Add instructions to 'standard-display-by-replacement-char'

* lisp/disp-table.el (standard-display-by-replacement-char): Add a
preamble to the generated code with instructions.  Suggested by
Richard Stallman <rms@gnu.org>.

1 files changed, 8 insertions, 1 deletions

diff --git a/lisp/disp-table.el b/lisp/disp-table.el
index 53dff1e7097..c762b88cb66 100644
--- a/lisp/disp-table.el
+++ b/lisp/disp-table.el
@@ -336,7 +336,14 @@ which characters can be displayed and which cannot."
         first)
     (with-current-buffer buf
       (erase-buffer)
-      (insert "(let ((tbl standard-display-table))\n")
+      (insert "\
+;; Evaluate the Lisp code below to make Emacs show the standard
+;; replacement character as a substitute for each undisplayable character.
+;; One way to do that is with \"C-x h M-x eval-region RET\".
+;; Normally you would put this code in your Emacs initialization file,
+;; perhaps conditionally based on the type of terminal, so that
+;; this setup happens automatically on each startup.
+(let ((tbl standard-display-table))\n")
       (while (<= ch to)
         (cond
          ((or (char-displayable-p ch)