl_tilemap_load_layer_image`,
   `akgl_tilemap_load_layer_object_actor`, `akgl_tilemap_load_physics`
   (`src/tilemap.c`); `akgl_path_relative_from`, `akgl_path_relative_root`
   (`src/util.c`); `gamepad_handle_added`, `gamepad_handle_button_down`,
   `gamepad_handle_button_up`, `gamepad_handle_removed` (`src/controller.c`).

   Each should be either declared in its header or made `static`. Note that
   `tilemap.h` already has a "part of the internal API, exposed here for unit
   testing" block — the tilemap entries belong there.

8. **`akgl_game_init_screen` is declared but never defined**
   (`include/akgl/game.h:100`). Same failure mode as **Defects → Known and still
   open #10**, which covers the four `akgl_controller_handle_*` declarations;
   fold this one into that item.

9. **Static helpers use three different naming styles.** `actor_visible`
   (`src/actor.c:185`) is bare; `akgl_character_load_json_inner` and
   `akgl_character_load_json_state_int_from_strings` (`src/character.c:101,132`)
   and `akgl_sprite_load_json_spritesheet` (`src/sprite.c:51`) carry the full
   public prefix; `gamepad_handle_*` (`src/controller.c:121+`) uses a third
   subsystem word that appears nowhere else. Adopt one rule — the clearest is
   that `static` helpers drop the `akgl_` prefix, since it exists to avoid
   external collisions.

10. **Parameter names disagree between declaration and definition.** Doxygen
    documents the header spelling, so the generated docs describe names the
    implementation does not use:

    | Header | Implementation |
    |---|---|
    | `character.h:41` `basechar` | `character.c:21` `obj` |
    | `character.h:69` `props` | `character.c:75` `registry` |
    | `heap.h:121` `ptr` | `heap.c:143` `basechar` |
    | `registry.h:97` `value` | `registry.c:163` `src` |
    | `json_helpers.h:134` `e` | `json_helpers.c:149` `err` |
    | `tilemap.h:134,143` `dest` | `tilemap.c:646,767` `map` |

    The `tilemap.h` pair is the most misleading: the parameter is the map being
    *read* and drawn, but it is named `dest` and documented as "Output
    destination populated by the function".

11. **Object-pool size macros are defined twice, and the override hook is
    dead.** `heap.h:15-29` wraps `AKGL_MAX_HEAP_ACTOR`, `_SPRITE`, `_SPRITESHEET`,
    `_CHARACTER`, and `_STRING` in `#ifndef` guards so a consumer can override
    them, but `actor.h:65`, `sprite.h:19-20`, and `character.h:14` define the same
    four unconditionally and are included from `heap.h:9-11`. Whichever header
    lands first wins and the `#ifndef` never fires, so the override mechanism
    cannot work. Define each pool size once — `heap.h` is the natural home.

12. **Headers rely on their includers for types.** `iterator.h` uses `uint32_t`
    without `<stdint.h>`; `json_helpers.h` uses `json_t` without `<jansson.h>`;
    `util.h` uses `SDL_FRect` and `bool` without any SDL include; `text.h` uses
    `SDL_Color` and `akerr_ErrorContext` without including SDL or `akerror.h`;
    `controller.h` uses `akgl_Actor` without including `actor.h`. Each compiles
    only because of `.c`-file include ordering. Headers should be self-contained.

13. **Include spelling is split between quoted and angled forms for the same
    directory.** `actor.h:10-11`, `character.h:10-11`, `controller.h:11`,
    `game.h:11-14`, `json_helpers.h:10`, and `staticstring.h:9` use
    `#include "sibling.h"`; `physics.h:11-13`, `registry.h:9-10`, `renderer.h:13`,
    `tilemap.h:10-12`, and `util.h:10` use `#include <akgl/sibling.h>`. The
    angled form is correct for an installed library.

14. **Empty parameter lists.** `akgl_heap_init()`, `akgl_heap_init_actor()`,
    `akgl_registry_init*()`, `akgl_game_init()`, `akgl_game_init_screen()`, and
    `akgl_game_updateFPS()` declare `()` rather than `(void)`, while
    `akgl_controller_list_keyboards(void)`, `akgl_controller_open_gamepads(void)`,
    `akgl_game_lowfps(void)`, and `akgl_game_state_lock(void)` use `(void)`.
    Before C23 the two are not equivalent — `()` suppresses argument checking.
    `akgl_heap_init_actor` is even declared `()` in `heap.h:57` and defined
    `(void)` in `heap.c:48`.

15. **`AKERR_NOIGNORE` is applied inconsistently at definition sites.** Headers
    use it uniformly (except `akgl_sprite_sheet_coords_for_frame`, `sprite.h:86`,
    which omits it). Definitions are split even within one file: `registry.c:55,120,163,172`
    repeat it, `registry.c:27,44,63,71,79,96,104,112` do not. Since the attribute
    is already on the declaration, drop it from all definitions.

### 3. Error-handling pattern

16. **`*_RETURN` macros are used inside `ATTEMPT` blocks, which skips `CLEANUP`.**
    The established pattern is `FAIL_*_BREAK` / `CATCH` inside `ATTEMPT` and
    `*_RETURN` outside it. Violations:
    - `src/tilemap.c:52` — `SUCCEED_RETURN` on the success path of
      `akgl_get_json_tilemap_property` returns directly from inside `ATTEMPT`,
      bypassing the `CLEANUP` at line 54 that releases `tmpstr` and `typestr`.
      Every successful property lookup leaks two heap strings, and the string
      pool is only 256 entries.
    - `src/tilemap.c:620` — `FAIL_RETURN` inside `ATTEMPT`.
    - `src/controller.c:286-289,306` — `FAIL_ZERO_RETURN` / `FAIL_NONZERO_RETURN`
      inside `ATTEMPT`; `src/controller.c:383` — `SUCCEED_RETURN` inside `ATTEMPT`,
      which also leaves `akgl_controller_default` with no return statement on the
      path that falls out of `FINISH`.
    - `src/game.c:457,462` — `FAIL_NONZERO_RETURN` inside `ATTEMPT`, skipping the
      `fclose` in `CLEANUP` at line 482.

17. **NULL-check discipline varies by function.** In `src/json_helpers.c` only
    `akgl_get_json_string_value` (line 71) and `akgl_get_json_array_index_string`
    (line 128) validate `key`/`dest`; the other eight accessors validate only the
    container and then dereference `dest` unconditionally. In `src/physics.c` the
    arcade backends check `actor` but `akgl_physics_null_gravity`,
    `_null_collide`, and `_null_move` (lines 15-34) check only `self`. In
    `src/renderer.c:65,74`, `akgl_render_2d_frame_start` and `_frame_end`
    dereference `self->sdl_renderer` with no check on `self`, while
    `akgl_render_2d_draw_texture` (line 82) checks `self` first.

18. **Error-context variable naming is split between `errctx` and `e`,
    sometimes within one file.** `src/util.c` uses `e` in the path helpers
    (lines 32-116) and `errctx` in the geometry helpers (lines 118-259);
    `src/heap.c` uses `errctx` everywhere except `akgl_heap_init_actor` (line 50).
    `src/actor.c`, `character.c`, `json_helpers.c`, `registry.c`, `sprite.c`, and
    `tilemap.c` favor `errctx`; `game.c`, `physics.c`, `renderer.c`, and
    `controller.c` favor `e`. Pick one.

### 4. Types and macros

19. **`float`/`double` are used raw where `types.h` defines aliases.** `types.h`
    exports `float32_t` and `float64_t`, and the actor and character structs use
    `float32_t` throughout — but `akgl_get_json_number_value` takes `float *`
    (`json_helpers.h:55`), `akgl_get_json_double_value` takes `double *` (line 66),
    `akgl_PhysicsBackend`'s six drag/gravity fields are `double`
    (`physics.h:22-27`), and `akgl_Tilemap`'s perspective fields are `float`
    (`tilemap.h:105-108`). Either use the aliases consistently or delete them.

20. **`AKGL_COLLIDE_RECTANGLES` (`include/akgl/util.h:27`) has unbalanced
    parentheses** — three opens, two closes — so any use is a syntax error. It has
    no callers and duplicates `akgl_collide_rectangles`. Delete it.

