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Allow comment-indent-functions to specify exact indentation (Bug#385)

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* lisp/newcomment.el (comment-choose-indent): Interpret a cons of two
integers as indicating a range of acceptable indentation.
(comment-indent): Don't apply `comment-inline-offset',
`comment-choose-indent' already does that.
(comment-indent-function):
* doc/emacs/programs.texi (Options for Comments): Document new
acceptable return values.
* etc/NEWS: Announce it.
This commit is contained in:
Noam Postavsky 2017-06-14 00:08:15 -04:00
parent 018600f896
commit e832febfb4
3 changed files with 28 additions and 20 deletions
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9
doc/emacs/programs.texi
View file

@ -1146,9 +1146,12 @@ comment or for aligning an existing comment. It is set differently by
various major modes. The function is called with no arguments, but with
point at the beginning of the comment, or at the end of a line if a new
comment is to be inserted. It should return the column in which the
comment ought to start. For example, in Lisp mode, the indent hook
function bases its decision on how many semicolons begin an existing
comment, and on the code in the preceding lines.
comment ought to start. For example, the default hook function bases
its decision on how many comment characters begin an existing comment.
Emacs also tries to align comments on adjacent lines. To override
this, the function may return a cons of two (possibly equal) integers
to indicate an acceptable range of indentation.
@node Documentation
@section Documentation Lookup

4
etc/NEWS
View file

@ -405,6 +405,10 @@ display of raw bytes from octal to hex.
** You can now provide explicit field numbers in format specifiers.
For example, '(format "%2$s %1$s" "X" "Y")' produces "Y X".
+++
** 'comment-indent-function' values may now return a cons to specify a
range of indentation.
* Editing Changes in Emacs 26.1

35
lisp/newcomment.el
View file

@ -142,9 +142,10 @@ Should be an empty string if comments are terminated by end-of-line.")
;;;###autoload
(defvar comment-indent-function 'comment-indent-default
"Function to compute desired indentation for a comment.
This function is called with no args with point at the beginning of
the comment's starting delimiter and should return either the desired
column indentation or nil.
This function is called with no args with point at the beginning
of the comment's starting delimiter and should return either the
desired column indentation, a range of acceptable
indentation (MIN . MAX), or nil.
If nil is returned, indentation is delegated to `indent-according-to-mode'.")
;;;###autoload
@ -649,13 +650,20 @@ The criteria are (in this order):
- prefer INDENT (or `comment-column' if nil).
Point is expected to be at the start of the comment."
(unless indent (setq indent comment-column))
;; Avoid moving comments past the fill-column.
(let ((max (+ (current-column)
(- (or comment-fill-column fill-column)
(save-excursion (end-of-line) (current-column)))))
(other nil)
(min (save-excursion (skip-chars-backward " \t")
(if (bolp) 0 (+ comment-inline-offset (current-column))))))
(let ((other nil)
min max)
(pcase indent
(`(,lo . ,hi) (setq min lo) (setq max hi)
(setq indent comment-column))
(_ ;; Avoid moving comments past the fill-column.
(setq max (+ (current-column)
(- (or comment-fill-column fill-column)
(save-excursion (end-of-line) (current-column)))))
(setq min (save-excursion
(skip-chars-backward " \t")
;; Leave at least `comment-inline-offset' space after
;; other nonwhite text on the line.
(if (bolp) 0 (+ comment-inline-offset (current-column)))))))
;; Fix up the range.
(if (< max min) (setq max min))
;; Don't move past the fill column.
@ -750,13 +758,6 @@ If CONTINUE is non-nil, use the `comment-continue' markers if any."
;; If the comment is at the right of code, adjust the indentation.
(unless (save-excursion (skip-chars-backward " \t") (bolp))
(setq indent (comment-choose-indent indent)))
;; Update INDENT to leave at least one space
;; after other nonwhite text on the line.
(save-excursion
(skip-chars-backward " \t")
(unless (bolp)
(setq indent (max indent
(+ (current-column) comment-inline-offset)))))
;; If that's different from comment's current position, change it.
(unless (= (current-column) indent)
(delete-region (point) (progn (skip-chars-backward " \t") (point)))