lisp/electric.el

   1 ;;; electric.el --- window maker and Command loop for `electric' modes.
   2
   3 ;; Author: K. Shane Hartman
   4 ;; Maintainer: FSF
   5 ;; Last-Modified: 09 Jun 1992
   6
   7 ;; Copyright (C) 1985, 1986 Free Software Foundation, Inc.
   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
  26 ; zaaaaaaap
  27
  28 ;; perhaps this should be in subr.el...
  29 (defun shrink-window-if-larger-than-buffer (window)
  30   (save-excursion
  31     (set-buffer (window-buffer window))
  32     (let ((w (selected-window)) ;save-window-excursion can't win
  33           (buffer-file-name buffer-file-name)
  34           (p (point))
  35           (n 0)
  36           (window-min-height 0)
  37           (buffer-read-only nil)
  38           (modified (buffer-modified-p))
  39           (buffer (current-buffer)))
  40       (unwind-protect
  41           (progn
  42             (select-window window)
  43             (goto-char (point-min))
  44             (while (pos-visible-in-window-p (point-max))
  45               ;; defeat file locking... don't try this at home, kids!
  46               (setq buffer-file-name nil)
  47               (insert ?\n) (setq n (1+ n)))
  48             (if (> n 0) (shrink-window (1- n))))
  49         (delete-region (point-min) (point))
  50         (set-buffer-modified-p modified)
  51         (goto-char p)
  52         (select-window w)
  53         ;; Make sure we unbind buffer-read-only
  54         ;; with the proper current buffer.
  55         (set-buffer buffer)))))
  56
  57 ;; This loop is the guts for non-standard modes which retain control
  58 ;; until some event occurs.  It is a `do-forever', the only way out is to
  59 ;; throw.  It assumes that you have set up the keymap, window, and
  60 ;; everything else: all it does is read commands and execute them -
  61 ;; providing error messages should one occur (if there is no loop
  62 ;; function - which see).  The required argument is a tag which should
  63 ;; expect a value of nil if the user decides to punt. The
  64 ;; second argument is a prompt string (defaults to "->").  Given third
  65 ;; argument non-nil, it INHIBITS quitting unless the user types C-g at
  66 ;; toplevel.  This is so user can do things like C-u C-g and not get
  67 ;; thrown out.  Fourth argument, if non-nil, should be a function of two
  68 ;; arguments which is called after every command is executed.  The fifth
  69 ;; argument, if provided, is the state variable for the function.  If the
  70 ;; loop-function gets an error, the loop will abort WITHOUT throwing
  71 ;; (moral: use unwind-protect around call to this function for any
  72 ;; critical stuff).  The second argument for the loop function is the
  73 ;; conditions for any error that occurred or nil if none.
  74
  75 (defun Electric-command-loop (return-tag
  76                               &optional prompt inhibit-quit
  77                                         loop-function loop-state)
  78   (if (not prompt) (setq prompt "->"))
  79   (let (cmd (err nil))
  80     (while t
  81       (setq cmd (read-key-sequence (if (stringp prompt)
  82                                        prompt (funcall prompt))))
  83       (setq last-command-char (aref cmd (1- (length cmd)))
  84             this-command (key-binding cmd)
  85             cmd this-command)
  86       (if (or (prog1 quit-flag (setq quit-flag nil))
  87               (= last-input-char ?\C-g))
  88           (progn (setq unread-command-char -1
  89                        prefix-arg nil)
  90                  ;; If it wasn't cancelling a prefix character, then quit.
  91                  (if (or (= (length (this-command-keys)) 1)
  92                          (not inhibit-quit)) ; safety
  93                      (progn (ding)
  94                             (message "Quit")
  95                             (throw return-tag nil))
  96                    (setq cmd nil))))
  97       (setq current-prefix-arg prefix-arg)
  98       (if cmd
  99           (condition-case conditions
 100               (progn (command-execute cmd)
 101                      (setq last-command this-command)
 102                      (if (or (prog1 quit-flag (setq quit-flag nil))
 103                              (= last-input-char ?\C-g))
 104                          (progn (setq unread-command-char -1)
 105                                 (if (not inhibit-quit)
 106                                     (progn (ding)
 107                                            (message "Quit")
 108                                            (throw return-tag nil))
 109                                   (ding)))))
 110             (buffer-read-only (if loop-function
 111                                   (setq err conditions)
 112                                 (ding)
 113                                 (message "Buffer is read-only")
 114                                 (sit-for 2)))
 115             (beginning-of-buffer (if loop-function
 116                                      (setq err conditions)
 117                                    (ding)
 118                                    (message "Beginning of Buffer")
 119                                    (sit-for 2)))
 120             (end-of-buffer (if loop-function
 121                                (setq err conditions)
 122                              (ding)
 123                              (message "End of Buffer")
 124                              (sit-for 2)))
 125             (error (if loop-function
 126                        (setq err conditions)
 127                      (ding)
 128                      (message "Error: %s"
 129                               (if (eq (car conditions) 'error)
 130                                   (car (cdr conditions))
 131                                 (prin1-to-string conditions)))
 132                      (sit-for 2))))
 133         (ding))
 134       (if loop-function (funcall loop-function loop-state err))))
 135   (ding)
 136   (throw return-tag nil))
 137
 138 ;; This function is like pop-to-buffer, sort of.
 139 ;; The algorithm is
 140 ;; If there is a window displaying buffer
 141 ;;      Select it
 142 ;; Else if there is only one window
 143 ;;      Split it, selecting the window on the bottom with height being
 144 ;;      the lesser of max-height (if non-nil) and the number of lines in
 145 ;;      the buffer to be displayed subject to window-min-height constraint.
 146 ;; Else
 147 ;;      Switch to buffer in the current window.
 148 ;;
 149 ;; Then if max-height is nil, and not all of the lines in the buffer
 150 ;; are displayed, grab the whole frame.
 151 ;;
 152 ;; Returns selected window on buffer positioned at point-min.
 153
 154 (defun Electric-pop-up-window (buffer &optional max-height)
 155   (let* ((win (or (get-buffer-window buffer) (selected-window)))
 156          (buf (get-buffer buffer))
 157          (one-window (one-window-p t))
 158          (pop-up-windows t)
 159          (target-height)
 160          (lines))
 161     (if (not buf)
 162         (error "Buffer %s does not exist" buffer)
 163       (save-excursion
 164         (set-buffer buf)
 165         (setq lines (count-lines (point-min) (point-max)))
 166         (setq target-height
 167               (min (max (if max-height (min max-height (1+ lines)) (1+ lines))
 168                         window-min-height)
 169                    (save-window-excursion
 170                      (delete-other-windows)
 171                      (1- (window-height (selected-window)))))))
 172       (cond ((and (eq (window-buffer win) buf))
 173              (select-window win))
 174             (one-window
 175              (goto-char (window-start win))
 176              (pop-to-buffer buffer)
 177              (setq win (selected-window))
 178              (enlarge-window (- target-height (window-height win))))
 179             (t
 180              (switch-to-buffer buf)))
 181       (if (and (not max-height)
 182                (> target-height (window-height (selected-window))))
 183           (progn (goto-char (window-start win))
 184                  (enlarge-window (- target-height (window-height win)))))
 185       (goto-char (point-min))
 186       win)))
 187
 188 (provide 'electric)
 189
 190 ; electric.el ends here