Allow access to MS-Windows Registry from Lisp programs

* src/w32.c (g_b_init_reg_open_key_ex_w)
(g_b_init_reg_query_value_ex_w)
(g_b_init_expand_environment_strings_w): New init flags.
(globals_of_w32): Initialize them at startup.
(RegOpenKeyExW_Proc, RegQueryValueExW_Proc)
(ExpandEnvironmentStringsW_Proc): New function typedefs.
(reg_open_key_ex_w, reg_query_value_ex_w)
(expand_environment_strings_w): New wrapper function.
(w32_read_registry): New function.
* src/w32fns.c (Fw32_read_registry) [WINDOWSNT]: New primitive.
(syms_of_w32fns) [WINDOWSNT]: Defsubr it.  DEFSYM "HKLM", "HKCU",
etc. root keys.

* etc/NEWS: Mention the new primitive.

1 files changed, 7 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 5ac803eec4b..ea4a657cba9 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -682,6 +682,13 @@ to 't' would enable the macOS proxy icon has been replaced with a
 separate variable, 'ns-use-proxy-icon'.  'frame-title-format' will now
 work as on other platforms.
 
+---
+** New primitive 'w32-read-registry'.
+This primitive lets Lisp programs access the MS-Windows Registry by
+retrieving values stored under a given key.  It is intended to be used
+for supporting features such as XDG-like location of important files
+and directories.
+
 
 ----------------------------------------------------------------------
 This file is part of GNU Emacs.