From 7235058f0990540562551036160589736224a892 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ricardo=20Lu=C3=ADs=20Vaz=20Silva?= <ricolvs123@gmail.com>
Date: Wed, 5 Jul 2023 21:31:52 -0300
Subject: [PATCH] scan secondary library folders on windows

---
 src/win32/i_steam.cpp | 128 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 123 insertions(+), 5 deletions(-)

diff --git a/src/win32/i_steam.cpp b/src/win32/i_steam.cpp
index 056b59364b..5b62ae4354 100644
--- a/src/win32/i_steam.cpp
+++ b/src/win32/i_steam.cpp
@@ -80,6 +80,112 @@
 #include "cmdlib.h"
 #include "i_interface.h"
 
+
+//TODO maybe move this code to a separate cpp file, so that there isn't code duplication between the win32 and posix backends
+static void PSR_FindEndBlock(FScanner &sc)
+{
+	int depth = 1;
+	do
+	{
+		if(sc.CheckToken('}'))
+			--depth;
+		else if(sc.CheckToken('{'))
+			++depth;
+		else
+			sc.MustGetAnyToken();
+	}
+	while(depth);
+}
+static void PSR_SkipBlock(FScanner &sc)
+{
+	sc.MustGetToken('{');
+	PSR_FindEndBlock(sc);
+}
+static bool PSR_FindAndEnterBlock(FScanner &sc, const char* keyword)
+{
+	// Finds a block with a given keyword and then enter it (opening brace)
+	// Should be closed with PSR_FindEndBlock
+	while(sc.GetToken())
+	{
+		if(sc.TokenType == '}')
+		{
+			sc.UnGet();
+			return false;
+		}
+
+		sc.TokenMustBe(TK_StringConst);
+		if(!sc.Compare(keyword))
+		{
+			if(!sc.CheckToken(TK_StringConst))
+				PSR_SkipBlock(sc);
+		}
+		else
+		{
+			sc.MustGetToken('{');
+			return true;
+		}
+	}
+	return false;
+}
+static TArray<FString> PSR_ReadBaseInstalls(FScanner &sc)
+{
+	TArray<FString> result;
+
+	// Get a list of possible install directories.
+	while(sc.GetToken())
+	{
+		if(sc.TokenType == '}')
+			break;
+
+		sc.TokenMustBe(TK_StringConst);
+		FString key(sc.String);
+		if(key.Left(18).CompareNoCase("BaseInstallFolder_") == 0)
+		{
+			sc.MustGetToken(TK_StringConst);
+			result.Push(FString(sc.String) + "/steamapps/common");
+		}
+		else
+		{
+			if(sc.CheckToken('{'))
+				PSR_FindEndBlock(sc);
+			else
+				sc.MustGetToken(TK_StringConst);
+		}
+	}
+
+	return result;
+}
+static TArray<FString> ParseSteamRegistry(const char* path)
+{
+	TArray<FString> dirs;
+
+	// Read registry data
+	FScanner sc;
+	if (sc.OpenFile(path))
+	{
+		sc.SetCMode(true);
+
+		// Find the SteamApps listing
+		if (PSR_FindAndEnterBlock(sc, "InstallConfigStore"))
+		{
+			if (PSR_FindAndEnterBlock(sc, "Software"))
+			{
+				if (PSR_FindAndEnterBlock(sc, "Valve"))
+				{
+					if (PSR_FindAndEnterBlock(sc, "Steam"))
+					{
+						dirs = PSR_ReadBaseInstalls(sc);
+					}
+					PSR_FindEndBlock(sc);
+				}
+				PSR_FindEndBlock(sc);
+			}
+			PSR_FindEndBlock(sc);
+		}
+	}
+	return dirs;
+}
+
 //==========================================================================
 //
 // QueryPathKey
@@ -240,18 +346,30 @@ TArray<FString> I_GetSteamPath()
 		"Doom 2/finaldoombase"
 	};
 
-	FString path;
+	FString steamPath;
 
-	if (!QueryPathKey(HKEY_CURRENT_USER, L"Software\\Valve\\Steam", L"SteamPath", path))
+	if (!QueryPathKey(HKEY_CURRENT_USER, L"Software\\Valve\\Steam", L"SteamPath", steamPath))
 	{
-		if (!QueryPathKey(HKEY_LOCAL_MACHINE, L"Software\\Valve\\Steam", L"InstallPath", path))
+		if (!QueryPathKey(HKEY_LOCAL_MACHINE, L"Software\\Valve\\Steam", L"InstallPath", steamPath))
 			return result;
 	}
-	path += "/SteamApps/common/";
+
+	TArray<FString> paths = ParseSteamRegistry(steamPath + "/config/config.vdf");
+
+	for(FString &path : paths)
+	{
+		path.ReplaceChars('\\','/');
+		path+="/";
+	}
+
+	paths.Push(steamPath + "/steamapps/common/");
 
 	for(unsigned int i = 0; i < countof(steam_dirs); ++i)
 	{
-		result.Push(path + steam_dirs[i]);
+		for(const FString &path : paths)
+		{
+			result.Push(path + steam_dirs[i]);
+		}
 	}
 
 	return result;