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Add new function 'add-display-text-property'

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* doc/lispref/display.texi (Display Property): Document it.
* lisp/emacs-lisp/subr-x.el (add-display-text-property): New function.
This commit is contained in:
Lars Ingebrigtsen 2021-11-24 19:38:41 +01:00
parent 34f2878ce2
commit fde9363a57
4 changed files with 95 additions and 0 deletions
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45
lisp/emacs-lisp/subr-x.el
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@ -469,6 +469,51 @@ This takes into account combining characters and grapheme clusters."
(setq start (1+ start))))
(nreverse result)))
;;;###autoload
(defun add-display-text-property (start end prop value
&optional append object)
"Add display property PROP with VALUE to the text from START to END.
If any text in the region has a non-nil `display' property, those
properties are retained.
If APPEND is non-nil, append to the list of display properties;
otherwise prepend.
If OBJECT is non-nil, it should be a string or a buffer. If nil,
this defaults to the current buffer."
(let ((sub-start start)
(sub-end 0)
disp)
(while (< sub-end end)
(setq sub-end (next-single-property-change sub-start 'display object
(if (stringp object)
(min (length object) end)
(min end (point-max)))))
(if (not (setq disp (get-text-property sub-start 'display object)))
;; No old properties in this range.
(put-text-property sub-start sub-end 'display (list prop value))
;; We have old properties.
(let ((vector nil))
;; Make disp into a list.
(setq disp
(cond
((vectorp disp)
(setq vector t)
(seq-into disp 'list))
((not (consp (car disp)))
(list disp))
(t
disp)))
(setq disp
(if append
(append disp (list (list prop value)))
(append (list (list prop value)) disp)))
(when vector
(setq disp (seq-into disp 'vector)))
;; Finally update the range.
(put-text-property sub-start sub-end 'display disp)))
(setq sub-start sub-end))))
(provide 'subr-x)
;;; subr-x.el ends here