1 /* $FreeBSD$ */ 2 /* 3 * Copyright (C) 1984-2005 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 26 extern int sigs; 27 extern int top_scroll; 28 extern int quiet; 29 extern int sc_width, sc_height; 30 extern int quit_at_eof; 31 extern int more_mode; 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 #if TAGS 39 extern char *tagoption; 40 #endif 41 42 /* 43 * Sound the bell to indicate user is trying to move past end of file. 44 */ 45 static void 46 eof_bell() 47 { 48 if (quiet == NOT_QUIET) 49 bell(); 50 else 51 vbell(); 52 } 53 54 /* 55 * Check to see if the end of file is currently "displayed". 56 */ 57 static void 58 eof_check() 59 { 60 POSITION pos; 61 62 if (ignore_eoi) 63 return; 64 if (ABORT_SIGS()) 65 return; 66 /* 67 * If the bottom line is empty, we are at EOF. 68 * If the bottom line ends at the file length, 69 * we must be just at EOF. 70 */ 71 pos = position(BOTTOM_PLUS_ONE); 72 if (pos == NULL_POSITION || pos == ch_length()) 73 hit_eof++; 74 } 75 76 /* 77 * If the screen is "squished", repaint it. 78 * "Squished" means the first displayed line is not at the top 79 * of the screen; this can happen when we display a short file 80 * for the first time. 81 */ 82 static void 83 squish_check() 84 { 85 if (!squished) 86 return; 87 squished = 0; 88 repaint(); 89 } 90 91 /* 92 * Display n lines, scrolling forward, 93 * starting at position pos in the input file. 94 * "force" means display the n lines even if we hit end of file. 95 * "only_last" means display only the last screenful if n > screen size. 96 * "nblank" is the number of blank lines to draw before the first 97 * real line. If nblank > 0, the pos must be NULL_POSITION. 98 * The first real line after the blanks will start at ch_zero(). 99 */ 100 public void 101 forw(n, pos, force, only_last, nblank) 102 register int n; 103 POSITION pos; 104 int force; 105 int only_last; 106 int nblank; 107 { 108 int eof = 0; 109 int nlines = 0; 110 int do_repaint; 111 static int first_time = 1; 112 113 squish_check(); 114 115 /* 116 * do_repaint tells us not to display anything till the end, 117 * then just repaint the entire screen. 118 * We repaint if we are supposed to display only the last 119 * screenful and the request is for more than a screenful. 120 * Also if the request exceeds the forward scroll limit 121 * (but not if the request is for exactly a screenful, since 122 * repainting itself involves scrolling forward a screenful). 123 */ 124 do_repaint = (only_last && n > sc_height-1) || 125 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1); 126 127 if (!do_repaint) 128 { 129 if (top_scroll && n >= sc_height - 1 && pos != ch_length()) 130 { 131 /* 132 * Start a new screen. 133 * {{ This is not really desirable if we happen 134 * to hit eof in the middle of this screen, 135 * but we don't yet know if that will happen. }} 136 */ 137 pos_clear(); 138 add_forw_pos(pos); 139 force = 1; 140 if (more_mode == 0) 141 { 142 if (top_scroll == OPT_ONPLUS || (first_time && top_scroll != OPT_ON)) 143 clear(); 144 home(); 145 } 146 } else 147 { 148 clear_bot(); 149 } 150 151 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen()) 152 { 153 /* 154 * This is not contiguous with what is 155 * currently displayed. Clear the screen image 156 * (position table) and start a new screen. 157 */ 158 pos_clear(); 159 add_forw_pos(pos); 160 force = 1; 161 if (top_scroll) 162 { 163 if (top_scroll == OPT_ONPLUS) 164 clear(); 165 home(); 166 } else if (!first_time) 167 { 168 putstr("...skipping...\n"); 169 } 170 } 171 } 172 173 while (--n >= 0) 174 { 175 /* 176 * Read the next line of input. 177 */ 178 if (nblank > 0) 179 { 180 /* 181 * Still drawing blanks; don't get a line 182 * from the file yet. 183 * If this is the last blank line, get ready to 184 * read a line starting at ch_zero() next time. 185 */ 186 if (--nblank == 0) 187 pos = ch_zero(); 188 } else 189 { 190 /* 191 * Get the next line from the file. 192 */ 193 pos = forw_line(pos); 194 if (pos == NULL_POSITION) 195 { 196 /* 197 * End of file: stop here unless the top line 198 * is still empty, or "force" is true. 199 * Even if force is true, stop when the last 200 * line in the file reaches the top of screen. 201 */ 202 eof = 1; 203 if (!force && position(TOP) != NULL_POSITION) 204 break; 205 if (!empty_lines(0, 0) && 206 !empty_lines(1, 1) && 207 empty_lines(2, sc_height-1)) 208 break; 209 } 210 } 211 /* 212 * Add the position of the next line to the position table. 