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Display some character widget values in a more user-friendly way

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* lisp/wid-edit.el (widget-character--escape-sequences-alist): New
variable.
(widget-character--change-character-display): New function.  Use the new
variable.
(widget-character-notify): New function, to keep track of the changes
in the character widget, and display characters like tab,
newline and spaces better.
(character widget): Use widget-character-notify as the notify
function.  Use widget-character--change-character-display for the
internal representation of value (bug#15925).
This commit is contained in:
Mauro Aranda 2020-09-26 17:09:22 +02:00 • committed by Lars Ingebrigtsen
parent 9b6f564227
commit 6cc0ff19dd
1 changed files with 62 additions and 4 deletions
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66
lisp/wid-edit.el
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@ -1369,7 +1369,8 @@ Unlike (get-char-property POS \\='field), this works with empty fields too."
(signal 'text-read-only
'("Attempt to change text outside editable field")))
(widget-field-use-before-change
(widget-apply from-field :notify from-field))))))
(widget-apply from-field :notify
from-field (list 'before-change from to)))))))
(defun widget-add-change ()
(remove-hook 'post-command-hook 'widget-add-change t)
@ -1406,7 +1407,7 @@ Unlike (get-char-property POS \\='field), this works with empty fields too."
(> (point) begin))
(delete-char -1)))))))
(widget-specify-secret field))
(widget-apply field :notify field))))
(widget-apply field :notify field (list 'after-change from to)))))
;;; Widget Functions
;;
@ -3532,13 +3533,70 @@ To use this type, you must define :match or :match-alternatives."
:value-to-internal (lambda (_widget value)
(if (stringp value)
value
(char-to-string value)))
(let ((disp
(widget-character--change-character-display
value)))
(if disp
(propertize (char-to-string value) 'display disp)
(char-to-string value)))))
:value-to-external (lambda (_widget value)
(if (stringp value)
(aref value 0)
value))
:match (lambda (_widget value)
(characterp value)))
(characterp value))
:notify #'widget-character-notify)
;; Only some escape sequences, not all of them. (Bug#15925)
(defvar widget-character--escape-sequences-alist
'((?\t . ?t)
(?\n . ?n)
(?\s . ?s))
"Alist that associates escape sequences to a character.
Each element has the form (ESCAPE-SEQUENCE . CHARACTER).
The character widget uses this alist to display the
non-printable character represented by ESCAPE-SEQUENCE as \\CHARACTER,
since that makes it easier to see what's in the widget.")
(defun widget-character--change-character-display (c)
"Return a string to represent the character C, or nil.
The character widget represents some characters (e.g., the newline character
or the tab character) specially, to make it easier for the user to see what's
in it. For those characters, return a string to display that character in a
more user-friendly way.
For the caller, nil should mean that it is good enough to use the return value
of `char-to-string' for the representation of C."
(let ((char (alist-get c widget-character--escape-sequences-alist)))
(and char (propertize (format "\\%c" char) 'face 'escape-glyph))))
(defun widget-character-notify (widget child &optional event)
"Notify function for the character widget.
This function allows the widget character to better display some characters,
like the newline character or the tab character."
(when (eq (car-safe event) 'after-change)
(let* ((start (nth 1 event))
(end (nth 2 event))
str)
(if (eql start end)
(when (char-equal (widget-value widget) ?\s)
;; The character widget is not really empty:
;; its value is a single space character.
;; We need to propertize it again, if it became empty for a while.
(let ((ov (widget-get widget :field-overlay)))
(put-text-property
(overlay-start ov) (overlay-end ov)
'display (widget-character--change-character-display ?\s))))
(setq str (buffer-substring-no-properties start end))
;; This assumes the user enters one character at a time,
;; and does nothing crazy, like yanking a long string.
(let ((disp (widget-character--change-character-display (aref str 0))))
(when disp
(put-text-property start end 'display disp))))))
(widget-default-notify widget child event))
(define-widget 'list 'group
"A Lisp list."