debug fps: log number of frames rendered in each second

c_src/scenic/comms.c

@@ -399,6 +399,14 @@ void receive_crash()
 //---------------------------------------------------------
 void render(driver_data_t* p_data)
 {
+  // Setup FPS calc
+  static int64_t start_real = 0;
+  static int64_t time_remaining = -1;
+  static clock_t render_fps = 0;
+  static uint32_t frames = 0;
+
+  clock_t begin_frame = clock();
+
   // prep the id to the root scene
   sid_t id;
   id.p_data = "_root_";
@@ -420,6 +428,27 @@ void render(driver_data_t* p_data)
   }
 
   device_end_render(p_data);
+  clock_t end_frame = clock();
+  clock_t delta_ticks = end_frame - begin_frame;
+
+  if (delta_ticks > 0) {
+    render_fps = CLOCKS_PER_SEC / delta_ticks;
+    // log_debug("render_fps (cpu time): %d", render_fps);
+  }
+
+  frames++;
+
+  int64_t end_real = monotonic_time();
+  int64_t delta_real = (end_real - start_real);
+  start_real = end_real;
+  time_remaining -= delta_real;
+
+  if (time_remaining <= 0) {
+    log_debug("real_fps: %d", frames);
+    start_real = monotonic_time();
+    time_remaining = 1000;
+    frames = 0;
+  }
 
   // all done
   send_ready();