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/cpuexec.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'source/cpuexec.cpp')

diff --git a/source/cpuexec.cpp b/source/cpuexec.cpp
index 21b1574..5fb79e5 100644
--- a/source/cpuexec.cpp
+++ b/source/cpuexec.cpp
@@ -105,6 +105,10 @@
 #include "sa1.h"
 #include "spc7110.h"
 
+#ifdef SYNC_JOYPAD_AT_HBLANK
+#include "display.h"
+#endif
+
 extern void S9xProcessSound (unsigned int);
 
 void S9xMainLoop (void)
@@ -226,6 +230,16 @@ void S9xDoHBlankProcessing ()
     switch (CPU.WhichEvent)
     {
 		case HBLANK_START_EVENT:
+#ifdef SYNC_JOYPAD_AT_HBLANK
+		// Re-get the controls every hblank. A resolution algorithm in
+		// ppu.cpp will determine with greater accuracy whether a key was
+		// pressed or released during the frame.
+		uint32 i;
+   		for (i = 0; i < 5; i++)
+   		{
+	        IPPU.JoypadsAtHBlanks [i][CPU.V_Counter] = S9xReadJoypad (i);
+    	}
+#endif
 		if (IPPU.HDMA && CPU.V_Counter <= PPU.ScreenHeight)
 			IPPU.HDMA = S9xDoHDMA (IPPU.HDMA);
 
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