1 /* 2 * Copyright (C) 1984-2025 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 * Routines which jump to a new location in the file. 13 */ 14 15 #include "less.h" 16 #include "position.h" 17 18 extern int jump_sline; 19 extern lbool squished; 20 extern int sc_width, sc_height; 21 extern int show_attn; 22 extern int top_scroll; 23 extern POSITION header_start_pos; 24 25 /* 26 * Jump to the end of the file. 27 */ 28 public void jump_forw(void) 29 { 30 POSITION pos; 31 POSITION end_pos; 32 33 if (ch_end_seek()) 34 { 35 error("Cannot seek to end of file", NULL_PARG); 36 return; 37 } 38 end_pos = ch_tell(); 39 if (position(sc_height-1) == end_pos) 40 { 41 eof_bell(); 42 return; 43 } 44 /* 45 * Note; lastmark will be called later by jump_loc, but it fails 46 * because the position table has been cleared by pos_clear below. 47 * So call it here before calling pos_clear. 48 */ 49 lastmark(); 50 /* 51 * Position the last line in the file at the last screen line. 52 * Go back one line from the end of the file 53 * to get to the beginning of the last line. 54 */ 55 pos_clear(); 56 pos = back_line(end_pos, NULL); 57 if (pos == NULL_POSITION) 58 jump_loc(ch_zero(), sc_height-1); 59 else 60 { 61 jump_loc(pos, sc_height-1); 62 if (position(sc_height-1) != end_pos) 63 repaint(); 64 } 65 } 66 67 /* 68 * Jump to the last buffered line in the file. 69 */ 70 public void jump_forw_buffered(void) 71 { 72 POSITION end; 73 74 if (ch_end_buffer_seek()) 75 { 76 error("Cannot seek to end of buffers", NULL_PARG); 77 return; 78 } 79 end = ch_tell(); 80 if (end != NULL_POSITION && end > 0) 81 jump_line_loc(end-1, sc_height-1); 82 } 83 84 /* 85 * Jump to line n in the file. 86 */ 87 public void jump_back(LINENUM linenum) 88 { 89 POSITION pos; 90 PARG parg; 91 92 /* 93 * Find the position of the specified line. 94 * If we can seek there, just jump to it. 95 * If we can't seek, but we're trying to go to line number 1, 96 * use ch_beg_seek() to get as close as we can. 97 */ 98 pos = find_pos(linenum); 99 if (pos != NULL_POSITION && ch_seek(pos) == 0) 100 { 101 if (show_attn) 102 set_attnpos(pos); 103 jump_loc(pos, jump_sline); 104 } else if (linenum <= 1 && ch_beg_seek() == 0) 105 { 106 jump_loc(ch_tell(), jump_sline); 107 error("Cannot seek to beginning of file", NULL_PARG); 108 } else 109 { 110 parg.p_linenum = linenum; 111 error("Cannot seek to line number %n", &parg); 112 } 113 } 114 115 /* 116 * Repaint the screen. 117 */ 118 public void repaint(void) 119 { 120 struct scrpos scrpos; 121 /* 122 * Start at the line currently at the top of the screen 123 * and redisplay the screen. 124 */ 125 get_scrpos(&scrpos, TOP); 126 pos_clear(); 127 if (scrpos.pos == NULL_POSITION) 128 /* Screen hasn't been drawn yet. */ 129 jump_loc(ch_zero(), 1); 130 else 131 jump_loc(scrpos.pos, scrpos.ln); 132 } 133 134 /* 135 * Jump to a specified percentage into the file. 136 */ 137 public void jump_percent(int percent, long fraction) 138 { 139 POSITION pos, len; 140 141 /* 142 * Determine the position in the file 143 * (the specified percentage of the file's length). 144 */ 145 if ((len = ch_length()) == NULL_POSITION) 146 { 147 ierror("Determining length of file", NULL_PARG); 148 ch_end_seek(); 149 } 150 if ((len = ch_length()) == NULL_POSITION) 151 { 152 error("Don't know length of file", NULL_PARG); 153 return; 154 } 155 pos = percent_pos(len, percent, fraction); 156 if (pos >= len) 157 pos = len-1; 158 159 jump_line_loc(pos, jump_sline); 160 } 161 162 /* 163 * Jump to a specified position in the file. 164 * Like jump_loc, but the position need not be 165 * the first character in a line. 166 */ 167 public void jump_line_loc(POSITION pos, int sline) 168 { 169 int c; 170 171 if (ch_seek(pos) == 0) 172 { 173 /* 174 * Back up to the beginning of the line. 175 */ 176 while ((c = ch_back_get()) != '\n' && c != EOI) 177 ; 178 if (c == '\n') 179 (void) ch_forw_get(); 180 pos = ch_tell(); 181 } 182 if (show_attn) 183 set_attnpos(pos); 184 jump_loc(pos, sline); 185 } 186 187 static void after_header_message(void) 188 { 189 #if HAVE_TIME 190 #define MSG_FREQ 1 /* seconds */ 191 static time_type last_msg = (time_type) 0; 192 time_type now = get_time(); 193 if (now < last_msg + MSG_FREQ) 194 return; 195 last_msg = now; 196 #endif 197 bell(); 198 /* {{ This message displays before the file text is updated, which is not a good UX. }} */ 199 /** error("Cannot display text before header; use --header=- to disable header", NULL_PARG); */ 200 } 201 202 /* 203 * Ensure that a position is not before the header. 