Fix Delete key on X by adapting normal-erase-is-backspace-mode for multi-tty. (Reported by Dan Waber and Dan Nicolaescu.)

* lisp/frame.el (terminal-parameter-p): New function.
  (terminal-parameter): Use it.

* lisp/simple.el (normal-erase-is-backspace): Add 'maybe option, set it as default.
  (normal-erase-is-backspace-mode): Rewrite for multiple display support.
  (normal-erase-is-backspace-setup-frame): New function.

* lisp/frame.el (make-frame): Call it.
* lisp/startup.el (command-line): Call it.

git-archimport-id: lorentey@elte.hu--2004/emacs--multi-tty--0--patch-427

4 files changed, 101 insertions, 59 deletions

diff --git a/README.multi-tty b/README.multi-tty
index ab77a707ede..75d9554f74f 100644
--- a/README.multi-tty
+++ b/README.multi-tty
@@ -391,6 +391,9 @@ THINGS TO DO
 ** Report GTK multi-display problems to GTK maintainers.  For extra
    credit, fix them.
 
+** Possibly turn off the double C-g feature when there is an X frame.
+   C.f. (emacs)Emergency Escape.
+
 ** frames-on-display-list should also accept frames.
 
 ** I smell something funny around pop_kboard's "deleted kboard" case.
@@ -483,6 +486,8 @@ THINGS TO DO
    `last-command', but SELECTED_FRAME()->display->kboard to get the
    value of `function-key-map'.
 
+** I think keyboard-translate-table should be made terminal-local.
+
 ** The single-keyboard mode of MULTI_KBOARD is extremely confusing
    sometimes; Emacs does not respond to stimuli from other keyboards.
    At least a beep or a message would be important, if the single-mode
@@ -533,9 +538,6 @@ THINGS TO DO
 
    See if xsmfns.c should be updated.
 
-** normal-erase-is-backspace-mode in simple.el needs to be updated for
-   multi-tty (rep. by Dan Waber).
-
 ** Hunt down display-related functions in frame.el and extend them all
    to accept display ids.
 
@@ -1249,5 +1251,11 @@ DIARY OF CHANGES
 
    (Fixed in patch-414 after detailed analysis by Kalle Olavi Niemitalo.)
 
+-- normal-erase-is-backspace-mode in simple.el needs to be updated for
+   multi-tty (rep. by Dan Waber).  (The Delete key is broken on X
+   because of this.)
+
+   (Fixed in patch-427.)
+
 ;;; arch-tag: 8da1619e-2e79-41a8-9ac9-a0485daad17d
 
diff --git a/lisp/frame.el b/lisp/frame.el
index 68dd7ddaf90..c8085762d2a 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -676,6 +676,7 @@ setup is for focus to follow the pointer."
       (error "Don't know how to create a frame on window system %s" w))
     (run-hooks 'before-make-frame-hook)
     (setq frame (funcall frame-creation-function (append parameters (cdr (assq w window-system-default-frame-alist)))))
+    (normal-erase-is-backspace-setup-frame frame)
     (run-hook-with-args 'after-make-frame-functions frame)
     frame))
 
@@ -1450,12 +1451,22 @@ TERMINAL can be a terminal id, a frame, or nil (meaning the
 selected frame's terminal)."
   (cdr (assq (terminal-id terminal) terminal-parameter-alist)))
 
+(defun terminal-parameter-p (terminal parameter)
+  "Return non-nil if PARAMETER is a terminal parameter on TERMINAL.
+
+The actual value returned in that case is a cell (PARAMETER . VALUE),
+where VALUE is the current value of PARAMETER.
+
+TERMINAL can be a terminal id, a frame, or nil (meaning the
+selected frame's terminal)."
+  (assq parameter (cdr (assq (terminal-id terminal) terminal-parameter-alist))))
+
 (defun terminal-parameter (terminal parameter)
   "Return TERMINAL's value for parameter PARAMETER.
 
 TERMINAL can be a terminal id, a frame, or nil (meaning the
 selected frame's terminal)."
-  (cdr (assq parameter (cdr (assq (terminal-id terminal) terminal-parameter-alist)))))
+  (cdr (terminal-parameter-p terminal parameter)))
 
 (defun set-terminal-parameter (terminal parameter value)
   "Set TERMINAL's value for parameter PARAMETER to VALUE.
diff --git a/lisp/simple.el b/lisp/simple.el
index 301b4cc996a..be5844fa794 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -5237,36 +5237,33 @@ the front of the list of recently selected ones."
 
