[libretro] Reverting back to the use of clock()

.github/workflows/build.yml

@@ -403,7 +403,7 @@ jobs:
       - name: Build
         run: |
           cd build
-          cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_STATIC=ON -DBUILD_SDLGPU=On -DBUILD_WITH_ALL=ON ..
+          cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_STATIC=ON -DBUILD_SDLGPU=On -DBUILD_WITH_ALL=ON -DCMAKE_POLICY_VERSION_MINIMUM=3.5 ..
           cmake --build . --parallel
 
       - name: Deploy

src/system/libretro/tic80_libretro.c

@@ -77,7 +77,7 @@ struct tic80_state
 	int mouseHideTimer;
 	int mouseHideTimerStart;
 	tic80* tic;
-	retro_usec_t frameTime;
+	retro_perf_get_time_usec_t get_time_usec; // Function pointer for the high-res timer
 };
 static struct tic80_state* state = NULL;
 
@@ -90,7 +90,9 @@ static u64 tic80_libretro_counter()
 		return 0;
 	}
 
-	return (u64)state->frameTime;
+    // return the elapsed microseconds since the game started
+	// adjusted by fast-forward or slow motion.
+	return state->get_time_usec();
 }
 
 /**
@@ -155,17 +157,6 @@ void tic80_libretro_fallback_log(enum retro_log_level level, const char *fmt, ..
 	va_end(va);
 }
 
-/**
- * libretro callback; Called to indicate how much time has passed since last retro_run().
- */
-void tic80_libretro_frame_time(retro_usec_t usec) {
-	if (state == NULL) {
-		return;
-	}
-
-	state->frameTime += usec;
-}
-
 /**
  * libretro callback; Global initialization.
  */
@@ -1116,16 +1107,6 @@ RETRO_API bool retro_load_game(const struct retro_game_info *info)
 		return false;
 	}
 
-	// Set up the frame time callback.
-	struct retro_frame_time_callback frame_time = {
-		.callback = tic80_libretro_frame_time,
-		.reference = TIC80_FREQUENCY / TIC80_FRAMERATE,
-	};
-	if (!environ_cb(RETRO_ENVIRONMENT_SET_FRAME_TIME_CALLBACK, &frame_time)) {
-		log_cb(RETRO_LOG_ERROR, "[TIC-80] Failed to set frame time callback.\n");
-		return false;
-	}
-
 	// Set up the TIC-80 environment.
 #if RETRO_IS_BIG_ENDIAN
 	state->tic = tic80_create(TIC80_SAMPLERATE, TIC80_PIXEL_COLOR_ARGB8888);
@@ -1156,6 +1137,22 @@ RETRO_API bool retro_load_game(const struct retro_game_info *info)
 		return false;
 	}
 
+	// --- TIMING INITIALIZATION --- Start
+
+	// Performance callback struct
+    struct retro_perf_callback perf_cb = {0};
+    state->get_time_usec = NULL;
+
+    // Request the performance interface from the frontend
+	if (!(environ_cb(RETRO_ENVIRONMENT_GET_PERF_INTERFACE, &perf_cb) && perf_cb.get_time_usec)) {
+		log_cb(RETRO_LOG_ERROR, "[TIC-80] Failed to get high-resolution timer.\n");
+		return false;
+	}
+
+	state->get_time_usec = perf_cb.get_time_usec;
+
+	// --- TIMING INITIALIZATION --- End
+
 	// Set up the input descriptors.
 	tic80_libretro_input_descriptors();