204 * If it is, print a message and return the position of the start of the header. 205 * {{ This is probably not being used correctly in all cases. 206 * It does not account for the location of pos on the screen, 207 * so lines before pos could be displayed. }} 208 */ 209 public POSITION after_header_pos(POSITION pos) 210 { 211 if (header_start_pos != NULL_POSITION && pos < header_start_pos) 212 { 213 after_header_message(); 214 pos = header_start_pos; 215 } 216 return pos; 217 } 218 219 /* 220 * Jump to a specified position in the file. 221 * The position must be the first character in a line. 222 * Place the target line on a specified line on the screen. 223 */ 224 public void jump_loc(POSITION pos, int sline) 225 { 226 int nline; 227 int sindex; 228 POSITION tpos; 229 POSITION bpos; 230 231 /* 232 * Normalize sline. 233 */ 234 pos = after_header_pos(pos); 235 pos = next_unfiltered(pos); 236 sindex = sindex_from_sline(sline); 237 238 if ((nline = onscreen(pos)) >= 0) 239 { 240 /* 241 * The line is currently displayed. 242 * Just scroll there. 243 */ 244 nline -= sindex; 245 if (nline > 0) 246 forw(nline, position(BOTTOM_PLUS_ONE), TRUE, FALSE, FALSE, 0); 247 else 248 back(-nline, position(TOP), TRUE, FALSE, FALSE); 249 #if HILITE_SEARCH 250 if (show_attn) 251 repaint_hilite(TRUE); 252 #endif 253 return; 254 } 255 256 /* 257 * Line is not on screen. 258 * Seek to the desired location. 259 */ 260 if (ch_seek(pos)) 261 { 262 error("Cannot seek to that file position", NULL_PARG); 263 return; 264 } 265 266 /* 267 * See if the desired line is before or after 268 * the currently displayed screen. 269 */ 270 tpos = position(TOP); 271 bpos = position(BOTTOM_PLUS_ONE); 272 if (tpos == NULL_POSITION || pos >= tpos) 273 { 274 /* 275 * The desired line is after the current screen. 276 * Move back in the file far enough so that we can 277 * call forw() and put the desired line at the 278 * sline-th line on the screen. 279 */ 280 for (nline = 0; nline < sindex; nline++) 281 { 282 if (bpos != NULL_POSITION && pos <= bpos) 283 { 284 /* 285 * Surprise! The desired line is 286 * close enough to the current screen 287 * that we can just scroll there after all. 288 */ 289 forw(sc_height-sindex+nline-1, bpos, TRUE, FALSE, FALSE, 0); 290 #if HILITE_SEARCH 291 if (show_attn) 292 repaint_hilite(TRUE); 293 #endif 294 return; 295 } 296 pos = back_line(pos, NULL); 297 if (pos == NULL_POSITION) 298 { 299 /* 300 * Oops. Ran into the beginning of the file. 301 * Exit the loop here and rely on forw() 302 * below to draw the required number of 303 * blank lines at the top of the screen. 304 */ 305 break; 306 } 307 } 308 lastmark(); 309 squished = FALSE; 310 screen_trashed_num(0); 311 forw(sc_height-1, pos, TRUE, FALSE, FALSE, sindex-nline); 312 } else 313 { 314 /* 315 * The desired line is before the current screen. 316 * Move forward in the file far enough so that we 317 * can call back() and put the desired line at the 318 * sindex-th line on the screen. 319 */ 320 for (nline = sindex; nline < sc_height - 1; nline++) 321 { 322 POSITION linepos; 323 pos = forw_line(pos, &linepos, NULL); 324 if (pos == NULL_POSITION) 325 { 326 /* 327 * Ran into end of file. 328 * This shouldn't normally happen, 329 * but may if there is some kind of read error. 330 */ 331 break; 332 } 333 if (linepos >= tpos) 334 { 335 /* 336 * Surprise! The desired line is 337 * close enough to the current screen 338 * that we can just scroll there after all. 339 */ 340 back(nline, tpos, TRUE, FALSE, FALSE); 341 #if HILITE_SEARCH 342 if (show_attn) 343 repaint_hilite(TRUE); 344 #endif 345 return; 346 } 347 } 348 lastmark(); 349 if (!top_scroll) 350 clear(); 351 else 352 home(); 353 screen_trashed_num(0); 354 add_back_pos(pos); 355 back(sc_height-1, pos, TRUE, FALSE, FALSE); 356 } 357 } 358