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.
---
 Makefile              |  2 +-
 source/cpuexec.cpp    | 14 ++++++++++++++
 source/nds/ds2_main.c | 52 +++++++++++++++++++++++++--------------------------
 source/nds/entry.cpp  | 10 ++++++----
 source/nds/gui.c      |  1 +
 source/ppu.cpp        | 35 +++++++++++++++++++++++++++++++++-
 source/ppu.h          |  3 +++
 7 files changed, 84 insertions(+), 33 deletions(-)

diff --git a/Makefile b/Makefile
index 255cf39..605d727 100644
--- a/Makefile
+++ b/Makefile
@@ -71,7 +71,7 @@ CFLAGS := -mips32 -Os -mno-abicalls -fno-pic -fno-builtin \
 DEFS   := -DSPC700_C -DEXECUTE_SUPERFX_PER_LINE -DSDD1_DECOMP \
           -DVAR_CYCLES -DCPU_SHUTDOWN -DSPC700_SHUTDOWN \
           -DNO_INLINE_SET_GET -DNOASM -DHAVE_MKSTEMP '-DACCEPT_SIZE_T=size_t' \
-          -DUNZIP_SUPPORT -DNO_OPEN_BUS
+          -DUNZIP_SUPPORT -DNO_OPEN_BUS -DSYNC_JOYPAD_AT_HBLANK
 
 .PHONY: clean makedirs
 .SUFFIXES: .elf .dat .plg
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);
 
diff --git a/source/nds/ds2_main.c b/source/nds/ds2_main.c
index 710215b..2d73313 100644
--- a/source/nds/ds2_main.c
+++ b/source/nds/ds2_main.c
@@ -15,19 +15,19 @@
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
- */
-
-#include <stdio.h>
-#include "console.h"
-#include "fs_api.h"
+ */
+
+#include <stdio.h>
+#include "console.h"
+#include "fs_api.h"
 #include "ds2io.h"
 #include "ds2_timer.h"
 #include "ds2_malloc.h"
-
-#define BLACK_COLOR		RGB15(0, 0, 0)
-#define WHITE_COLOR		RGB15(31, 31, 31)
-
-extern int sfc_main (int argc, char **argv);
+
+#define BLACK_COLOR		RGB15(0, 0, 0)
+#define WHITE_COLOR		RGB15(31, 31, 31)
+
+extern int sfc_main (int argc, char **argv);
 
 #if 0
 void ddump_mem(unsigned char* addr, unsigned int len)
@@ -42,24 +42,22 @@ void ddump_mem(unsigned char* addr, unsigned int len)
 }
 #endif
 
+void ds2_main(void)
+{
+	int err;
+ds2_setCPUclocklevel(13);
+	//Initial video and audio and other input and output
+	err = ds2io_initb(512, 22050, 0, 0);
+	if(err) goto _failure;
 
-
-void ds2_main(void)
-{
-	int err;
-ds2_setCPUclocklevel(13);
-	//Initial video and audio and other input and output
-	err = ds2io_initb(512, 22050, 0, 0);
-	if(err) goto _failure;
+	//Initial file system
+	err = fat_init();
+	if(err) goto _failure;
 
-	//Initial file system
-	err = fat_init();
-	if(err) goto _failure;
+	//go to user main funtion
+	sfc_main (0, 0);
 
-	//go to user main funtion
-	sfc_main (0, 0);
-
 _failure:
-	ds2_plug_exit();
-}
-
+	ds2_plug_exit();
+}
+
diff --git a/source/nds/entry.cpp b/source/nds/entry.cpp
index 24c0e03..467461b 100644
--- a/source/nds/entry.cpp
+++ b/source/nds/entry.cpp
@@ -90,6 +90,7 @@ void S9xParseDisplayArg (char **argv, int &ind, int)
 
 void S9xExit ()
 {
+  ds2_setCPUclocklevel(13); // Crank it up to exit quickly
   if(Settings.SPC7110)
     (*CleanUp7110)();
 
@@ -382,15 +383,15 @@ void init_sfc_setting(void)
     Settings.SixteenBit = TRUE;
 
     Settings.SupportHiRes = FALSE;
-    Settings.NetPlay = FALSE;
-    Settings.ServerName [0] = 0;
     Settings.ThreadSound = FALSE;
 	Settings.SoundSync = TRUE;
     Settings.AutoSaveDelay = 0;
 #ifdef _NETPLAY_SUPPORT
+    Settings.NetPlay = FALSE;
+    Settings.ServerName [0] = 0;
     Settings.Port = NP_DEFAULT_PORT;
 #endif
-    Settings.ApplyCheats =FALSE;
+    Settings.ApplyCheats = FALSE;
     Settings.TurboMode = FALSE;
     Settings.TurboSkipFrames = 40;
     Settings.StretchScreenshots = 1;
@@ -1009,7 +1010,8 @@ unsigned int S9xReadJoypad (int which1)
 			key |= (inputdata.key & (1<<i)) ? keymap[i] : 0;
 		}
 
-		return (key | 0x80000000);
+		// return (key | 0x80000000);
+		return key; // ??? [Neb]
 	}
 	else
 		return 0;
diff --git a/source/nds/gui.c b/source/nds/gui.c
index bf85b67..4a04efc 100644
--- a/source/nds/gui.c
+++ b/source/nds/gui.c
@@ -1714,6 +1714,7 @@ u32 menu(u16 *screen)
 
 	void menu_exit()
 	{
+		ds2_setCPUclocklevel(13); // Crank it up, leave quickly
         if(gamepak_name[0] != 0)
         {
 			game_config.clock_speed_number = clock_speed_number;
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();
 
diff --git a/source/ppu.h b/source/ppu.h
index 6daf473..065ad5f 100644
--- a/source/ppu.h
+++ b/source/ppu.h
@@ -151,6 +151,9 @@ struct InternalPPU {
     int	   CurrentLine;
     int	   Controller;
     uint32 Joypads[5];
+#ifdef SYNC_JOYPAD_AT_HBLANK
+	uint32 JoypadsAtHBlanks[5][SNES_MAX_PAL_VCOUNTER];
+#endif
     uint32 SuperScope;
     uint32 Mouse[2];
     int    PrevMouseX[2];
-- 
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