hardscroll.c revision 50276
1/**************************************************************************** 2 * Copyright (c) 1998 Free Software Foundation, Inc. * 3 * * 4 * Permission is hereby granted, free of charge, to any person obtaining a * 5 * copy of this software and associated documentation files (the * 6 * "Software"), to deal in the Software without restriction, including * 7 * without limitation the rights to use, copy, modify, merge, publish, * 8 * distribute, distribute with modifications, sublicense, and/or sell * 9 * copies of the Software, and to permit persons to whom the Software is * 10 * furnished to do so, subject to the following conditions: * 11 * * 12 * The above copyright notice and this permission notice shall be included * 13 * in all copies or substantial portions of the Software. * 14 * * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * 16 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * 18 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, * 19 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * 20 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR * 21 * THE USE OR OTHER DEALINGS IN THE SOFTWARE. * 22 * * 23 * Except as contained in this notice, the name(s) of the above copyright * 24 * holders shall not be used in advertising or otherwise to promote the * 25 * sale, use or other dealings in this Software without prior written * 26 * authorization. * 27 ****************************************************************************/ 28 29/**************************************************************************** 30 * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 * 31 * and: Eric S. Raymond <esr@snark.thyrsus.com> * 32 ****************************************************************************/ 33 34 35/****************************************************************************** 36 37NAME 38 hardscroll.c -- hardware-scrolling optimization for ncurses 39 40SYNOPSIS 41 void _nc_scroll_optimize(void) 42 43DESCRIPTION 44 OVERVIEW 45 46This algorithm for computes optimum hardware scrolling to transform an 47old screen (curscr) into a new screen (newscr) via vertical line moves. 48 49Because the screen has a `grain' (there are insert/delete/scroll line 50operations but no insert/delete/scroll column operations), it is efficient 51break the update algorithm into two pieces: a first stage that does only line 52moves, optimizing the end product of user-invoked insertions, deletions, and 53scrolls; and a second phase (corresponding to the present doupdate code in 54ncurses) that does only line transformations. 55 56The common case we want hardware scrolling for is to handle line insertions 57and deletions in screen-oriented text-editors. This two-stage approach will 58accomplish that at a low computation and code-size cost. 59 60 LINE-MOVE COMPUTATION 61 62Now, to a discussion of the line-move computation. 63 64For expository purposes, consider the screen lines to be represented by 65integers 0..23 (with the understanding that the value of 23 may vary). 66Let a new line introduced by insertion, scrolling, or at the bottom of 67the screen following a line delete be given the index -1. 68 69Assume that the real screen starts with lines 0..23. Now, we have 70the following possible line-oriented operations on the screen: 71 72Insertion: inserts a line at a given screen row, forcing all lines below 73to scroll forward. The last screen line is lost. For example, an insertion 74at line 5 would produce: 0..4 -1 5..23. 75 76Deletion: deletes a line at a given screen row, forcing all lines below 77to scroll forward. The last screen line is made new. For example, a deletion 78at line 7 would produce: 0..6 8..23 -1. 79 80Scroll up: move a range of lines up 1. The bottom line of the range 81becomes new. For example, scrolling up the region from 9 to 14 will 82produce 0..8 10..14 -1 15..23. 83 84Scroll down: move a range of lines down 1. The top line of the range 85becomes new. For example, scrolling down the region from 12 to 16 will produce 860..11 -1 12..15 17..23. 87 88Now, an obvious property of all these operations is that they preserve the 89order of old lines, though not their position in the sequence. 90 91The key trick of this algorithm is that the original line indices described 92above are actually maintained as _line[].oldindex fields in the window 93structure, and stick to each line through scroll and insert/delete operations. 94 95Thus, it is possible at update time to look at the oldnum fields and compute 96an optimal set of il/dl/scroll operations that will take the real screen 97lines to the virtual screen lines. Once these vertical moves have been done, 98we can hand off to the second stage of the update algorithm, which does line 99transformations. 100 101Note that the move computation does not need to have the full generality 102of a diff algorithm (which it superficially resembles) because lines cannot 103be moved out of order. 