Andrew Kesterson
9924d74dcc
Closes internal-consistency items 1 through 6, 12 and 13. Every include guard is _AKGL_<FILE>_H_, every in-project header include is angled, and every exported function, type and global carries the akgl_ prefix. This is an ABI break; the soname goes to libakgl.so.0.5. TODO.md carries the full rename table. The renames were driven by renaming each declaration and letting the compiler find the uses, not by pattern substitution: renderer, physics and camera are also parameter and struct-member names, and a sed would have rewritten map->physics and every akgl_RenderBackend *renderer parameter without a word. Item 4 turned out not to be cosmetic. The library exported a global called renderer and tests/character.c defined an SDL_Renderer *renderer of its own; the executable's definition preempted the library's, akgl_sprite_load_json read a SDL_Renderer * through an akgl_RenderBackend *, and every texture load in that suite failed. The suite reported success anyway, because libakerror's unhandled-error handler ends in exit(errctx->status), exit keeps only the low byte, and AKGL_ERR_SDL is exactly 256. So character had been green while running one of its four tests, and every suite in the tree was unable to fail on the most common status in a library built on SDL. Both are fixed. tests/testutil.h gains TEST_TRAP_UNHANDLED_ERRORS(), which collapses any status a byte cannot carry onto 1, and every suite installs it. character binds a real backend with akgl_render_2d_bind. Its fourth test then runs for the first time and fails on a defect it has asserted all along, so akgl_heap_release_character now walks state_sprites with AKGL_ITERATOR_OP_RELEASE and destroys the property set before zeroing the slot -- TODO.md Defects item 21 and half of Carried over item 1. AKGL_TIME_ONESEC_MS said "one second in milliseconds" and held 1000000, so akgl_game_state_lock waited roughly sixteen minutes rather than one second. It is AKGL_TIME_ONEMS_NS now, the budget is its own named constant, and tests/game.c holds the mutex from a second thread to assert the wait -- the contended path had no coverage at all. Headers are self-contained and it is enforced: AKGL_PUBLIC_HEADERS drives both install() and a generated translation unit per header, so a header that ships is a header that is checked. Writing that found registry.h, which used SDL_PropertiesID in eight declarations and included no SDL header. 23/23 suites pass, memcheck is clean, reindent --check is clean. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
239 lines
13 KiB
C
239 lines
13 KiB
C
/**
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* @file physics.h
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* @brief The pluggable physics backend, and the two implementations that ship.
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*
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* Same shape as the renderer: a record of function pointers plus an initializer
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* that fills it in. `null` accepts every call and changes nothing, which is what
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* a menu screen or a test harness wants; `arcade` applies gravity, drag, thrust
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* and a speed cap. Selecting between them is akgl_physics_factory, driven by the
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* `physics.engine` configuration property -- not a branch in the simulation.
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*
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* The model an actor is simulated under, and the fields on akgl_Actor that carry
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* it:
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*
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* | Term | Fields | Comes from |
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* |-----------------------|--------------|-----------------------------------------------|
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* | thrust | `tx, ty, tz` | the actor's own acceleration while it is moving |
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* | environmental | `ex, ey, ez` | gravity, less drag |
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* | velocity | `vx, vy, vz` | thrust + environmental |
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* | max speed | `sx, sy, sz` | the character; caps thrust, not velocity |
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* | acceleration | `ax, ay, az` | the character |
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*
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* Each step: movement logic, then gravity, then drag, then velocity, then move.
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* Because the cap is applied to thrust rather than to velocity, gravity can
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* carry an actor faster than its stated top speed -- which is the point, for a
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* falling one.