21. **Bitmask macros are unparenthesized.** `AKGL_BITMASK_HAS(x, y)` expands to
    `(x & y) == y` with no outer parens, so `!AKGL_BITMASK_HAS(a, b)` parses as
    `!(a & b) == b`. No in-tree caller negates it today (`AKGL_BITMASK_HASNOT`
    exists for that), so this is latent rather than live. `AKGL_BITMASK_CLEAR(x)`
    (`game.h:86`) also carries a trailing semicolon inside the macro body, so
    normal use produces an empty statement. Parenthesize all five and drop the
    semicolon.

22. **The state and iterator bit macros mix forms.** `AKGL_ITERATOR_OP_UPDATE`
    (`iterator.h:15`) is written `1` while its 31 siblings are `1 << n`, and none
    of the `1 << n` values in `iterator.h` or `actor.h:15-49` are parenthesized.
    The hand-maintained trailing bit-pattern comments in `actor.h:34-49` are also
    wrong for the high word — they restart at `0000 0000 0000 0001` for bit 16
    rather than showing the full 32-bit value.

23. **`akgl_Frame` (`game.h:27-31`) is defined and never used** anywhere in
    `src/`, `include/`, `tests/`, or `util/`.

### 5. `AKGL_ACTOR_STATE_STRING_NAMES` disagrees with `actor.h`

24. **The array bound differs between declaration and definition.**
    `include/akgl/actor.h:57` declares `[AKGL_ACTOR_MAX_STATES+1]` (33);
    `src/actor_state_string_names.c:6` defines `[32]`. Any consumer that trusts
    the declared bound and reads index 32 reads past the object.

25. **Two entries name the wrong bit.** `actor.h` assigns bit 11 to
    `AKGL_ACTOR_STATE_MOVING_IN` and bit 12 to `AKGL_ACTOR_STATE_MOVING_OUT`, but
    `actor_state_string_names.c:18-19` puts `"AKGL_ACTOR_STATE_UNDEFINED_11"` and
    `"AKGL_ACTOR_STATE_UNDEFINED_12"` at those indices — names for macros that do
    not exist. Since `akgl_registry_init_actor_state_strings`
    (`src/registry.c:79-94`) builds `AKGL_REGISTRY_ACTOR_STATE_STRINGS` from this
    array and `akgl_character_load_json_state_int_from_strings`
    (`src/character.c:101`) resolves character-JSON state names through it, a
    character JSON can never bind a sprite to `MOVING_IN` or `MOVING_OUT`.

26. **The generation comment is stale.** `actor.h:53-55` says the file "is built
    by a utility script and not kept in git, see the Makefile for
    lib_src/actor_state_string_names.c". There is no Makefile (the project is
    CMake), no `lib_src/`, no such script under `scripts/` or `util/`, and the
    file *is* tracked in git at `src/actor_state_string_names.c`. Either restore
    the generator — which would fix items 24 and 25 by construction — or delete
    the comment and maintain the file by hand.

### 6. Doxygen drift

27. **Three struct doc comments in `tilemap.h` are rotated by one.**
    `akgl_TilemapObject` (line 31) is documented as "Stores tileset metadata,
    texture, and frame offsets" (that is `akgl_Tileset`); `akgl_TilemapLayer`
    (line 46) as "Represents an object embedded in a tilemap layer" (that is
    `akgl_TilemapObject`); `akgl_Tileset` (line 61) as "Stores tile, image, or
    object data for one map layer" (that is `akgl_TilemapLayer`).

28. **`point` is documented as "Represents a two-dimensional point"**
    (`util.h:12`) but has `x`, `y`, and `z`.

29. **Doc comments live on the definition for public functions.** The convention
    is header-side documentation, but `akgl_path_relative_root` (`util.c:23`),
    `akgl_path_relative_from` (`util.c:97`), the four `gamepad_handle_*`
    (`controller.c:114+`), the `akgl_game_save_*` iterators and
    `akgl_game_load_*` helpers (`game.c:173+`), and the tilemap helpers
    (`tilemap.c:90+`) are documented only in the `.c`. This is the same set as
    item 7 — resolving that resolves this.

### 7. Formatting

30. **A minority of files use a 2-column offset instead of the canonical
    4-column one.** The mix of tabs and spaces across most of `src/` is *not*
    disorder: it is exactly what Emacs `cc-mode` emits for the `stroustrup` style
    with `indent-tabs-mode t` and `tab-width 8` — depth 1 is four spaces, depth 2
    is one tab, depth 3 is a tab plus four spaces, and so on. Twelve of the
    seventeen `.c` files follow that ladder cleanly.

    The genuine outliers indent at 2 columns: `src/json_helpers.c` (82 lines,
    except `akgl_get_json_with_default` at line 149 which is 4), `src/util.c`
    (37 lines, from `akgl_rectangle_points` at line 118 onward), `src/assets.c`
    (9), `src/staticstring.c` (7), `src/actor.c` (8, in `akgl_actor_add_child`
    at line 272), plus `include/akgl/util.h` (7) and
    `include/akgl/staticstring.h` (2).

    **Resolved.** `AGENTS.md` now specifies the canonical style and the exact
    `cc-mode` settings; `.dir-locals.el` applies them in Emacs; and
    `scripts/reindent.sh` applies them in batch. The whole tree (32 files across
    `src/`, `include/`, `tests/`, and `util/`) has been reindented and is a fixed
    point of `scripts/reindent.sh --check`. Verified whitespace-only: apart from
    three trailing blank lines removed at EOF in `src/heap.c`, `src/registry.c`,
    and `tests/tilemap.c`, `git diff -w` over the reindent is empty, and the test
    results are unchanged (13/14, `character` still the intentional failure).
    `scripts/hooks/pre-commit` keeps it that way — enable with
    `git config core.hooksPath scripts/hooks`.

31. **Leftover debug code ships in the library.** `src/controller.c:91-97` logs
    four lines whenever `event->type == 768 && event->key.which == 11 &&
    event->key.key == 13` — hardcoded decimal values for a specific keyboard ID
    on a specific developer's machine, inside the per-event inner loop.

32. **Large commented-out blocks.** `src/sprite.c:115-120,157,185-198,210`;
    `src/character.c:192-199,215`; `src/assets.c:18-27,50`;
    `src/tilemap.c:583,596-598,640`. All are the same abandoned
    `SDL_GetBasePath()` path-prefixing approach, superseded by
    `akgl_path_relative`. Delete them.

33. **Unused locals.** `screenwidth`/`screenheight` (`game.c:53-54`), `curTime`
    (`game.c:499`), `curTime` and `j` (`renderer.c:114,116` — `j` is also shadowed
    by the inner loop at line 128), `target` (`character.c:59`), `result`
    (`util.c:37,73`), `opflags` (`heap.c:146`, declared and cleared but never
    read).

34. **`akgl_game_update`'s default flags OR the same bit twice.**
    `src/game.c:496` reads
    `(AKGL_ITERATOR_OP_LAYERMASK | AKGL_ITERATOR_OP_LAYERMASK)`. Given the loop
    that follows walks layers and calls `updatefunc`, the intent was almost
    certainly `AKGL_ITERATOR_OP_UPDATE | AKGL_ITERATOR_OP_LAYERMASK`.

35. **`akgl_draw_background` is the only public function outside the error
    protocol.** `include/akgl/draw.h:14` returns `void` and reports nothing;
    every other public entry point returns `akerr_ErrorContext *`. It also calls
    `SDL_SetRenderDrawColor` and `SDL_RenderFillRect` without checking `renderer`
    or `renderer->sdl_renderer`.

36. **`akgl_registry_init_actor` is the only registry initializer that destroys
    an existing registry** before recreating it (`src/registry.c:47-49`). The
    other seven leak the old `SDL_PropertiesID` on a second call. Either all of
    them should do it or none should.

37. **Redundant casts obscure the code.** `(json_t *)json` where `json` is
    already `json_t *`, `(akgl_Tilemap *)dest`, `(akgl_Actor *)actorobj`,
    `(char *)&obj->name` on an array that already decays — roughly 180 pointer
    casts across `src/`, a large majority of them no-ops, densest in
    `src/tilemap.c:150-624` and `src/character.c:144-172`.
    They suppress exactly the conversion warnings that would catch a real
    mismatch.

