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 * Primitives for displaying the file on the screen,
14 * scrolling either forward or backward.
20 public int hit_eof; /* Keeps track of how many times we hit end of file */
21 public int screen_trashed;
23 public int no_back_scroll = 0;
24 public int forw_prompt;
27 extern int top_scroll;
29 extern int sc_width, sc_height;
30 extern int plusoption;
31 extern int forw_scroll;
32 extern int back_scroll;
33 extern int ignore_eoi;
35 extern int final_attr;
38 extern char *tagoption;
42 * Sound the bell to indicate user is trying to move past end of file.
47 if (quiet == NOT_QUIET)
54 * Check to see if the end of file is currently "displayed".
66 * If the bottom line is empty, we are at EOF.
67 * If the bottom line ends at the file length,
68 * we must be just at EOF.
70 pos = position(BOTTOM_PLUS_ONE);
71 if (pos == NULL_POSITION || pos == ch_length())
76 * If the screen is "squished", repaint it.
77 * "Squished" means the first displayed line is not at the top
78 * of the screen; this can happen when we display a short file
91 * Display n lines, scrolling forward,
92 * starting at position pos in the input file.
93 * "force" means display the n lines even if we hit end of file.
94 * "only_last" means display only the last screenful if n > screen size.
95 * "nblank" is the number of blank lines to draw before the first
96 * real line. If nblank > 0, the pos must be NULL_POSITION.
97 * The first real line after the blanks will start at ch_zero().
100 forw(n, pos, force, only_last, nblank)
110 static int first_time = 1;
115 * do_repaint tells us not to display anything till the end,
116 * then just repaint the entire screen.
117 * We repaint if we are supposed to display only the last
118 * screenful and the request is for more than a screenful.
119 * Also if the request exceeds the forward scroll limit
120 * (but not if the request is for exactly a screenful, since
121 * repainting itself involves scrolling forward a screenful).
123 do_repaint = (only_last && n > sc_height-1) ||
124 (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
128 if (top_scroll && n >= sc_height - 1 && pos != ch_length())
131 * Start a new screen.
132 * {{ This is not really desirable if we happen
133 * to hit eof in the middle of this screen,
134 * but we don't yet know if that will happen. }}
146 if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
149 * This is not contiguous with what is
150 * currently displayed. Clear the screen image
151 * (position table) and start a new screen.
160 } else if (!first_time)
162 putstr("...skipping...\n");
170 * Read the next line of input.
175 * Still drawing blanks; don't get a line
177 * If this is the last blank line, get ready to
178 * read a line starting at ch_zero() next time.
185 * Get the next line from the file.
187 pos = forw_line(pos);
188 if (pos == NULL_POSITION)
191 * End of file: stop here unless the top line
192 * is still empty, or "force" is true.
193 * Even if force is true, stop when the last
194 * line in the file reaches the top of screen.
197 if (!force && position(TOP) != NULL_POSITION)
199 if (!empty_lines(0, 0) &&
200 !empty_lines(1, 1) &&
201 empty_lines(2, sc_height-1))
206 * Add the position of the next line to the position table.
207 * Display the current line on the screen.
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.
223 if (first_time && pos == NULL_POSITION && !top_scroll &&
235 * Can't call clear_eol here. The cursor might be at end of line
236 * on an ignaw terminal, so clear_eol would clear the last char
237 * of the current line instead of all of the next line.
238 * If we really need to do this on clear_bg terminals, we need
239 * to find a better way.
242 if (clear_bg && apply_at_specials(final_attr) != AT_NORMAL)
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.
259 else if (eof && !ABORT_SIGS())
268 (void) currline(BOTTOM);
272 * Display n lines, scrolling backward.
275 back(n, pos, force, only_last)
285 do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
290 * Get the previous line of input.
292 pos = back_line(pos);
293 if (pos == NULL_POSITION)
296 * Beginning of file: stop here unless "force" is true.
302 * Add the position of the previous line to the position table.
303 * Display the line on the screen.
322 (void) currline(BOTTOM);
326 * Display n more lines, forward.
327 * Start just after the line currently displayed at the bottom of the screen.
330 forward(n, force, only_last)
337 if (get_quit_at_eof() && hit_eof && !(ch_getflags() & CH_HELPFILE))
340 * If the -e flag is set and we're trying to go
341 * forward from end-of-file, go on to the next file.
348 pos = position(BOTTOM_PLUS_ONE);
349 if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
354 * ignore_eoi is to support A_F_FOREVER.
355 * Back up until there is a line at the bottom
364 back(1, position(TOP), 1, 0);
365 pos = position(BOTTOM_PLUS_ONE);
366 } while (pos == NULL_POSITION);
375 forw(n, pos, force, only_last, 0);
379 * Display n more lines, backward.
380 * Start just before the line currently displayed at the top of the screen.
383 backward(n, force, only_last)
391 if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
396 back(n, pos, force, only_last);
400 * Get the backwards scroll limit.
401 * Must call this function instead of just using the value of
402 * back_scroll, because the default case depends on sc_height and
403 * top_scroll, as well as back_scroll.
410 if (back_scroll >= 0)
411 return (back_scroll);
413 return (sc_height - 2);
414 return (10000); /* infinity */