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198 lines
7.2 KiB
EmacsLisp
198 lines
7.2 KiB
EmacsLisp
;;; reposition.el --- center a Lisp function or comment on the screen
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;; Copyright (C) 1991, 1994 Free Software Foundation, Inc.
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;; Author: Michael D. Ernst <mernst@theory.lcs.mit.edu>
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;; Created: Jan 1991
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;; Maintainer: FSF
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to
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;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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;;; Commentary:
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;;; Reposition-window makes an entire function definition or comment visible,
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;;; or, if it is already visible, places it at the top of the window;
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;;; additional invocations toggle the visibility of comments preceding the
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;;; code. For the gory details, see the documentation for reposition-window;
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;;; rather than reading that, you may just want to play with it.
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;;; This tries pretty hard to do the recentering correctly; the precise
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;;; action depends on what the buffer looks like. If you find a situation
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;;; where it doesn't behave well, let me know. This function is modeled
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;;; after one of the same name in ZMACS, but the code is all-new and the
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;;; behavior in some situations differs.
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;;; Code:
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;;;###autoload
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(defun reposition-window (&optional arg)
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"Make the current definition and/or comment visible.
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Further invocations move it to the top of the window or toggle the
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visibility of comments that precede it.
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Point is left unchanged unless prefix ARG is supplied.
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If the definition is fully onscreen, it is moved to the top of the
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window. If it is partly offscreen, the window is scrolled to get the
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definition (or as much as will fit) onscreen, unless point is in a comment
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which is also partly offscreen, in which case the scrolling attempts to get
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as much of the comment onscreen as possible.
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Initially `reposition-window' attempts to make both the definition and
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preceding comments visible. Further invocations toggle the visibility of
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the comment lines.
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If ARG is non-nil, point may move in order to make the whole defun
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visible (if only part could otherwise be made so), to make the defun line
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visible (if point is in code and it could not be made so, or if only
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comments, including the first comment line, are visible), or to make the
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first comment line visible (if point is in a comment)."
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(interactive "P")
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(let* (;; (here (save-excursion (beginning-of-line) (point)))
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(here (point))
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;; change this name once I've gotten rid of references to ht.
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;; this is actually the number of the last screen line
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(ht (- (window-height (selected-window)) 2))
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(line (repos-count-screen-lines (window-start) (point)))
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(comment-height
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;; The call to max deals with the case of cursor between defuns.
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(max 0
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(repos-count-screen-lines-signed
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;; the beginning of the preceding comment
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(save-excursion
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(if (not (eobp)) (forward-char 1))
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(end-of-defun -1)
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;; Skip whitespace, newlines, and form feeds.
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(if (re-search-forward "[^ \t\n\f]" nil t)
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(backward-char 1))
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(point))
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here)))
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(defun-height
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(repos-count-screen-lines-signed
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(save-excursion
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(end-of-defun 1) ; so comments associate with following defuns
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(beginning-of-defun 1)
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(point))
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here))
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;; This must be positive, so don't use the signed version.
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(defun-depth (repos-count-screen-lines here
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(save-excursion
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(end-of-defun 1)
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(point))))
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(defun-line-onscreen-p
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(and (<= defun-height line)
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(<= (- line defun-height) ht))))
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(cond ((or (= comment-height line)
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(and (= line ht)
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(> comment-height line)
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;; if defun line offscreen, we should be in case 4
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defun-line-onscreen-p))
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;; Either first comment line is at top of screen or (point at
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;; bottom of screen, defun line onscreen, and first comment line
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;; off top of screen). That is, it looks like we just did
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;; recenter-definition, trying to fit as much of the comment
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;; onscreen as possible. Put defun line at top of screen; that
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;; is, show as much code, and as few comments, as possible.
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(if (and arg (> defun-depth (1+ ht)))
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;; Can't fit whole defun onscreen without moving point.
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(progn (end-of-defun) (beginning-of-defun) (recenter 0))
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(recenter (max defun-height 0)))
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;;(repos-debug-macro "1")
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)
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((or (= defun-height line)
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(= line 0)
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(and (< line comment-height)
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(< defun-height 0)))
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;; Defun line or cursor at top of screen, OR cursor in comment
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;; whose first line is offscreen.
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;; Avoid moving definition up even if defun runs offscreen;
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;; we care more about getting the comment onscreen.
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(cond ((= line ht)
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;; cursor on last screen line (and so in a comment)
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(if arg (progn (end-of-defun) (beginning-of-defun)))
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(recenter 0)
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;;(repos-debug-macro "2a")
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)
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;; This condition, copied from case 4, may not be quite right
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((and arg (< ht comment-height))
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;; Can't get first comment line onscreen.
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;; Go there and try again.
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(forward-line (- comment-height))
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(beginning-of-line)
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;; was (reposition-window)
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(recenter 0)
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;;(repos-debug-macro "2b")
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)
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(t
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(recenter (min ht comment-height))
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;;(repos-debug-macro "2c")
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))
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;; (recenter (min ht comment-height))
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)
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((and (> (+ line defun-depth -1) ht)
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defun-line-onscreen-p)
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;; Defun runs off the bottom of the screen and the defun line
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;; is onscreen.
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;; Move the defun up.
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(recenter (max 0 (1+ (- ht defun-depth)) defun-height))
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;;(repos-debug-macro "3")
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)
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(t
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;; If on the bottom line and comment start is offscreen
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;; then just move all comments offscreen, or at least as
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;; far as they'll go.
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;; Try to get as much of the comments onscreen as possible.
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(if (and arg (< ht comment-height))
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;; Can't get defun line onscreen; go there and try again.
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(progn (forward-line (- defun-height))
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(beginning-of-line)
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(reposition-window))
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(recenter (min ht comment-height)))
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;;(repos-debug-macro "4")
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))))
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;;;###autoload (define-key esc-map "\C-l" 'reposition-window)
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;;; Auxiliary functions
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;; Return number of screen lines between START and END.
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(defun repos-count-screen-lines (start end)
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(save-excursion
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(save-restriction
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(narrow-to-region start end)
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(goto-char (point-min))
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(vertical-motion (- (point-max) (point-min))))))
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;; Return number of screen lines between START and END; returns a negative
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;; number if END precedes START.
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(defun repos-count-screen-lines-signed (start end)
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(let ((lines (repos-count-screen-lines start end)))
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(if (< start end)
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lines
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(- lines))))
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; (defmacro repos-debug-macro (case-no)
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; (` (message
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; (concat "Case " (, case-no) ": %s %s %s %s %s")
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; ht line comment-height defun-height defun-depth)))
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;;; reposition.el ends here
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