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*/
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#ifndef _AKGL_PHYSICS_H_
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#define _AKGL_PHYSICS_H_
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#include <SDL3/SDL.h>
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#include <akerror.h>
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#include <akgl/actor.h>
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#include <akgl/iterator.h>
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#include <akgl/staticstring.h>
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/** @brief Defines a pluggable physics backend and its environmental parameters. */
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typedef struct akgl_PhysicsBackend {
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akerr_ErrorContext AKERR_NOIGNORE *(*simulate)(struct akgl_PhysicsBackend *self, akgl_Iterator *opflags); /**< Step the whole world. Both backends point this at akgl_physics_simulate. */
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akerr_ErrorContext AKERR_NOIGNORE *(*gravity)(struct akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt); /**< Apply environmental acceleration to one actor. */
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akerr_ErrorContext AKERR_NOIGNORE *(*collide)(struct akgl_PhysicsBackend *self, akgl_Actor *a1, akgl_Actor *a2); /**< Resolve a collision between two actors. Not called by the simulation loop yet. */
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akerr_ErrorContext AKERR_NOIGNORE *(*move)(struct akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt); /**< Commit one actor's velocity to its position. */
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double drag_x; /**< Fraction of environmental velocity shed per second along x. 0 disables. From `physics.drag.x`. */
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double drag_y; /**< Drag along y. From `physics.drag.y`. */
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double drag_z; /**< Drag along z. From `physics.drag.z`. */
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double gravity_x; /**< Acceleration along x, world units per second squared. Applied toward screen left. From `physics.gravity.x`. */
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double gravity_y; /**< Acceleration along y. Applied down the screen, since y grows downward. From `physics.gravity.y`. */
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double gravity_z; /**< Acceleration along z. Applied away from the camera. From `physics.gravity.z`. */
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SDL_Time gravity_time; /**< Timestamp of the previous step, in nanoseconds. The simulation's `dt` is measured from this. */
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SDL_Time timer_gravity; /**< Unused. Nothing in the library reads or writes it. */
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} akgl_PhysicsBackend;
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/**
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* @brief Gravity for the null backend: accept the call and change nothing.
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* @param self The backend. Required -- the one thing this does check.
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* @param actor The actor that would have been accelerated. Ignored; `NULL` is
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* accepted.
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* @param dt Seconds since the previous step. Ignored.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_null_gravity(akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt);
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/**
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* @brief Collision for the null backend: accept the call and change nothing.
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*
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* Note that this *succeeds* where the arcade backend's collide refuses -- the
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* null backend's contract is "nothing collides", which is an answer, not a gap.
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*
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* @param self The backend. Required.
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* @param a1 First actor. Ignored; `NULL` is accepted.
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* @param a2 Second actor. Ignored; `NULL` is accepted.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_null_collide(akgl_PhysicsBackend *self, akgl_Actor *a1, akgl_Actor *a2);
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/**
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* @brief Movement for the null backend: accept the call and change nothing.
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*
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* Actors under the null backend do not move on their own. Anything that sets an
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* actor's `x`/`y` directly still works -- this only declines to integrate
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* velocity.
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*
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* @param self The backend. Required.
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* @param actor The actor that would have moved. Ignored; `NULL` is accepted.
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* @param dt Seconds since the previous step. Ignored.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_null_move(akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt);
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/**
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* @brief Install the null backend's methods.
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*
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* Reads no configuration and touches no gravity or drag fields, so whatever was
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* in them stays -- harmlessly, since none of the null methods look.
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*
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* @param self The backend to initialize. Required.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_init_null(akgl_PhysicsBackend *self);
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/**
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* @brief Accelerate one actor's environmental velocity by gravity.
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*
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* Adds `gravity * dt` to the actor's `ex`/`ey`/`ez` on each axis whose gravity
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* is non-zero, with the sign chosen for screen space: x pulls left, y pulls
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* down, z pulls away from the camera. It touches only the environmental term, so
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* an actor's own thrust is unaffected and the speed cap does not apply -- which
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* is why a falling actor keeps accelerating past its character's top speed.
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*
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* @param self The backend supplying the gravity constants. Required.
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* @param actor The actor to accelerate. Required.
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* @param dt Seconds since the previous step. A `dt` of 0 is a no-op; a
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* negative one accelerates backwards.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self or @p actor is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_arcade_gravity(akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt);
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/**
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* @brief Collision for the arcade backend. Not implemented.
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*
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* Deliberately loud rather than silently permissive: unlike
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* akgl_physics_null_collide, which means "nothing collides", this means "nobody
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* has written this yet", and a caller that reaches it should find out.
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*
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* @param self The backend. Required, and checked before the refusal.
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* @param a1 First actor. Never examined.
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* @param a2 Second actor. Never examined.
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* @return Never `NULL`.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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* @throws AKERR_API Otherwise, always, with the message "Not implemented".
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_arcade_collide(akgl_PhysicsBackend *self, akgl_Actor *a1, akgl_Actor *a2);
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/**
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* @brief Commit an actor's velocity to its position.
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*
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* The last step of a simulation tick: `position += velocity * dt` on all three
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* axes. It does not clamp to the map, consult the tilemap, or test for
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* collisions -- an actor will walk straight through a wall and off the edge of
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* the world.
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*
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* @param self The backend. Required, though nothing on it is read.
