Use a header line in calc mode instead of a regular in-buffer line

* lisp/calc/calc.el (calc-trail-here): Use a header line.
(calc--header-line): New function.
(calc-trail-mode): Use a header line.

diff --git a/lisp/calc/calc.el b/lisp/calc/calc.el
index fb1287baaa6f1cae3ab9ece4aa73a0877c7d77eb..9b95bc149a65c07102864dfa501257b5cc9a8c5b 100644 (file)
--- a/lisp/calc/calc.el
+++ b/lisp/calc/calc.el
@@ -1382,6 +1382,29 @@ Notations:  3.14e6     3.14 * 10^6
     (set-keymap-parent map calc-mode-map)
     map))
 
+(defun calc--header-line (long short width &optional fudge)
+  "Return a Calc header line appropriate for the buffer width.
+
+LONG is a desired text for a wide window, SHORT is a desired
+abbreviated text, and width is the buffer width, which will be
+some fraction of the 'parent' window width (At the time of
+writing, 2/3 for calc, 1/3 for trail). The optional FUDGE is a
+trial-and-error adjustment number for the edge-cases at the
+border of the two cases."
+  ;; TODO: This could be called as part of a 'window-resize' hook.
+  (setq header-line-format
+        (let* ((len-long (length long))
+               (len-short (length short))
+               (fudge (or fudge 0))
+               ;; fudge for trail is: -3 (added to len-long)
+               ;; (width  ) for trail
+               (factor (if (> width (+ len-long fudge)) len-long len-short))
+               (size   (/ (- width factor) 2))
+               (fill (make-string size ?-))
+               (pre  (replace-regexp-in-string ".$" " " fill))
+               (post (replace-regexp-in-string "^." " " fill)))
+          (concat pre (if (= factor len-long) long short) post))))
+
 (define-derived-mode calc-trail-mode fundamental-mode "Calc Trail"
   "Calc Trail mode.
 This mode is used by the *Calc Trail* buffer, which records all results
@@ -1396,9 +1419,9 @@ commands given here will actually operate on the *Calculator* stack."
   (setq buffer-read-only t)
   (make-local-variable 'overlay-arrow-position)
   (make-local-variable 'overlay-arrow-string)
-  (when (= (buffer-size) 0)
-    (let ((inhibit-read-only t))
-      (insert (propertize "Emacs Calculator Trail\n" 'face 'italic)))))
+  (when calc-show-banner
+    (calc--header-line "Emacs Calculator Trail" "Calc Trail"
+                       (/ (window-width) 3) -3)))
 
 (defun calc-create-buffer ()
   "Create and initialize a buffer for the Calculator."
@@ -1451,7 +1474,6 @@ commands given here will actually operate on the *Calculator* stack."
                 (pop-to-buffer (current-buffer)))))))
       (with-current-buffer (calc-trail-buffer)
         (and calc-display-trail
-             (= (window-width) (frame-width))
              (calc-trail-display 1 t)))
       (message "Welcome to the GNU Emacs Calculator!  Press `?' or `h' for help, `q' to quit")
       (run-hooks 'calc-start-hook)
@@ -1986,13 +2008,11 @@ See calc-keypad for details."
              (calc-any-evaltos nil))
         (setq calc-any-selections nil)
         (erase-buffer)
-        (when calc-show-banner
-          (insert (propertize "--- Emacs Calculator Mode ---\n"
-                              'face 'italic)))
+         (when calc-show-banner
+           (calc--header-line  "Emacs Calculator Mode" "Emacs Calc"
+                       (* 2 (/ (window-width) 3)) -3))
         (while thing
           (goto-char (point-min))
-          (when calc-show-banner
-            (forward-line 1))
           (insert (math-format-stack-value (car thing)) "\n")
           (setq thing (cdr thing)))
         (calc-renumber-stack)
@@ -2076,7 +2096,6 @@ the United States."
           (eq (marker-buffer calc-trail-pointer) calc-trail-buffer))
       (with-current-buffer calc-trail-buffer
        (goto-char (point-min))
-       (forward-line 1)
        (setq calc-trail-pointer (point-marker))))
   calc-trail-buffer)
 
@@ -2144,10 +2163,8 @@ the United States."
   (if (derived-mode-p 'calc-trail-mode)
       (progn
        (beginning-of-line)
-       (if (bobp)
-           (forward-line 1)
-         (if (eobp)
-             (forward-line -1)))
+       (if (eobp)
+            (forward-line -1))
        (if (or (bobp) (eobp))
            (setq overlay-arrow-position nil)   ; trail is empty
          (set-marker calc-trail-pointer (point) (current-buffer))
@@ -2161,7 +2178,7 @@ the United States."
            (if win
                (save-excursion
                  (forward-line (/ (window-height win) 2))
-                 (forward-line (- 1 (window-height win)))
+                 (forward-line (- 2 (window-height win)))
                  (set-window-start win (point))
                  (set-window-point win (+ calc-trail-pointer 4))
                  (set-buffer calc-main-buffer)