38. **`struct`-qualified parameters in two definitions.**
    `akgl_physics_null_move` (`src/physics.c:29`) and `akgl_physics_arcade_move`
    (`src/physics.c:80`) are defined with `struct akgl_PhysicsBackend *self`
    while the header and the other eight physics functions use the typedef.

39. **`text.c:19` validates the wrong argument.**
    `FAIL_ZERO_RETURN(errctx, name, AKERR_NULLPOINTER, "Null filepath")` checks
    `name` a second time; `filepath` is never checked and is passed straight to
    `TTF_OpenFont`. Copy-paste of line 18.

    **Resolved** alongside the text measurement work; `tests/text.c` asserts a
    NULL filepath reports `AKERR_NULLPOINTER`.

40. **`akgl_path_relative` and `akgl_path_relative_from` disagree on the output
    parameter.** `akgl_path_relative` and `akgl_path_relative_root` take
    `akgl_String *dst`; `akgl_path_relative_from` takes `akgl_String **dst`
    (`src/util.c:105`). The `**` form matches the rest of the library
    (`akgl_get_json_string_value`, `akgl_get_property`, `akgl_heap_next_string`),
    which allocate when `*dest` is NULL. Related: **Defects → Known and still
    open #4**, which covers the fact that `akgl_path_relative_from` never writes
    `*dst` at all.

41. **`dst` vs `dest` for output parameters.** `akgl_string_copy` and the
    `akgl_path_relative*` family use `dst`; everything else uses `dest`.

## Coverage status

Generated with:

```sh
cmake -S . -B build-coverage -DAKGL_COVERAGE=ON -DCMAKE_BUILD_TYPE=Debug
cmake --build build-coverage --parallel
ctest --test-dir build-coverage --output-on-failure
```

Reports land in `build-coverage/coverage/` (`index.html`, `coverage.xml`).

**Line coverage 77.2%, function coverage 83.1%** (2035/2637 lines), up from a
39.6% / 44.3% baseline. All 19 suites pass. (An earlier revision of this file
recorded `character` as an intentionally failing suite; it passes now, and
nothing in `tests/character.c` or `src/character.c` has changed since — the fix
came from elsewhere in the tree and this note was never updated.)

| File | Lines | Functions |
|---|---|---|
| `src/actor.c` | 205/258 (79%) | 16/18 |
| `src/assets.c` | 0/21 (0%) | 0/1 |
| `src/audio.c` | 189/207 (91%) | 19/20 |
| `src/character.c` | 104/118 (88%) | 6/7 |
| `src/controller.c` | 247/270 (91%) | 12/12 |
| `src/draw.c` | 253/267 (95%) | 11/12 |
| `src/error.c` | 9/9 (100%) | 1/1 |
| `src/game.c` | 124/231 (54%) | 10/15 |
| `src/heap.c` | 111/111 (100%) | 12/12 |
| `src/json_helpers.c` | 111/111 (100%) | 11/11 |
| `src/physics.c` | 140/140 (100%) | 10/10 |
| `src/registry.c` | 76/102 (75%) | 11/12 |
| `src/renderer.c` | 7/70 (10%) | 1/7 |
| `src/sprite.c` | 93/101 (92%) | 5/5 |
| `src/staticstring.c` | 16/17 (94%) | 2/2 |
| `src/text.c` | 26/45 (58%) | 3/4 |
| `src/tilemap.c` | 201/426 (47%) | 10/20 |
| `src/util.c` | 121/131 (92%) | 7/8 |
| `src/version.c` | 2/2 (100%) | 1/1 |

Branch coverage reads 21.2% and should not be used as a target. The akerror
control-flow macros (`ATTEMPT`/`CATCH`/`PROCESS`/`FINISH`, `FAIL_*_RETURN`)
expand into large branch trees per call site, most of them unreachable in normal
operation — `src/game.c` reports over 1700 branches across 230 lines. Track line
and function coverage; treat branch coverage as a relative signal within a file.

### Mutation testing

`scripts/mutation_test.py` was run over the three new files as a smoke check
(`--max-mutants 8` to 10 each, so these are samples rather than exhaustive
scores):

| File | Score | Surviving mutants |
|---|---|---|
| `src/draw.c` | 90% | Deleting the `FAIL_ZERO_BREAK` on `SDL_CreateTextureFromSurface` in `akgl_draw_flood_fill` |
| `src/audio.c` | 75% | Deleting `SUCCEED_RETURN` from the static `check_voice`; deleting `spec.freq` before opening a device |
| `src/text.c` | 50% | Three in `akgl_text_rendertextat`, which has no test yet, plus one `SUCCEED_RETURN` deletion |

The first pass over `src/audio.c` scored 50% and named two real gaps, both of
which are now tested: nothing asserted that an *unconfigured* voice is audible
(the whole reason the table defaults to a square wave at full level rather than
a zeroed struct), and no envelope test used a non-zero attack *and* decay
together, so the decay measuring from the wrong origin survived. `src/draw.c`
scored 70% first and named one: the circle was only checked at its four axis
points, which a mis-signed octant reflection survives, so it now checks that
every plotted pixel has a mirror in the other three quadrants.

What is left is honestly untestable from here. Deleting a `SUCCEED_RETURN`
leaves a non-void function falling off its end, which is undefined rather than
observably wrong, and the surviving SDL branches are allocation failures the
suite has no way to provoke. The `src/text.c` survivors go away with the
offscreen harness.

### Suites

Every suite is registered through the `AKGL_TEST_SUITES` list in
`CMakeLists.txt`, which drives target creation, CTest registration, the
`WORKING_DIRECTORY`/`TIMEOUT` properties, the link line, and the
`FIXTURES_REQUIRED akgl_coverage` list together. Adding `tests/<name>.c` and the
name to that list is all a new suite needs; it can no longer be accidentally
left out of the coverage fixture.

Shared assertion helpers are in `tests/testutil.h`: `TEST_ASSERT`,
`TEST_ASSERT_FEQ`, `TEST_EXPECT_STATUS`, `TEST_EXPECT_OK`, `TEST_EXPECT_ANY_ERROR`,
and `TEST_ASSERT_FLAG`. All except the last expand to a `break` on failure, so
they belong directly inside an `ATTEMPT` block, not inside a loop nested in one.

Done:

- `tests/physics.c` — both backends, the factory, and the full simulation loop
  including thrust clamping, drag, layer masking, parent/child positioning, and
  logic-interrupt handling. 100%.
- `tests/heap.c` — pool exhaustion for all five pools, refcount clamping,
  recursive child release, registry cleanup on release. 100%.
- `tests/json_helpers.c` — every typed accessor, both string accessors'
  allocate-vs-reuse paths, array bounds, and `akgl_get_json_with_default`. 100%.
- `tests/controller.c` — control map push and capacity, the default binding set,
  keyboard and gamepad dispatch including cross-device rejection, the dpad
  handlers, and device add/remove against the dummy drivers. 90%.
- `tests/game.c` — version gating, the save/load roundtrip, foreign-save
  rejection, truncated-table detection, the state lock, and FPS accounting. 54%.
- `tests/actor.c` — extended with the eight control-map handlers, automatic
  facing, movement logic, the animation frame state machine, `akgl_actor_update`,
  and character/sprite binding lookups. 80%.
- `tests/audio.c` — every waveform, the ADSR envelope stage by stage, gate
  expiry and release, voice summing and clamping, the master level, and device
  open/shutdown under the dummy driver. 91%.
- `tests/draw.c` — every primitive against a 64x64 software renderer with the
  pixels read back, including flood-fill containment, save/paste roundtrip, and
  that drawing restores the renderer's draw color. 95%.
- `tests/text.c` — font loading into the registry and both measurement entry
  points against a monospaced fixture font. 58%; the rest of `src/text.c` is
  `akgl_text_rendertextat`, which needs the harness.

## Remaining work

### Needs the offscreen renderer harness

`src/renderer.c` (63 lines), `akgl_text_rendertextat` in `src/text.c` (19),
`akgl_draw_background` in `src/draw.c` (13), `src/assets.c` (21),
`akgl_actor_render`/`actor_visible` in `src/actor.c` (53), and the drawing half
of `src/tilemap.c` all need a live `renderer` global.

