Added Fast Forward key to speed up emulation when desired

README.md

@@ -30,6 +30,7 @@ You can configure your own keys in the Settings menu, these are the default I fo
 : Turbo B: X^2
 - Save State : X (multiply), which is the alpha 'S' key for save
 - Load State : -> (store), which is the alpha 'L' key for load
+- Fast Forward: ^ (caret), runs CPU at full speed running rendering every 8th frame, about 3x speed
 
 Note that if you set the turbo setting to 30 Hz, this may be too fast for some games causing them to malfunction.
 

src/frontend.cpp

@@ -598,6 +598,7 @@ MenuOption remapOptions[] =
 	{ "P1 Turbo B", "", false, Option_RemapKey, Option_GetKeyDetails, NES_P1_TURBO_B},
 	{ "Save State", "", false, Option_RemapKey, Option_GetKeyDetails, NES_SAVESTATE},
 	{ "Load State", "", false, Option_RemapKey, Option_GetKeyDetails, NES_LOADSTATE},
+	{ "Fast Fwd", "", false, Option_RemapKey, Option_GetKeyDetails, NES_FASTFORWARD},
 	{ "P2 A", "", false, Option_RemapKey, Option_GetKeyDetails, NES_P2_A},
 	{ "P2 B", "", false, Option_RemapKey, Option_GetKeyDetails, NES_P2_B},
 	{ "P2 Select", "", false, Option_RemapKey, Option_GetKeyDetails, NES_P2_SELECT},

src/nes.h

@@ -22,6 +22,7 @@ enum NesKeys {
 	NES_P1_TURBO_B,
 	NES_SAVESTATE,
 	NES_LOADSTATE,
+	NES_FASTFORWARD,
 	NES_P2_A,
 	NES_P2_B,
 	NES_P2_SELECT,

src/nes_input.cpp

@@ -45,6 +45,10 @@ inline unsigned char readButton(int buttonNo) {
 	return isDown[buttonNo];
 }
 
+bool EmulatorSettings::CheckCachedKey(NesKeys key) {
+	return isDown[(int)key];
+}
+
 void input_writeStrobe(unsigned char value) {
 	value &= 1;
 

src/nes_ppu.cpp

@@ -502,6 +502,10 @@ void nes_ppu::step() {
 				skipFrame = (frameCounter % frameSkipValue) != 0;
 		}
 
+		if (nesSettings.CheckCachedKey(NES_FASTFORWARD)) {
+			skipFrame = (frameCounter & 7) != 0;
+		}
+
 		// clear vblank and sprite 0 flag
 		SetPPUSTATUS(PPUSTATUS & ~(PPUSTAT_NMI | PPUSTAT_SPRITE0));		
 
@@ -607,19 +611,19 @@ void nes_ppu::step() {
 		}
 #endif
 
-		if (keyDown_fast(nesSettings.keyMap[NES_SAVESTATE])) // F3 in simulator, 'S" on device
+		input_cacheKeys();
+
+		if (nesSettings.CheckCachedKey(NES_SAVESTATE)) // F3 in simulator, 'S" on device
 		{
 			nesCart.SaveState();
 			nesCart.BuildFileBlocks();
 		}
 
-		if (keyDown_fast(nesSettings.keyMap[NES_LOADSTATE])) // F4 in simulator, 'L' on device
+		if (nesSettings.CheckCachedKey(NES_LOADSTATE)) // F4 in simulator, 'L' on device
 		{
 			nesCart.LoadState();
 		}
 
-		input_cacheKeys();
-
 	} else if (scanline == 243) {
 		// frame is over, don't run until scanline 262, so add 18 scanlines worth (2047 extra clocks!)
 		if (nesCart.isPAL == 0) {

src/scanline_dma.cpp

@@ -129,7 +129,7 @@ void nes_ppu::resolveScanline(int scrollOffset) {
 
 void nes_ppu::finishFrame(bool bSkippedFrame) {
 	// run frame timing
-	if (nesSettings.GetSetting(ST_Speed) != 4) {
+	if (nesSettings.GetSetting(ST_Speed) != 4 && nesSettings.CheckCachedKey(NES_FASTFORWARD) == false) {
 		// use TMU1 to establish time between frames
 		static unsigned int counterStart = 0x7FFFFFFF;		// max int
 		unsigned int counterRegs = 0x0004;

src/settings.cpp

@@ -152,6 +152,7 @@ void EmulatorSettings::SetDefaults() {
 	keyMap[NES_P1_DOWN] = 37;
 	keyMap[NES_SAVESTATE] = 43;		// 'S'
 	keyMap[NES_LOADSTATE] = 25;		// 'L'
+	keyMap[NES_FASTFORWARD] = 57;	// '^'
 
 	// simulator only defaults
 #if TARGET_WINSIM

src/settings.h

@@ -47,6 +47,7 @@ struct EmulatorSettings {
 	static SettingGroup GetSettingGroup(SettingType setting);
 	static bool GetSettingAvailable(SettingType setting);
 
+	static bool CheckCachedKey(NesKeys key);
 private:
 	uint8 values[MAX_SETTINGS];
 };