vi/v_undo.c

   1 /*-
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * %sccs.include.redist.c%
   6  */
   7
   8 #ifndef lint
   9 static char sccsid[] = "$Id: v_undo.c,v 8.6 1994/01/08 13:56:10 bostic Exp $ (Berkeley) $Date: 1994/01/08 13:56:10 $";
  10 #endif /* not lint */
  11
  12 #include <sys/types.h>
  13
  14 #include <errno.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17
  18 #include "vi.h"
  19 #include "vcmd.h"
  20
  21 /*
  22  * v_Undo -- U
  23  *      Undo changes to this line.
  24  */
  25 int
  26 v_Undo(sp, ep, vp, fm, tm, rp)
  27         SCR *sp;
  28         EXF *ep;
  29         VICMDARG *vp;
  30         MARK *fm, *tm, *rp;
  31 {
  32         /*
  33          * Historically, U reset the cursor to the first column in the line
  34          * (not the first non-blank).  This seems a bit non-intuitive, but,
  35          * considering that we may have undone multiple changes, anything
  36          * else (including the cursor position stored in the logging records)
  37          * is going to appear random.
  38          */
  39         rp->lno = fm->lno;
  40         rp->cno = 0;
  41
  42         /*
  43          * !!!
  44          * Set up the flags so that an immediately subsequent 'u' will roll
  45          * forward, instead of backward.  In historic vi, a 'u' following a
  46          * 'U' redid all of the changes to the line.  Given that the user has
  47          * explicitly discarded those changes by entering 'U', it seems likely
  48          * that the user wants something between the original and end forms of
  49          * the line, so starting to replay the changes seems the best way to
  50          * get to there.
  51          */
  52         F_SET(ep, F_UNDO);
  53         ep->lundo = BACKWARD;
  54
  55         return (log_setline(sp, ep));
  56 }
  57
  58 /*
  59  * v_undo -- u
  60  *      Undo the last change.
  61  */
  62 int
  63 v_undo(sp, ep, vp, fm, tm, rp)
  64         SCR *sp;
  65         EXF *ep;
  66         VICMDARG *vp;
  67         MARK *fm, *tm, *rp;
  68 {
  69         /* Set the command count. */
  70         VIP(sp)->u_ccnt = sp->ccnt;
  71
  72         /*
  73          * !!!
  74          * In historic vi, 'u' toggled between "undo" and "redo", i.e. 'u'
  75          * undid the last undo.  However, if there has been a change since
  76          * the last undo/redo, we always do an undo.  To make this work when
  77          * the user can undo multiple operations, we leave the old semantic
  78          * unchanged, but make '.' after a 'u' do another undo/redo operation.
  79          * This has two problems.
  80          *
  81          * The first is that 'u' didn't set '.' in historic vi.  So, if a
  82          * user made a change, realized it was in the wrong place, does a
  83          * 'u' to undo it, moves to the right place and then does '.', the
  84          * change was reapplied.  To make this work, we only apply the '.'
  85          * to the undo command if it's the command immediately following an
  86          * undo command.  See vi/vi.c:getcmd() for the details.
  87          *
  88          * The second is that the traditional way to view the numbered cut
  89          * buffers in vi was to enter the commands "1pu.u.u.u. which will
  90          * no longer work because the '.' immediately follows the 'u' command.
  91          * Since we provide a much better method of viewing buffers, and
  92          * nobody can think of a better way of adding in multiple undo, this
  93          * remains broken.
  94          */
  95         if (!F_ISSET(ep, F_UNDO)) {
  96                 F_SET(ep, F_UNDO);
  97                 ep->lundo = BACKWARD;
  98         } else if (!F_ISSET(vp, VC_ISDOT))
  99                 ep->lundo = ep->lundo == BACKWARD ? FORWARD : BACKWARD;
 100
 101         switch (ep->lundo) {
 102         case BACKWARD:
 103                 return (log_backward(sp, ep, rp));
 104         case FORWARD:
 105                 return (log_forward(sp, ep, rp));
 106         default:
 107                 abort();
 108         }
 109         /* NOTREACHED */
 110 }