From a0d0c5e7a5bdc396b4c370a750273b6e3b963bb0 Mon Sep 17 00:00:00 2001
From: Nebuleon Fumika
Date: Fri, 21 Dec 2012 03:50:10 -0500
Subject: Eliminate the latency of button press recognition, which was bad
 enough to lose keys entirely sometimes, and could otherwise delay a button
 press or release by 200 ms.

This was the entire reason I created the fork, and I finally did it! It syncs the controls every scanline of a frame, which costs about 60,000 MIPS instructions per frame to deal with. Luckily, the processor runs at 396 MHz, which means the cost of checking the controls is 1% of the CPU's power.
---
 source/ppu.cpp | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

(limited to 'source/ppu.cpp')

diff --git a/source/ppu.cpp b/source/ppu.cpp
index 8ba7a5f..e0c6e24 100644
--- a/source/ppu.cpp
+++ b/source/ppu.cpp
@@ -3202,12 +3202,45 @@ void S9xUpdateJustifiers()
 
 void S9xUpdateJoypads ()
 {
-    int i;
+    uint32 i;
 
+#ifdef SYNC_JOYPAD_AT_HBLANK
+	uint32 j, k, KeyValue;
+	bool8 StartedPressed;
+
+	// For each joypad
+	for (i = 0; i < 5; i++)
+	{
+		IPPU.Joypads [i] = 0;
+		// Sync each key
+		for (k = 1; k != 0x80000000; k <<= 1)
+		{
+			KeyValue = IPPU.JoypadsAtHBlanks[i][0] & k;
+			StartedPressed = KeyValue != 0;
+			// from each line.
+			// If, initially, the key is NOT pressed, one line of it being
+			// pressed means that the key MUST be pressed.
+			// Otherwise, the key MUST be pressed if it doesn't start as such.
+			for (j = 1; j < (Settings.PAL ? SNES_MAX_PAL_VCOUNTER : SNES_MAX_NTSC_VCOUNTER); j++)
+			{
+				if ((StartedPressed) && ((IPPU.JoypadsAtHBlanks[i][j] & k) == 0)) {
+					KeyValue = 0;
+					break;
+				}
+				else if ((!StartedPressed) && ((IPPU.JoypadsAtHBlanks[i][j] & k) != 0)) {
+					KeyValue = k;
+					break;
+				}
+			}
+			IPPU.Joypads [i] |= KeyValue;
+		}
+	}
+#else
 	for (i = 0; i < 5; i++)
 	{
 		IPPU.Joypads [i] = S9xReadJoypad (i);
 	}
+#endif
 
 //	S9xMovieUpdate();
 
-- 
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