From 06d407f130ca454bc23668051a7b73a84b9c1dd7 Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Mon, 24 Jun 2019 09:05:38 -0700
Subject: [PATCH] GB Video: Increment BCPS/OCPS even in mode 3 (fixes #1462)

---
 CHANGES        |  1 +
 src/gb/io.c    |  4 ++--
 src/gb/video.c | 32 ++++++++++++++++++--------------
 3 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/CHANGES b/CHANGES
index 5b4a414a9..3a5e1033b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -27,6 +27,7 @@ Emulation fixes:
  - GBA Memory: Fix STM to VRAM (fixes mgba.io/i/1430)
  - GB Audio: Only reset channel 3 sample in DMG mode
  - GB Audio: Sample inactive channels (fixes mgba.io/i/1455, mgba.io/i/1456)
+ - GB Video: Increment BCPS/OCPS even in mode 3 (fixes mgba.io/i/1462)
 Other fixes:
  - Qt: Fix some Qt display driver race conditions
  - Core: Improved lockstep driver reliability (Le Hoang Quyen)
diff --git a/src/gb/io.c b/src/gb/io.c
index e008dbb26..2c4b9b4b3 100644
--- a/src/gb/io.c
+++ b/src/gb/io.c
@@ -499,8 +499,8 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 			case REG_BCPD:
 				if (gb->video.mode != 3) {
 					GBVideoProcessDots(&gb->video, 0);
-					GBVideoWritePalette(&gb->video, address, value);
 				}
+				GBVideoWritePalette(&gb->video, address, value);
 				return;
 			case REG_OCPS:
 				gb->video.ocpIndex = value & 0x3F;
@@ -510,8 +510,8 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 			case REG_OCPD:
 				if (gb->video.mode != 3) {
 					GBVideoProcessDots(&gb->video, 0);
-					GBVideoWritePalette(&gb->video, address, value);
 				}
+				GBVideoWritePalette(&gb->video, address, value);
 				return;
 			case REG_SVBK:
 				GBMemorySwitchWramBank(&gb->memory, value);
diff --git a/src/gb/video.c b/src/gb/video.c
index cfe80f913..020889ca9 100644
--- a/src/gb/video.c
+++ b/src/gb/video.c
@@ -505,14 +505,16 @@ void GBVideoWritePalette(struct GBVideo* video, uint16_t address, uint8_t value)
 	} else {
 		switch (address) {
 		case REG_BCPD:
-			if (video->bcpIndex & 1) {
-				video->palette[video->bcpIndex >> 1] &= 0x00FF;
-				video->palette[video->bcpIndex >> 1] |= value << 8;
-			} else {
-				video->palette[video->bcpIndex >> 1] &= 0xFF00;
-				video->palette[video->bcpIndex >> 1] |= value;
+			if (video->mode != 3) {
+				if (video->bcpIndex & 1) {
+					video->palette[video->bcpIndex >> 1] &= 0x00FF;
+					video->palette[video->bcpIndex >> 1] |= value << 8;
+				} else {
+					video->palette[video->bcpIndex >> 1] &= 0xFF00;
+					video->palette[video->bcpIndex >> 1] |= value;
+				}
+				video->renderer->writePalette(video->renderer, video->bcpIndex >> 1, video->palette[video->bcpIndex >> 1]);
 			}
-			video->renderer->writePalette(video->renderer, video->bcpIndex >> 1, video->palette[video->bcpIndex >> 1]);
 			if (video->bcpIncrement) {
 				++video->bcpIndex;
 				video->bcpIndex &= 0x3F;
@@ -522,14 +524,16 @@ void GBVideoWritePalette(struct GBVideo* video, uint16_t address, uint8_t value)
 			video->p->memory.io[REG_BCPD] = video->palette[video->bcpIndex >> 1] >> (8 * (video->bcpIndex & 1));
 			break;
 		case REG_OCPD:
-			if (video->ocpIndex & 1) {
-				video->palette[8 * 4 + (video->ocpIndex >> 1)] &= 0x00FF;
-				video->palette[8 * 4 + (video->ocpIndex >> 1)] |= value << 8;
-			} else {
-				video->palette[8 * 4 + (video->ocpIndex >> 1)] &= 0xFF00;
-				video->palette[8 * 4 + (video->ocpIndex >> 1)] |= value;
+			if (video->mode != 3) {
+				if (video->ocpIndex & 1) {
+					video->palette[8 * 4 + (video->ocpIndex >> 1)] &= 0x00FF;
+					video->palette[8 * 4 + (video->ocpIndex >> 1)] |= value << 8;
+				} else {
+					video->palette[8 * 4 + (video->ocpIndex >> 1)] &= 0xFF00;
+					video->palette[8 * 4 + (video->ocpIndex >> 1)] |= value;
+				}
+				video->renderer->writePalette(video->renderer, 8 * 4 + (video->ocpIndex >> 1), video->palette[8 * 4 + (video->ocpIndex >> 1)]);
 			}
-			video->renderer->writePalette(video->renderer, 8 * 4 + (video->ocpIndex >> 1), video->palette[8 * 4 + (video->ocpIndex >> 1)]);
 			if (video->ocpIncrement) {
 				++video->ocpIndex;
 				video->ocpIndex &= 0x3F;