Build `tests/harness.c` / `tests/harness.h` with `akgl_test_init_headless()` and
`akgl_test_shutdown_headless()`: set the dummy video and audio drivers,
`SDL_Init()`, `akgl_heap_init()`, `akgl_registry_init()`, create a software
`SDL_CreateWindowAndRenderer`, and point the global `renderer` at it. Four
existing tests hand-roll this today (`tests/sprite.c:194`, `tests/character.c:200`,
`tests/tilemap.c:421`, `tests/charviewer.c:42`); collapse them onto the shared
harness in the same change. The new suites set the driver hints inline and need
no window, so they are unaffected.

Then:

- **`tests/renderer.c`** — `akgl_render_init2d` populating all six function
  pointers and the camera; frame start/end against a NULL `sdl_renderer`; the
  rotated `draw_texture` path including `angle != 0` with a NULL center; the
  `draw_mesh` "not implemented" stub; and `draw_world` layer ordering. Note
  `defflags` at `src/renderer.c:113` is uninitialized until the `if` body runs.
- **`tests/assets.c`** — BGM loading into `AKGL_REGISTRY_MUSIC` under the dummy
  audio driver.
- **`tests/text.c` extensions** — text rendering with wrap on and off.
  `tests/text.c` exists and covers font loading and measurement; only
  `akgl_text_rendertextat` is left.
- **`tests/draw.c` extensions** — `akgl_draw_background` at zero, negative and
  oversized dimensions. `tests/draw.c` exists and covers every other primitive
  against a software renderer; `akgl_draw_background` is the one function in the
  file that still reads the global `renderer` rather than taking a backend.
- **`tests/tilemap.c` extensions** — `akgl_tilemap_draw`, `_draw_tileset`, and
  `akgl_tilemap_load_layer_image`.

### Does not need a renderer

- **`src/tilemap.c`** — `akgl_tilemap_scale_actor` is pure math over three
  branches (`src/tilemap.c:824-830`); `akgl_get_json_properties_number`,
  `_float`, and `_double` need only a JSON snippet; `akgl_tilemap_load_physics`
  needs a fixture with the physics property block present, absent, and
  malformed. Together roughly 100 of the 225 uncovered lines.
- **`src/game.c`** — `akgl_game_init`, `akgl_game_update`, `akgl_game_lowfps`,
  and `akgl_game_updateFPS`'s frame loop need a window; revisit after the
  harness lands.
- **`src/registry.c`** — `akgl_registry_load_properties` needs a fixture with a
  `properties` object, plus the missing-file, missing-key, and wrong-value-type
  cases. Assert the loop at `src/registry.c:148-158` does not leak the string
  heap.

## Defects

### Fixed while building the suites

Each was found by a test written to assert correct behavior.

1. **`akgl_physics_simulate` dereferenced `self` before its NULL check.**
   `src/physics.c:132` read `self->gravity_time` at declaration time, three
   lines above `FAIL_ZERO_RETURN(e, self, ...)`. A NULL backend segfaulted.
2. **`akgl_game_save` never flushed or closed its stream.** `CLEANUP` and
   `PROCESS` were transposed, which put the `fclose` inside the `PROCESS`
   switch, where it only ran if an error context existed and reported success.
   An ordinary save produced an empty file.
3. **`akgl_game_save_actors` wrote name-table terminators from a single char.**
   `aksl_fwrite((void *)&nullval, 1, AKGL_ACTOR_MAX_NAME_LENGTH, fp)` emitted
   127 bytes of adjacent stack memory into the save file and produced a sentinel
   the loader could not recognize.
4. **`akgl_game_load_objectnamemap` swallowed read failures.** `CATCH` used
   directly inside `while (1)` breaks the loop, not the function, so a truncated
   or corrupt name table loaded as a successful game.
5. **`akgl_Actor_cmhf_up_on` and `_down_on` dereferenced `basechar` unguarded**,
   unlike their left and right counterparts.
6. **`akgl_actor_logic_movement` checked `actor` twice** instead of checking
   `actor->basechar` before dereferencing it.
7. **The gamepad handlers checked `appstate` three times each**, so a NULL event
   or a missing player actor was never caught and `player->state` was
   dereferenced regardless.

### Known and still open

1. **`akgl_render_and_compare` compares a texture against itself.**
   `src/util.c:228` and `src/util.c:245` both draw `t1`; `t2` is never rendered,
   so the function always passes and the image assertions in `tests/sprite.c`
   assert nothing.
2. **`akgl_tilemap_release` double-frees tileset textures.**
   `src/tilemap.c:849` destroys `dest->tilesets[i].texture` inside the *layers*
   loop; it should be `dest->layers[i].texture`. It also never NULLs the
   pointers, so a second release is a use-after-free.
3. **`akgl_registry_init` never initializes the properties registry.**
   `akgl_registry_init_properties()` is not called from `akgl_registry_init()`
   (`src/registry.c:27`), so `AKGL_REGISTRY_PROPERTIES` stays 0 unless the
   caller initializes it separately. `akgl_set_property` is then a silent no-op
   and `akgl_get_property` always returns the caller's default, which means
   `akgl_physics_init_arcade` and `akgl_render_init2d` silently ignore
   configuration. `akgl_game_init` does call it; a caller that does not use
   `akgl_game_init` does not get it.
4. **`akgl_path_relative_from` is a stub that leaks.** `src/util.c:105` claims a
   heap string, never writes `*dst`, and never releases it. 256 calls exhaust
   the string pool.
5. **`akgl_compare_sdl_surfaces` memcmps without checking geometry.**
   `src/util.c:208` compares `s1->pitch * s1->h` bytes of `s2` without verifying
   the surfaces share dimensions, pitch, or format.
6. **`akgl_string_initialize` overflows by four bytes when `init` is NULL.**
   `src/staticstring.c:17` does `memset(&obj->data, 0x00, sizeof(akgl_String))`,
   but `data` starts four bytes into the struct (after `refcount`), so the memset
   runs four bytes past the end.
7. **Savegame name lengths disagree between writer and reader.**
   `akgl_game_save_actors` writes spritesheet names at
   `AKGL_SPRITE_SHEET_MAX_FILENAME_LENGTH` (512) and character names at
   `AKGL_SPRITE_MAX_CHARACTER_NAME_LENGTH` (128), but `akgl_game_load` reads
   every table at `AKGL_ACTOR_MAX_NAME_LENGTH` (128). A save with any registered
   spritesheet cannot be read back. The current roundtrip test passes only
   because empty registries write nothing but zeroed sentinels.
8. **Heap acquire functions are asymmetric.** `akgl_heap_next_string` increments
   `refcount`; `next_actor`, `next_sprite`, `next_spritesheet`, and
   `next_character` do not. `tests/heap.c` pins the current behavior and says so;
   decide whether to make them symmetric or document the split.
9. **`tests/util.c` defines `test_akgl_collide_point_rectangle_logic` but
   `main()` never calls it.**
10. **`controller.h` declares functions that do not exist.** It declares
    `akgl_controller_handle_button_down`, `_button_up`, `_added`, and `_removed`,
    but `src/controller.c` defines them as `gamepad_handle_*`. Anything compiled
    against the header alone fails to link.
11. **`akgl_controller_pushmap` and `akgl_controller_default` accept negative map
    ids.** Both check `controlmapid >= AKGL_MAX_CONTROL_MAPS` but not
    `controlmapid < 0`, so a negative id indexes before `GAME_ControlMaps`.
12. **A failed controller-DB fetch silently destroys the tracked fallback.**
    `include/akgl/SDL_GameControllerDB.h` is committed deliberately so the
    library still builds if upstream disappears. But `mkcontrollermappings.sh`
    has no `set -e` and never checks `curl`'s exit status: on a failed fetch it
    writes `mappings.txt` empty, then overwrites the good tracked header with
    `AKGL_SDL_GAMECONTROLLER_DB_LEN 0` and an empty initializer — and exits 0.
    Verified by pointing the script at an unresolvable host.

    Two compounding problems:

    - `add_custom_command` at `CMakeLists.txt:89-93` declares
      `OUTPUT include/akgl/SDL_GameControllerDB.h` as a *relative* path, which
      CMake resolves against the binary directory, while the script writes to
      the source directory. The declared output never appears, so the command is
      permanently out of date and re-runs on every build — making every build
      depend on network access and leaving the file dirty in the working tree
      each time.
    - `const char *SDL_GAMECONTROLLER_DB[] = {\n};` is an empty initializer,
      which is a constraint violation in ISO C and compiles only as a GCC
      extension.

