From c5286054ec711bdd17424f29adf20c1eca5b0994 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=CE=A3=CF=84=CE=AD=CF=86=CE=B1=CE=BD=CE=BF=CF=82=20=22Coor?=
 =?UTF-8?q?nio/8924th=22=20=CE=92=CE=BB=CE=B1=CF=83=CF=84=CF=8C=CF=82?=
 <8924th@gmail.com>
Date: Sun, 15 Sep 2024 18:48:43 +0300
Subject: [PATCH] Fix mistake in SCHIP_MODERN drawing causing incorrect
 clipping, fix mistake in XOCHIP which would prevent multi-plane sprites from
 rendering correctly when partially clipped and wrapping was disabled.

---
 src/Systems/CHIP8/Cores/SCHIP_MODERN.cpp | 12 +++++++-----
 src/Systems/CHIP8/Cores/XOCHIP.cpp       | 18 +++++++++---------
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/Systems/CHIP8/Cores/SCHIP_MODERN.cpp b/src/Systems/CHIP8/Cores/SCHIP_MODERN.cpp
index 0cceb08..100815a 100644
--- a/src/Systems/CHIP8/Cores/SCHIP_MODERN.cpp
+++ b/src/Systems/CHIP8/Cores/SCHIP_MODERN.cpp
@@ -16,6 +16,8 @@ SCHIP_MODERN::SCHIP_MODERN()
 	: mDisplayBuffer{ {cScreenSizeY, cScreenSizeX} }
 {
 	if (getCoreState() != EmuState::FAILED) {
+		Quirk.shiftVX = true;
+		Quirk.idxRegNoInc = true;
 
 		copyGameToMemory(mMemoryBank.data(), cGameLoadPos);
 		copyFontToMemory(mMemoryBank.data(), 0x0, 0xF0);
@@ -576,7 +578,7 @@ void SCHIP_MODERN::scrollDisplayRT() {
 				{
 					drawByte(pX + 0, tY, readMemoryI(tN + 0));
 					drawByte(pX + 8, tY, readMemoryI(tN + 1));
-					if (!Quirk.wrapSprite && pY == mDisplayHb) { break; }
+					if (!Quirk.wrapSprite && tY == mDisplayHb) { break; }
 					else { tN += 2; ++tY &= mDisplayHb; }
 				}
 				break;
@@ -586,7 +588,7 @@ void SCHIP_MODERN::scrollDisplayRT() {
 				for (auto tN{ 0 }, tY{ pY }; tN < N;)
 				{
 					drawByte(pX, tY, readMemoryI(tN));
-					if (!Quirk.wrapSprite && pY == mDisplayHb) { break; }
+					if (!Quirk.wrapSprite && tY == mDisplayHb) { break; }
 					else { tN += 1; ++tY &= mDisplayHb; }
 				}
 				break;
@@ -627,7 +629,7 @@ void SCHIP_MODERN::scrollDisplayRT() {
 		mSoundTimer = mRegisterV[X] + (mRegisterV[X] == 1);
 	}
 	void SCHIP_MODERN::instruction_Fx1E(const s32 X) noexcept {
-		mRegisterI = mRegisterI + mRegisterV[X] & 0xFFF;
+		mRegisterI = mRegisterI + mRegisterV[X] & 0xFFFF;
 	}
 	void SCHIP_MODERN::instruction_Fx29(const s32 X) noexcept {
 		mRegisterI = (mRegisterV[X] & 0xF) * 5;
@@ -644,13 +646,13 @@ void SCHIP_MODERN::scrollDisplayRT() {
 		for (auto idx{ 0 }; idx <= N; ++idx)
 			{ writeMemoryI(mRegisterV[idx], idx); }
 		if (!Quirk.idxRegNoInc) [[likely]]
-			{ mRegisterI = mRegisterI + N + 1 & 0xFFF; }
+			{ mRegisterI = mRegisterI + N + 1 & 0xFFFF; }
 	}
 	void SCHIP_MODERN::instruction_FN65(const s32 N) noexcept {
 		for (auto idx{ 0 }; idx <= N; ++idx)
 			{ mRegisterV[idx] = readMemoryI(idx); }
 		if (!Quirk.idxRegNoInc) [[likely]]
-			{ mRegisterI = mRegisterI + N + 1 & 0xFFF; }
+			{ mRegisterI = mRegisterI + N + 1 & 0xFFFF; }
 	}
 	void SCHIP_MODERN::instruction_FN75(const s32 N) noexcept {
 		if (setPermaRegs(N + 1)) [[unlikely]]
diff --git a/src/Systems/CHIP8/Cores/XOCHIP.cpp b/src/Systems/CHIP8/Cores/XOCHIP.cpp
index bc5d87e..c3593d6 100644
--- a/src/Systems/CHIP8/Cores/XOCHIP.cpp
+++ b/src/Systems/CHIP8/Cores/XOCHIP.cpp
@@ -683,24 +683,24 @@ void XOCHIP::scrollDisplayRT() {
 			mRegisterV[0xF] = 0;
 
 			if (N == 0) {
-				for (auto P{ 0 }, I{ 0 }; P < 4; ++P) {
+				for (auto P{ 0 }, I{ 0 }; P < 4; ++P, I += 32) {
 					if (!(mPlanarMask & 1 << P)) { continue; }
 
-					for (auto tN{ 0 }, tY{ pY }; tN < 16; ++tN) {
-						drawByte(pX + 0, tY, P, readMemoryI(I + 0));
-						drawByte(pX + 8, tY, P, readMemoryI(I + 1));
+					for (auto tN{ 0 }, tY{ pY }; tN < 32;) {
+						drawByte(pX + 0, tY, P, readMemoryI(I + tN + 0));
+						drawByte(pX + 8, tY, P, readMemoryI(I + tN + 1));
 						if (!Quirk.wrapSprite && tY == mDisplayHb) { break; }
-						else { I += 2; ++tY &= mDisplayHb; }
+						else { tN += 2; ++tY &= mDisplayHb; }
 					}
 				}
 			} else [[likely]] {
-				for (auto P{ 0 }, I{ 0 }; P < 4; ++P) {
+				for (auto P{ 0 }, I{ 0 }; P < 4; ++P, I += N) {
 					if (!(mPlanarMask & 1 << P)) { continue; }
 
-					for (auto tN{ 0 }, tY{ pY }; tN < N; ++tN) {
-						drawByte(pX, tY, P, readMemoryI(I));
+					for (auto tN{ 0 }, tY{ pY }; tN < N;) {
+						drawByte(pX, tY, P, readMemoryI(I + tN));
 						if (!Quirk.wrapSprite && tY == mDisplayHb) { break; }
-						else { I += 1; ++tY &= mDisplayHb; }
+						else { tN += 1; ++tY &= mDisplayHb; }
 					}
 				}
 			}