 ;;; Handling of Backspace and Delete keys.
 
-(defcustom normal-erase-is-backspace
-  (and (not noninteractive)
-       (or (memq system-type '(ms-dos windows-nt))
-           (eq initial-window-system 'mac)
-           (and (memq initial-window-system '(x))
-                (fboundp 'x-backspace-delete-keys-p)
-                (x-backspace-delete-keys-p))
-           ;; If the terminal Emacs is running on has erase char
-           ;; set to ^H, use the Backspace key for deleting
-           ;; backward and, and the Delete key for deleting forward.
-           (and (null initial-window-system)
-                (eq tty-erase-char ?\^H))))
-  "If non-nil, Delete key deletes forward and Backspace key deletes backward.
-
-On window systems, the default value of this option is chosen
-according to the keyboard used.  If the keyboard has both a Backspace
-key and a Delete key, and both are mapped to their usual meanings, the
-option's default value is set to t, so that Backspace can be used to
-delete backward, and Delete can be used to delete forward.
-
-If not running under a window system, customizing this option accomplishes
-a similar effect by mapping C-h, which is usually generated by the
-Backspace key, to DEL, and by mapping DEL to C-d via
-`keyboard-translate'.  The former functionality of C-h is available on
-the F1 key.  You should probably not use this setting if you don't
-have both Backspace, Delete and F1 keys.
+(defcustom normal-erase-is-backspace 'maybe
+  "Set the default behaviour of the Delete and Backspace keys.
+
+If set to t, Delete key deletes forward and Backspace key deletes
+backward.
+
+If set to nil, both Delete and Backspace keys delete backward.
+
+If set to 'maybe (which is the default), Emacs automatically
+selects a behaviour.  On window systems, the behaviour depends on
+the keyboard used.  If the keyboard has both a Backspace key and
+a Delete key, and both are mapped to their usual meanings, the
+option's default value is set to t, so that Backspace can be used
+to delete backward, and Delete can be used to delete forward.
+
+If not running under a window system, customizing this option
+accomplishes a similar effect by mapping C-h, which is usually
+generated by the Backspace key, to DEL, and by mapping DEL to C-d
+via `keyboard-translate'.  The former functionality of C-h is
+available on the F1 key.  You should probably not use this
+setting if you don't have both Backspace, Delete and F1 keys.
 
 Setting this variable with setq doesn't take effect.  Programmatically,
 call `normal-erase-is-backspace-mode' (which see) instead."
-  :type 'boolean
+  :type '(choice (const :tag "Off" nil)
+                 (const :tag "Maybe" maybe)
+                 (other :tag "On" t))
   :group 'editing-basics
   :version "21.1"
   :set (lambda (symbol value)
@@ -5276,17 +5273,40 @@ call `normal-erase-is-backspace-mode' (which see) instead."
              (normal-erase-is-backspace-mode (or value 0))
            (set-default symbol value))))
 
+(defun normal-erase-is-backspace-setup-frame (&optional frame)
+  "Set up `normal-erase-is-backspace-mode' on FRAME, if necessary."
+  (unless frame (setq frame (selected-frame)))
+  (with-selected-frame frame
+    (unless (terminal-parameter-p nil 'normal-erase-is-backspace)
+      (if (cond ((terminal-parameter-p nil 'normal-erase-is-backspace)
+                 (terminal-parameter nil 'normal-erase-is-backspace))
+                ((eq normal-erase-is-backspace 'maybe)
+                 (and (not noninteractive)
+                      (or (memq system-type '(ms-dos windows-nt))
+                          (eq window-system 'mac)
+                          (and (memq window-system '(x))
+                               (fboundp 'x-backspace-delete-keys-p)
+                               (x-backspace-delete-keys-p))
+                          ;; If the terminal Emacs is running on has erase char
+                          ;; set to ^H, use the Backspace key for deleting
+                          ;; backward and, and the Delete key for deleting forward.
+                          (and (null window-system)
+                               (eq tty-erase-char ?\^H)))))
+                (t
+                 normal-erase-is-backspace))
+          (normal-erase-is-backspace-mode 1)
+        (normal-erase-is-backspace-mode 0)))))
 
 (defun normal-erase-is-backspace-mode (&optional arg)
   "Toggle the Erase and Delete mode of the Backspace and Delete keys.
 
 With numeric arg, turn the mode on if and only if ARG is positive.
 
