ncurses/tty/hardscroll.c

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  29 /****************************************************************************
  30  *  Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995               *
  31  *     and: Eric S. Raymond <esr@snark.thyrsus.com>                         *
  32  *     and: Thomas E. Dickey                        1996-on                 *
  33  *     and: Alexander V Lukyanov                    1997-1998               *
  34  ****************************************************************************/
  35
  36 /******************************************************************************
  37
  38 NAME
  39    hardscroll.c -- hardware-scrolling optimization for ncurses
  40
  41 SYNOPSIS
  42    void _nc_scroll_optimize(void)
  43
  44 DESCRIPTION
  45                         OVERVIEW
  46
  47 This algorithm for computes optimum hardware scrolling to transform an
  48 old screen (curscr) into a new screen (newscr) via vertical line moves.
  49
  50 Because the screen has a `grain' (there are insert/delete/scroll line
  51 operations but no insert/delete/scroll column operations), it is efficient
  52 break the update algorithm into two pieces: a first stage that does only line
  53 moves, optimizing the end product of user-invoked insertions, deletions, and
  54 scrolls; and a second phase (corresponding to the present doupdate code in
  55 ncurses) that does only line transformations.
  56
  57 The common case we want hardware scrolling for is to handle line insertions
  58 and deletions in screen-oriented text-editors.  This two-stage approach will
  59 accomplish that at a low computation and code-size cost.
  60
  61                         LINE-MOVE COMPUTATION
  62
  63 Now, to a discussion of the line-move computation.
  64
  65 For expository purposes, consider the screen lines to be represented by
  66 integers 0..23 (with the understanding that the value of 23 may vary).
  67 Let a new line introduced by insertion, scrolling, or at the bottom of
  68 the screen following a line delete be given the index -1.
  69
  70 Assume that the real screen starts with lines 0..23.  Now, we have
  71 the following possible line-oriented operations on the screen:
  72
  73 Insertion: inserts a line at a given screen row, forcing all lines below
  74 to scroll forward.  The last screen line is lost.  For example, an insertion
  75 at line 5 would produce: 0..4 -1 5..23.
  76
  77 Deletion: deletes a line at a given screen row, forcing all lines below
  78 to scroll forward.  The last screen line is made new.  For example, a deletion
  79 at line 7 would produce: 0..6 8..23 -1.
  80
  81 Scroll up: move a range of lines up 1.  The bottom line of the range
  82 becomes new.  For example, scrolling up the region from 9 to 14 will
  83 produce 0..8 10..14 -1 15..23.
  84
  85 Scroll down: move a range of lines down 1.  The top line of the range
  86 becomes new.  For example, scrolling down the region from 12 to 16 will produce
  87 0..11 -1 12..15 17..23.
  88
  89 Now, an obvious property of all these operations is that they preserve the
  90 order of old lines, though not their position in the sequence.
  91
  92 The key trick of this algorithm is that the original line indices described
  93 above are actually maintained as _line[].oldindex fields in the window
  94 structure, and stick to each line through scroll and insert/delete operations.
  95
  96 Thus, it is possible at update time to look at the oldnum fields and compute
  97 an optimal set of il/dl/scroll operations that will take the real screen
  98 lines to the virtual screen lines.  Once these vertical moves have been done,
  99 we can hand off to the second stage of the update algorithm, which does line
 100 transformations.
 101
 102 Note that the move computation does not need to have the full generality
 103 of a diff algorithm (which it superficially resembles) because lines cannot
 104 be moved out of order.
 105
 106                         THE ALGORITHM
 107
 108 The scrolling is done in two passes. The first pass is from top to bottom
 109 scroling hunks UP. The second one is from bottom to top scrolling hunks DOWN.
