Fixups for frame time callback.

audio/thread_wrapper.c

@@ -81,6 +81,7 @@ static void audio_thread_free(void *data)
 {
    audio_thread_t *thr = (audio_thread_t*)data;
    slock_lock(thr->lock);
+   thr->stopped = false;
    thr->alive = false;
    scond_signal(thr->cond);
    slock_unlock(thr->lock);

dynamic.c

@@ -737,12 +737,14 @@ static bool environment_cb(unsigned cmd, void *data)
 #endif
 
       case RETRO_ENVIRONMENT_SET_FRAME_TIME_CALLBACK:
+      {
          RARCH_LOG("Environ SET_FRAME_TIME_CALLBACK.\n");
          if (g_extern.netplay_enable) // retro_run() will be called in very strange and mysterious ways, have to disable it.
             return false;
          const struct retro_frame_time_callback *info = (const struct retro_frame_time_callback*)data;
-         g_extern.system.frame_time_callback = info->callback;
+         g_extern.system.frame_time = *info;
          break;
+      }
 
       default:
          RARCH_LOG("Environ UNSUPPORTED (#%u).\n", cmd);

general.h

@@ -388,12 +388,12 @@ struct global
       retro_keyboard_event_t key_event;
       retro_audio_callback_t audio_callback;
 
-      retro_usec_t frame_time_last;
-      retro_frame_time_callback_t frame_time_callback;
-
       struct retro_disk_control_callback disk_control; 
       struct retro_hw_render_callback hw_render_callback;
 
+      struct retro_frame_time_callback frame_time;
+      retro_usec_t frame_time_last;
+
       core_option_manager_t *core_options;
    } system;
 

libretro.h

@@ -508,7 +508,7 @@ enum retro_mod
                                            // const struct retro_frame_time_callback * --
                                            // Lets the core know how much time has passed since last invocation of retro_run().
                                            // The frontend can tamper with the timing to fake fast-forward, slow-motion, frame stepping, etc.
-                                           // In this case the delta time will use the FPS value reported in get_av_info().
+                                           // In this case the delta time will use the reference value in frame_time_callback..
                                           
 
 // Notifies libretro that audio data should be written.
@@ -521,12 +521,13 @@ struct retro_audio_callback
 // Notifies a libretro core of time spent since last invocation of retro_run() in microseconds.
 // It will be called right before retro_run() every frame.
 // The frontend can tamper with timing to support cases like fast-forward, slow-motion and framestepping.
-// In those scenarios the FPS value in av_info will be used to fake the frame time.
+// In those scenarios the reference frame time value will be used.
 typedef int64_t retro_usec_t;
 typedef void (*retro_frame_time_callback_t)(retro_usec_t usec);
 struct retro_frame_time_callback
 {
    retro_frame_time_callback_t callback;
+   retro_usec_t reference; // Represents the time of one frame. It is computed as 1000000 / fps, but the implementation will resolve the rounding to ensure that framestepping, etc is exact.
 };
 
 // Pass this to retro_video_refresh_t if rendering to hardware.

retroarch.c

@@ -2975,6 +2975,7 @@ static inline bool check_enter_rgui(void)
    {
       g_extern.lifecycle_mode_state |= (1ULL << MODE_MENU);
       old_rmenu_toggle = true;
+      g_extern.system.frame_time_last = 0;
       return true;
    }
    else
@@ -2986,22 +2987,21 @@ static inline bool check_enter_rgui(void)
 
 static inline void update_frame_time(void)
 {
-   if (!g_extern.system.frame_time_callback)
+   if (!g_extern.system.frame_time.callback)
       return;
 
    rarch_time_t time = rarch_get_time_usec();
    rarch_time_t delta = 0;
+
+   bool is_locked_fps = g_extern.is_paused || driver.nonblock_state || g_extern.recording;
    
-   if (!g_extern.system.frame_time_last || g_extern.is_paused || driver.nonblock_state || g_extern.recording)
-   {
-      rarch_time_t reference_delta = (rarch_time_t)roundf(1000000LL / g_extern.system.av_info.timing.fps);
-      delta = reference_delta;
-   }
+   if (!g_extern.system.frame_time_last || is_locked_fps)
+      delta = g_extern.system.frame_time.reference;
    else
       delta = time - g_extern.system.frame_time_last;
 
-   g_extern.system.frame_time_last = time;
-   g_extern.system.frame_time_callback(delta);
+   g_extern.system.frame_time_last = is_locked_fps ? 0 : time;
+   g_extern.system.frame_time.callback(delta);
 }
 
 bool rarch_main_iterate(void)