    Fix: have the script fetch to a temporary file, check `curl`'s status and a
    plausible minimum line count, and leave the existing header untouched on
    failure (exiting non-zero). Separately, make regeneration explicit — a
    dedicated `controllerdb` target, or an `OUTPUT` that matches where the
    script actually writes — so an ordinary build neither needs the network nor
    dirties the tree.
13. **A stale build tree in the source directory breaks the coverage run.**
    `CMakeLists.txt:208` and `CMakeLists.txt:223` pass
    `--root "${CMAKE_CURRENT_SOURCE_DIR}"` to gcovr, and gcovr searches for
    `.gcda`/`.gcno` files under the root. The `--object-directory` argument on
    the line below each does *not* narrow that search: per `gcovr --help` it
    only identifies "the path between gcda files and the directory where the
    compiler was originally run". So every instrumented build tree left inside
    the source directory is folded into the report alongside the one actually
    being measured.

    With a `build-coverage/` from an earlier session still present, a freshly
    configured `-DAKGL_COVERAGE=ON` tree fails in `coverage_reset`, before any
    test runs:

        AssertionError: Got function akgl_game_lowfps on multiple lines: 45, 46.

    45 and 46 are that function's line numbers before and after an unrelated
    `#include` was added to `src/game.c`: gcovr found 18 stale `.gcno` files
    describing the old layout, merged them with the current ones, and could not
    reconcile the two. Moving `build-coverage/` aside makes the same tree pass
    18/18. Verified with gcovr 7.0.

    The `build*/` entry in `.gitignore` hides these trees from `git status`,
    which makes the state easier to get into and no easier to notice.

    A second, smaller version of the same thing: rebuilding an existing
    coverage tree after editing a test leaves `.gcda` files describing the old
    object layout, and `coverage_reset` -- whose whole job is to delete them --
    fails with `GCOV returncode was 5` before it gets the chance. `find
    build-coverage -name '*.gcda' -delete` clears it. Observed with gcovr 7.0.

    Fix: pass the build tree to gcovr as an explicit search path instead of
    letting it default to `--root`, so only the tree under measurement is
    considered. Touches the two `add_test` blocks at `CMakeLists.txt:204-211`
    and `CMakeLists.txt:220-229`; nothing outside the `AKGL_COVERAGE` branch.

14. **22 public symbols shipped without a version or soname bump.** 42b60f7 added
    `akgl_draw_point`, `_line`, `_rect`, `_filled_rect`, `_circle`, `_flood_fill`,
    `_copy_region` and `_paste_region`; `akgl_audio_init`, `_shutdown`, `_tone`, `_stop`,
    `_waveform`, `_envelope`, `_volume`, `_voice_active` and `_mix`;
    `akgl_controller_poll_key` and `_flush_keys`; and `akgl_text_measure` and
    `_measure_wrapped`. `project(akgl VERSION 0.1.0)` and the `libakgl.so.0.1` soname were
    both left alone.

    That contradicts this repository's own stated rule, which `akbasic`'s `CLAUDE.md` quotes
    back: *"for both 0.x libraries the soname carries `MAJOR.MINOR` deliberately: 0.1 and 0.2
    are different ABIs."* Adding exported symbols under an unchanged soname has two
    consequences, and the first is the one that bites:

    - A binary compiled against the new headers links happily against a `libakgl.so.0.1`
      built from the old tree, because the soname says they are the same ABI. It fails at
      symbol resolution rather than at configure time.
    - `AKGL_VERSION_AT_LEAST(0, 1, 0)` is true for both trees, so a consumer cannot
      feature-test for the new API at all. `akbasic` pins the requirement by submodule commit
      instead, and says so in its README, which is not a thing a released library should make
      anybody do.

    Fix: bump `project()` to 0.2.0, which carries the soname to `libakgl.so.0.2` through the
    existing logic at `CMakeLists.txt:138`. `akstdlibConfigVersion.cmake`'s `SameMinorVersion`
    equivalent then refuses the mismatch at configure time as well.

    **Resolved by 1066ac7**, which did exactly that while this was being written — the two
    crossed, rather than one following the other. Kept rather than deleted because the *reason*
    is still the useful part: `akbasic` could not feature-test for the new API and had to pin
    `libakgl` by submodule commit in its README until this landed, which is the concrete cost of
    an additive release under an unchanged soname. Worth remembering the next time a handful of
    symbols looks too small to bump for.

### Found while rewriting the Doxygen comments

Each of these came out of reading an implementation against the contract its
header claimed. They are recorded inline as `@note` or `@warning` on the
function concerned, so a reader of the generated documentation finds them
without coming here first. Ordered by blast radius.

15. **`akgl_path_relative` leaks one error-context slot per call on its fallback
    path.** `src/util.c:120` returns `akgl_path_relative_root(...)` from inside
    the `HANDLE(e, ENOENT)` block. `FINISH` is what carries `RELEASE_ERROR`, so
    returning before it never gives the context back. libakerror hands these out
    of a fixed `AKERR_ARRAY_ERROR[128]`, and this is not a rare path — it is the
    *ordinary* one, taken every time an asset names a neighbour relative to its
    own file rather than to the working directory. Every tileset image, layer
    image and spritesheet in a map costs a slot, permanently. Once the array is
    exhausted every subsequent failure anywhere in the process has nowhere to
    report from.

    Fix: assign the result to a local, `break`, and return after `FINISH`; or
    hoist the fallback out of the handler entirely and let the `HANDLE` block
    only record that a retry is wanted. Touches `src/util.c:117-121` only.

16. **`akgl_sprite_load_json` does not bound the `frames` array.**
    `src/sprite.c:165` sets `obj->frames` from `json_array_size()` and
    `src/sprite.c:167` then writes that many entries into
    `frameids[AKGL_SPRITE_MAX_FRAMES]`, which is 16. A sprite definition with 17
    or more frames writes past the array into the rest of `akgl_Sprite`, and
    past the struct into the neighbouring pool slot. It is also written through
    a `uint32_t *` cast of a `uint8_t *`, so each element write touches four
    bytes; that happens to work on a little-endian machine because the following
    iterations overwrite the spill and the last write lands in the struct's
    alignment padding, but it is not portable and it is what makes the overflow
    reach four bytes past `frames` rather than one.

    Fix: refuse a `frames` array longer than `AKGL_SPRITE_MAX_FRAMES` with
    `AKERR_OUTOFBOUNDS`, and read into an `int` local before narrowing to
    `uint8_t`. Touches `src/sprite.c:164-169`.

17. **Two more unbounded array loads in the tilemap loader.**
    `src/tilemap.c:387-389` walks a Tiled object layer straight into
    `curlayer->objects[j]` with no check against
    `AKGL_TILEMAP_MAX_OBJECTS_PER_LAYER` (128), and `src/tilemap.c:278-280`
    fills `dest->tilesets[i]` with no check against `AKGL_TILEMAP_MAX_TILESETS`
    (16).
    Both are the same shape as item 16 and both are reachable from an ordinary
    map file: 128 objects is not a large object layer. Note that
    `akgl_tilemap_load_layers` *does* bound its loop and raises
    `AKERR_OUTOFBOUNDS`, so the pattern to copy is already in the same file.

    Fix: add the bound check at the top of each loop body, matching
    `akgl_tilemap_load_layers`. Touches `src/tilemap.c:387` and
    `src/tilemap.c:278`.

18. **`akgl_get_json_with_default` defaults on a status the array accessors never
    raise.** `src/json_helpers.c:164-165` handles `AKERR_KEY` and `AKERR_INDEX`,
    but `akgl_get_json_array_index_object`, `_integer` and `_string` all report
    a short array as `AKERR_OUTOFBOUNDS`. So the "this element is optional" form
    silently does not work for an array — the error propagates instead of being
    replaced by the default. Only the object accessors, which do raise
    `AKERR_KEY`, are actually served by this function today. Nothing in tree
    passes an array accessor's error here, which is why it has not been noticed.

