1 /*- 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. 6 * 7 * See the LICENSE file for redistribution information. 8 */ 9 10 #include "config.h" 11 12 #ifndef lint 13 static const char sccsid[] = "$Id: v_undo.c,v 10.6 2001/06/25 15:19:36 skimo Exp $"; 14 #endif /* not lint */ 15 16 #include <sys/types.h> 17 #include <sys/queue.h> 18 #include <sys/time.h> 19 20 #include <bitstring.h> 21 #include <errno.h> 22 #include <limits.h> 23 #include <stdio.h> 24 #include <stdlib.h> 25 #include <string.h> 26 27 #include "../common/common.h" 28 #include "vi.h" 29 30 /* 31 * v_Undo -- U 32 * Undo changes to this line. 33 * 34 * PUBLIC: int v_Undo(SCR *, VICMD *); 35 */ 36 int 37 v_Undo(SCR *sp, VICMD *vp) 38 { 39 /* 40 * Historically, U reset the cursor to the first column in the line 41 * (not the first non-blank). This seems a bit non-intuitive, but, 42 * considering that we may have undone multiple changes, anything 43 * else (including the cursor position stored in the logging records) 44 * is going to appear random. 45 */ 46 vp->m_final.cno = 0; 47 48 /* 49 * !!! 50 * Set up the flags so that an immediately subsequent 'u' will roll 51 * forward, instead of backward. In historic vi, a 'u' following a 52 * 'U' redid all of the changes to the line. Given that the user has 53 * explicitly discarded those changes by entering 'U', it seems likely 54 * that the user wants something between the original and end forms of 55 * the line, so starting to replay the changes seems the best way to 56 * get to there. 57 */ 58 F_SET(sp->ep, F_UNDO); 59 sp->ep->lundo = BACKWARD; 60 61 return (log_setline(sp)); 62 } 63 64 /* 65 * v_undo -- u 66 * Undo the last change. 67 * 68 * PUBLIC: int v_undo(SCR *, VICMD *); 69 */ 70 int 71 v_undo(SCR *sp, VICMD *vp) 72 { 73 EXF *ep; 74 75 /* Set the command count. */ 76 VIP(sp)->u_ccnt = sp->ccnt; 77 78 /* 79 * !!! 80 * In historic vi, 'u' toggled between "undo" and "redo", i.e. 'u' 81 * undid the last undo. However, if there has been a change since 82 * the last undo/redo, we always do an undo. To make this work when 83 * the user can undo multiple operations, we leave the old semantic 84 * unchanged, but make '.' after a 'u' do another undo/redo operation. 85 * This has two problems. 86 * 87 * The first is that 'u' didn't set '.' in historic vi. So, if a 88 * user made a change, realized it was in the wrong place, does a 89 * 'u' to undo it, moves to the right place and then does '.', the 90 * change was reapplied. To make this work, we only apply the '.' 91 * to the undo command if it's the command immediately following an 92 * undo command. See vi/vi.c:getcmd() for the details. 93 * 94 * The second is that the traditional way to view the numbered cut 95 * buffers in vi was to enter the commands "1pu.u.u.u. which will 96 * no longer work because the '.' immediately follows the 'u' command. 97 * Since we provide a much better method of viewing buffers, and 98 * nobody can think of a better way of adding in multiple undo, this 99 * remains broken. 100 * 101 * !!! 102 * There is change to historic practice for the final cursor position 103 * in this implementation. In historic vi, if an undo was isolated to 104 * a single line, the cursor moved to the start of the change, and 105 * then, subsequent 'u' commands would not move it again. (It has been 106 * pointed out that users used multiple undo commands to get the cursor 107 * to the start of the changed text.) Nvi toggles between the cursor 108 * position before and after the change was made. One final issue is 109 * that historic vi only did this if the user had not moved off of the 110 * line before entering the undo command; otherwise, vi would move the 111 * cursor to the most attractive position on the changed line. 112 * 113 * It would be difficult to match historic practice in this area. You 114 * not only have to know that the changes were isolated to one line, 115 * but whether it was the first or second undo command as well. And, 116 * to completely match historic practice, we'd have to track users line 117 * changes, too. This isn't worth the effort. 118 */ 119 ep = sp->ep; 120 if (!F_ISSET(ep, F_UNDO)) { 121 F_SET(ep, F_UNDO); 122 ep->lundo = BACKWARD; 123 } else if (!F_ISSET(vp, VC_ISDOT)) 124 ep->lundo = ep->lundo == BACKWARD ? FORWARD : BACKWARD; 125 126 switch (ep->lundo) { 127 case BACKWARD: 128 return (log_backward(sp, &vp->m_final)); 129 case FORWARD: 130 return (log_forward(sp, &vp->m_final)); 131 default: 132 abort(); 133 } 134 /* NOTREACHED */ 135 } 136