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#include <simloop.h>
#include <assert.h>
static uint64_t ddt_from_fps(int fps) {
static constexpr double NANOSECONDS = 1e9;
return (fps == 0) ? 0 : (uint64_t)(NANOSECONDS / (double)fps);
}
Simloop simloop_make(const SimloopArgs* args) {
assert(args);
assert(args->update_fps > 0);
return (Simloop){
.frame = 0,
.update = (SimloopTimeline){.ddt = ddt_from_fps(args->update_fps),
.last_step = args->timer->start_time},
.render = (SimloopTimeline){ .ddt = ddt_from_fps(args->max_render_fps),
.last_step = args->timer->start_time},
.timer = args->timer,
};
}
static time_delta time_elapsed(const Simloop* sim, time_point t) {
assert(sim);
return time_diff(sim->timer->start_time, t);
}
static int step_update(const Simloop* sim, SimloopTimeline* timeline) {
assert(sim);
assert(timeline);
assert(timeline->ddt > 0);
const time_delta dt = time_diff(timeline->last_step, sim->timer->last_tick);
const time_delta steps = dt / timeline->ddt;
timeline->last_step = time_add(timeline->last_step, dt);
return (int)steps;
}
static bool step_render(const Simloop* sim, SimloopTimeline* timeline) {
assert(sim);
assert(timeline);
bool render = false;
if (timeline->ddt > 0) {
render = step_update(sim, timeline) > 0;
} else {
timeline->last_step = sim->timer->last_tick;
render = true;
}
return render;
}
void simloop_update(Simloop* sim, SimloopOut* out) {
assert(sim);
assert(out);
const int new_frames = step_update(sim, &sim->update);
out->updates_pending = new_frames;
out->should_render =
step_render(sim, &sim->render) ||
(sim->frame == 0); // Trigger an initial render on the first frame.
sim->frame += new_frames;
out->frame = sim->frame;
out->render_elapsed = time_elapsed(sim, sim->render.last_step);
out->update_elapsed = time_elapsed(sim, sim->update.last_step);
out->update_dt = sim->update.ddt;
}
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