104 105 THE ALGORITHM 106 107The scrolling is done in two passes. The first pass is from top to bottom 108scroling hunks UP. The second one is from bottom to top scrolling hunks DOWN. 109Obviously enough, no lines to be scrolled will be destroyed. (lav) 110 111HOW TO TEST THIS: 112 113Use the following production: 114 115hardscroll: hardscroll.c 116 $(CC) -g -DSCROLLDEBUG hardscroll.c -o hardscroll 117 118Then just type scramble vectors and watch. The following test loads are 119a representative sample of cases: 120 121----------------------------- CUT HERE ------------------------------------ 122# No lines moved 123 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 124# 125# A scroll up 126 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -1 127# 128# A scroll down 129-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 130# 131# An insertion (after line 12) 132 0 1 2 3 4 5 6 7 8 9 10 11 12 -1 13 14 15 16 17 18 19 20 21 22 133# 134# A simple deletion (line 10) 135 0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 -1 136# 137# A more complex case 138-1 -1 -1 -1 -1 3 4 5 6 7 -1 -1 8 9 10 11 12 13 14 15 16 17 -1 -1 139----------------------------- CUT HERE ------------------------------------ 140 141AUTHOR 142 Eric S. Raymond <esr@snark.thyrsus.com>, November 1994 143 New algorithm by Alexander V. Lukyanov <lav@yars.free.net>, Aug 1997 144 145*****************************************************************************/ 146 147#include <curses.priv.h> 148 149MODULE_ID("$Id: hardscroll.c,v 1.33 1999/02/27 20:01:29 tom Exp $") 150 151#if defined(SCROLLDEBUG) || defined(HASHDEBUG) 152 153# undef screen_lines 154# define screen_lines MAXLINES 155int oldnums[MAXLINES]; 156# define OLDNUM(n) oldnums[n] 157# define _tracef printf 158# undef TR 159# define TR(n, a) if (_nc_tracing & (n)) { _tracef a ; putchar('\n'); } 160 161#else /* no debug */ 162 163/* OLDNUM(n) indicates which line will be shifted to the position n. 164 if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from 165 somewhere. */ 166# if USE_HASHMAP 167int *_nc_oldnums = 0; 168static int oldnums_allocated = 0; 169# define oldnums _nc_oldnums 170# define OLDNUM(n) oldnums[n] 171# else /* !USE_HASHMAP */ 172# define OLDNUM(n) newscr->_line[n].oldindex 173# endif /* !USE_HASHMAP */ 174 175#endif /* defined(SCROLLDEBUG) || defined(HASHDEBUG) */ 176 177 178void _nc_scroll_optimize(void) 179/* scroll optimization to transform curscr to newscr */ 180{ 181 int i; 182 int start, end, shift; 183 184 TR(TRACE_ICALLS, ("_nc_scroll_optimize() begins")); 185 186#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG) 187#if USE_HASHMAP 188 /* get enough storage */ 189 if (oldnums_allocated < screen_lines) 190 { 191 int *new_oldnums = typeRealloc(int, screen_lines, oldnums); 192 if (!new_oldnums) 193 return; 194 oldnums = new_oldnums; 195 oldnums_allocated = screen_lines; 196 } 197 /* calculate the indices */ 198 _nc_hash_map(); 199#endif 200#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */ 201 202#ifdef TRACE 203 if (_nc_tracing & (TRACE_UPDATE | TRACE_MOVE)) 204 _nc_linedump(); 205#endif /* TRACE */ 206 207 /* pass 1 - from top to bottom scrolling up */ 208 for (i = 0; i < screen_lines; ) 209 { 210 while (i < screen_lines && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) <= i)) 211 i++; 212 if (i >= screen_lines) 213 break; 214 215 shift = OLDNUM(i) - i; /* shift > 0 */ 216 start = i; 217 218 i++; 219 while (i < screen_lines && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i == shift) 220 i++; 221 end = i-1 + shift; 222 223 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift)); 224#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG) 225 if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR) 226 { 227 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll")); 228 continue; 229 } 230#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */ 231 } 232 233 /* pass 2 - from bottom to top scrolling down */ 234 for (i = screen_lines-1; i >= 0; ) 235 { 236 while (i >= 0 && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) >= i)) 237 i--; 238 if (i < 0) 239 break; 240 241 shift = OLDNUM(i) - i; /* shift < 0 */ 242 end = i; 243 244 i--; 245 while (i >= 0 && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i == shift) 246 i--; 247 start = i+1 - (-shift); 248 249 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift)); 250#if !defined(SCROLLDEBUG) && !defined(HASHDEBUG) 251 if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR) 252 { 253 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll")); 254 continue; 255 } 256#endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */ 257 } 258} 259 260#if defined(TRACE) || defined(SCROLLDEBUG) || defined(HASHDEBUG) 261void _nc_linedump(void) 262/* dump the state of the real and virtual oldnum fields */ 263{ 264 static size_t have; 265 static char *buf; 266 267 int n; 268 size_t want = (screen_lines + 1) * 4; 269 270 if (have < want) 271 buf = typeMalloc(char, have = want); 272 273 (void) strcpy(buf, "virt"); 274 for (n = 0; n < screen_lines; n++) 275 (void) sprintf(buf + strlen(buf), " %02d", OLDNUM(n)); 276 TR(TRACE_UPDATE | TRACE_MOVE, (buf)); 277#if NO_LEAKS 278 free(buf); 279 have = 0; 280#endif 281} 282#endif /* defined(TRACE) || defined(SCROLLDEBUG) */ 283 284#ifdef SCROLLDEBUG 285 286int 287main(int argc GCC_UNUSED, char *argv[] GCC_UNUSED) 288{ 289 char line[BUFSIZ], *st; 290 291#ifdef TRACE 292 _nc_tracing = TRACE_MOVE; 293#endif 294 for (;;) 295 { 296 int n; 297 298 for (n = 0; n < screen_lines; n++) 299 oldnums[n] = _NEWINDEX; 300 301 /* grab the test vector */ 302 if (fgets(line, sizeof(line), stdin) == (char *)NULL) 303 exit(EXIT_SUCCESS); 304 305 /* parse it */ 306 n = 0; 307 if (line[0] == '#') 308 { 309 (void) fputs(line, stderr); 310 continue; 311 } 312 st = strtok(line, " "); 313 do { 314 oldnums[n++] = atoi(st); 315 } while 316 ((st = strtok((char *)NULL, " ")) != 0); 317 318 /* display it */ 319 (void) fputs("Initial input:\n", stderr); 320 _nc_linedump(); 321 322 _nc_scroll_optimize(); 323 } 324} 325 326#endif /* SCROLLDEBUG */ 327 328/* hardscroll.c ends here */ 329