contrib/less/forwback.c

   1 /* $FreeBSD$ */
   2 /*
   3  * Copyright (C) 1984-2007  Mark Nudelman
   4  *
   5  * You may distribute under the terms of either the GNU General Public
   6  * License or the Less License, as specified in the README file.
   7  *
   8  * For more information about less, or for information on how to
   9  * contact the author, see the README file.
  10  */
  11
  12
  13 /*
  14  * Primitives for displaying the file on the screen,
  15  * scrolling either forward or backward.
  16  */
  17
  18 #include "less.h"
  19 #include "position.h"
  20
  21 public int hit_eof;     /* Keeps track of how many times we hit end of file */
  22 public int screen_trashed;
  23 public int squished;
  24 public int no_back_scroll = 0;
  25 public int forw_prompt;
  26
  27 extern int sigs;
  28 extern int top_scroll;
  29 extern int quiet;
  30 extern int sc_width, sc_height;
  31 extern int less_is_more;
  32 extern int plusoption;
  33 extern int forw_scroll;
  34 extern int back_scroll;
  35 extern int ignore_eoi;
  36 extern int clear_bg;
  37 extern int final_attr;
  38 extern int oldbot;
  39 #if TAGS
  40 extern char *tagoption;
  41 #endif
  42
  43 /*
  44  * Sound the bell to indicate user is trying to move past end of file.
  45  */
  46         static void
  47 eof_bell()
  48 {
  49         if (quiet == NOT_QUIET)
  50                 bell();
  51         else
  52                 vbell();
  53 }
  54
  55 /*
  56  * Check to see if the end of file is currently "displayed".
  57  */
  58         static void
  59 eof_check()
  60 {
  61         POSITION pos;
  62
  63         if (ignore_eoi)
  64                 return;
  65         if (ABORT_SIGS())
  66                 return;
  67         /*
  68          * If the bottom line is empty, we are at EOF.
  69          * If the bottom line ends at the file length,
  70          * we must be just at EOF.
  71          */
  72         pos = position(BOTTOM_PLUS_ONE);
  73         if (pos == NULL_POSITION || pos == ch_length())
  74                 hit_eof++;
  75 }
  76
  77 /*
  78  * If the screen is "squished", repaint it.
  79  * "Squished" means the first displayed line is not at the top
  80  * of the screen; this can happen when we display a short file
  81  * for the first time.
  82  */
  83         public void
  84 squish_check()
  85 {
  86         if (!squished)
  87                 return;
  88         squished = 0;
  89         repaint();
  90 }
  91
  92 /*
  93  * Display n lines, scrolling forward,
  94  * starting at position pos in the input file.
  95  * "force" means display the n lines even if we hit end of file.
  96  * "only_last" means display only the last screenful if n > screen size.
  97  * "nblank" is the number of blank lines to draw before the first
  98  *   real line.  If nblank > 0, the pos must be NULL_POSITION.
  99  *   The first real line after the blanks will start at ch_zero().
 100  */
 101         public void
 102 forw(n, pos, force, only_last, nblank)
 103         register int n;
 104         POSITION pos;
 105         int force;
 106         int only_last;
 107         int nblank;
 108 {
 109         int eof = 0;
 110         int nlines = 0;
 111         int do_repaint;
 112         static int first_time = 1;
 113
 114         squish_check();
 115
 116         /*
 117          * do_repaint tells us not to display anything till the end,
 118          * then just repaint the entire screen.
 119          * We repaint if we are supposed to display only the last
 120          * screenful and the request is for more than a screenful.
 121          * Also if the request exceeds the forward scroll limit
 122          * (but not if the request is for exactly a screenful, since
 123          * repainting itself involves scrolling forward a screenful).
 124          */
 125         do_repaint = (only_last && n > sc_height-1) ||
 126                 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
 127
 128         if (!do_repaint)
 129         {
 130                 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
 131                 {
 132                         /*
 133                          * Start a new screen.
