contrib/less/forwback.c

   1 /*
   2  * Copyright (C) 1984-2015  Mark Nudelman
   3  *
   4  * You may distribute under the terms of either the GNU General Public
   5  * License or the Less License, as specified in the README file.
   6  *
   7  * For more information, see the README file.
   8  */
   9
  10
  11 /*
  12  * Primitives for displaying the file on the screen,
  13  * scrolling either forward or backward.
  14  */
  15
  16 #include "less.h"
  17 #include "position.h"
  18
  19 public int screen_trashed;
  20 public int squished;
  21 public int no_back_scroll = 0;
  22 public int forw_prompt;
  23 public int same_pos_bell = 1;
  24
  25 extern int sigs;
  26 extern int top_scroll;
  27 extern int quiet;
  28 extern int sc_width, sc_height;
  29 extern int plusoption;
  30 extern int forw_scroll;
  31 extern int back_scroll;
  32 extern int ignore_eoi;
  33 extern int clear_bg;
  34 extern int final_attr;
  35 extern int oldbot;
  36 #if HILITE_SEARCH
  37 extern int size_linebuf;
  38 extern int hilite_search;
  39 extern int status_col;
  40 #endif
  41 #if TAGS
  42 extern char *tagoption;
  43 #endif
  44
  45 /*
  46  * Sound the bell to indicate user is trying to move past end of file.
  47  */
  48         static void
  49 eof_bell()
  50 {
  51         if (quiet == NOT_QUIET)
  52                 bell();
  53         else
  54                 vbell();
  55 }
  56
  57 /*
  58  * Check to see if the end of file is currently displayed.
  59  */
  60         public int
  61 eof_displayed()
  62 {
  63         POSITION pos;
  64
  65         if (ignore_eoi)
  66                 return (0);
  67
  68         if (ch_length() == NULL_POSITION)
  69                 /*
  70                  * If the file length is not known,
  71                  * we can't possibly be displaying EOF.
  72                  */
  73                 return (0);
  74
  75         /*
  76          * If the bottom line is empty, we are at EOF.
  77          * If the bottom line ends at the file length,
  78          * we must be just at EOF.
  79          */
  80         pos = position(BOTTOM_PLUS_ONE);
  81         return (pos == NULL_POSITION || pos == ch_length());
  82 }
  83
  84 /*
  85  * Check to see if the entire file is currently displayed.
  86  */
  87         public int
  88 entire_file_displayed()
  89 {
  90         POSITION pos;
  91
  92         /* Make sure last line of file is displayed. */
  93         if (!eof_displayed())
  94                 return (0);
  95
  96         /* Make sure first line of file is displayed. */
  97         pos = position(0);
  98         return (pos == NULL_POSITION || pos == 0);
  99 }
 100
 101 /*
 102  * If the screen is "squished", repaint it.
 103  * "Squished" means the first displayed line is not at the top
 104  * of the screen; this can happen when we display a short file
 105  * for the first time.
 106  */
 107         public void
 108 squish_check()
 109 {
 110         if (!squished)
 111                 return;
 112         squished = 0;
 113         repaint();
 114 }
 115
 116 /*
 117  * Display n lines, scrolling forward,
 118  * starting at position pos in the input file.
 119  * "force" means display the n lines even if we hit end of file.
 120  * "only_last" means display only the last screenful if n > screen size.
 121  * "nblank" is the number of blank lines to draw before the first
 122  *   real line.  If nblank > 0, the pos must be NULL_POSITION.
 123  *   The first real line after the blanks will start at ch_zero().
 124  */
 125         public void
 126 forw(n, pos, force, only_last, nblank)
 127         register int n;
 128         POSITION pos;
 129         int force;
 130         int only_last;
 131         int nblank;
 132 {
 133         int nlines = 0;
 134         int do_repaint;
 135         static int first_time = 1;
 136
 137         squish_check();
 138
 139         /*
 140          * do_repaint tells us not to display anything till the end,
 141          * then just repaint the entire screen.
 142          * We repaint if we are supposed to display only the last
 143          * screenful and the request is for more than a screenful.
 144          * Also if the request exceeds the forward scroll limit
 145          * (but not if the request is for exactly a screenful, since
 146          * repainting itself involves scrolling forward a screenful).
