bin/less/forwback.c

   1 /*
   2  * Copyright (C) 1984-2012  Mark Nudelman
   3  * Modified for use with illumos by Garrett D'Amore.
   4  * Copyright 2014 Garrett D'Amore <garrett@damore.org>
   5  *
   6  * You may distribute under the terms of either the GNU General Public
   7  * License or the Less License, as specified in the README file.
   8  *
   9  * For more information, see the README file.
  10  */
  11
  12 /*
  13  * Primitives for displaying the file on the screen,
  14  * scrolling either forward or backward.
  15  */
  16
  17 #include "less.h"
  18 #include "position.h"
  19
  20 int screen_trashed;
  21 int squished;
  22 int no_back_scroll = 0;
  23 int forw_prompt;
  24
  25 extern volatile sig_atomic_t 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 extern char *tagoption;
  37
  38 /*
  39  * Sound the bell to indicate user is trying to move past end of file.
  40  */
  41 static void
  42 eof_bell(void)
  43 {
  44         if (quiet == NOT_QUIET)
  45                 ring_bell();
  46         else
  47                 vbell();
  48 }
  49
  50 /*
  51  * Check to see if the end of file is currently displayed.
  52  */
  53 int
  54 eof_displayed(void)
  55 {
  56         off_t pos;
  57
  58         if (ignore_eoi)
  59                 return (0);
  60
  61         if (ch_length() == -1)
  62                 /*
  63                  * If the file length is not known,
  64                  * we can't possibly be displaying EOF.
  65                  */
  66                 return (0);
  67
  68         /*
  69          * If the bottom line is empty, we are at EOF.
  70          * If the bottom line ends at the file length,
  71          * we must be just at EOF.
  72          */
  73         pos = position(BOTTOM_PLUS_ONE);
  74         return (pos == -1 || pos == ch_length());
  75 }
  76
  77 /*
  78  * Check to see if the entire file is currently displayed.
  79  */
  80 int
  81 entire_file_displayed(void)
  82 {
  83         off_t pos;
  84
  85         /* Make sure last line of file is displayed. */
  86         if (!eof_displayed())
  87                 return (0);
  88
  89         /* Make sure first line of file is displayed. */
  90         pos = position(0);
  91         return (pos == -1 || pos == 0);
  92 }
  93
  94 /*
  95  * If the screen is "squished", repaint it.
  96  * "Squished" means the first displayed line is not at the top
  97  * of the screen; this can happen when we display a short file
  98  * for the first time.
  99  */
 100 void
 101 squish_check(void)
 102 {
 103         if (!squished)
 104                 return;
 105         squished = 0;
 106         repaint();
 107 }
 108
 109 /*
 110  * Display n lines, scrolling forward,
 111  * starting at position pos in the input file.
 112  * "force" means display the n lines even if we hit end of file.
 113  * "only_last" means display only the last screenful if n > screen size.
 114  * "nblank" is the number of blank lines to draw before the first
 115  *   real line.  If nblank > 0, the pos must be -1.
 116  *   The first real line after the blanks will start at ch_zero().
 117  */
 118 void
 119 forw(int n, off_t pos, int force, int only_last, int nblank)
 120 {
 121         int nlines = 0;
 122         int do_repaint;
 123         static int first_time = 1;
 124
 125         squish_check();
 126
 127         /*
 128          * do_repaint tells us not to display anything till the end,
 129          * then just repaint the entire screen.
 130          * We repaint if we are supposed to display only the last
 131          * screenful and the request is for more than a screenful.
 132          * Also if the request exceeds the forward scroll limit
 133          * (but not if the request is for exactly a screenful, since
 134          * repainting itself involves scrolling forward a screenful).
 135          */
 136         do_repaint = (only_last && n > sc_height-1) ||
 137             (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
 138
 139         if (!do_repaint) {
 140                 if (top_scroll && n >= sc_height - 1 && pos != ch_length()) {
 141                         /*
 142                          * Start a new screen.
 143                          * {{ This is not really desirable if we happen
 144                          *    to hit eof in the middle of this screen,
 145                          *    but we don't yet know if that will happen. }}
 146                          */
 147                         pos_clear();
 148                         add_forw_pos(pos);
 149                         force = 1;
 150                         do_clear();
 151                         home();
 152                 }
 153
 154                 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen()) {
 155                         /*
 156                          * This is not contiguous with what is
 157                          * currently displayed.  Clear the screen image
 158                          * (position table) and start a new screen.
 159                          */
 160                         pos_clear();
 161                         add_forw_pos(pos);
 162                         force = 1;
 163                         if (top_scroll) {
 164                                 do_clear();
 165                                 home();
 166                         } else if (!first_time) {
 167                                 putstr("...skipping...\n");
 168                         }
 169                 }
 170         }
 171
 172         while (--n >= 0) {
 173                 /*
 174                  * Read the next line of input.
 175                  */
 176                 if (nblank > 0) {
 177                         /*
 178                          * Still drawing blanks; don't get a line
 179                          * from the file yet.
 180                          * If this is the last blank line, get ready to
 181                          * read a line starting at ch_zero() next time.
