From 089e692bd1f18ef4ea687606903c8bcf9098b4be Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 29 Dec 2015 22:59:36 -0500
Subject: [PATCH] GBA: Allow blocking of opposing directional input

---
 src/gba/gba.c |  1 +
 src/gba/gba.h |  1 +
 src/gba/io.c  | 11 +++++++++++
 3 files changed, 13 insertions(+)

diff --git a/src/gba/gba.c b/src/gba/gba.c
index 3bfdb4eec..30df843a7 100644
--- a/src/gba/gba.c
+++ b/src/gba/gba.c
@@ -101,6 +101,7 @@ static void GBAInit(struct ARMCore* cpu, struct ARMComponent* component) {
 
 	gba->realisticTiming = true;
 	gba->hardCrash = true;
+	gba->allowOpposingDirections = true;
 
 	gba->performingDMA = false;
 
diff --git a/src/gba/gba.h b/src/gba/gba.h
index 961d871ba..846f58492 100644
--- a/src/gba/gba.h
+++ b/src/gba/gba.h
@@ -128,6 +128,7 @@ struct GBA {
 
 	bool realisticTiming;
 	bool hardCrash;
+	bool allowOpposingDirections;
 };
 
 struct GBACartridge {
diff --git a/src/gba/io.c b/src/gba/io.c
index bda2d3562..b56d6e82b 100644
--- a/src/gba/io.c
+++ b/src/gba/io.c
@@ -674,6 +674,17 @@ uint16_t GBAIORead(struct GBA* gba, uint32_t address) {
 			} else if (gba->keySource) {
 				input = *gba->keySource;
 			}
+			if (!gba->allowOpposingDirections) {
+				unsigned rl = input & 0x030;
+				unsigned ud = input & 0x0C0;
+				input &= 0x30F;
+				if (rl != 0x030) {
+					input |= rl;
+				}
+				if (ud != 0x0C0) {
+					input |= ud;
+				}
+			}
 			if (gba->rr && gba->rr->isRecording(gba->rr)) {
 				gba->rr->logInput(gba->rr, input);
 			}