1;;; electric.el --- window maker and Command loop for `electric' modes
2
3;; Copyright (C) 1985, 1986, 1995, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Author: K. Shane Hartman
7;; Maintainer: FSF
8;; Keywords: extensions
9
10;; This file is part of GNU Emacs.
11
12;; GNU Emacs is free software; you can redistribute it and/or modify
13;; it under the terms of the GNU General Public License as published by
14;; the Free Software Foundation; either version 2, or (at your option)
15;; any later version.
16
17;; GNU Emacs is distributed in the hope that it will be useful,
18;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
20;; GNU General Public License for more details.
21
22;; You should have received a copy of the GNU General Public License
23;; along with GNU Emacs; see the file COPYING.  If not, write to the
24;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
25;; Boston, MA 02110-1301, USA.
26
27;;; Commentary:
28
29; zaaaaaaap
30
31;;; Code:
32
33;; This loop is the guts for non-standard modes which retain control
34;; until some event occurs.  It is a `do-forever', the only way out is
35;; to throw.  It assumes that you have set up the keymap, window, and
36;; everything else: all it does is read commands and execute them -
37;; providing error messages should one occur (if there is no loop
38;; function - which see).  The required argument is a tag which should
39;; expect a value of nil if the user decides to punt. The second
40;; argument is the prompt to be used: if nil, use "->", if 'noprompt,
41;; don't use a prompt, if a string, use that string as prompt, and if
42;; a function of no variable, it will be evaluated in every iteration
43;; of the loop and its return value, which can be nil, 'noprompt or a
44;; string, will be used as prompt.  Given third argument non-nil, it
45;; INHIBITS quitting unless the user types C-g at toplevel.  This is
46;; so user can do things like C-u C-g and not get thrown out.  Fourth
47;; argument, if non-nil, should be a function of two arguments which
48;; is called after every command is executed.  The fifth argument, if
49;; provided, is the state variable for the function.  If the
50;; loop-function gets an error, the loop will abort WITHOUT throwing
51;; (moral: use unwind-protect around call to this function for any
52;; critical stuff).  The second argument for the loop function is the
53;; conditions for any error that occurred or nil if none.
54
55(defun Electric-command-loop (return-tag
56			      &optional prompt inhibit-quit
57					loop-function loop-state)
58
59  (let (cmd
60        (err nil)
61        (prompt-string prompt))
62    (while t
63      (if (not (or (stringp prompt) (eq prompt nil) (eq prompt 'noprompt)))
64          (setq prompt-string (funcall prompt)))
65      (if (not (stringp prompt-string))
66          (if (eq prompt-string 'noprompt)
67              (setq prompt-string nil)
68            (setq prompt-string "->")))
69      (setq cmd (read-key-sequence prompt-string))
70      (setq last-command-char (aref cmd (1- (length cmd)))
71	    this-command (key-binding cmd t)
72	    cmd this-command)
73      ;; This makes universal-argument-other-key work.
74      (setq universal-argument-num-events 0)
75      (if (or (prog1 quit-flag (setq quit-flag nil))
76	      (eq last-input-char ?\C-g))
77	  (progn (setq unread-command-events nil
78		       prefix-arg nil)
79		 ;; If it wasn't cancelling a prefix character, then quit.
80		 (if (or (= (length (this-command-keys)) 1)
81			 (not inhibit-quit)) ; safety
82		     (progn (ding)
83			    (message "Quit")
84			    (throw return-tag nil))
85		   (setq cmd nil))))
86      (setq current-prefix-arg prefix-arg)
87      (if cmd
88	  (condition-case conditions
89	      (progn (command-execute cmd)
90		     (setq last-command this-command)
91		     (if (or (prog1 quit-flag (setq quit-flag nil))
92			     (eq last-input-char ?\C-g))
93			 (progn (setq unread-command-events nil)
94				(if (not inhibit-quit)
95				    (progn (ding)
96					   (message "Quit")
97					   (throw return-tag nil))
98				  (ding)))))
99	    (buffer-read-only (if loop-function
100				  (setq err conditions)
101				(ding)
102				(message "Buffer is read-only")
103				(sit-for 2)))
104	    (beginning-of-buffer (if loop-function
105				     (setq err conditions)
106				   (ding)
107				   (message "Beginning of Buffer")
108				   (sit-for 2)))
109	    (end-of-buffer (if loop-function
110			       (setq err conditions)
111			     (ding)
112			     (message "End of Buffer")
113			     (sit-for 2)))
114	    (error (if loop-function
115		       (setq err conditions)
116		     (ding)
117		     (message "Error: %s"
118			      (if (eq (car conditions) 'error)
119				  (car (cdr conditions))
120				(prin1-to-string conditions)))
121		     (sit-for 2))))
122	(ding))
123      (if loop-function (funcall loop-function loop-state err))))
124  (ding)
125  (throw return-tag nil))
126
127;; This function is like pop-to-buffer, sort of.
128;; The algorithm is
129;; If there is a window displaying buffer
130;; 	Select it
131;; Else if there is only one window
132;; 	Split it, selecting the window on the bottom with height being
133;; 	the lesser of max-height (if non-nil) and the number of lines in
134;;      the buffer to be displayed subject to window-min-height constraint.
135;; Else
136;; 	Switch to buffer in the current window.
137;;
138;; Then if max-height is nil, and not all of the lines in the buffer
139;; are displayed, grab the whole frame.
140;;
141;; Returns selected window on buffer positioned at point-min.
142
143(defun Electric-pop-up-window (buffer &optional max-height)
144  (let* ((win (or (get-buffer-window buffer) (selected-window)))
145	 (buf (get-buffer buffer))
146	 (one-window (one-window-p t))
147	 (pop-up-windows t)
148	 (pop-up-frames nil))
149    (if (not buf)
150	(error "Buffer %s does not exist" buffer)
151      (cond ((and (eq (window-buffer win) buf))
152	     (select-window win))
153	    (one-window
154	     (pop-to-buffer buffer)
155	     (setq win (selected-window)))
156	    (t
157	     (switch-to-buffer buf)))
158      (fit-window-to-buffer win max-height)
159      (goto-char (point-min))
160      win)))
161
162(provide 'electric)
163
164;;; arch-tag: dae045eb-dc2d-4fb7-9f27-9cc2ce277be8
165;;; electric.el ends here
166