Function: describe-variable
describe-variable is an autoloaded, interactive and byte-compiled
function defined in help-fns.el.gz.
Signature
(describe-variable VARIABLE &optional BUFFER FRAME)
Documentation
Display the full documentation of VARIABLE (a symbol).
Returns the documentation as a string, also.
If VARIABLE has a buffer-local value in BUFFER or FRAME
(default to the current buffer and current frame),
it is displayed along with the global value.
Probably introduced at or before Emacs version 27.1.
Key Bindings
Source Code
;; Defined in /usr/src/emacs/lisp/help-fns.el.gz
;;;###autoload
(defun describe-variable (variable &optional buffer frame)
"Display the full documentation of VARIABLE (a symbol).
Returns the documentation as a string, also.
If VARIABLE has a buffer-local value in BUFFER or FRAME
\(default to the current buffer and current frame),
it is displayed along with the global value."
(interactive
(let ((v (variable-at-point))
(enable-recursive-minibuffers t)
(orig-buffer (current-buffer))
val)
(setq val (completing-read
(format-prompt "Describe variable" (and (symbolp v) v))
#'help--symbol-completion-table
(lambda (vv)
(or (get vv 'variable-documentation)
(and (not (keywordp vv))
;; Since the variable may only exist in the
;; original buffer, we have to look for it
;; there.
(buffer-local-boundp vv orig-buffer))))
t nil nil
(if (symbolp v) (symbol-name v))))
(list (if (equal val "")
v (intern val)))))
(let (file-name)
(unless (buffer-live-p buffer) (setq buffer (current-buffer)))
(unless (frame-live-p frame) (setq frame (selected-frame)))
(if (not (symbolp variable))
(user-error "You didn't specify a variable")
(save-excursion
(let ((valvoid (not (with-current-buffer buffer (boundp variable))))
val val-start-pos locus)
;; Extract the value before setting up the output buffer,
;; in case `buffer' *is* the output buffer.
(unless valvoid
(with-selected-frame frame
(with-current-buffer buffer
(setq val (symbol-value variable)
locus (variable-binding-locus variable)))))
(help-setup-xref (list #'describe-variable variable buffer)
(called-interactively-p 'interactive))
(with-help-window (help-buffer)
(with-current-buffer buffer
(prin1 variable)
(setq file-name (find-lisp-object-file-name variable 'defvar))
(princ (if file-name
(progn
(princ (format-message
" is a variable defined in `%s'.\n\n"
(if (eq file-name 'C-source)
"C source code"
(help-fns-short-filename file-name))))
(with-current-buffer standard-output
(setq help-mode--current-data
(list :symbol variable
:type (if (eq file-name 'C-source)
'variable
'defvar)
:file file-name))
(save-excursion
(re-search-backward (substitute-command-keys
"`\\([^`']+\\)'")
nil t)
(help-xref-button 1 'help-variable-def
variable file-name)))
(if valvoid
"It is void as a variable."
"Its "))
(with-current-buffer standard-output
(setq help-mode--current-data (list :symbol variable
:type 'variable)))
(if valvoid
" is void as a variable."
(substitute-command-keys "'s ")))))
(unless valvoid
(with-current-buffer standard-output
(setq val-start-pos (point))
(princ "value is")
(let ((line-beg (line-beginning-position))
(print-rep
(let ((rep
(let ((print-quoted t)
(print-circle t))
(cl-prin1-to-string val))))
(if (and (symbolp val) (not (booleanp val)))
(format-message "`%s'" rep)
rep))))
(if (< (+ (length print-rep) (point) (- line-beg)) 68)
(insert " " print-rep)
(terpri)
(let ((buf (current-buffer)))
(with-temp-buffer
(lisp-mode-variables nil)
(set-syntax-table emacs-lisp-mode-syntax-table)
(insert print-rep)
(pp-buffer)
(let ((pp-buffer (current-buffer)))
(with-current-buffer buf
(insert-buffer-substring pp-buffer)))))
;; Remove trailing newline.
(and (= (char-before) ?\n) (delete-char -1)))
(let* ((sv (get variable 'standard-value))
(origval (and (consp sv)
(condition-case nil
(eval (car sv) t)
(error :help-eval-error))))
from)
(when (and (consp sv)
(not (equal origval val))
(not (equal origval :help-eval-error)))
(princ "\nOriginal value was \n")
(setq from (point))
(if (and (symbolp origval) (not (booleanp origval)))
(let* ((rep (cl-prin1-to-string origval))
(print-rep (format-message "`%s'" rep)))
(insert print-rep))
(cl-prin1 origval))
(save-restriction
(narrow-to-region from (point))
(save-excursion (pp-buffer)))
(if (< (point) (+ from 20))
(delete-region (1- from) from)))))))
(terpri)
(when locus
(cond
((bufferp locus)
(princ (format "Local in buffer %s; "
(buffer-name buffer))))
((terminal-live-p locus)
(princ "It is a terminal-local variable; "))
(t
(princ (format "It is local to %S" locus))))
(if (not (default-boundp variable))
(princ "globally void")
(let ((global-val (default-value variable)))
(with-current-buffer standard-output
(princ "global value is ")
(if (eq val global-val)
(princ "the same.")
(terpri)
;; Fixme: pp can take an age if you happen to
;; ask for a very large expression. We should
;; probably print it raw once and check it's a
;; sensible size before prettyprinting. -- fx
(let ((from (point)))
(cl-prin1 global-val)
(save-restriction
(narrow-to-region from (point))
(save-excursion (pp-buffer)))
;; See previous comment for this function.
;; (help-xref-on-pp from (point))
(if (< (point) (+ from 20))
(delete-region (1- from) from)))))))
(terpri))
;; If the value is large, move it to the end.
(with-current-buffer standard-output
(when (> (count-lines (point-min) (point-max)) 10)
;; Note that setting the syntax table like below
;; makes forward-sexp move over a `'s' at the end
;; of a symbol.
(set-syntax-table emacs-lisp-mode-syntax-table)
(goto-char val-start-pos)
(when (looking-at "value is") (replace-match ""))
(save-excursion
(insert "\n\nValue:")
(setq-local help-button-cache (point-marker)))
(insert "value is shown ")
(insert-button "below"
'action help-button-cache
'follow-link t
'help-echo "mouse-2, RET: show value")
(insert ".\n")))
(terpri)
(let* ((alias (condition-case nil
(indirect-variable variable)
(error variable)))
(doc (or (documentation-property
variable 'variable-documentation)
(documentation-property
alias 'variable-documentation))))
(with-current-buffer standard-output
(insert (or doc "Not documented as a variable.")))
;; Output the indented administrative bits.
(with-current-buffer buffer
(help-fns--run-describe-functions
help-fns-describe-variable-functions variable))
(with-current-buffer standard-output
;; If we have the long value of the variable at the
;; end, remove superfluous empty lines before it.
(unless (eobp)
(while (looking-at-p "\n")
(delete-char 1)))))
(with-current-buffer standard-output
;; Return the text we displayed.
(buffer-string))))))))