    Fix: add a third `HANDLE_GROUP(err, AKERR_OUTOFBOUNDS)`. Note that the
    existing two rely on `HANDLE_GROUP` not emitting a `break`, so the `KEY`
    case falls through into the `INDEX` body — a third arm has to go *above* the
    one holding the `memcpy`, not below it. Touches `src/json_helpers.c:164-167`.

19. **The background music never loops.** `src/assets.c:20` initialises
    `bgmprops` to 0, `src/assets.c:44` sets `MIX_PROP_PLAY_LOOPS_NUMBER` on it,
    and `src/assets.c:46` plays the track with it. 0 is SDL's "no property set"
    sentinel, not a set this function owns, so the write is rejected —
    unchecked — and the play call is given no options. The music plays once and
    stops. `akgl_load_start_bgm` reports success either way.

    Fix: `SDL_CreateProperties()` into `bgmprops`, check it, and destroy it in
    `CLEANUP`. Touches `src/assets.c:20-47`.

20. **`akgl_character_sprite_add` leaks a sprite reference when a state is
    remapped.** `src/character.c:51` writes the new sprite over any existing
    entry for that state without releasing the one it displaces, whose refcount
    was incremented when it was added. The displaced sprite's pool slot is never
    reclaimed. The write itself is also unchecked, so a failure to record the
    mapping is reported as success.

    Fix: read the existing entry first and `akgl_heap_release_sprite` it, and
    check `SDL_SetPointerProperty`'s return. Touches `src/character.c:43-55`.

21. **`akgl_heap_release_character` abandons the whole state-to-sprite map.**
    `src/heap.c:150` zeroes the character without walking `state_sprites`, so
    every sprite reference the character took in `akgl_character_sprite_add` is
    lost and the `SDL_PropertiesID` holding the map is never destroyed. Loading
    and releasing characters in a loop — level to level — exhausts the sprite
    pool and leaks an SDL property set each time.
    `akgl_character_state_sprites_iterate` with `AKGL_ITERATOR_OP_RELEASE` exists
    precisely to do this walk and is not called from here.

    Fix: enumerate `state_sprites` with that iterator, then
    `SDL_DestroyProperties`, before the `memset`. Touches `src/heap.c:145-151`.

22. **`akgl_path_relative_root` uses `FAIL_RETURN` inside its `ATTEMPT` block.**
    `src/util.c:75` returns past `CLEANUP` on the over-long-path branch, so the
    two scratch strings claimed at `src/util.c:67-68` are never released. This is
    the exact hazard AGENTS.md documents under the error-handling protocol, and
    the same class as the heap-string leak already fixed in
    `akgl_get_json_tilemap_property`. Smaller blast radius than item 15 because
    the branch is rare, but it is a mechanical fix.

    Fix: `FAIL_BREAK`. Touches `src/util.c:75`.

23. **Three smaller leaks on failure paths.** All the same shape: a resource
    acquired before an `ATTEMPT`/`CLEANUP` pair, or released only on the success
    path.

    - `src/renderer.c:26-32` — `akgl_render_init2d` releases the two pooled
      strings holding the screen dimensions only after both `aksl_atoi` calls
      succeed, so a non-numeric `game.screenwidth` leaks two string slots.
    - `src/controller.c:80` — `akgl_controller_open_gamepads` calls
      `SDL_free(gamepads)` only after the loop completes, so a gamepad that
      fails to open leaks the enumeration array.
    - `src/text.c:57-64` — `akgl_text_rendertextat` destroys the surface and
      texture only on the success path, so a failed texture upload or a failed
      draw leaks both. On a HUD line redrawn every frame that is a leak per
      frame.

24. **`akgl_get_property` reads past the end of the property value.**
    `src/registry.c:182` copies a fixed `AKGL_MAX_STRING_LENGTH` bytes out of
    whatever `SDL_GetStringProperty` returned, rather than that string's length.
    The destination is a full-sized pool string so nothing is corrupted, but the
    source is an ordinary NUL-terminated string owned by SDL and the read runs
    up to PATH_MAX bytes past its end. Benign in practice and immediately fatal
    under ASAN, which is the reason to fix it rather than leave it.

    Fix: `aksl_strlcpy` or an explicit length. Touches `src/registry.c:181-186`.

25. **`akgl_character_load_json_state_int_from_strings` checks the same argument
    twice.** `src/character.c:123` guards `states` and `src/character.c:124`
    guards `states` again under the message "NULL destination integer" — the
    guard for `dest` was never written. A `NULL` `dest` is dereferenced at
    `src/character.c:132`. Only reachable from inside the character loader, which
    always passes a real pointer, so it is a latent hole rather than a live bug.

    Fix: change the second guard's subject to `dest`. Touches
    `src/character.c:124`.

26. **`akgl_actor_render` computes a sprite's drawn height from its width.**
    `src/actor.c:276` sets `dest.h = curSprite->width * obj->scale` where it
    should read `curSprite->height`. Every actor is therefore drawn square, and
    a non-square sprite is stretched or squashed. Invisible in the current
    assets because they are square; it will not stay that way.

    Fix: one word. Touches `src/actor.c:276`. Worth a test that renders a
    deliberately non-square sprite and asserts on the destination rectangle.

## Build notes

The vendored SDL satellite libraries are built into per-project subdirectories
that are not on the loader's default search path, and `LD_LIBRARY_PATH` is
searched ahead of RPATH — so a developer who has previously run `rebuild.sh` had
their installed `libakgl.so` shadow the one under test, and a developer who had
not saw every test abort before `main()` with "cannot open shared object file".
`CMakeLists.txt` now sets `BUILD_RPATH` on the library, the utility, and every
test target, and prepends the build tree to `LD_LIBRARY_PATH` for the CTest run.

## API gaps blocking akbasic

`akbasic` (the C port of the BASIC interpreter, `source.starfort.tech/andrew/akbasic`) is
being built to link into `libakgl` as a scripting engine for game authors.

**Items 1 through 4 are all resolved, and `akbasic` has since consumed every one of them.**
Its `libakgl`-backed text sink, its graphics backend, its sound backend and its input backend
are written and tested, and the BASIC 7.0 graphics verbs (`GRAPHIC`, `COLOR`, `DRAW`, `BOX`,
`CIRCLE`, `PAINT`, `SCALE`, `SSHAPE`, `GSHAPE`, `LOCATE`), the sound verbs (`SOUND`,
`ENVELOPE`, `VOL`, `PLAY`, `TEMPO`) and the console input verbs (`GET`, `GETKEY`, `SCNCLR`)
all work against them.

Doing that turned up **items 5 through 9**, filed below. Four are things `akbasic` had to work
around to build at all; each workaround is commented at its site over there with the words
"filed upstream", so they can be found and deleted when these land.

Building the *standalone* SDL frontend on top of all that — a real window, a real event pump
and a line editor — turned up **item 10**, and re-confirmed items 6 and 7: both workarounds
had to be written a second time, in `src/frontend_akgl.c`, because a host that owns a window is
exactly the caller they inconvenience.

These are filed here rather than worked around in `akbasic` because growing `libakgl` to serve
a consumer is the wanted outcome. Each entry says what the BASIC verb needs, what the
`akgl_*` entry point should look like, and what would cover it.

1. **No way to measure rendered text.** `include/akgl/text.h` exposes `akgl_text_loadfont()`
   and `akgl_text_rendertextat()`, and nothing that reports how large a string will be in a
   given font. A terminal-style text surface cannot be built on that: a cursor needs the
   advance width of one cell, and wrapping needs to know where a string crosses the right
   margin. The reference interpreter got this from SDL2_ttf's `font.SizeUTF8("A")` and derived
   its whole character grid from it.

   Wants `akerr_ErrorContext AKERR_NOIGNORE *akgl_text_measure(TTF_Font *font, char *text, int *w, int *h);`
   over `TTF_GetStringSize`, and probably a companion
   `akgl_text_measure_wrapped(font, text, wraplength, w, h)` matching the `wraplength`
   argument `akgl_text_rendertextat` already takes. Tests: a known string in a known font at a
   known size, the empty string, and a wrapped string wide enough to force two lines.

