Improve loop with fps control

include/app/app.h

@@ -252,26 +252,35 @@ struct App {
     current_scene_id = scene_pool.acquire(loading_scene);
   }
 
-  void loop() {
-    const uint64_t TARGET_NS = 1e9 / 60;
+  void set_fps(float fps) {
+    this->fps = fps;
+    target_frame_time = 1e9 / fps;
+  }
 
-    uint64_t time_a = window.get_time();
-    uint64_t time_b = window.get_time();
+  uint64_t get_fps() const {
+    return fps;
+  }
+
+  void loop() {
+    uint64_t frame_start = window.get_time();
+    uint64_t frame_end = window.get_time();
+    uint64_t previous_frame_end = 0;
 
     while (running) {
-      time_a = window.get_time();
-      uint64_t frame_time = time_a - time_b;
+      frame_start = window.get_time();
+      uint64_t frame_time = frame_start - frame_end;
 
-      if (frame_time <= TARGET_NS) {
+      if (frame_time <= target_frame_time) {
         struct timespec req;
         req.tv_sec = 0;
-        req.tv_nsec = TARGET_NS - frame_time;
+        req.tv_nsec = target_frame_time - frame_time;
         nanosleep(&req, nullptr);
       }
 
-      time_b = window.get_time();
+      previous_frame_end = frame_end;
+      frame_end = window.get_time();
 
-      uint64_t dt = window.delta_time();
+      float dt = frame_end - previous_frame_end;
 
       Scene *scene = scene_pool[current_scene_id];
 
@@ -329,6 +338,10 @@ struct App {
       window.clear();
     }
   }
+
+private:
+  uint64_t fps = 60;
+  uint64_t target_frame_time = 1e9 / fps;
 };
 } // namespace app
 

include/binding/definitions.h

@@ -1487,11 +1487,29 @@ static mrb_value scene_hash(mrb_state *mrb, mrb_value self) {
 
 static mrb_value app_run(mrb_state *mrb, mrb_value) {
   mrb_int width, height;
+  mrb_value options_hash;
   char *title = nullptr;
-  mrb_get_args(mrb, "iiz", &width, &height, &title);
+  mrb_get_args(mrb, "iiz|H", &width, &height, &title, &options_hash);
 
   app_ = new app::App({(float)width, (float)height}, title);
 
+  float fps = 60;
+  if (!mrb_nil_p(options_hash))
+    HASH_FLOAT(options_hash, fps, fps);
+
+  app_->set_fps(fps);
+
+  return mrb_nil_value();
+}
+
+static mrb_value app_fps_get(mrb_state *mrb, mrb_value) {
+  return mrb_float_value(mrb, app_->get_fps());
+}
+
+static mrb_value app_fps_set(mrb_state *mrb, mrb_value) {
+  mrb_float fps;
+  mrb_get_args(mrb, "f", &fps);
+  app_->set_fps(fps);
   return mrb_nil_value();
 }
 
@@ -1750,9 +1768,11 @@ inline void setup() {
   ADD_METHOD(Scene, "elements", scene_elements, MRB_ARGS_NONE());
 
   DEF_MODULE(App);
-  ADD_MODULE_METHOD(App, "run", app_run, MRB_ARGS_REQ(3));
+  ADD_MODULE_METHOD(App, "run", app_run, MRB_ARGS_REQ(3) | MRB_ARGS_OPT(1));
   ADD_MODULE_METHOD(App, "start", app_start, MRB_ARGS_REQ(1));
   ADD_MODULE_METHOD(App, "switch_to", app_switch_to, MRB_ARGS_REQ(1));
+  ADD_MODULE_METHOD(App, "fps=", app_fps_set, MRB_ARGS_REQ(1));
+  ADD_MODULE_METHOD(App, "fps", app_fps_get, MRB_ARGS_NONE());
   ADD_MODULE_METHOD(App, "localize", app_localize, MRB_ARGS_REQ(3));
   ADD_MODULE_METHOD(App, "language=", app_language_set, MRB_ARGS_REQ(1));
   ADD_MODULE_METHOD(App, "language", app_language_get, MRB_ARGS_NONE());

include/window/window.h

@@ -341,8 +341,7 @@ public:
 
   // Time
 
-  uint64_t get_time();   // returns the time in nanoseconds since the window was created
-  uint64_t delta_time(); // returns the time in nanoseconds since the last render call
+  uint64_t get_time(); // returns the time in nanoseconds since the window was created
 
 private:
   // internal data and functions