Handle thread-signal towards the main thread (Bug#32502)

* doc/lispref/threads.texi (Basic Thread Functions):
* etc/NEWS: Document thread-signal towards the main thread.

* lisp/emacs-lisp/thread.el: New package.

* src/keyboard.c (read_char): Check for Qthread_event.
(kbd_buffer_get_event, make_lispy_event): Handle THREAD_EVENT.
(syms_of_keyboard): Declare Qthread_event.
(keys_of_keyboard): Add thread-handle-event to special-event-map.

* src/termhooks.h (enum event_kind): Add THREAD_EVENT.

* src/thread.c: Include "keyboard.h".
(poll_suppress_count) Don't declare extern.
(Fthread_signal): Raise event if THREAD is the main thread.  (Bug#32502)

* test/src/thread-tests.el (thread): Require it.
(threads-signal-main-thread): New test.

1 files changed, 42 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/thread.el b/lisp/emacs-lisp/thread.el
new file mode 100644
index 00000000000..02cf9b9e53f
--- /dev/null
+++ b/lisp/emacs-lisp/thread.el
@@ -0,0 +1,42 @@
+;;; thread.el --- List active threads in a buffer -*- lexical-binding: t -*-
+
+;; Copyright (C) 2018 Free Software Foundation, Inc.
+
+;; Author: Gemini Lasswell <gazally@runbox.com>
+;; Maintainer: emacs-devel@gnu.org
+;; Keywords: lisp, tools, maint
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+;;;###autoload
+(defun thread-handle-event (event)
+  "Handle thread events, propagated by `thread-signal'.
+An EVENT has the format
+  (thread-event THREAD ERROR-SYMBOL DATA)"
+  (interactive "e")
+  (if (and (consp event)
+           (eq (car event) 'thread-event)
+	   (= (length event) 4))
+      (let ((thread (cadr event))
+            (err (cddr event)))
+        (message "Error %s: %S" thread err))))
+
+(provide 'thread)
+;;; thread.el ends here