From 7d6257cb1e1115c58b279f8357118091a24b2457 Mon Sep 17 00:00:00 2001
From: David Hogan <david.q.hogan@gmail.com>
Date: Wed, 12 Jan 2022 21:41:02 +0100
Subject: [PATCH] gdkkeys-win32: Perform keyboard layout substitution

For some users, GetKeyboardLayoutNameA() returns an alias instead of the
fully resolved keyboard layout identifier. In that case, we have to
query the registry to resolve the alias before we can look up the DLL
path.

See comments under https://gitlab.gnome.org/GNOME/gtk/-/issues/4610
---
 gdk/win32/gdkkeys-win32.c | 97 +++++++++++++++++++++++++++++++++++----
 1 file changed, 87 insertions(+), 10 deletions(-)

diff --git a/gdk/win32/gdkkeys-win32.c b/gdk/win32/gdkkeys-win32.c
index 514988edee..caa170b20a 100644
--- a/gdk/win32/gdkkeys-win32.c
+++ b/gdk/win32/gdkkeys-win32.c
@@ -168,6 +168,67 @@ vk_to_char_fuzzy (GdkWin32Keymap           *keymap,
                                                          consumed_mod_bits, is_dead, vk);
 }
 
+/*
+ * Return the keyboard layout according to the user's keyboard layout
+ * substitution preferences.
+ *
+ * The result is heap-allocated and should be freed with g_free().
+ */
+static char*
+get_keyboard_layout_substituted_name (const char *layout_name)
+{
+  HKEY     hkey     = 0;
+  DWORD    var_type = REG_SZ;
+  char    *result   = NULL;
+  DWORD    buf_len  = 0;
+  LSTATUS  status;
+
+  static const char *substitute_path = "Keyboard Layout\\Substitutes";
+
+  status = RegOpenKeyExA (HKEY_CURRENT_USER, substitute_path, 0,
+                          KEY_QUERY_VALUE, &hkey);
+  if (status != ERROR_SUCCESS)
+    {
+      /* No substitute set for this value, not sure if this is a normal case */
+      g_warning("Could not open registry key '%s'. Error code: %d",
+                substitute_path, (int)status);
+
+      goto fail1;
+    }
+
+  status = RegQueryValueExA (hkey, layout_name, 0, &var_type, 0, &buf_len);
+  if (status != ERROR_SUCCESS)
+    {
+      g_debug("Could not query registry key '%s\\%s'. Error code: %d",
+              substitute_path, layout_name, (int)status);
+      goto fail2;
+    }
+
+  /* Allocate buffer */
+  result = (char*) g_malloc (buf_len);
+
+  /* Retrieve substitute name */
+  status = RegQueryValueExA (hkey, layout_name, 0, &var_type,
+                             (LPBYTE) result, &buf_len);
+  if (status != ERROR_SUCCESS)
+    {
+      g_warning("Could not obtain registry value at key '%s\\%s'. "
+                "Error code: %d",
+                substitute_path, layout_name, (int)status);
+      goto fail3;
+    }
+
+  RegCloseKey (hkey);
+  return result;
+
+fail3:
+  g_free (result);
+fail2:
+  RegCloseKey (hkey);
+fail1:
+  return NULL;
+}
+
 /* 
  * Get the file path of the keyboard layout dll.
  * The result is heap-allocated and should be freed with g_free().
@@ -175,21 +236,37 @@ vk_to_char_fuzzy (GdkWin32Keymap           *keymap,
 static char*
 get_keyboard_layout_file (const char *layout_name)
 {
-  HKEY   hkey          = 0;
-  DWORD  var_type      = REG_SZ;
-  char  *result        = NULL;
-  DWORD  file_name_len = 0;
-  int    dir_len       = 0;
-  int    buf_len       = 0;
-  LSTATUS status;
+  char    *final_layout_name = NULL;
+  HKEY     hkey              = 0;
+  DWORD    var_type          = REG_SZ;
+  char    *result            = NULL;
+  DWORD    file_name_len     = 0;
+  int      dir_len           = 0;
+  int      buf_len           = 0;
+  LSTATUS  status;
 
   static const char prefix[] = "SYSTEM\\CurrentControlSet\\Control\\"
                                "Keyboard Layouts\\";
   char kbdKeyPath[sizeof (prefix) + KL_NAMELENGTH];
 
-  g_snprintf (kbdKeyPath, sizeof (prefix) + KL_NAMELENGTH, "%s%s", prefix,
-              layout_name);
-
+  /* The user may have a keyboard substitute configured */
+  final_layout_name = get_keyboard_layout_substituted_name (layout_name);
+  if (final_layout_name != NULL)
+    {
+      g_debug ("Substituting keyboard layout name from '%s' to '%s'",
+               layout_name, final_layout_name);
+      g_snprintf (kbdKeyPath, sizeof (prefix) + KL_NAMELENGTH, "%s%s",
+                  prefix, final_layout_name);
+      g_free (final_layout_name);
+      final_layout_name = NULL;
+    }
+  else
+    {
+      g_debug ("Could not get substitute keyboard layout name for '%s', "
+               "will use '%s' directly", layout_name, layout_name);
+      g_snprintf (kbdKeyPath, sizeof (prefix) + KL_NAMELENGTH, "%s%s",
+                  prefix, layout_name);
+    }
 
   status = RegOpenKeyExA (HKEY_LOCAL_MACHINE, (LPCSTR) kbdKeyPath, 0,
                           KEY_QUERY_VALUE, &hkey);
-- 
2.30.2