Make calc plotting through gnuplot work on non-X gnuplots

* lisp/calc/calc-graph.el (calc-graph-plot): Fall back on "dumb"
if we don't support the terminal (bug#50237).
(calc-gnuplot-command): Say whether the command errored out.

diff --git a/lisp/calc/calc-graph.el b/lisp/calc/calc-graph.el
index 9ac24bf188941049bc0f3839ebc2790f1a793fa6..9dfdba3930808b774f1fff46e1ad6e486fe8c26f 100644 (file)
--- a/lisp/calc/calc-graph.el
+++ b/lisp/calc/calc-graph.el
@@ -391,6 +391,13 @@
                    ((>= calc-gnuplot-version 3)
                     "dumb")
                    (t "postscript"))))
+        (unless (equal device calc-graph-last-device)
+          (setq calc-graph-last-device device)
+          (unless (calc-gnuplot-command "set terminal" device)
+             ;; If gnuplot doesn't support the terminal, then set it
+             ;; to "dumb".
+             (calc-gnuplot-command "set terminal dumb")
+             (setq device "dumb")))
         (if (equal device "dumb")
             (setq device (format "dumb %d %d"
                                  (1- (frame-width)) (1- (frame-height)))))
@@ -404,10 +411,6 @@
                 (setq tempoutfile (calc-temp-file-name -1)
                       output tempoutfile))
           (setq output (eval output t)))
-        (or (equal device calc-graph-last-device)
-            (progn
-              (setq calc-graph-last-device device)
-              (calc-gnuplot-command "set terminal" device)))
         (or (equal output calc-graph-last-output)
             (progn
               (setq calc-graph-last-output output)
@@ -1411,6 +1414,8 @@ This \"dumb\" driver will be present in Gnuplot 3.0."
       (calc-graph-view-trail)))
 
 (defun calc-gnuplot-command (&rest args)
+  "Send ARGS to Gnuplot.
+Returns nil if Gnuplot signalled an error."
   (calc-graph-init)
   (let ((cmd (concat (mapconcat 'identity args " ") "\n")))
     (or (calc-graph-w32-p)
@@ -1428,9 +1433,11 @@ This \"dumb\" driver will be present in Gnuplot 3.0."
       (or (calc-graph-w32-p)
          (accept-process-output (and (not calc-graph-no-wait)
                                      calc-gnuplot-process)))
-      (calc-gnuplot-check-for-errors)
-      (if (get-buffer-window calc-gnuplot-buffer)
-         (calc-graph-view-trail)))))
+      (prog1
+          ;; Return nil if we got an error.
+          (not (calc-gnuplot-check-for-errors))
+        (if (get-buffer-window calc-gnuplot-buffer)
+           (calc-graph-view-trail))))))
 
 (defun calc-graph-init-buffers ()
   (or (and calc-gnuplot-buffer