 134                          * {{ This is not really desirable if we happen
 135                          *    to hit eof in the middle of this screen,
 136                          *    but we don't yet know if that will happen. }}
 137                          */
 138                         pos_clear();
 139                         add_forw_pos(pos);
 140                         force = 1;
 141                         if (less_is_more == 0) {
 142                                 clear();
 143                                 home();
 144                         }
 145                 }
 146
 147                 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
 148                 {
 149                         /*
 150                          * This is not contiguous with what is
 151                          * currently displayed.  Clear the screen image
 152                          * (position table) and start a new screen.
 153                          */
 154                         pos_clear();
 155                         add_forw_pos(pos);
 156                         force = 1;
 157                         if (top_scroll)
 158                         {
 159                                 clear();
 160                                 home();
 161                         } else if (!first_time)
 162                         {
 163                                 putstr("...skipping...\n");
 164                         }
 165                 }
 166         }
 167
 168         while (--n >= 0)
 169         {
 170                 /*
 171                  * Read the next line of input.
 172                  */
 173                 if (nblank > 0)
 174                 {
 175                         /*
 176                          * Still drawing blanks; don't get a line
 177                          * from the file yet.
 178                          * If this is the last blank line, get ready to
 179                          * read a line starting at ch_zero() next time.
 180                          */
 181                         if (--nblank == 0)
 182                                 pos = ch_zero();
 183                 } else
 184                 {
 185                         /*
 186                          * Get the next line from the file.
 187                          */
 188                         pos = forw_line(pos);
 189                         if (pos == NULL_POSITION)
 190                         {
 191                                 /*
 192                                  * End of file: stop here unless the top line
 193                                  * is still empty, or "force" is true.
 194                                  * Even if force is true, stop when the last
 195                                  * line in the file reaches the top of screen.
 196                                  */
 197                                 eof = 1;
 198                                 if (!force && position(TOP) != NULL_POSITION)
 199                                         break;
 200                                 if (!empty_lines(0, 0) &&
 201                                     !empty_lines(1, 1) &&
 202                                      empty_lines(2, sc_height-1))
 203                                         break;
 204                         }
 205                 }
 206                 /*
 207                  * Add the position of the next line to the position table.
 208                  * Display the current line on the screen.
 209                  */
 210                 add_forw_pos(pos);
 211                 nlines++;
 212                 if (do_repaint)
 213                         continue;
 214                 /*
 215                  * If this is the first screen displayed and
 216                  * we hit an early EOF (i.e. before the requested
 217                  * number of lines), we "squish" the display down
 218                  * at the bottom of the screen.
 219                  * But don't do this if a + option or a -t option
 220                  * was given.  These options can cause us to
 221                  * start the display after the beginning of the file,
 222                  * and it is not appropriate to squish in that case.
 223                  */
 224                 if ((first_time || less_is_more) &&
 225                     pos == NULL_POSITION && !top_scroll &&
 226 #if TAGS
 227                     tagoption == NULL &&
 228 #endif
 229                     !plusoption)
 230                 {
 231                         squished = 1;
 232                         continue;
 233                 }
 234                 put_line();
 235 #if 0
 236                 /* {{
 237                  * Can't call clear_eol here.  The cursor might be at end of line
 238                  * on an ignaw terminal, so clear_eol would clear the last char
 239                  * of the current line instead of all of the next line.
 240                  * If we really need to do this on clear_bg terminals, we need
 241                  * to find a better way.
 242                  * }}
 243                  */
 244                 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
 245                 {
 246                         /*
 247                          * Writing the last character on the last line
 248                          * of the display may have scrolled the screen.
 249                          * If we were in standout mode, clear_bg terminals
 250                          * will fill the new line with the standout color.
 251                          * Now we're in normal mode again, so clear the line.
 252                          */
 253                         clear_eol();
 254                 }
 255 #endif
 256                 forw_prompt = 1;
 257         }
 258
 259         if (ignore_eoi)
 260                 hit_eof = 0;
 261         else if (eof && !ABORT_SIGS())
 262                 hit_eof++;
 263         else
 264                 eof_check();
 265         if (nlines == 0)
 266                 eof_bell();
 267         else if (do_repaint)
 268                 repaint();
 269         first_time = 0;
 270         (void) currline(BOTTOM);
 271 }
 272
 273 /*
 274  * Display n lines, scrolling backward.
