From 2bca72186d9b0958826de63b9aafcb26ace46307 Mon Sep 17 00:00:00 2001
From: retro-wertz <retro-wertz@users.noreply.github.com>
Date: Fri, 15 Jun 2018 11:30:23 +0800
Subject: [PATCH] Mapper30: Backport 4-screen mirroring support

https://github.com/TASVideos/fceux/commit/9b6ff8fe490cae56f6a3bc24e0ac19e47b5eaa41
---
 src/boards/unrom512.c | 18 +++++++++++++++++-
 src/ines.h            |  9 ++++++---
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/boards/unrom512.c b/src/boards/unrom512.c
index f82d7f9..9bc4736 100644
--- a/src/boards/unrom512.c
+++ b/src/boards/unrom512.c
@@ -210,6 +210,8 @@ static void UNROM512HSync(void) {
 }
 
 void UNROM512_Init(CartInfo *info) {
+	int mirror;
+
 	memset(fceumm_flash_buf, 0x00, fceumm_flash_buf_size);
 	flash_state = 0;
 	flash_bank = 0;
@@ -222,7 +224,21 @@ void UNROM512_Init(CartInfo *info) {
 	else
 		chrram_mask = 0x60;
 
-	SetupCartMirroring(info->mirror, (info->mirror >= MI_0) ? 0 : 1, 0);
+	mirror = (head.ROM_type & 1) | ((head.ROM_type & 8) >> 2);
+	switch (mirror) {
+	case 0: // hard horizontal, internal
+		SetupCartMirroring(MI_H, 1, NULL);
+		break;
+	case 1: // hard vertical, internal
+		SetupCartMirroring(MI_V, 1, NULL);
+		break;
+	case 2: // switchable 1-screen, internal (flags: 4-screen + horizontal)
+		SetupCartMirroring(MI_0, 0, NULL);
+		break;
+	case 3: // hard four screen, last 8k of 32k RAM (flags: 4-screen + vertical)
+		SetupCartMirroring(4, 1, VROM + (info->vram_size - 8192));
+		break;
+	}
 	bus_conflict = !info->battery;
 	latcheinit = 0;
 	WLSync = UNROM512LSync;
diff --git a/src/ines.h b/src/ines.h
index 2f94261..b3d07ba 100644
--- a/src/ines.h
+++ b/src/ines.h
@@ -22,9 +22,6 @@
 #ifndef _FCEU_INES_H
 #define _FCEU_INES_H
 
-extern uint32 ROM_size;
-extern uint32 VROM_size;
-
 typedef struct {
 	char ID[4];		/*NES^Z*/
 	uint8 ROM_size;
@@ -34,6 +31,12 @@ typedef struct {
 	uint8 reserve[8];
 } iNES_HEADER;
 
+extern uint8 *ROM;
+extern uint8 *VROM;
+extern uint32 ROM_size;
+extern uint32 VROM_size;
+extern iNES_HEADER head;
+
 void NSFVRC6_Init(void);
 void NSFMMC5_Init(void);
 void NSFAY_Init(void);