-On window systems, when this mode is on, Delete is mapped to C-d and
-Backspace is mapped to DEL; when this mode is off, both Delete and
-Backspace are mapped to DEL.  (The remapping goes via
-`function-key-map', so binding Delete or Backspace in the global or
-local keymap will override that.)
+On window systems, when this mode is on, Delete is mapped to C-d
+and Backspace is mapped to DEL; when this mode is off, both
+Delete and Backspace are mapped to DEL.  (The remapping goes via
+`local-function-key-map', so binding Delete or Backspace in the
+global or local keymap will override that.)
 
 In addition, on window systems, the bindings of C-Delete, M-Delete,
 C-M-Delete, C-Backspace, M-Backspace, and C-M-Backspace are changed in
@@ -5308,33 +5328,34 @@ have both Backspace, Delete and F1 keys.
 
 See also `normal-erase-is-backspace'."
   (interactive "P")
-  (setq normal-erase-is-backspace
-        (if arg
-            (> (prefix-numeric-value arg) 0)
-          (not normal-erase-is-backspace)))
+  (set-terminal-parameter
+   nil 'normal-erase-is-backspace
+   (if arg
+       (> (prefix-numeric-value arg) 0)
+     (not (terminal-parameter nil 'normal-erase-is-backspace))))
 
   (cond ((or (memq window-system '(x w32 mac pc))
              (memq system-type '(ms-dos windows-nt)))
-         (let ((bindings
-                `(([C-delete] [C-backspace])
-                  ([M-delete] [M-backspace])
-                  ([C-M-delete] [C-M-backspace])
-                  (,esc-map
-                   [C-delete] [C-backspace])))
-               (old-state (lookup-key function-key-map [delete])))
-
-           (if normal-erase-is-backspace
+         (let* ((lfkm (terminal-local-value 'local-function-key-map nil))
+                (bindings
+                 `(([C-delete] [C-backspace])
+                   ([M-delete] [M-backspace])
+                   ([C-M-delete] [C-M-backspace])
+                   (,esc-map
+                    [C-delete] [C-backspace])))
+                (old-state (lookup-key lfkm [delete])))
+
+           (if (terminal-parameter nil 'normal-erase-is-backspace)
                (progn
-                 ;; XXX Perhaps this mode should be terminal-local, not global -- lorentey
-                 (define-key function-key-map [delete] [?\C-d])
-                 (define-key function-key-map [kp-delete] [?\C-d])
-                 (define-key function-key-map [backspace] [?\C-?]))
-             (define-key function-key-map [delete] [?\C-?])
-             (define-key function-key-map [kp-delete] [?\C-?])
-             (define-key function-key-map [backspace] [?\C-?]))
+                 (define-key lfkm [delete] [?\C-d])
+                 (define-key lfkm [kp-delete] [?\C-d])
+                 (define-key lfkm [backspace] [?\C-?]))
+             (define-key lfkm [delete] [?\C-?])
+             (define-key lfkm [kp-delete] [?\C-?])
+             (define-key lfkm [backspace] [?\C-?]))
 
            ;; Maybe swap bindings of C-delete and C-backspace, etc.
-           (unless (equal old-state (lookup-key function-key-map [delete]))
+           (unless (equal old-state (lookup-key lfkm [delete]))
              (dolist (binding bindings)
                (let ((map global-map))
                  (when (keymapp (car binding))
@@ -5346,8 +5367,9 @@ See also `normal-erase-is-backspace'."
                    (define-key map key1 binding2)
                    (define-key map key2 binding1)))))))
          (t
-          (if normal-erase-is-backspace
+          (if (terminal-parameter nil 'normal-erase-is-backspace)
               (progn
+                ;; XXX This should be terminal-local -- lorentey
                 (keyboard-translate ?\C-h ?\C-?)
                 (keyboard-translate ?\C-? ?\C-d))
             (keyboard-translate ?\C-h ?\C-h)
diff --git a/lisp/startup.el b/lisp/startup.el
index f5b01809512..c7bd6b323e9 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -756,9 +756,10 @@ opening the first frame (e.g. open a connection to an X server).")
   ;; Can't do this init in defcustom because the relevant variables
   ;; are not set.
   (custom-reevaluate-setting 'blink-cursor-mode)
-  (custom-reevaluate-setting 'normal-erase-is-backspace)
   (custom-reevaluate-setting 'tooltip-mode)
 
+  (normal-erase-is-backspace-setup-frame)
+
   ;; Register default TTY colors for the case the terminal hasn't a
   ;; terminal init file.
   ;; We do this regardles of whether the terminal supports colors