From aedb7d39721ff705706f4db3f276019155435cf4 Mon Sep 17 00:00:00 2001
From: feos <feos-theos@yandex.ru>
Date: Mon, 24 May 2021 23:15:38 +0300
Subject: [PATCH] mame: figure out default bios properly

---
 .../Arcades/MAME/LibMAME.cs                   |  6 ++++
 .../MAME/MAME.ISettable.ComponentModel.cs     |  1 -
 .../Arcades/MAME/MAME.ISettable.cs            |  4 +--
 .../Arcades/MAME/MAME.cs                      | 30 ++++++++++++++-----
 4 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/src/BizHawk.Emulation.Cores/Arcades/MAME/LibMAME.cs b/src/BizHawk.Emulation.Cores/Arcades/MAME/LibMAME.cs
index ac6877f6b7..3321bc885a 100644
--- a/src/BizHawk.Emulation.Cores/Arcades/MAME/LibMAME.cs
+++ b/src/BizHawk.Emulation.Cores/Arcades/MAME/LibMAME.cs
@@ -18,6 +18,12 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 			NONE, NOT_FOUND, ILLEGAL_REGISTRATIONS, INVALID_HEADER, READ_ERROR, WRITE_ERROR, DISABLED
 		}
 
+		public const int ROMENTRYTYPE_SYSTEM_BIOS = 9;
+		public const int ROMENTRYTYPE_DEFAULT_BIOS = 10;
+		public const int ROMENTRY_TYPEMASK = 15;
+		public const int BIOS_INDEX = 24;
+		public const int BIOS_FIRST = 1;
+
 		// main launcher
 		[DllImport(dll, CallingConvention = cc)]
 		public static extern uint mame_launch(int argc, string[] argv);
diff --git a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.ComponentModel.cs b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.ComponentModel.cs
index 5dcb2b975c..2c9d7a1f41 100644
--- a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.ComponentModel.cs
+++ b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.ComponentModel.cs
@@ -4,7 +4,6 @@ using System.ComponentModel;
 using System.Globalization;
 using System.Linq;
 using static BizHawk.Emulation.Cores.Arcades.MAME.MAME;
-using static BizHawk.Emulation.Cores.Arcades.MAME.MAME.DriverSetting;
 
 namespace BizHawk.Emulation.Cores.Arcades.MAME
 {
diff --git a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.cs b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.cs
index da095f881f..0e8cdd46dc 100644
--- a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.cs
+++ b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.ISettable.cs
@@ -100,7 +100,7 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 			public string LuaCode { get; set; }
 			public string DefaultValue { get; set; }
 			public SettingType Type { get; set; }
-			public Dictionary<string, string> Options { get; set; }
+			public SortedDictionary<string, string> Options { get; set; }
 			public string LookupKey => $"[{ GameName }] { LuaCode }";
 
 			public DriverSetting()
@@ -108,7 +108,7 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 				Name = null;
 				GameName = null;
 				DefaultValue = null;
-				Options = new Dictionary<string, string>();
+				Options = new SortedDictionary<string, string>();
 			}
 		}
 
diff --git a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs
index c69ad86bbf..50bc12591a 100644
--- a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs
+++ b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.cs
@@ -73,11 +73,10 @@ made that way to make the buffer persist actoss C API calls.
 */
 
 using System;
-using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using System.Threading;
 using System.Diagnostics;
-using System.Dynamic;
+using System.Linq;
 using BizHawk.Common;
 using BizHawk.Emulation.Common;
 
@@ -274,13 +273,13 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 			LibMAME.mame_lua_execute(MAMELuaCommand.Pause);
 
 			CheckVersions();
-			GetInputFields();
-			GetROMsInfo();
+			UpdateGameName();
 			UpdateVideo();
 			UpdateAspect();
 			UpdateFramerate();
-			UpdateGameName();
 			InitMemoryDomains();
+			GetInputFields();
+			GetROMsInfo();
 			FetchDefaultGameSettings();
 			OverrideGameSettings();
 
@@ -316,7 +315,8 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 		private void GetROMsInfo()
 		{
 			string ROMsInfo = MameGetString(MAMELuaCommand.GetROMsInfo);
-			string[] ROMs = ROMsInfo.Split(';');
+			string[] ROMs = ROMsInfo.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries);
+			string tempDefault = "";
 
 			DriverSetting setting = new DriverSetting()
 			{
@@ -335,11 +335,20 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 					string hashdata = substrings[1];
 					long flags = long.Parse(substrings[2]);
 
-					if ((flags & 0xf) == 9 || (flags & 0xf) == 10)
+					if ((flags & LibMAME.ROMENTRY_TYPEMASK) == LibMAME.ROMENTRYTYPE_SYSTEM_BIOS
+						|| (flags & LibMAME.ROMENTRY_TYPEMASK) == LibMAME.ROMENTRYTYPE_DEFAULT_BIOS)
 					{
 						setting.Options.Add(name, hashdata);
 
-						if ((flags & 0xf) == 10)
+						// if no bios is explicitly marked as default
+						// mame uses the first one in the list
+						// and its index is reflected in the flags (ROM_BIOSFLAGSMASK)
+						if ((flags >> LibMAME.BIOS_INDEX) == LibMAME.BIOS_FIRST)
+						{
+							tempDefault = name;
+						}
+
+						if ((flags & LibMAME.ROMENTRY_TYPEMASK) == LibMAME.ROMENTRYTYPE_DEFAULT_BIOS)
 						{
 							setting.DefaultValue = name;
 						}
@@ -354,6 +363,11 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 
 			if (setting.Options.Count > 0)
 			{
+				if (setting.DefaultValue == null)
+				{
+					setting.DefaultValue = tempDefault;
+				}
+
 				CurrentDriverSettings.Add(setting);
 			}
 		}