2 * Copyright (c) 1992, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 1992, 1993, 1994, 1995, 1996
5 * Keith Bostic. All rights reserved.
7 * See the LICENSE file for redistribution information.
12 #include <sys/types.h>
13 #include <sys/queue.h>
16 #include <bitstring.h>
23 #include "../common/common.h"
28 * Undo changes to this line.
30 * PUBLIC: int v_Undo(SCR *, VICMD *);
33 v_Undo(SCR *sp, VICMD *vp)
36 * Historically, U reset the cursor to the first column in the line
37 * (not the first non-blank). This seems a bit non-intuitive, but,
38 * considering that we may have undone multiple changes, anything
39 * else (including the cursor position stored in the logging records)
40 * is going to appear random.
46 * Set up the flags so that an immediately subsequent 'u' will roll
47 * forward, instead of backward. In historic vi, a 'u' following a
48 * 'U' redid all of the changes to the line. Given that the user has
49 * explicitly discarded those changes by entering 'U', it seems likely
50 * that the user wants something between the original and end forms of
51 * the line, so starting to replay the changes seems the best way to
54 F_SET(sp->ep, F_UNDO);
55 sp->ep->lundo = BACKWARD;
57 return (log_setline(sp));
62 * Undo the last change.
64 * PUBLIC: int v_undo(SCR *, VICMD *);
67 v_undo(SCR *sp, VICMD *vp)
71 /* Set the command count. */
72 VIP(sp)->u_ccnt = sp->ccnt;
76 * In historic vi, 'u' toggled between "undo" and "redo", i.e. 'u'
77 * undid the last undo. However, if there has been a change since
78 * the last undo/redo, we always do an undo. To make this work when
79 * the user can undo multiple operations, we leave the old semantic
80 * unchanged, but make '.' after a 'u' do another undo/redo operation.
81 * This has two problems.
83 * The first is that 'u' didn't set '.' in historic vi. So, if a
84 * user made a change, realized it was in the wrong place, does a
85 * 'u' to undo it, moves to the right place and then does '.', the
86 * change was reapplied. To make this work, we only apply the '.'
87 * to the undo command if it's the command immediately following an
88 * undo command. See vi/vi.c:getcmd() for the details.
90 * The second is that the traditional way to view the numbered cut
91 * buffers in vi was to enter the commands "1pu.u.u.u. which will
92 * no longer work because the '.' immediately follows the 'u' command.
93 * Since we provide a much better method of viewing buffers, and
94 * nobody can think of a better way of adding in multiple undo, this
98 * There is change to historic practice for the final cursor position
99 * in this implementation. In historic vi, if an undo was isolated to
100 * a single line, the cursor moved to the start of the change, and
101 * then, subsequent 'u' commands would not move it again. (It has been
102 * pointed out that users used multiple undo commands to get the cursor
103 * to the start of the changed text.) Nvi toggles between the cursor
104 * position before and after the change was made. One final issue is
105 * that historic vi only did this if the user had not moved off of the
106 * line before entering the undo command; otherwise, vi would move the
107 * cursor to the most attractive position on the changed line.
109 * It would be difficult to match historic practice in this area. You
110 * not only have to know that the changes were isolated to one line,
111 * but whether it was the first or second undo command as well. And,
112 * to completely match historic practice, we'd have to track users line
113 * changes, too. This isn't worth the effort.
116 if (!F_ISSET(ep, F_UNDO)) {
118 ep->lundo = BACKWARD;
119 } else if (!F_ISSET(vp, VC_ISDOT))
120 ep->lundo = ep->lundo == BACKWARD ? FORWARD : BACKWARD;
124 return (log_backward(sp, &vp->m_final));
126 return (log_forward(sp, &vp->m_final));