From 8bb9d2d647c4a9c49e696efb14d976682ad28647 Mon Sep 17 00:00:00 2001
From: Jon Turney <jon.turney@dronecode.org.uk>
Date: Wed, 24 Aug 2022 13:31:49 +0100
Subject: [PATCH setup] Drop setting root_scope as a side-effect of
 read_mounts()

Default root_scope as appropriate, allowing GUI to override it
Only enable 'Install For All Users' if we have Admin privs
Drop some comment cruft
---
 mount.cc | 30 +++++++++++++++++++++++-------
 mount.h  |  9 +--------
 root.cc  | 12 ++++++++++++
 3 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/mount.cc b/mount.cc
index 0136396..a38f52c 100644
--- a/mount.cc
+++ b/mount.cc
@@ -140,10 +140,6 @@ create_install_root ()
 						      : "LOCAL_MACHINE\\")
 		      << buf << "\\rootdir = \"" << get_root_dir () << "\""
 		      << endLog;
-
-  // The mount table is already in the right shape at this point.
-  // Reading it again is not necessary.
-  //read_mounts (std::string ());
 }
 
 inline char *
@@ -316,8 +312,6 @@ read_mounts (const std::string val)
     }
   got_usr_bin = got_usr_lib = false;
 
-  root_scope = (nt_sec.isRunAsAdmin ())? IDC_ROOT_SYSTEM : IDC_ROOT_USER;
-
   if (val.size ())
     {
       /* Cygwin rootdir always < MAX_PATH. */
@@ -353,7 +347,6 @@ read_mounts (const std::string val)
 	    {
 	      m->native = std::string (aBuffer);
 	      m->posix = "/";
-	      root_scope = isuser ? IDC_ROOT_USER : IDC_ROOT_SYSTEM;
 	      root_here = m++;
 	      from_fstab (m, root_here->native);
 	      add_usr_mnts (m);
@@ -376,6 +369,29 @@ read_mounts (const std::string val)
     }
 }
 
+// set default root_scope: USER if only HKEY_CURRENT_USER registry key exists,
+// otherwise SYSTEM.
+void set_default_root_scope()
+{
+  root_scope = IDC_ROOT_SYSTEM;
+
+  char buf[10000];
+  for (int isuser = 0; isuser <= 1; isuser++)
+    {
+      snprintf (buf, sizeof(buf), "Software\\%s\\%s",
+                CYGWIN_INFO_CYGWIN_REGISTRY_NAME,
+                CYGWIN_INFO_CYGWIN_SETUP_REGISTRY_NAME);
+      HKEY key = isuser ? HKEY_CURRENT_USER : HKEY_LOCAL_MACHINE;
+      if (RegOpenKeyEx (key, buf, 0, KEY_ALL_ACCESS | SETUP_KEY_WOW64,
+                        &key) == ERROR_SUCCESS)
+        {
+          RegCloseKey (key);
+          root_scope = isuser ? IDC_ROOT_USER : IDC_ROOT_SYSTEM;
+          break;
+        }
+    }
+}
+
 void
 set_root_dir (const std::string val)
 {
diff --git a/mount.h b/mount.h
index a7d7e39..c451a02 100644
--- a/mount.h
+++ b/mount.h
@@ -15,11 +15,6 @@
 
 #ifndef SETUP_MOUNT_H
 #define SETUP_MOUNT_H
-
-/* Finds the existing root mount, or returns NULL.  istext is set to
-   nonzero if the existing mount is a text mount, else zero for
-   binary. */
-
 #include <string>
 #include "String++.h"
 
@@ -27,9 +22,7 @@
 
 void create_install_root ();
 void read_mounts (const std::string);
-
-/* Sets the cygdrive flags.  Used to make the automounted drives' binary/text
-mode consistent with the standard Cygwin mounts. */
+void set_default_root_scope();
 
 std::string cygpath (const std::string&);
 void set_root_dir (const std::string);
diff --git a/root.cc b/root.cc
index 9f072d7..ccbd6ae 100644
--- a/root.cc
+++ b/root.cc
@@ -259,6 +259,18 @@ RootPage::OnInit ()
   if (!get_root_dir ().size())
     read_mounts (std::string ());
   orig_root_dir = get_root_dir();
+
+  if (!nt_sec.isRunAsAdmin())
+    {
+      // disable IDC_ROOT_SYSTEM if not running as admin
+      EnableWindow(GetDlgItem(IDC_ROOT_SYSTEM), FALSE);
+      root_scope = IDC_ROOT_USER;
+    }
+  else
+    {
+      set_default_root_scope();
+    }
+
   load_dialog (GetHWND ());
 }
 
-- 
2.37.2