From e5fe20ad83e01b3c8262ac90af984da47d8a16a1 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Sun, 12 Apr 2026 10:48:04 -0700
Subject: Work in terms of time deltas; remove dependency on timer module

---
 simloop/src/simloop.c | 56 +++++++++++++++++++++++++++------------------------
 1 file changed, 30 insertions(+), 26 deletions(-)

(limited to 'simloop/src')

diff --git a/simloop/src/simloop.c b/simloop/src/simloop.c
index 606f5ed..bd5a72d 100644
--- a/simloop/src/simloop.c
+++ b/simloop/src/simloop.c
@@ -2,9 +2,9 @@
 
 #include <assert.h>
 
-static uint64_t ddt_from_fps(int fps) {
+static simloop_time_t ddt_from_fps(int fps) {
   static constexpr double NANOSECONDS = 1e9;
-  return (fps == 0) ? 0 : (uint64_t)(NANOSECONDS / (double)fps);
+  return (fps == 0) ? 0 : (simloop_time_t)(NANOSECONDS / (double)fps);
 }
 
 Simloop simloop_make(const SimloopArgs* args) {
@@ -12,31 +12,30 @@ Simloop simloop_make(const SimloopArgs* 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,
-      .first_iter = true,
+      .frame = 0,
+      .update =
+          (SimloopTimeline){
+                            .ddt  = ddt_from_fps(args->update_fps),
+                            .time = 0,
+                            },
+      .render =
+          (SimloopTimeline){
+                            .ddt  = ddt_from_fps(args->max_render_fps),
+                            .time = 0,
+                            },
+      .first_iter                = true,
       .updates_since_last_render = false,
   };
 }
 
-static time_delta time_elapsed(const Simloop* sim, time_point t) {
-  assert(sim);
-  return time_diff(sim->timer->start_time, t);
-}
-
 static bool 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 bool       should_step = dt >= timeline->ddt;
-  timeline->last_step =
-      should_step ? time_add(timeline->last_step, dt) : timeline->last_step;
+  const simloop_time_t dt          = sim->clock - timeline->time;
+  const bool           should_step = dt >= timeline->ddt;
+  timeline->time += should_step ? timeline->ddt : 0;
   return should_step;
 }
 
@@ -48,32 +47,37 @@ static bool step_render(const Simloop* sim, SimloopTimeline* timeline) {
   if (timeline->ddt > 0) {
     render = step_update(sim, timeline);
   } else {
-    timeline->last_step = sim->timer->last_tick;
-    render              = true;
+    timeline->time = sim->clock;
+    render         = true;
   }
   return render;
 }
 
-void simloop_update(Simloop* sim, SimloopOut* out) {
+void simloop_update(Simloop* sim, simloop_time_t dt, SimloopOut* out) {
   assert(sim);
   assert(out);
 
+  sim->clock += dt;
+
   // Simulation update.
   const bool updated             = step_update(sim, &sim->update);
-  out->should_update             = updated;
   sim->updates_since_last_render = sim->updates_since_last_render || updated;
+
   // Simulation render.
   const bool rendered =
       (sim->updates_since_last_render && step_render(sim, &sim->render)) ||
       (sim->first_iter); // Trigger an initial render on the first frame.
-  out->should_render = rendered;
   sim->updates_since_last_render =
       sim->updates_since_last_render && !out->should_render;
+
   // Loop state update.
   sim->frame += (updated ? 1 : 0);
-  sim->first_iter     = false;
+  sim->first_iter = false;
+
   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->render_elapsed = sim->render.time;
+  out->update_elapsed = sim->update.time;
   out->update_dt      = sim->update.ddt;
+  out->should_update  = updated;
+  out->should_render  = rendered;
 }
-- 
cgit v1.2.3