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* @param actor The actor to move. Required. Its `vx`/`vy`/`vz` must already have
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* been computed; akgl_physics_simulate does that immediately
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* before calling this.
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* @param dt Seconds since the previous step.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self or @p actor is `NULL`.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_arcade_move(akgl_PhysicsBackend *self, akgl_Actor *actor, float32_t dt);
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/**
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* @brief Install the arcade backend's methods and read its constants from configuration.
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*
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* Reads `physics.gravity.x`, `.y`, `.z` and `physics.drag.x`, `.y`, `.z` from
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* the property registry, all defaulting to `"0.0"` -- so an arcade backend with
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* no configuration behaves like the null one until something is set.
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*
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* @param self The backend to initialize. Required. Its method pointers are
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* installed before the properties are read, so a failure part-way
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* leaves a usable backend with some constants still at their
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* previous values.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self is `NULL`.
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* @throws AKERR_VALUE If one of the six properties is set to something that is
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* not a number.
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* @throws ERANGE If one of them does not fit a `double`.
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* @throws AKGL_ERR_HEAP If the string pool is exhausted.
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*
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* @note With #AKGL_REGISTRY_PROPERTIES uninitialized every property reads back
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* as its default, so this silently configures zero gravity and zero drag
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* rather than reporting anything. See the warning in registry.h.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_init_arcade(akgl_PhysicsBackend *self);
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/**
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* @brief Select and initialize a physics backend by name.
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*
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* The dispatch point for the whole subsystem: `"null"` and `"arcade"` are the
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* two names, and akgl_game_init passes whatever the `physics.engine` property
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* holds. Adding a backend means adding a name here, not a branch in the
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* simulation.
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*
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* @param self The backend to initialize. Required.
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* @param type The backend name. Required. Matched on its leading characters, so
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* `"nullify"` selects `null` and `"arcadia"` selects `arcade`.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self or @p type is `NULL`.
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* @throws AKERR_KEY If @p type matches neither name. The message quotes what was
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* asked for.
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* @throws AKERR_* Whatever the selected initializer raises.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_factory(akgl_PhysicsBackend *self, akgl_String *type);
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/**
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* @brief Step every live actor forward by the time elapsed since the previous call.
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*
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* Shared by both backends -- what differs is the `gravity` and `move` they point
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* at. For each live actor, in pool order:
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*
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* - a child actor is snapped to its parent's position plus its own `v` as an
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* offset, and skipped entirely -- children do not simulate;
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* - an actor with no character is skipped, since the speed and acceleration
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* constants live there;
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* - thrust accumulates along an axis the actor is moving on, then is clamped to
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* the character's maximum speed;
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* - the backend's `gravity` runs, drag is applied to the environmental term,
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* velocity becomes environmental plus thrust, and the backend's `move`
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* commits it.
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*
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* `dt` is measured from `self->gravity_time`, which is stamped at the end. The
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* first call after initialization therefore measures from 0 and produces an
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* enormous `dt` -- initialize `gravity_time` from `SDL_GetTicksNS()` before the
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* first step if that matters.
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*
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* @param self The backend. Required, along with its `move` pointer.
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* @param opflags Iterator flags. Optional -- `NULL` means "simulate everything".
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* Only #AKGL_ITERATOR_OP_LAYERMASK is honoured, restricting the
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* step to actors on `layerid`; the update, render, and release
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* bits are ignored here.
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* @return `NULL` on success, otherwise an error context owned by the caller.
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* @throws AKERR_NULLPOINTER If @p self or `self->move` is `NULL`.
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* @throws AKERR_* Whatever an actor's `movementlogicfunc`, or the backend's
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* `gravity` or `move`, raises. The first failure aborts the whole step,
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* leaving the actors already processed advanced and the rest not.
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*
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* @note An actor's `movementlogicfunc` can raise AKGL_ERR_LOGICINTERRUPT to say
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* "skip the rest of the simulation for me this tick". It is handled here
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* and does not propagate -- it is a control signal wearing an error's
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* clothes, not a failure. Only `movementlogicfunc` gets that treatment:
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* the `gravity` and `move` calls return straight out of the loop on any
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* status, LOGICINTERRUPT included, so a backend must not use it to opt an
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* actor out from there.
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*/
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akerr_ErrorContext AKERR_NOIGNORE *akgl_physics_simulate(akgl_PhysicsBackend *self, akgl_Iterator *opflags);
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#endif // _AKGL_PHYSICS_H_
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