 147          */
 148         do_repaint = (only_last && n > sc_height-1) ||
 149                 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
 150
 151 #if HILITE_SEARCH
 152         if (hilite_search == OPT_ONPLUS || is_filtering() || status_col) {
 153                 prep_hilite(pos, pos + 4*size_linebuf, ignore_eoi ? 1 : -1);
 154                 pos = next_unfiltered(pos);
 155         }
 156 #endif
 157
 158         if (!do_repaint)
 159         {
 160                 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
 161                 {
 162                         /*
 163                          * Start a new screen.
 164                          * {{ This is not really desirable if we happen
 165                          *    to hit eof in the middle of this screen,
 166                          *    but we don't yet know if that will happen. }}
 167                          */
 168                         pos_clear();
 169                         add_forw_pos(pos);
 170                         force = 1;
 171                         clear();
 172                         home();
 173                 }
 174
 175                 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
 176                 {
 177                         /*
 178                          * This is not contiguous with what is
 179                          * currently displayed.  Clear the screen image
 180                          * (position table) and start a new screen.
 181                          */
 182                         pos_clear();
 183                         add_forw_pos(pos);
 184                         force = 1;
 185                         if (top_scroll)
 186                         {
 187                                 clear();
 188                                 home();
 189                         } else if (!first_time)
 190                         {
 191                                 putstr("...skipping...\n");
 192                         }
 193                 }
 194         }
 195
 196         while (--n >= 0)
 197         {
 198                 /*
 199                  * Read the next line of input.
 200                  */
 201                 if (nblank > 0)
 202                 {
 203                         /*
 204                          * Still drawing blanks; don't get a line
 205                          * from the file yet.
 206                          * If this is the last blank line, get ready to
 207                          * read a line starting at ch_zero() next time.
 208                          */
 209                         if (--nblank == 0)
 210                                 pos = ch_zero();
 211                 } else
 212                 {
 213                         /*
 214                          * Get the next line from the file.
 215                          */
 216                         pos = forw_line(pos);
 217 #if HILITE_SEARCH
 218                         pos = next_unfiltered(pos);
 219 #endif
 220                         if (pos == NULL_POSITION)
 221                         {
 222                                 /*
 223                                  * End of file: stop here unless the top line
 224                                  * is still empty, or "force" is true.
 225                                  * Even if force is true, stop when the last
 226                                  * line in the file reaches the top of screen.
 227                                  */
 228                                 if (!force && position(TOP) != NULL_POSITION)
 229                                         break;
 230                                 if (!empty_lines(0, 0) &&
 231                                     !empty_lines(1, 1) &&
 232                                      empty_lines(2, sc_height-1))
 233                                         break;
 234                         }
 235                 }
 236                 /*
 237                  * Add the position of the next line to the position table.
 238                  * Display the current line on the screen.
 239                  */
 240                 add_forw_pos(pos);
 241                 nlines++;
 242                 if (do_repaint)
 243                         continue;
 244                 /*
 245                  * If this is the first screen displayed and
 246                  * we hit an early EOF (i.e. before the requested
 247                  * number of lines), we "squish" the display down
 248                  * at the bottom of the screen.
 249                  * But don't do this if a + option or a -t option
 250                  * was given.  These options can cause us to
 251                  * start the display after the beginning of the file,
 252                  * and it is not appropriate to squish in that case.
 253                  */
 254                 if (first_time && pos == NULL_POSITION && !top_scroll &&
 255 #if TAGS
 256                     tagoption == NULL &&
 257 #endif
 258                     !plusoption)
 259                 {
 260                         squished = 1;
 261                         continue;
 262                 }
 263                 put_line();
 264 #if 0
 265                 /* {{
 266                  * Can't call clear_eol here.  The cursor might be at end of line
 267                  * on an ignaw terminal, so clear_eol would clear the last char
 268                  * of the current line instead of all of the next line.
 269                  * If we really need to do this on clear_bg terminals, we need
 270                  * to find a better way.
 271                  * }}
 272                  */
 273                 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
 274                 {
 275                         /*
 276                          * Writing the last character on the last line
 277                          * of the display may have scrolled the screen.
 278                          * If we were in standout mode, clear_bg terminals
 279                          * will fill the new line with the standout color.
 280                          * Now we're in normal mode again, so clear the line.
