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[] = "@(#)v_undo.c 10.5 (Berkeley) 3/6/96"; 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 __P((SCR *, VICMD *)); 35 */ 36 int 37 v_Undo(sp, vp) 38 SCR *sp; 39 VICMD *vp; 40 { 41 /* 42 * Historically, U reset the cursor to the first column in the line 43 * (not the first non-blank). This seems a bit non-intuitive, but, 44 * considering that we may have undone multiple changes, anything 45 * else (including the cursor position stored in the logging records) 46 * is going to appear random. 47 */ 48 vp->m_final.cno = 0; 49 50 /* 51 * !!! 52 * Set up the flags so that an immediately subsequent 'u' will roll 53 * forward, instead of backward. In historic vi, a 'u' following a 54 * 'U' redid all of the changes to the line. Given that the user has 55 * explicitly discarded those changes by entering 'U', it seems likely 56 * that the user wants something between the original and end forms of 57 * the line, so starting to replay the changes seems the best way to 58 * get to there. 59 */ 60 F_SET(sp->ep, F_UNDO); 61 sp->ep->lundo = BACKWARD; 62 63 return (log_setline(sp)); 64 } 65 66 /* 67 * v_undo -- u 68 * Undo the last change. 69 * 70 * PUBLIC: int v_undo __P((SCR *, VICMD *)); 71 */ 72 int 73 v_undo(sp, vp) 74 SCR *sp; 75 VICMD *vp; 76 { 77 EXF *ep; 78 79 /* Set the command count. */ 80 VIP(sp)->u_ccnt = sp->ccnt; 81 82 /* 83 * !!! 84 * In historic vi, 'u' toggled between "undo" and "redo", i.e. 'u' 85 * undid the last undo. However, if there has been a change since 86 * the last undo/redo, we always do an undo. To make this work when 87 * the user can undo multiple operations, we leave the old semantic 88 * unchanged, but make '.' after a 'u' do another undo/redo operation. 89 * This has two problems. 90 * 91 * The first is that 'u' didn't set '.' in historic vi. So, if a 92 * user made a change, realized it was in the wrong place, does a 93 * 'u' to undo it, moves to the right place and then does '.', the 94 * change was reapplied. To make this work, we only apply the '.' 95 * to the undo command if it's the command immediately following an 96 * undo command. See vi/vi.c:getcmd() for the details. 97 * 98 * The second is that the traditional way to view the numbered cut 99 * buffers in vi was to enter the commands "1pu.u.u.u. which will 100 * no longer work because the '.' immediately follows the 'u' command. 101 * Since we provide a much better method of viewing buffers, and 102 * nobody can think of a better way of adding in multiple undo, this 103 * remains broken. 104 * 105 * !!! 106 * There is change to historic practice for the final cursor position 107 * in this implementation. In historic vi, if an undo was isolated to 108 * a single line, the cursor moved to the start of the change, and 109 * then, subsequent 'u' commands would not move it again. (It has been 110 * pointed out that users used multiple undo commands to get the cursor 111 * to the start of the changed text.) Nvi toggles between the cursor 112 * position before and after the change was made. One final issue is 113 * that historic vi only did this if the user had not moved off of the 114 * line before entering the undo command; otherwise, vi would move the 115 * cursor to the most attractive position on the changed line. 116 * 117 * It would be difficult to match historic practice in this area. You 118 * not only have to know that the changes were isolated to one line, 119 * but whether it was the first or second undo command as well. And, 120 * to completely match historic practice, we'd have to track users line 121 * changes, too. This isn't worth the effort. 122 */ 123 ep = sp->ep; 124 if (!F_ISSET(ep, F_UNDO)) { 125 F_SET(ep, F_UNDO); 126 ep->lundo = BACKWARD; 127 } else if (!F_ISSET(vp, VC_ISDOT)) 128 ep->lundo = ep->lundo == BACKWARD ? FORWARD : BACKWARD; 129 130 switch (ep->lundo) { 131 case BACKWARD: 132 return (log_backward(sp, &vp->m_final)); 133 case FORWARD: 134 return (log_forward(sp, &vp->m_final)); 135 default: 136 abort(); 137 } 138 /* NOTREACHED */ 139 } 140