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