 110 Obviously enough, no lines to be scrolled will be destroyed. (lav)
 111
 112 HOW TO TEST THIS:
 113
 114 Use the following production:
 115
 116 hardscroll: hardscroll.c
 117         $(CC) -g -DSCROLLDEBUG hardscroll.c -o hardscroll
 118
 119 Then just type scramble vectors and watch.  The following test loads are
 120 a representative sample of cases:
 121
 122 -----------------------------  CUT HERE ------------------------------------
 123 # No lines moved
 124  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
 125 #
 126 # A scroll up
 127  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
 128 #
 129 # A scroll down
 130 -1  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22
 131 #
 132 # An insertion (after line 12)
 133  0  1  2  3  4  5  6  7  8  9 10 11 12 -1 13 14 15 16 17 18 19 20 21 22
 134 #
 135 # A simple deletion (line 10)
 136  0  1  2  3  4  5  6  7  8  9  11 12 13 14 15 16 17 18 19 20 21 22 23 -1
 137 #
 138 # A more complex case
 139 -1 -1 -1 -1 -1  3  4  5  6  7  -1 -1  8  9 10 11 12 13 14 15 16 17 -1 -1
 140 -----------------------------  CUT HERE ------------------------------------
 141
 142 AUTHOR
 143     Eric S. Raymond <esr@snark.thyrsus.com>, November 1994
 144     New algorithm by Alexander V. Lukyanov <lav@yars.free.net>, Aug 1997
 145
 146 *****************************************************************************/
 147
 148 #include <curses.priv.h>
 149
 150 MODULE_ID("$Id: hardscroll.c,v 1.47 2010/04/24 23:46:47 tom Exp $")
 151
 152 #if defined(SCROLLDEBUG) || defined(HASHDEBUG)
 153
 154 # undef screen_lines
 155 # define screen_lines(sp) MAXLINES
 156 NCURSES_EXPORT_VAR (int)
 157   oldnums[MAXLINES];
 158 # define OLDNUM(sp,n)   oldnums[n]
 159 # define _tracef        printf
 160 # undef TR
 161 # define TR(n, a)       if (_nc_tracing & (n)) { _tracef a ; putchar('\n'); }
 162
 163 extern                          NCURSES_EXPORT_VAR(unsigned) _nc_tracing;
 164
 165 #else /* no debug */
 166
 167 /* OLDNUM(n) indicates which line will be shifted to the position n.
 168    if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from
 169    somewhere. */
 170 NCURSES_EXPORT_VAR (int *)
 171   _nc_oldnums = 0;              /* obsolete: keep for ABI compat */
 172
 173 # ifdef USE_HASHMAP
 174 #  define oldnums(sp)   (sp)->_oldnum_list
 175 #  define OLDNUM(sp,n)  oldnums(sp)[n]
 176 # else                          /* !USE_HASHMAP */
 177 #  define OLDNUM(sp,n)  NewScreen(sp)->_line[n].oldindex
 178 # endif                         /* !USE_HASHMAP */
 179
 180 #define OLDNUM_SIZE(sp) (sp)->_oldnum_size
 181
 182 #endif /* defined(SCROLLDEBUG) || defined(HASHDEBUG) */
 183
 184 NCURSES_EXPORT(void)
 185 NCURSES_SP_NAME(_nc_scroll_optimize) (NCURSES_SP_DCL0)
 186 /* scroll optimization to transform curscr to newscr */
 187 {
 188     int i;
 189     int start, end, shift;
 190
 191     TR(TRACE_ICALLS, (T_CALLED("_nc_scroll_optimize(%p)"), (void *) SP_PARM));
 192
 193 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
 194 #ifdef USE_HASHMAP
 195     /* get enough storage */
 196     if (OLDNUM_SIZE(SP_PARM) < screen_lines(SP_PARM)) {
 197         int *new_oldnums = typeRealloc(int,
 198                                        (size_t) screen_lines(SP_PARM),
 199                                        oldnums(SP_PARM));
 200         if (!new_oldnums)
 201             return;
 202         oldnums(SP_PARM) = new_oldnums;
 203         OLDNUM_SIZE(SP_PARM) = screen_lines(SP_PARM);
 204     }
 205     /* calculate the indices */
 206     NCURSES_SP_NAME(_nc_hash_map) (NCURSES_SP_ARG);
 207 #endif
 208 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
 209
 210 #ifdef TRACE
 211     if (USE_TRACEF(TRACE_UPDATE | TRACE_MOVE)) {
 212         NCURSES_SP_NAME(_nc_linedump) (NCURSES_SP_ARG);
 213         _nc_unlock_global(tracef);
 214     }
 215 #endif /* TRACE */
 216
 217     /* pass 1 - from top to bottom scrolling up */
 218     for (i = 0; i < screen_lines(SP_PARM);) {
 219         while (i < screen_lines(SP_PARM)
 220                && (OLDNUM(SP_PARM, i) == _NEWINDEX || OLDNUM(SP_PARM, i) <= i))
 221             i++;
 222         if (i >= screen_lines(SP_PARM))
 223             break;
 224
 225         shift = OLDNUM(SP_PARM, i) - i;         /* shift > 0 */
 226         start = i;
 227
 228         i++;
