Read Steam location and user from registry

GCMM/GCMM.csproj

@@ -24,6 +24,7 @@
   <ItemGroup>
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="System.IO.Compression" Version="4.3.0" />
+    <PackageReference Include="System.ValueTuple" Version="4.5.0" />
   </ItemGroup>
 
   <ItemGroup>

GCMM/MainForm.cs

@@ -64,6 +64,7 @@ You may also want to verify the game's files by right clicking the game in Steam
             mods.Clear(); //This method may get called twice when ran from the command line
             UpdateButton(installbtn, false);
             modinfobox.Text = defaultInfo;
+            GetSteamLocationAndUser(); //TODO: If user is null then start Steam
             if (string.IsNullOrWhiteSpace(Settings.Default.GamePath) || GetExe() == null)
             {
                 Settings.Default.GamePath = GetGameFolder();

GCMM/MainUtils.cs

@@ -1,4 +1,5 @@
 using GCMM.Properties;
+using Microsoft.Win32;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -35,7 +36,7 @@ namespace GCMM
         { //TODO
             string libs;
             if (Environment.OSVersion.Platform == PlatformID.Win32NT)
-                libs = Settings.Default.SteamConfigFileForAutoLaunch + @"\steamapps\libraryfolders.vdf";
+                libs = Settings.Default.SteamConfigFileForAutoLaunch + @"\steamapps\libraryfolders.vdf"; //TODO: Not the Steam folder anymore!
             else
                 return null;
             foreach (var line in File.ReadAllLines(libs).Concat(new[] {@"C:\Program Files (x86)\Steam\"}))
@@ -83,7 +84,17 @@ namespace GCMM
 
         private void UpdateSteamConfigToAutoStart(bool autoLaunch)
         {
+            //TODO
+        }
 
+        private (string, int) GetSteamLocationAndUser()
+        {
+            if (Environment.OSVersion.Platform != PlatformID.Win32NT) return (null, 0);
+            using (var key = Registry.CurrentUser.OpenSubKey(@"Software\Valve\Steam\ActiveProcess"))
+            {
+                string path = Directory.GetParent((string)key.GetValue("SteamClientDll")).FullName;
+                return (path, (int)key.GetValue("ActiveUser"));
+            }
         }
 
         private void CheckStartGame(object sender, EventArgs e)