bugfix: keyboard led synchronization now compares against LEDs bitmask,

and only updates then, just like a real BIOS. this fixes LED flickering
when running code that directly communicates with the controller.

src/hardware/keyboard.cpp

@@ -302,18 +302,6 @@ void KEYBOARD_SetLEDs(Bit8u bits) {
 	LOG(LOG_KEYBOARD,LOG_DEBUG)("Keyboard LEDs: SCR=%u NUM=%u CAPS=%u",bits&1,(bits>>1)&1,(bits>>2)&1);
 }
 
-// believe it or not most BIOSes will also periodically check the BIOS data area
-// and send updated keyboard LED state from it if it changes, from within IRQ 0 (INT 8h).
-// This is not documented anywhere I know, but it's been my experience with DOS
-// programming and Windows 3.1/9x keyboard handling seems to rely on it.
-void KEYBOARD_BIOS_CheckLEDs_From_DataArea(Bitu bits) {
-	if ((bits & 7) != (keyb.led_state & 7)) {
-		keyb.led_state = bits;
-		UpdateKeyboardLEDState(bits);
-		LOG(LOG_KEYBOARD, LOG_DEBUG)("Keyboard LEDs (from BIOS data area update): SCR=%u NUM=%u CAPS=%u", bits & 1, (bits >> 1) & 1, (bits >> 2) & 1);
-	}
-}
-
 static Bitu read_p60(Bitu port,Bitu iolen) {
 	keyb.p60changed=false;
 	keyb.auxchanged=false;

src/ints/bios.cpp

@@ -1894,7 +1894,16 @@ static void BIOS_HostTimeSync() {
 // TODO: make option
 bool enable_bios_timer_synchronize_keyboard_leds = true;
 
-void KEYBOARD_BIOS_CheckLEDs_From_DataArea(Bitu x);
+void KEYBOARD_SetLEDs(Bit8u bits);
+
+void BIOS_KEYBOARD_SetLEDs(Bitu state) {
+	Bitu x = mem_readb(BIOS_KEYBOARD_LEDS);
+
+	x &= ~7;
+	x |= (state & 7);
+	mem_writeb(BIOS_KEYBOARD_LEDS,x);
+	KEYBOARD_SetLEDs(state);
+}
 
 static Bitu INT8_Handler(void) {
 	/* Increase the bios tick counter */
@@ -1913,8 +1922,13 @@ static Bitu INT8_Handler(void) {
 	   it when handling the keyboard from it's own driver. Their driver does
 	   hook the keyboard and handles keyboard I/O by itself, but it still
 	   allows the BIOS to do the keyboard magic from IRQ 0 (INT 8h). Yech. */
-	if (enable_bios_timer_synchronize_keyboard_leds)
+	if (enable_bios_timer_synchronize_keyboard_leds) {
-		KEYBOARD_BIOS_CheckLEDs_From_DataArea((mem_readb(BIOS_KEYBOARD_STATE) >> 4) & 7);
+		Bitu should_be = (mem_readb(BIOS_KEYBOARD_STATE) >> 4) & 7;
+		Bitu led_state = (mem_readb(BIOS_KEYBOARD_LEDS) & 7);
+
+		if (should_be != led_state)
+			BIOS_KEYBOARD_SetLEDs(should_be);
+	}
 
 #if DOSBOX_CLOCKSYNC
 	static bool check = false;