Annotation of src/usr.bin/less/forwback.c, Revision 1.11
1.1 etheisen 1: /*
1.9 shadchin 2: * Copyright (C) 1984-2012 Mark Nudelman
1.11 ! nicm 3: * Modified for use with illumos by Garrett D'Amore.
! 4: * Copyright 2014 Garrett D'Amore <garrett@damore.org>
1.1 etheisen 5: *
1.5 millert 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.
1.1 etheisen 8: *
1.9 shadchin 9: * For more information, see the README file.
1.10 nicm 10: */
1.1 etheisen 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:
1.10 nicm 20: int screen_trashed;
21: int squished;
22: int no_back_scroll = 0;
23: int forw_prompt;
1.1 etheisen 24:
1.8 millert 25: extern volatile sig_atomic_t sigs;
1.1 etheisen 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;
1.5 millert 33: extern int clear_bg;
34: extern int final_attr;
1.7 shadchin 35: extern int oldbot;
1.1 etheisen 36: extern char *tagoption;
37:
38: /*
39: * Sound the bell to indicate user is trying to move past end of file.
40: */
1.10 nicm 41: static void
42: eof_bell(void)
1.1 etheisen 43: {
44: if (quiet == NOT_QUIET)
1.10 nicm 45: ring_bell();
1.1 etheisen 46: else
47: vbell();
48: }
49:
50: /*
1.7 shadchin 51: * Check to see if the end of file is currently displayed.
1.1 etheisen 52: */
1.10 nicm 53: int
54: eof_displayed(void)
1.1 etheisen 55: {
1.10 nicm 56: off_t pos;
1.1 etheisen 57:
58: if (ignore_eoi)
1.7 shadchin 59: return (0);
60:
1.10 nicm 61: if (ch_length() == -1)
1.7 shadchin 62: /*
63: * If the file length is not known,
64: * we can't possibly be displaying EOF.
65: */
66: return (0);
67:
1.1 etheisen 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);
1.10 nicm 74: return (pos == -1 || pos == ch_length());
1.7 shadchin 75: }
76:
77: /*
78: * Check to see if the entire file is currently displayed.
79: */
1.10 nicm 80: int
81: entire_file_displayed(void)
1.7 shadchin 82: {
1.10 nicm 83: off_t pos;
1.7 shadchin 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);
1.10 nicm 91: return (pos == -1 || pos == 0);
1.1 etheisen 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: */
1.10 nicm 100: void
101: squish_check(void)
1.1 etheisen 102: {
103: if (!squished)
104: return;
105: squished = 0;
106: repaint();
107: }
108:
109: /*
1.10 nicm 110: * Display n lines, scrolling forward,
1.1 etheisen 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
1.10 nicm 115: * real line. If nblank > 0, the pos must be -1.
1.1 etheisen 116: * The first real line after the blanks will start at ch_zero().
117: */
1.10 nicm 118: void
119: forw(int n, off_t pos, int force, int only_last, int nblank)
1.1 etheisen 120: {
121: int nlines = 0;
122: int do_repaint;
123: static int first_time = 1;
124:
125: squish_check();
126:
127: /*
1.10 nicm 128: * do_repaint tells us not to display anything till the end,
1.1 etheisen 129: * then just repaint the entire screen.
1.10 nicm 130: * We repaint if we are supposed to display only the last
1.1 etheisen 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: */
1.10 nicm 136: do_repaint = (only_last && n > sc_height-1) ||
137: (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
1.1 etheisen 138:
1.10 nicm 139: if (!do_repaint) {
140: if (top_scroll && n >= sc_height - 1 && pos != ch_length()) {
1.1 etheisen 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: */
1.5 millert 147: pos_clear();
148: add_forw_pos(pos);
149: force = 1;
1.10 nicm 150: do_clear();
1.1 etheisen 151: home();
152: }
153:
1.10 nicm 154: if (pos != position(BOTTOM_PLUS_ONE) || empty_screen()) {
1.1 etheisen 155: /*
156: * This is not contiguous with what is
1.10 nicm 157: * currently displayed. Clear the screen image
1.1 etheisen 158: * (position table) and start a new screen.
