Detect GOG install path

code/sys/sys_unix.c

@@ -47,6 +47,9 @@ static char homePath[ MAX_OSPATH ] = { 0 };
 // Used to store the Steam Quake 3 installation path
 static char steamPath[ MAX_OSPATH ] = { 0 };
 
+// Used to store the GOG Quake 3 installation path
+static char gogPath[ MAX_OSPATH ] = { 0 };
+
 /*
 ==================
 Sys_DefaultHomePath
@@ -106,6 +109,17 @@ char *Sys_SteamPath( void )
 	return steamPath;
 }
 
+/*
+================
+Sys_GogPath
+================
+*/
+char *Sys_GogPath( void )
+{
+	// GOG also doesn't let you install Quake 3 on Mac/Linux
+	return gogPath;
+}
+
 /*
 ================
 Sys_Milliseconds

code/sys/sys_win32.c

@@ -45,6 +45,9 @@ static char homePath[ MAX_OSPATH ] = { 0 };
 // Used to store the Steam Quake 3 installation path
 static char steamPath[ MAX_OSPATH ] = { 0 };
 
+// Used to store the GOG Quake 3 installation path
+static char gogPath[ MAX_OSPATH ] = { 0 };
+
 #ifndef DEDICATED
 static UINT timerResolution = 0;
 #endif
@@ -183,6 +186,38 @@ char *Sys_SteamPath( void )
 	return steamPath;
 }
 
+/*
+================
+Sys_GogPath
+================
+*/
+char *Sys_GogPath( void )
+{
+#ifdef GOGPATH_ID
+	HKEY gogRegKey;
+	DWORD pathLen = MAX_OSPATH;
+
+	if (!gogPath[0] && !RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\GOG.com\\Games\\" GOGPATH_ID, 0, KEY_QUERY_VALUE | KEY_WOW64_32KEY, &gogRegKey))
+	{
+		pathLen = MAX_OSPATH;
+		if (RegQueryValueEx(gogRegKey, "PATH", NULL, NULL, (LPBYTE)gogPath, &pathLen))
+			gogPath[0] = '\0';
+
+		RegCloseKey(gogRegKey);
+	}
+
+	if (gogPath[0])
+	{
+		if (pathLen == MAX_OSPATH)
+			pathLen--;
+
+		gogPath[pathLen] = '\0';
+	}
+#endif
+
+	return gogPath;
+}
+
 /*
 ================
 Sys_Milliseconds