From 748cf44f351fc787395b6db5e825d258eca9ea7f Mon Sep 17 00:00:00 2001
From: byuu <2107894+byuu@users.noreply.github.com>
Date: Thu, 19 Dec 2019 22:04:14 +0900
Subject: [PATCH] Added run-ahead support to libretro target [realnc] Fixed
 typo in the GUI regarding HD mode 7 +/- hotkeys

---
 bsnes/target-bsnes/input/hotkeys.cpp |  4 +--
 bsnes/target-libretro/libretro.cpp   | 37 +++++++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/bsnes/target-bsnes/input/hotkeys.cpp b/bsnes/target-bsnes/input/hotkeys.cpp
index 0913c59e..70774910 100644
--- a/bsnes/target-bsnes/input/hotkeys.cpp
+++ b/bsnes/target-bsnes/input/hotkeys.cpp
@@ -130,14 +130,14 @@ auto InputManager::bindHotkeys() -> void {
     program.frameAdvanceLock = false;
   }));
 
-  hotkeys.append(InputHotkey("Increase HD Mode 7").onPress([] {
+  hotkeys.append(InputHotkey("Decrease HD Mode 7").onPress([] {
     int index = enhancementSettings.mode7Scale.selected().offset() - 1;
     if(index < 0) return;
     enhancementSettings.mode7Scale.item(index).setSelected();
     enhancementSettings.mode7Scale.doChange();
   }));
 
-  hotkeys.append(InputHotkey("Decrease HD Mode 7").onPress([] {
+  hotkeys.append(InputHotkey("Increase HD Mode 7").onPress([] {
     int index = enhancementSettings.mode7Scale.selected().offset() + 1;
     if(index >= enhancementSettings.mode7Scale.itemCount()) return;
     enhancementSettings.mode7Scale.item(index).setSelected();
diff --git a/bsnes/target-libretro/libretro.cpp b/bsnes/target-libretro/libretro.cpp
index 11e45338..11bd97d9 100644
--- a/bsnes/target-libretro/libretro.cpp
+++ b/bsnes/target-libretro/libretro.cpp
@@ -1,3 +1,4 @@
+#include <cassert>
 #include "libretro.h"
 
 static retro_environment_t environ_cb;
@@ -14,6 +15,8 @@ static int16_t audio_buffer[AUDIOBUFSIZE];
 static uint16_t audio_buffer_index = 0;
 static uint16_t audio_buffer_max = AUDIOBUFSIZE;
 
+static int run_ahead_frames = 0;
+
 static void audio_queue(int16_t left, int16_t right)
 {
 	audio_buffer[audio_buffer_index++] = left;
@@ -231,6 +234,15 @@ static void flush_variables()
 	{
 		sgb_bios = variable.value;
 	}
+
+	variable = { "bsnes_run_ahead_frames", nullptr };
+	if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &variable) && variable.value)
+	{
+		if (strcmp(variable.value, "OFF") == 0)
+			run_ahead_frames = 0;
+		else
+			run_ahead_frames = atoi(variable.value);
+	}
 }
 
 static void check_variables()
@@ -409,6 +421,7 @@ static void set_environment_info(retro_environment_t cb)
 		{ "bsnes_coprocessor_delayed_sync", "Coprocessor Delayed Sync; ON|OFF" },
 		{ "bsnes_coprocessor_prefer_hle", "Coprocessor Prefer HLE; ON|OFF" },
 		{ "bsnes_sgb_bios", "Preferred Super GameBoy BIOS (restart); SGB1.sfc|SGB2.sfc" },
+		{ "bsnes_run_ahead_frames", "Amount of frames for run-ahead; OFF|1|2|3|4" },
 		{ nullptr },
 	};
 	cb(RETRO_ENVIRONMENT_SET_VARIABLES, const_cast<retro_variable *>(vars));
@@ -502,11 +515,33 @@ RETRO_API void retro_reset()
 	emulator->reset();
 }
 
+static void run_with_runahead(const int frames)
+{
+	assert(frames > 0);
+
+	emulator->setRunAhead(true);
+	emulator->run();
+	auto state = emulator->serialize(0);
+	for (int i = 0; i < frames - 1; ++i) {
+		emulator->run();
+	}
+	emulator->setRunAhead(false);
+	emulator->run();
+	state.setMode(serializer::Mode::Load);
+	emulator->unserialize(state);
+}
+
 RETRO_API void retro_run()
 {
 	check_variables();
 	input_poll();
-	emulator->run();
+
+	bool is_fast_forwarding = false;
+	environ_cb(RETRO_ENVIRONMENT_GET_FASTFORWARDING, &is_fast_forwarding);
+	if (is_fast_forwarding || run_ahead_frames == 0)
+		emulator->run();
+	else
+		run_with_runahead(run_ahead_frames);
 }
 
 RETRO_API size_t retro_serialize_size()