 275  */
 276         public void
 277 back(n, pos, force, only_last)
 278         register int n;
 279         POSITION pos;
 280         int force;
 281         int only_last;
 282 {
 283         int nlines = 0;
 284         int do_repaint;
 285
 286         squish_check();
 287         do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
 288         hit_eof = 0;
 289         while (--n >= 0)
 290         {
 291                 /*
 292                  * Get the previous line of input.
 293                  */
 294                 pos = back_line(pos);
 295                 if (pos == NULL_POSITION)
 296                 {
 297                         /*
 298                          * Beginning of file: stop here unless "force" is true.
 299                          */
 300                         if (!force)
 301                                 break;
 302                 }
 303                 /*
 304                  * Add the position of the previous line to the position table.
 305                  * Display the line on the screen.
 306                  */
 307                 add_back_pos(pos);
 308                 nlines++;
 309                 if (!do_repaint)
 310                 {
 311                         home();
 312                         add_line();
 313                         put_line();
 314                 }
 315         }
 316
 317         eof_check();
 318         if (nlines == 0)
 319                 eof_bell();
 320         else if (do_repaint)
 321                 repaint();
 322         else if (!oldbot)
 323                 lower_left();
 324         (void) currline(BOTTOM);
 325 }
 326
 327 /*
 328  * Display n more lines, forward.
 329  * Start just after the line currently displayed at the bottom of the screen.
 330  */
 331         public void
 332 forward(n, force, only_last)
 333         int n;
 334         int force;
 335         int only_last;
 336 {
 337         POSITION pos;
 338
 339         if (get_quit_at_eof() && hit_eof && !(ch_getflags() & CH_HELPFILE))
 340         {
 341                 /*
 342                  * If the -e flag is set and we're trying to go
 343                  * forward from end-of-file, go on to the next file.
 344                  */
 345                 if (edit_next(1))
 346                         quit(QUIT_OK);
 347                 return;
 348         }
 349
 350         pos = position(BOTTOM_PLUS_ONE);
 351         if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
 352         {
 353                 if (ignore_eoi)
 354                 {
 355                         /*
 356                          * ignore_eoi is to support A_F_FOREVER.
 357                          * Back up until there is a line at the bottom
 358                          * of the screen.
 359                          */
 360                         if (empty_screen())
 361                                 pos = ch_zero();
 362                         else
 363                         {
 364                                 do
 365                                 {
 366                                         back(1, position(TOP), 1, 0);
 367                                         pos = position(BOTTOM_PLUS_ONE);
 368                                 } while (pos == NULL_POSITION);
 369                         }
 370                 } else
 371                 {
 372                         eof_bell();
 373                         hit_eof++;
 374                         return;
 375                 }
 376         }
 377         forw(n, pos, force, only_last, 0);
 378 }
 379
 380 /*
 381  * Display n more lines, backward.
 382  * Start just before the line currently displayed at the top of the screen.
 383  */
 384         public void
 385 backward(n, force, only_last)
 386         int n;
 387         int force;
 388         int only_last;
 389 {
 390         POSITION pos;
 391
 392         pos = position(TOP);
 393         if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
 394         {
 395                 eof_bell();
 396                 return;
 397         }
 398         back(n, pos, force, only_last);
 399 }
 400
 401 /*
 402  * Get the backwards scroll limit.
 403  * Must call this function instead of just using the value of
 404  * back_scroll, because the default case depends on sc_height and
 405  * top_scroll, as well as back_scroll.
 406  */
 407         public int
 408 get_back_scroll()
 409 {
 410         if (no_back_scroll)
 411                 return (0);
 412         if (back_scroll >= 0)
 413                 return (back_scroll);
 414         if (top_scroll)
 415                 return (sc_height - 2);
 416         return (10000); /* infinity */
 417 }