lisp/electric.el

   1 ;;; electric.el --- window maker and Command loop for `electric' modes.
   2
   3 ;; Copyright (C) 1985, 1986 Free Software Foundation, Inc.
   4
   5 ;; Author: K. Shane Hartman
   6 ;; Maintainer: FSF
   7 ;; Keywords: extensions
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  23 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  24
  25 ;;; Commentary:
  26
  27 ; zaaaaaaap
  28
  29 ;;; Code:
  30
  31 ;; perhaps this should be in subr.el...
  32 (defun shrink-window-if-larger-than-buffer (window)
  33   (save-excursion
  34     (set-buffer (window-buffer window))
  35     (let ((w (selected-window)) ;save-window-excursion can't win
  36           (buffer-file-name buffer-file-name)
  37           (p (point))
  38           (n 0)
  39           (window-min-height 0)
  40           (buffer-read-only nil)
  41           (modified (buffer-modified-p))
  42           (buffer (current-buffer)))
  43       (unwind-protect
  44           (progn
  45             (select-window window)
  46             (goto-char (point-min))
  47             (while (pos-visible-in-window-p (point-max))
  48               ;; defeat file locking... don't try this at home, kids!
  49               (setq buffer-file-name nil)
  50               (insert ?\n) (setq n (1+ n)))
  51             (if (> n 0) (shrink-window (1- n))))
  52         (delete-region (point-min) (point))
  53         (set-buffer-modified-p modified)
  54         (goto-char p)
  55         (select-window w)
  56         ;; Make sure we unbind buffer-read-only
  57         ;; with the proper current buffer.
  58         (set-buffer buffer)))))
  59
  60 ;; This loop is the guts for non-standard modes which retain control
  61 ;; until some event occurs.  It is a `do-forever', the only way out is to
  62 ;; throw.  It assumes that you have set up the keymap, window, and
  63 ;; everything else: all it does is read commands and execute them -
  64 ;; providing error messages should one occur (if there is no loop
  65 ;; function - which see).  The required argument is a tag which should
  66 ;; expect a value of nil if the user decides to punt. The
  67 ;; second argument is a prompt string (defaults to "->").  Given third
  68 ;; argument non-nil, it INHIBITS quitting unless the user types C-g at
  69 ;; toplevel.  This is so user can do things like C-u C-g and not get
  70 ;; thrown out.  Fourth argument, if non-nil, should be a function of two
  71 ;; arguments which is called after every command is executed.  The fifth
  72 ;; argument, if provided, is the state variable for the function.  If the
  73 ;; loop-function gets an error, the loop will abort WITHOUT throwing
  74 ;; (moral: use unwind-protect around call to this function for any
  75 ;; critical stuff).  The second argument for the loop function is the
  76 ;; conditions for any error that occurred or nil if none.
  77
  78 (defun Electric-command-loop (return-tag
  79                               &optional prompt inhibit-quit
  80                                         loop-function loop-state)
  81   (if (not prompt) (setq prompt "->"))
  82   (let (cmd (err nil))
  83     (while t
  84       (setq cmd (read-key-sequence (if (stringp prompt)
  85                                        prompt (funcall prompt))))
  86       (setq last-command-char (aref cmd (1- (length cmd)))
  87             this-command (key-binding cmd)
  88             cmd this-command)
  89       (if (or (prog1 quit-flag (setq quit-flag nil))
  90               (= last-input-char ?\C-g))
  91           (progn (setq unread-command-events nil
  92                        prefix-arg nil)
  93                  ;; If it wasn't cancelling a prefix character, then quit.
  94                  (if (or (= (length (this-command-keys)) 1)
  95                          (not inhibit-quit)) ; safety
  96                      (progn (ding)
  97                             (message "Quit")
  98                             (throw return-tag nil))
  99                    (setq cmd nil))))
 100       (setq current-prefix-arg prefix-arg)
 101       (if cmd
 102           (condition-case conditions
 103               (progn (command-execute cmd)
 104                      (setq last-command this-command)
 105                      (if (or (prog1 quit-flag (setq quit-flag nil))
 106                              (= last-input-char ?\C-g))
 107                          (progn (setq unread-command-events nil)
 108                                 (if (not inhibit-quit)
 109                                     (progn (ding)
 110                                            (message "Quit")
 111                                            (throw return-tag nil))
 112                                   (ding)))))
 113             (buffer-read-only (if loop-function
 114                                   (setq err conditions)
 115                                 (ding)
 116                                 (message "Buffer is read-only")
 117                                 (sit-for 2)))
 118             (beginning-of-buffer (if loop-function
 119                                      (setq err conditions)
 120                                    (ding)
 121                                    (message "Beginning of Buffer")
 122                                    (sit-for 2)))
 123             (end-of-buffer (if loop-function
 124                                (setq err conditions)
 125                              (ding)
 126                              (message "End of Buffer")
 127                              (sit-for 2)))
 128             (error (if loop-function
 129                        (setq err conditions)
 130                      (ding)
 131                      (message "Error: %s"
 132                               (if (eq (car conditions) 'error)
 133                                   (car (cdr conditions))
 134                                 (prin1-to-string conditions)))
 135                      (sit-for 2))))
 136         (ding))
 137       (if loop-function (funcall loop-function loop-state err))))
 138   (ding)
 139   (throw return-tag nil))
 140
 141 ;; This function is like pop-to-buffer, sort of.
 142 ;; The algorithm is
 143 ;; If there is a window displaying buffer
 144 ;;      Select it
 145 ;; Else if there is only one window
 146 ;;      Split it, selecting the window on the bottom with height being
 147 ;;      the lesser of max-height (if non-nil) and the number of lines in
 148 ;;      the buffer to be displayed subject to window-min-height constraint.
 149 ;; Else
 150 ;;      Switch to buffer in the current window.
 151 ;;
 152 ;; Then if max-height is nil, and not all of the lines in the buffer
 153 ;; are displayed, grab the whole frame.
 154 ;;
 155 ;; Returns selected window on buffer positioned at point-min.
 156
 157 (defun Electric-pop-up-window (buffer &optional max-height)
 158   (let* ((win (or (get-buffer-window buffer) (selected-window)))
 159          (buf (get-buffer buffer))
 160          (one-window (one-window-p t))
 161          (pop-up-windows t)
 162          (target-height)
 163          (lines))
 164     (if (not buf)
 165         (error "Buffer %s does not exist" buffer)
 166       (save-excursion
 167         (set-buffer buf)
 168         (setq lines (count-lines (point-min) (point-max)))
 169         (setq target-height
 170               (min (max (if max-height (min max-height (1+ lines)) (1+ lines))
 171                         window-min-height)
 172                    (save-window-excursion
 173                      (delete-other-windows)
 174                      (1- (window-height (selected-window)))))))
 175       (cond ((and (eq (window-buffer win) buf))
 176              (select-window win))
 177             (one-window
 178              (goto-char (window-start win))
 179              (pop-to-buffer buffer)
 180              (setq win (selected-window))
 181              (enlarge-window (- target-height (window-height win))))
 182             (t
 183              (switch-to-buffer buf)))
 184       (if (and (not max-height)
 185                (> target-height (window-height (selected-window))))
 186           (progn (goto-char (window-start win))
 187                  (enlarge-window (- target-height (window-height win)))))
 188       (goto-char (point-min))
 189       win)))
 190
 191 (provide 'electric)
 192
 193 ;;; electric.el ends here