   This is the only one of the four that blocks work already designed and waiting. **`akbasic`
   cannot render any output through `libakgl` until it lands.**

   **Resolved.** `akgl_text_measure(font, text, w, h)` and
   `akgl_text_measure_wrapped(font, text, wraplength, w, h)` are in
   `include/akgl/text.h`, over `TTF_GetStringSize` and `TTF_GetStringSizeWrapped`.
   Neither needs a renderer. A negative `wraplength` is refused with
   `AKERR_OUTOFBOUNDS` rather than passed through, because SDL_ttf reads it as a
   very large unsigned width and silently stops wrapping. `tests/text.c` covers
   both against `tests/assets/akgl_test_mono.ttf`, a 10 KB monospaced ASCII
   subset added for the purpose — being monospaced, it lets the suite assert
   `width("AAAA") == 4 * width("A")` instead of hardcoding glyph metrics that
   FreeType is free to round differently. Same change fixed item 39 below:
   `akgl_text_loadfont` checked `name` twice and never checked `filepath`.

2. **No immediate-mode drawing.** `include/akgl/draw.h` declares exactly one function,
   `akgl_draw_background(int w, int h)`, and `src/draw.c` is at 0% coverage. BASIC 7.0's
   graphics verbs are all immediate-mode plotting against the current screen: `DRAW` (line and
   point), `BOX`, `CIRCLE`, `PAINT` (flood fill), `LOCATE` (set the pixel cursor), `COLOR`,
   and `SSHAPE`/`GSHAPE` (save and restore a rectangle of pixels).

   Wants an `akgl_draw_*` family taking the renderer the host already initialized --
   `akgl_draw_line`, `_rect`, `_filled_rect`, `_circle`, `_point`, `_flood_fill`,
   `_copy_region` -- in the shape of the existing `akgl_render_2d_draw_texture`. SDL3's
   `SDL_RenderLine`/`SDL_RenderRect`/`SDL_RenderFillRect` cover most of it; the circle and the
   flood fill do not exist in SDL3 and need writing. Tests belong with the offscreen renderer
   harness described under "Remaining work": render a known shape, read the target back, and
   compare against a reference surface with the existing `akgl_compare_sdl_surfaces`.

   **Resolved.** `include/akgl/draw.h` now declares `akgl_draw_point`, `_line`,
   `_rect`, `_filled_rect`, `_circle`, `_flood_fill`, `_copy_region` and
   `_paste_region`, all taking the `akgl_RenderBackend *` the host initialized,
   in the shape of `akgl_render_2d_draw_texture`. Decisions worth knowing:

   - **Color is an argument, not state.** There is no current-color global to
     get out of step with the caller's own. Each call saves and restores the
     renderer's draw color, so drawing a line does not change what the host's
     next `SDL_RenderClear` paints. `tests/draw.c` asserts that.
   - **The circle is a midpoint circle**, integer arithmetic with eight-way
     symmetry, plotted eight points per step through `SDL_RenderPoints`.
   - **The flood fill reads the target back, fills on the CPU, and blits only
     the bounding box of what changed.** It keeps a fixed
     `AKGL_DRAW_MAX_FLOOD_SPANS` (4096) stack of horizontal runs at file scope
     rather than recursing per pixel; running out reports `AKERR_OUTOFBOUNDS`
     and leaves the region partially filled, which is stated in the header. It
     is therefore not reentrant — neither is anything else that draws to a
     single `SDL_Renderer`.
   - `_copy_region` allocates when `*dest` is `NULL` and otherwise copies into
     the caller's surface, matching `akgl_get_json_string_value` and friends. A
     region that would be clipped by the target edge is refused rather than
     silently returning a smaller surface.

   `tests/draw.c` draws into a 64x64 software renderer under the dummy video
   driver and reads pixels back, so it did not need the offscreen harness. That
   harness is still wanted for `src/renderer.c`, `src/text.c` and `src/assets.c`.
   `akgl_draw_background` is untouched and still outside the error protocol
   (item 35).

3. **No audio API at all.** `SDL3_mixer` is a vendored dependency and `registry.h` declares
   `AKGL_REGISTRY_MUSIC`, but there is no `src/audio.c`, no `include/akgl/audio.h`, and no
   `akgl_*` symbol that opens a mixer, loads a chunk, or plays a note. BASIC 7.0's sound verbs
   are `SOUND` (a tone on a voice, with a duration), `PLAY` (a string of notes in a
   Commodore-specific notation), `ENVELOPE` (ADSR per voice), `FILTER`, `VOL` and `TEMPO`.

   `PLAY` and `ENVELOPE` want a synthesised voice rather than a sample, which SDL3_mixer does
   not provide directly -- the honest first step is a small tone generator feeding
   `SDL_AudioStream`, with `akgl_audio_init`, `akgl_audio_tone(voice, hz, ms)`,
   `akgl_audio_envelope(voice, a, d, s, r)` and `akgl_audio_volume(level)`. This is the largest
   of the four and the one most worth designing before writing. Tests can run under the dummy
   audio driver and assert state transitions rather than sound.

   **Resolved.** `include/akgl/audio.h` and `src/audio.c` add a three-voice tone
   generator over `SDL_AudioStream`: `akgl_audio_init`, `_shutdown`, `_tone`,
   `_stop`, `_waveform`, `_envelope`, `_volume`, `_voice_active` and `_mix`.
   It is deliberately separate from the SDL3_mixer side of the library, which
   plays audio *assets*; nothing in `audio.c` reads a file. Decisions worth
   knowing:

   - **The voice table works with no device open.** `akgl_audio_init` connects
     it to one; without that a host can still pull samples itself through
     `akgl_audio_mix`. That is not only for embedding — it is what makes the
     suite deterministic. A device pulls samples on SDL's audio thread whenever
     it likes, so a test that opened one and then asserted on voice state would
     be racing the callback. `tests/audio.c` mixes by hand and opens a device
     only in its last test.
   - **Phase is derived from the frame counter, not accumulated.** A float
     increment of `hz / 44100` is not exact, and adding it 44100 times a second
     walks a held note off pitch.
   - **A voice that was never configured is audible.** A zeroed voice has a
     sustain of 0.0, which is silence with no error to explain it, so the table
     defaults to a square wave held at full level.
   - **Three voices summing past full scale are clamped, not scaled**, so one
     voice plays at the level it was asked for rather than a third of it.
   - Everything that touches the table takes the stream lock when a device is
     open, since the callback reads it on another thread.

   Still missing for a complete BASIC sound vocabulary: `FILTER` (SDL3 has no
   filter primitive; this would need writing), `TEMPO` and the `PLAY` note-string
   parser, both of which belong in the interpreter rather than here.

4. **No non-blocking keystroke read.** `include/akgl/controller.h` is built around SDL event
   handlers the host pumps (`akgl_controller_handle_event` and friends), which suits a game
   loop and does not suit `GET` and `GETKEY` -- those ask "is there a keystroke waiting, yes or
   no" and must not require the interpreter to own the event loop. Goal 3 of `akbasic` forbids
   it owning one.

   Wants `akerr_ErrorContext AKERR_NOIGNORE *akgl_controller_poll_key(int *keycode, bool *available);`
   reading a small ring buffer that `akgl_controller_handle_event` already fills, so the host
   keeps pumping events and the interpreter drains characters at its own pace. Tests: push
   synthetic `SDL_EVENT_KEY_DOWN` events through the existing handler and drain them, plus the
   empty-buffer and overflow cases.

   **Resolved.** `akgl_controller_poll_key(int *keycode, bool *available)` and
   `akgl_controller_flush_keys(void)` are in `include/akgl/controller.h`, over a
   fixed `AKGL_CONTROLLER_KEY_BUFFER` (32) ring in `src/controller.c`.
   `akgl_controller_handle_event` records every `SDL_EVENT_KEY_DOWN` *before* it
   scans the control maps, so a key bound to an actor still reaches a polling
   caller — the scan returns as soon as a binding claims the event, and doing it
   afterwards would have lost exactly the keys a game also acts on. An empty
   buffer is success with `available` false, not an error. A full buffer drops
   the newest key rather than overwriting the oldest, matching the Commodore
   keyboard buffer and keeping what was typed first. `tests/controller.c` covers
   drain order, the release-is-not-a-keystroke case, a key shared with a control
   map, flush, both NULL arguments, and overflow plus reuse afterwards.