 229         while (i < screen_lines(SP_PARM)
 230                && OLDNUM(SP_PARM, i) != _NEWINDEX
 231                && OLDNUM(SP_PARM, i) - i == shift)
 232             i++;
 233         end = i - 1 + shift;
 234
 235         TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
 236 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
 237         if (NCURSES_SP_NAME(_nc_scrolln) (NCURSES_SP_ARGx
 238                                           shift,
 239                                           start,
 240                                           end,
 241                                           screen_lines(SP_PARM) - 1) == ERR) {
 242             TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
 243             continue;
 244         }
 245 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
 246     }
 247
 248     /* pass 2 - from bottom to top scrolling down */
 249     for (i = screen_lines(SP_PARM) - 1; i >= 0;) {
 250         while (i >= 0
 251                && (OLDNUM(SP_PARM, i) == _NEWINDEX
 252                    || OLDNUM(SP_PARM, i) >= i)) {
 253             i--;
 254         }
 255         if (i < 0)
 256             break;
 257
 258         shift = OLDNUM(SP_PARM, i) - i;         /* shift < 0 */
 259         end = i;
 260
 261         i--;
 262         while (i >= 0
 263                && OLDNUM(SP_PARM, i) != _NEWINDEX
 264                && OLDNUM(SP_PARM, i) - i == shift) {
 265             i--;
 266         }
 267         start = i + 1 - (-shift);
 268
 269         TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
 270 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
 271         if (NCURSES_SP_NAME(_nc_scrolln) (NCURSES_SP_ARGx
 272                                           shift,
 273                                           start,
 274                                           end,
 275                                           screen_lines(SP_PARM) - 1) == ERR) {
 276             TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
 277             continue;
 278         }
 279 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
 280     }
 281     TR(TRACE_ICALLS, (T_RETURN("")));
 282 }
 283
 284 #if NCURSES_SP_FUNCS
 285 NCURSES_EXPORT(void)
 286 _nc_scroll_optimize(void)
 287 {
 288     NCURSES_SP_NAME(_nc_scroll_optimize) (CURRENT_SCREEN);
 289 }
 290 #endif
 291
 292 #if defined(TRACE) || defined(SCROLLDEBUG) || defined(HASHDEBUG)
 293 NCURSES_EXPORT(void)
 294 NCURSES_SP_NAME(_nc_linedump) (NCURSES_SP_DCL0)
 295 /* dump the state of the real and virtual oldnum fields */
 296 {
 297     int n;
 298     char *buf = 0;
 299     size_t want = ((size_t) screen_lines(SP_PARM) + 1) * 4;
 300
 301     if ((buf = typeMalloc(char, want)) != 0) {
 302
 303         *buf = '\0';
 304         for (n = 0; n < screen_lines(SP_PARM); n++)
 305             (void) sprintf(buf + strlen(buf), " %02d", OLDNUM(SP_PARM, n));
 306         TR(TRACE_UPDATE | TRACE_MOVE, ("virt %s", buf));
 307         free(buf);
 308     }
 309 }
 310
 311 #if NCURSES_SP_FUNCS
 312 NCURSES_EXPORT(void)
 313 _nc_linedump(void)
 314 {
 315     NCURSES_SP_NAME(_nc_linedump) (CURRENT_SCREEN);
 316 }
 317 #endif
 318
 319 #endif /* defined(TRACE) || defined(SCROLLDEBUG) */
 320
 321 #ifdef SCROLLDEBUG
 322
 323 int
 324 main(int argc GCC_UNUSED, char *argv[]GCC_UNUSED)
 325 {
 326     char line[BUFSIZ], *st;
 327
 328 #ifdef TRACE
 329     _nc_tracing = TRACE_MOVE;
 330 #endif
 331     for (;;) {
 332         int n;
 333
 334         for (n = 0; n < screen_lines; n++)
 335             oldnums[n] = _NEWINDEX;
 336
 337         /* grab the test vector */
 338         if (fgets(line, sizeof(line), stdin) == (char *) NULL)
 339             exit(EXIT_SUCCESS);
 340
 341         /* parse it */
 342         n = 0;
 343         if (line[0] == '#') {
 344             (void) fputs(line, stderr);
 345             continue;
 346         }
 347         st = strtok(line, " ");
 348         do {
 349             oldnums[n++] = atoi(st);
 350         } while
 351             ((st = strtok((char *) NULL, " ")) != 0);
 352
 353         /* display it */
 354         (void) fputs("Initial input:\n", stderr);
 355         _nc_linedump();
 356
 357         _nc_scroll_optimize();
 358     }
 359 }
 360
 361 #endif /* SCROLLDEBUG */
 362
 363 /* hardscroll.c ends here */