159: */
160: pos_clear();
161: add_forw_pos(pos);
162: force = 1;
1.10 nicm 163: if (top_scroll) {
164: do_clear();
1.1 etheisen 165: home();
1.10 nicm 166: } else if (!first_time) {
1.1 etheisen 167: putstr("...skipping...\n");
168: }
169: }
170: }
171:
1.10 nicm 172: while (--n >= 0) {
1.1 etheisen 173: /*
174: * Read the next line of input.
175: */
1.10 nicm 176: if (nblank > 0) {
1.1 etheisen 177: /*
1.10 nicm 178: * Still drawing blanks; don't get a line
1.1 etheisen 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();
1.10 nicm 185: } else {
186: /*
1.1 etheisen 187: * Get the next line from the file.
188: */
189: pos = forw_line(pos);
1.10 nicm 190: if (pos == -1) {
1.1 etheisen 191: /*
1.10 nicm 192: * End of file: stop here unless the top line
1.1 etheisen 193: * is still empty, or "force" is true.
1.5 millert 194: * Even if force is true, stop when the last
195: * line in the file reaches the top of screen.
1.1 etheisen 196: */
1.10 nicm 197: if (!force && position(TOP) != -1)
1.1 etheisen 198: break;
1.10 nicm 199: if (!empty_lines(0, 0) &&
1.5 millert 200: !empty_lines(1, 1) &&
1.10 nicm 201: empty_lines(2, sc_height-1))
1.5 millert 202: break;
1.1 etheisen 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: */
1.10 nicm 223: if (first_time && pos == -1 && !top_scroll &&
224: tagoption == NULL && !plusoption) {
1.1 etheisen 225: squished = 1;
226: continue;
227: }
228: put_line();
1.7 shadchin 229: forw_prompt = 1;
1.1 etheisen 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: */
1.10 nicm 243: void
244: back(int n, off_t pos, int force, int only_last)
1.1 etheisen 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));
1.10 nicm 251: while (--n >= 0) {
1.1 etheisen 252: /*
253: * Get the previous line of input.
254: */
255: pos = back_line(pos);
1.10 nicm 256: if (pos == -1) {
1.1 etheisen 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++;
1.10 nicm 269: if (!do_repaint) {
1.1 etheisen 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();
1.7 shadchin 280: else if (!oldbot)
281: lower_left();
1.1 etheisen 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: */
1.10 nicm 289: void
290: forward(int n, int force, int only_last)
1.1 etheisen 291: {
1.10 nicm 292: off_t pos;
1.1 etheisen 293:
1.10 nicm 294: if (get_quit_at_eof() && eof_displayed() &&
295: !(ch_getflags() & CH_HELPFILE)) {
1.1 etheisen 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);
1.10 nicm 306: if (pos == -1 && (!force || empty_lines(2, sc_height-1))) {
307: if (ignore_eoi) {
1.1 etheisen 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: */
1.10 nicm 313: if (empty_screen()) {
1.1 etheisen 314: pos = ch_zero();
1.10 nicm 315: } else {
316: do {
1.1 etheisen 317: back(1, position(TOP), 1, 0);
318: pos = position(BOTTOM_PLUS_ONE);
1.10 nicm 319: } while (pos == -1);
1.1 etheisen 320: }
1.10 nicm 321: } else {
1.1 etheisen 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: */
1.10 nicm 333: void
334: backward(int n, int force, int only_last)
1.1 etheisen 335: {
1.10 nicm 336: off_t pos;
1.1 etheisen 337:
338: pos = position(TOP);
1.10 nicm 339: if (pos == -1 && (!force || position(BOTTOM) == 0)) {
1.1 etheisen 340: eof_bell();
1.10 nicm 341: return;
1.1 etheisen 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: */
1.10 nicm 352: int
353: get_back_scroll(void)
1.1 etheisen 354: {
1.5 millert 355: if (no_back_scroll)
356: return (0);
1.1 etheisen 357: if (back_scroll >= 0)
358: return (back_scroll);
359: if (top_scroll)
360: return (sc_height - 2);
361: return (10000); /* infinity */
362: }
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