5. **An embedded `libakgl` demands its dependencies be installed, while vendoring them.**
   `CMakeLists.txt:17` gates the whole vendored-dependency block on
   `CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR`, so `deps/SDL`, `deps/SDL_image`,
   `deps/SDL_mixer`, `deps/SDL_ttf` and `deps/jansson` are added only when this repository is
   the top-level project. Embedded with `add_subdirectory()`, the `else()` branch at `:51`
   runs `find_package(SDL3 REQUIRED)` and friends instead, and configure fails on a machine
   that has none of them installed — with the submodules sitting right there in `deps/`,
   already checked out by the recursive clone the consumer just did.

   `akbasic` works around it by adding those five subdirectories itself, immediately before
   `add_subdirectory(deps/libakgl)`. That works only because every lookup in the `else()`
   branch is guarded with `if(NOT TARGET ...)` — which is the same escape hatch
   `akerror::akerror` and `akstdlib::akstdlib` already rely on, and it should not be the
   documented answer. **Fix:** add the vendored dependencies on both paths, still guarded by
   `if(NOT TARGET ...)` so a consumer that has already declared them wins. The suppression of
   their CTest registration should move with them.

6. **`include/akgl/controller.h` does not compile on its own.** Lines 35, 36 and 41 declare
   handler function pointers taking an `akgl_Actor *`, and the header includes only
   `SDL3/SDL.h`, `akerror.h` and `types.h` — none of which declares that type. Any translation
   unit that includes `akgl/controller.h` before `akgl/actor.h` fails with *"unknown type name
   'akgl_Actor'"*. `src/controller.c` never notices because it includes `akgl/game.h` first.

   This is the house rule in `AGENTS.md` — keep headers self-contained, include what you use.
   **Fix:** `#include "actor.h"` in `controller.h`, or forward-declare
   `struct akgl_Actor` if the include order makes that circular. A one-line test that includes
   only `akgl/controller.h` would have caught it and would keep catching it.

7. **There is no way to attach a 2D backend to a renderer the caller already has.**
   `akgl_render_init2d()` (`src/renderer.c:17`) does two separable things: it creates a window
   and an `SDL_Renderer` from the `game.screenwidth`/`game.screenheight` properties and writes
   to the `camera` global, and it installs the six function pointers that make an
   `akgl_RenderBackend` usable. A caller who already owns an `SDL_Renderer` wants only the
   second half — and that caller is not hypothetical, it is precisely the embedding host the
   API-gap section above exists to serve, since an embedded interpreter must not create the
   window.

   Today the only options are to call `akgl_game_init()` and let libakgl own the window, or to
   assign the six pointers by hand, which is what `akbasic`'s `tests/akgl_backends.c` does.
   **Fix:** split out `akgl_render_bind2d(akgl_RenderBackend *self)` that installs the vtable
   and nothing else, and have `akgl_render_init2d()` call it after it has made its window.
   `tests/renderer.c` could then cover the vtable half without a display at all.

8. **`akgl_text_rendertextat()` dereferences an uninitialised backend vtable.**
   `src/text.c` calls `renderer->draw_texture(renderer, ...)` with no NULL check on either
   `renderer` or the function pointer, so a backend that has an `SDL_Renderer` but has not been
   through `akgl_render_init2d()` segfaults on the first line of text. That is exactly the
   state item 7 leaves a host in, and it is the same class of defect the draw commit at
   42b60f7 added a test for — *"a backend that exists but was never given an SDL_Renderer,
   which is the state a host is in between allocating one and initializing it; every draw
   entry point has to report it rather than dereference it."* The text path still has it.

   **Fix:** `FAIL_ZERO_RETURN` on `renderer`, on `renderer->sdl_renderer` and on
   `renderer->draw_texture`, reporting `AKGL_ERR_SDL` or `AKERR_NULLPOINTER` as the draw
   entry points do. Test alongside the existing `tests/draw.c` backend-without-a-renderer case.

9. **`SOUND`'s frequency sweep has no `akgl_audio_*` equivalent.** BASIC 7.0's
   `SOUND voice, freq, dur, dir, min, step` ramps the pitch from `freq` toward `min` in `step`
   increments per tick, in the direction `dir` selects — a siren, a laser, the whole reason
   `SOUND` has six arguments. `akgl_audio_tone(voice, hz, ms)` holds one pitch for one
   duration, and nothing changes pitch over the life of a note.

   `akbasic` refuses those three arguments rather than faking them, and the reasoning is worth
   recording because it is what makes this a `libakgl` gap rather than an interpreter one: the
   only way to fake a sweep from the interpreter is to re-issue tones from its step loop, which
   ties audible pitch to how often the host happens to call it — a tune that changes key with
   the frame rate. It has to be advanced on the mixer's own frame counter, which is where the
   phase is already derived from and which only this library can see.

   **Fix:** `akgl_audio_sweep(int voice, float32_t from_hz, float32_t to_hz, float32_t step_hz, uint32_t ms)`,
   advanced in `akgl_audio_mix()` beside the envelope. Tests would drive `akgl_audio_mix` by
   hand and assert the frame at which the pitch has moved, exactly as `tests/audio.c` already
   does for the envelope stages.

10. **The keystroke ring carries a keycode and nothing else, so Shift is invisible.**
    `akgl_controller_handle_event()` (`src/controller.c:104-105`) pushes `event->key.key` into
    the ring and drops the rest of the event, and `akgl_controller_poll_key(int *keycode, bool
    *available)` hands back only that. Item 4 asked for a non-blocking keystroke read and got
    one; what it did not ask for, and what a *line editor* turns out to need, is which
    character the keystroke actually produced.

    `akbasic` has now built one — an `INPUT` and a REPL prompt drawn in the window, in
    `src/sink_akgl.c` — and the consequence is concrete: no shifted character is reachable, so
    `"`, `!`, `(`, `)`, `:` and `;` cannot be typed at all, and lower case cannot be typed
    either. A BASIC line editor that cannot type a double quote cannot enter a string literal.
    The interpreter folds letters to upper case, which is what a C128 does anyway and is the
    right resolution for letters; it is not a resolution for punctuation, and there is nothing
    the caller can do about it because the modifier state was discarded two layers down.

    Note this is not solvable by the caller polling `SDL_GetModState()` at read time: by then
    the key is long released, and the whole point of a ring is that reads are decoupled from
    events.

    **Fix:** widen the ring entry to carry the modifier state and the composed text SDL already
    computes. Either

    ```c
    typedef struct akgl_Keystroke {
        SDL_Keycode key;
        SDL_Keymod  mod;
        char        text[8];    /* UTF-8, from SDL_EVENT_TEXT_INPUT; "" for a non-printing key */
    } akgl_Keystroke;

    akerr_ErrorContext AKERR_NOIGNORE *akgl_controller_poll_keystroke(akgl_Keystroke *dest, bool *available);
    ```

    alongside the existing `akgl_controller_poll_key()`, which stays as it is so nothing
    breaks — a game asking "was the up arrow pressed" wants exactly what it already gets.
    Filling `text` means handling `SDL_EVENT_TEXT_INPUT` as well as `SDL_EVENT_KEY_DOWN`, which
    is the only correct way to get a character out of SDL anyway: it is what makes a keyboard
    layout, a compose key and a dead key work, none of which a keycode can express.

    Tests would push a shifted key-down plus its text-input event through
    `akgl_controller_handle_event()` and assert both the keycode and the composed character
    come back, mirroring what `tests/controller.c` already does for the plain ring.

## Carried over

1. **Make character-to-sprite state bindings release their references symmetrically.**
   `akgl_character_sprite_add()` increments the sprite refcount for every state-map
   binding, but no corresponding removal API exists. Replacing a state binding
   also leaves the previous sprite's refcount incremented. When
   `akgl_heap_release_character()` drops the character refcount to zero, it clears
   the character registry entry and zeroes the structure without enumerating
   `state_sprites`, decrementing the bound sprites, or destroying the SDL property
   map. Implement binding removal/replacement so each removed binding releases
   exactly one sprite reference. On final character release, enumerate every
   remaining binding (the existing `akgl_character_state_sprites_iterate()` release
   path may be reusable), release each reference, destroy `state_sprites`, and then
   clear the character. Add tests for removal, replacement, duplicate sprite
   bindings across multiple states, and final character release.

   `akgl_character_state_sprites_iterate` is still uncovered and is the natural
   place to start; `tests/actor.c` now covers `akgl_character_sprite_get` and the
   composite-state binding behavior it depends on.