Add user option to inhibit Calc startup message (bug#79143)

* doc/misc/calc.texi (Customizing Calc): Document the new option.
* etc/NEWS: Document the new option.
* lisp/calc/calc.el (calc-inhibit-startup-message): New option to
inhibit Calc’s startup message.
(calc): Respect the option in Calc’s startup code.
* test/lisp/calc/calc-tests.el (ert): Require ert-x for
'ert-with-message-capture'.
(calc-inhibit-startup-message): Test the new user option.

doc/misc/calc.texi

@@ -35714,6 +35714,14 @@ The default value of @code{calc-string-maximum-character} is @code{0xFF}
 or 255.
 @end defvar
 
+@defvar calc-inhibit-startup-message
+The variable @code{calc-inhibit-startup-message} controls display of a
+welcome message when starting Calc.  If it is @code{nil} (the default),
+Calc will print a brief message listing key bindings to get help or to
+quit.  If it is non-@code{nil}, Calc will start without printing
+anything.
+@end defvar
+
 @node Reporting Bugs
 @appendix Reporting Bugs
 

etc/NEWS

@@ -2605,6 +2605,11 @@ Latin-1 range 0-255.  This hard-coded maximum is replaced by
 the display of matching vectors as Unicode strings.  The default value
 is 0xFF or 255 to preserve the existing behavior.
 
++++
+*** New user option 'calc-inhibit-startup-message'.
+If it is non-nil, inhibit Calc from printing its startup message.  The
+default value is nil to preserve the existing behavior.
+
 ** Time
 
 *** New user option 'world-clock-sort-order'.

lisp/calc/calc.el

@@ -1473,6 +1473,11 @@ commands given here will actually operate on the *Calculator* stack."
     (require 'calc-ext)
     (calc-set-language calc-language calc-language-option t)))
 
+(defcustom calc-inhibit-startup-message nil
+  "If non-nil, inhibit the Calc startup message."
+  :version "31.1"
+  :type 'boolean)
+
 (defcustom calc-make-windows-dedicated nil
   "If non-nil, windows displaying Calc buffers will be marked dedicated.
 See `window-dedicated-p' for what that means."
@@ -1524,9 +1529,10 @@ See `window-dedicated-p' for what that means."
         (with-current-buffer (calc-trail-buffer)
           (and calc-display-trail
                (calc-trail-display 1 t)))
-        (message (substitute-command-keys
-                  (concat "Welcome to the GNU Emacs Calculator!  \\<calc-mode-map>"
-                          "Press \\[calc-help] or \\[calc-help-prefix] for help, \\[calc-quit] to quit")))
+        (unless calc-inhibit-startup-message
+          (message (substitute-command-keys
+                    (concat "Welcome to the GNU Emacs Calculator!  \\<calc-mode-map>"
+                            "Press \\[calc-help] or \\[calc-help-prefix] for help, \\[calc-quit] to quit"))))
         (run-hooks 'calc-start-hook)
         (and (windowp full-display)
              (window-point full-display)
@@ -1534,10 +1540,11 @@ See `window-dedicated-p' for what that means."
         (and calc-make-windows-dedicated
              (set-window-dedicated-p nil t))
         (calc-check-defines)
-        (when (and calc-said-hello interactive)
-          (sit-for 2)
-          (message ""))
-        (setq calc-said-hello t)))))
+        (unless calc-inhibit-startup-message
+          (when (and calc-said-hello interactive)
+            (sit-for 2)
+            (message ""))
+          (setq calc-said-hello t))))))
 
 ;;;###autoload
 (defun full-calc (&optional interactive)

test/lisp/calc/calc-tests.el

@@ -26,6 +26,7 @@
 
 (require 'cl-lib)
 (require 'ert)
+(require 'ert-x)
 (require 'calc)
 (require 'calc-ext)
 (require 'calc-units)
@@ -946,5 +947,19 @@ an error in the comparison."
       (should-error (math-vector-is-string cplx-vec)
                     :type 'wrong-type-argument))))
 
+(ert-deftest calc-inhibit-startup-message ()
+  "Test user option `calc-inhibit-startup-message'."
+  (let ((welcome-message "Welcome to the GNU Emacs Calculator!"))
+    (ert-with-message-capture messages
+      (let ((calc-inhibit-startup-message t))
+        (calc))
+      (should-not (string-match-p welcome-message messages))
+      (calc-quit))
+    (ert-with-message-capture messages
+      (let ((calc-inhibit-startup-message nil))
+        (calc))
+      (should (string-match-p welcome-message messages))
+      (calc-quit))))
+
 (provide 'calc-tests)
 ;;; calc-tests.el ends here