 281                          */
 282                         clear_eol();
 283                 }
 284 #endif
 285                 forw_prompt = 1;
 286         }
 287
 288         if (nlines == 0 && same_pos_bell)
 289                 eof_bell();
 290         else if (do_repaint)
 291                 repaint();
 292         first_time = 0;
 293         (void) currline(BOTTOM);
 294 }
 295
 296 /*
 297  * Display n lines, scrolling backward.
 298  */
 299         public void
 300 back(n, pos, force, only_last)
 301         register int n;
 302         POSITION pos;
 303         int force;
 304         int only_last;
 305 {
 306         int nlines = 0;
 307         int do_repaint;
 308
 309         squish_check();
 310         do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
 311 #if HILITE_SEARCH
 312         if (hilite_search == OPT_ONPLUS || is_filtering() || status_col) {
 313                 prep_hilite((pos < 3*size_linebuf) ?  0 : pos - 3*size_linebuf, pos, -1);
 314         }
 315 #endif
 316         while (--n >= 0)
 317         {
 318                 /*
 319                  * Get the previous line of input.
 320                  */
 321 #if HILITE_SEARCH
 322                 pos = prev_unfiltered(pos);
 323 #endif
 324
 325                 pos = back_line(pos);
 326                 if (pos == NULL_POSITION)
 327                 {
 328                         /*
 329                          * Beginning of file: stop here unless "force" is true.
 330                          */
 331                         if (!force)
 332                                 break;
 333                 }
 334                 /*
 335                  * Add the position of the previous line to the position table.
 336                  * Display the line on the screen.
 337                  */
 338                 add_back_pos(pos);
 339                 nlines++;
 340                 if (!do_repaint)
 341                 {
 342                         home();
 343                         add_line();
 344                         put_line();
 345                 }
 346         }
 347
 348         if (nlines == 0 && same_pos_bell)
 349                 eof_bell();
 350         else if (do_repaint)
 351                 repaint();
 352         else if (!oldbot)
 353                 lower_left();
 354         (void) currline(BOTTOM);
 355 }
 356
 357 /*
 358  * Display n more lines, forward.
 359  * Start just after the line currently displayed at the bottom of the screen.
 360  */
 361         public void
 362 forward(n, force, only_last)
 363         int n;
 364         int force;
 365         int only_last;
 366 {
 367         POSITION pos;
 368
 369         if (get_quit_at_eof() && eof_displayed() && !(ch_getflags() & CH_HELPFILE))
 370         {
 371                 /*
 372                  * If the -e flag is set and we're trying to go
 373                  * forward from end-of-file, go on to the next file.
 374                  */
 375                 if (edit_next(1))
 376                         quit(QUIT_OK);
 377                 return;
 378         }
 379
 380         pos = position(BOTTOM_PLUS_ONE);
 381         if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
 382         {
 383                 if (ignore_eoi)
 384                 {
 385                         /*
 386                          * ignore_eoi is to support A_F_FOREVER.
 387                          * Back up until there is a line at the bottom
 388                          * of the screen.
 389                          */
 390                         if (empty_screen())
 391                                 pos = ch_zero();
 392                         else
 393                         {
 394                                 do
 395                                 {
 396                                         back(1, position(TOP), 1, 0);
 397                                         pos = position(BOTTOM_PLUS_ONE);
 398                                 } while (pos == NULL_POSITION);
 399                         }
 400                 } else
 401                 {
 402                         eof_bell();
 403                         return;
 404                 }
 405         }
 406         forw(n, pos, force, only_last, 0);
 407 }
 408
 409 /*
 410  * Display n more lines, backward.
 411  * Start just before the line currently displayed at the top of the screen.
 412  */
 413         public void
 414 backward(n, force, only_last)
 415         int n;
 416         int force;
 417         int only_last;
 418 {
 419         POSITION pos;
 420
 421         pos = position(TOP);
 422         if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
 423         {
 424                 eof_bell();
 425                 return;
 426         }
 427         back(n, pos, force, only_last);
 428 }
 429
 430 /*
 431  * Get the backwards scroll limit.
 432  * Must call this function instead of just using the value of
 433  * back_scroll, because the default case depends on sc_height and
 434  * top_scroll, as well as back_scroll.
 435  */
 436         public int
 437 get_back_scroll()
 438 {
 439         if (no_back_scroll)
 440                 return (0);
 441         if (back_scroll >= 0)
 442                 return (back_scroll);
 443         if (top_scroll)
 444                 return (sc_height - 2);
 445         return (10000); /* infinity */
 446 }