2 * Copyright (C) 1984-2007 Mark Nudelman
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.
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
13 * Routines which jump to a new location in the file.
20 extern int jump_sline;
22 extern int screen_trashed;
23 extern int sc_width, sc_height;
25 extern int top_scroll;
28 * Jump to the end of the file.
38 error("Cannot seek to end of file", NULL_PARG);
42 * Position the last line in the file at the last screen line.
43 * Go back one line from the end of the file
44 * to get to the beginning of the last line.
48 pos = back_line(end_pos);
49 if (pos == NULL_POSITION)
50 jump_loc((POSITION)0, sc_height-1);
53 jump_loc(pos, sc_height-1);
54 if (position(sc_height-1) != end_pos)
60 * Jump to line n in the file.
70 * Find the position of the specified line.
71 * If we can seek there, just jump to it.
72 * If we can't seek, but we're trying to go to line number 1,
73 * use ch_beg_seek() to get as close as we can.
75 pos = find_pos(linenum);
76 if (pos != NULL_POSITION && ch_seek(pos) == 0)
80 jump_loc(pos, jump_sline);
81 } else if (linenum <= 1 && ch_beg_seek() == 0)
83 jump_loc(ch_tell(), jump_sline);
84 error("Cannot seek to beginning of file", NULL_PARG);
87 parg.p_linenum = linenum;
88 error("Cannot seek to line number %n", &parg);
100 * Start at the line currently at the top of the screen
101 * and redisplay the screen.
105 jump_loc(scrpos.pos, scrpos.ln);
109 * Jump to a specified percentage into the file.
112 jump_percent(percent, fraction)
119 * Determine the position in the file
120 * (the specified percentage of the file's length).
122 if ((len = ch_length()) == NULL_POSITION)
124 ierror("Determining length of file", NULL_PARG);
127 if ((len = ch_length()) == NULL_POSITION)
129 error("Don't know length of file", NULL_PARG);
132 pos = percent_pos(len, percent, fraction);
136 jump_line_loc(pos, jump_sline);
140 * Jump to a specified position in the file.
141 * Like jump_loc, but the position need not be
142 * the first character in a line.
145 jump_line_loc(pos, sline)
151 if (ch_seek(pos) == 0)
154 * Back up to the beginning of the line.
156 while ((c = ch_back_get()) != '\n' && c != EOI)
159 (void) ch_forw_get();
164 jump_loc(pos, sline);
168 * Jump to a specified position in the file.
169 * The position must be the first character in a line.
170 * Place the target line on a specified line on the screen.
184 sline = adjsline(sline);
186 if ((nline = onscreen(pos)) >= 0)
189 * The line is currently displayed.
194 forw(nline, position(BOTTOM_PLUS_ONE), 1, 0, 0);
196 back(-nline, position(TOP), 1, 0);
203 * Line is not on screen.
204 * Seek to the desired location.
208 error("Cannot seek to that file position", NULL_PARG);
213 * See if the desired line is before or after
214 * the currently displayed screen.
216 tpos = position(TOP);
217 bpos = position(BOTTOM_PLUS_ONE);
218 if (tpos == NULL_POSITION || pos >= tpos)
221 * The desired line is after the current screen.
222 * Move back in the file far enough so that we can
223 * call forw() and put the desired line at the
224 * sline-th line on the screen.
226 for (nline = 0; nline < sline; nline++)
228 if (bpos != NULL_POSITION && pos <= bpos)
231 * Surprise! The desired line is
232 * close enough to the current screen
233 * that we can just scroll there after all.
235 forw(sc_height-sline+nline-1, bpos, 1, 0, 0);
240 pos = back_line(pos);
241 if (pos == NULL_POSITION)
244 * Oops. Ran into the beginning of the file.
245 * Exit the loop here and rely on forw()
246 * below to draw the required number of
247 * blank lines at the top of the screen.
256 forw(sc_height-1, pos, 1, 0, sline-nline);
260 * The desired line is before the current screen.
261 * Move forward in the file far enough so that we
262 * can call back() and put the desired line at the
263 * sline-th line on the screen.
265 for (nline = sline; nline < sc_height - 1; nline++)
267 pos = forw_line(pos);
268 if (pos == NULL_POSITION)
271 * Ran into end of file.
272 * This shouldn't normally happen,
273 * but may if there is some kind of read error.
280 * Surprise! The desired line is
281 * close enough to the current screen
282 * that we can just scroll there after all.
284 back(nline+1, tpos, 1, 0);
297 back(sc_height-1, pos, 1, 0);