213 * Display the current line on the screen. 214 */ 215 add_forw_pos(pos); 216 nlines++; 217 if (do_repaint) 218 continue; 219 /* 220 * If this is the first screen displayed and 221 * we hit an early EOF (i.e. before the requested 222 * number of lines), we "squish" the display down 223 * at the bottom of the screen. 224 * But don't do this if a + option or a -t option 225 * was given. These options can cause us to 226 * start the display after the beginning of the file, 227 * and it is not appropriate to squish in that case. 228 */ 229 if ((first_time || more_mode) && 230 pos == NULL_POSITION && !top_scroll && 231 #if TAGS 232 tagoption == NULL && 233 #endif 234 !plusoption) 235 { 236 squished = 1; 237 continue; 238 } 239 if (top_scroll == OPT_ON) 240 clear_eol(); 241 put_line(); 242 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL) 243 { 244 /* 245 * Writing the last character on the last line 246 * of the display may have scrolled the screen. 247 * If we were in standout mode, clear_bg terminals 248 * will fill the new line with the standout color. 249 * Now we're in normal mode again, so clear the line. 250 */ 251 clear_eol(); 252 } 253 } 254 255 if (ignore_eoi) 256 hit_eof = 0; 257 else if (eof && !ABORT_SIGS()) 258 hit_eof++; 259 else 260 eof_check(); 261 if (nlines == 0) 262 eof_bell(); 263 else if (do_repaint) 264 repaint(); 265 first_time = 0; 266 (void) currline(BOTTOM); 267 } 268 269 /* 270 * Display n lines, scrolling backward. 271 */ 272 public void 273 back(n, pos, force, only_last) 274 register int n; 275 POSITION pos; 276 int force; 277 int only_last; 278 { 279 int nlines = 0; 280 int do_repaint; 281 282 squish_check(); 283 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1)); 284 hit_eof = 0; 285 while (--n >= 0) 286 { 287 /* 288 * Get the previous line of input. 289 */ 290 pos = back_line(pos); 291 if (pos == NULL_POSITION) 292 { 293 /* 294 * Beginning of file: stop here unless "force" is true. 295 */ 296 if (!force) 297 break; 298 } 299 /* 300 * Add the position of the previous line to the position table. 301 * Display the line on the screen. 302 */ 303 add_back_pos(pos); 304 nlines++; 305 if (!do_repaint) 306 { 307 home(); 308 add_line(); 309 put_line(); 310 } 311 } 312 313 eof_check(); 314 if (nlines == 0) 315 eof_bell(); 316 else if (do_repaint) 317 repaint(); 318 (void) currline(BOTTOM); 319 } 320 321 /* 322 * Display n more lines, forward. 323 * Start just after the line currently displayed at the bottom of the screen. 324 */ 325 public void 326 forward(n, force, only_last) 327 int n; 328 int force; 329 int only_last; 330 { 331 POSITION pos; 332 333 if (quit_at_eof && hit_eof && !(ch_getflags() & CH_HELPFILE)) 334 { 335 /* 336 * If the -e flag is set and we're trying to go 337 * forward from end-of-file, go on to the next file. 338 */ 339 if (edit_next(1)) 340 quit(QUIT_OK); 341 return; 342 } 343 344 pos = position(BOTTOM_PLUS_ONE); 345 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1))) 346 { 347 if (ignore_eoi) 348 { 349 /* 350 * ignore_eoi is to support A_F_FOREVER. 351 * Back up until there is a line at the bottom 352 * of the screen. 353 */ 354 if (empty_screen()) 355 pos = ch_zero(); 356 else 357 { 358 do 359 { 360 back(1, position(TOP), 1, 0); 361 pos = position(BOTTOM_PLUS_ONE); 362 } while (pos == NULL_POSITION); 363 } 364 } else 365 { 366 eof_bell(); 367 hit_eof++; 368 return; 369 } 370 } 371 forw(n, pos, force, only_last, 0); 372 } 373 374 /* 375 * Display n more lines, backward. 376 * Start just before the line currently displayed at the top of the screen. 377 */ 378 public void 379 backward(n, force, only_last) 380 int n; 381 int force; 382 int only_last; 383 { 384 POSITION pos; 385 386 pos = position(TOP); 387 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0)) 388 { 389 eof_bell(); 390 return; 391 } 392 back(n, pos, force, only_last); 393 } 394 395 /* 396 * Get the backwards scroll limit. 397 * Must call this function instead of just using the value of 398 * back_scroll, because the default case depends on sc_height and 399 * top_scroll, as well as back_scroll. 400 */ 401 public int 402 get_back_scroll() 403 { 404 if (no_back_scroll) 405 return (0); 406 if (back_scroll >= 0) 407 return (back_scroll); 408 if (top_scroll) 409 return (sc_height - 2); 410 return (10000); /* infinity */ 411 } 412