 182                          */
 183                         if (--nblank == 0)
 184                                 pos = ch_zero();
 185                 } else {
 186                         /*
 187                          * Get the next line from the file.
 188                          */
 189                         pos = forw_line(pos);
 190                         if (pos == -1) {
 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                                 if (!force && position(TOP) != -1)
 198                                         break;
 199                                 if (!empty_lines(0, 0) &&
 200                                     !empty_lines(1, 1) &&
 201                                     empty_lines(2, sc_height-1))
 202                                         break;
 203                         }
 204                 }
 205                 /*
 206                  * Add the position of the next line to the position table.
 207                  * Display the current line on the screen.
 208                  */
 209                 add_forw_pos(pos);
 210                 nlines++;
 211                 if (do_repaint)
 212                         continue;
 213                 /*
 214                  * If this is the first screen displayed and
 215                  * we hit an early EOF (i.e. before the requested
 216                  * number of lines), we "squish" the display down
 217                  * at the bottom of the screen.
 218                  * But don't do this if a + option or a -t option
 219                  * was given.  These options can cause us to
 220                  * start the display after the beginning of the file,
 221                  * and it is not appropriate to squish in that case.
 222                  */
 223                 if (first_time && pos == -1 && !top_scroll &&
 224                     tagoption == NULL && !plusoption) {
 225                         squished = 1;
 226                         continue;
 227                 }
 228                 put_line();
 229                 forw_prompt = 1;
 230         }
 231
 232         if (nlines == 0)
 233                 eof_bell();
 234         else if (do_repaint)
 235                 repaint();
 236         first_time = 0;
 237         (void) currline(BOTTOM);
 238 }
 239
 240 /*
 241  * Display n lines, scrolling backward.
 242  */
 243 void
 244 back(int n, off_t pos, int force, int only_last)
 245 {
 246         int nlines = 0;
 247         int do_repaint;
 248
 249         squish_check();
 250         do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
 251         while (--n >= 0) {
 252                 /*
 253                  * Get the previous line of input.
 254                  */
 255                 pos = back_line(pos);
 256                 if (pos == -1) {
 257                         /*
 258                          * Beginning of file: stop here unless "force" is true.
 259                          */
 260                         if (!force)
 261                                 break;
 262                 }
 263                 /*
 264                  * Add the position of the previous line to the position table.
 265                  * Display the line on the screen.
 266                  */
 267                 add_back_pos(pos);
 268                 nlines++;
 269                 if (!do_repaint) {
 270                         home();
 271                         add_line();
 272                         put_line();
 273                 }
 274         }
 275
 276         if (nlines == 0)
 277                 eof_bell();
 278         else if (do_repaint)
 279                 repaint();
 280         else if (!oldbot)
 281                 lower_left();
 282         (void) currline(BOTTOM);
 283 }
 284
 285 /*
 286  * Display n more lines, forward.
 287  * Start just after the line currently displayed at the bottom of the screen.
 288  */
 289 void
 290 forward(int n, int force, int only_last)
 291 {
 292         off_t pos;
 293
 294         if (get_quit_at_eof() && eof_displayed() &&
 295             !(ch_getflags() & CH_HELPFILE)) {
 296                 /*
 297                  * If the -e flag is set and we're trying to go
 298                  * forward from end-of-file, go on to the next file.
 299                  */
 300                 if (edit_next(1))
 301                         quit(QUIT_OK);
 302                 return;
 303         }
 304
 305         pos = position(BOTTOM_PLUS_ONE);
 306         if (pos == -1 && (!force || empty_lines(2, sc_height-1))) {
 307                 if (ignore_eoi) {
 308                         /*
 309                          * ignore_eoi is to support A_F_FOREVER.
 310                          * Back up until there is a line at the bottom
 311                          * of the screen.
 312                          */
 313                         if (empty_screen()) {
 314                                 pos = ch_zero();
 315                         } else {
 316                                 do {
 317                                         back(1, position(TOP), 1, 0);
 318                                         pos = position(BOTTOM_PLUS_ONE);
 319                                 } while (pos == -1);
 320                         }
 321                 } else {
 322                         eof_bell();
 323                         return;
 324                 }
 325         }
 326         forw(n, pos, force, only_last, 0);
 327 }
 328
 329 /*
 330  * Display n more lines, backward.
 331  * Start just before the line currently displayed at the top of the screen.
 332  */
 333 void
 334 backward(int n, int force, int only_last)
 335 {
 336         off_t pos;
 337
 338         pos = position(TOP);
 339         if (pos == -1 && (!force || position(BOTTOM) == 0)) {
 340                 eof_bell();
 341                 return;
 342         }
 343         back(n, pos, force, only_last);
 344 }
 345
 346 /*
 347  * Get the backwards scroll limit.
 348  * Must call this function instead of just using the value of
 349  * back_scroll, because the default case depends on sc_height and
 350  * top_scroll, as well as back_scroll.
 351  */
 352 int
 353 get_back_scroll(void)
 354 {
 355         if (no_back_scroll)
 356                 return (0);
 357         if (back_scroll >= 0)
 358                 return (back_scroll);
 359         if (top_scroll)
 360                 return (sc_height - 2);
 361         return (10000); /* infinity */
 362 }