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1.1 etheisen 1: /*
1.5 millert 2: * Copyright (C) 1984-2002 Mark Nudelman
1.1 etheisen 3: *
1.5 millert 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.
1.1 etheisen 6: *
1.5 millert 7: * For more information about less, or for information on how to
8: * contact the author, see the README file.
1.1 etheisen 9: */
10:
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:
20: public int hit_eof; /* Keeps track of how many times we hit end of file */
21: public int screen_trashed;
22: public int squished;
1.5 millert 23: public int no_back_scroll = 0;
1.1 etheisen 24:
25: extern int sigs;
26: extern int top_scroll;
27: extern int quiet;
28: extern int sc_width, sc_height;
29: extern int quit_at_eof;
30: extern int plusoption;
31: extern int forw_scroll;
32: extern int back_scroll;
33: extern int ignore_eoi;
1.5 millert 34: extern int clear_bg;
35: extern int final_attr;
1.1 etheisen 36: #if TAGS
37: extern char *tagoption;
38: #endif
39:
40: /*
41: * Sound the bell to indicate user is trying to move past end of file.
42: */
43: static void
44: eof_bell()
45: {
46: if (quiet == NOT_QUIET)
47: bell();
48: else
49: vbell();
50: }
51:
52: /*
53: * Check to see if the end of file is currently "displayed".
54: */
55: static void
56: eof_check()
57: {
58: POSITION pos;
59:
60: if (ignore_eoi)
61: return;
62: if (ABORT_SIGS())
63: return;
64: /*
65: * If the bottom line is empty, we are at EOF.
66: * If the bottom line ends at the file length,
67: * we must be just at EOF.
68: */
69: pos = position(BOTTOM_PLUS_ONE);
70: if (pos == NULL_POSITION || pos == ch_length())
71: hit_eof++;
72: }
73:
74: /*
75: * If the screen is "squished", repaint it.
76: * "Squished" means the first displayed line is not at the top
77: * of the screen; this can happen when we display a short file
78: * for the first time.
79: */
80: static void
81: squish_check()
82: {
83: if (!squished)
84: return;
85: squished = 0;
86: repaint();
87: }
88:
89: /*
90: * Display n lines, scrolling forward,
91: * starting at position pos in the input file.
92: * "force" means display the n lines even if we hit end of file.
93: * "only_last" means display only the last screenful if n > screen size.
94: * "nblank" is the number of blank lines to draw before the first
95: * real line. If nblank > 0, the pos must be NULL_POSITION.
96: * The first real line after the blanks will start at ch_zero().
97: */
98: public void
99: forw(n, pos, force, only_last, nblank)
1.5 millert 100: register int n;
1.1 etheisen 101: POSITION pos;
102: int force;
103: int only_last;
104: int nblank;
105: {
106: int eof = 0;
107: int nlines = 0;
108: int do_repaint;
109: static int first_time = 1;
110:
111: squish_check();
112:
113: /*
114: * do_repaint tells us not to display anything till the end,
115: * then just repaint the entire screen.
116: * We repaint if we are supposed to display only the last
117: * screenful and the request is for more than a screenful.
118: * Also if the request exceeds the forward scroll limit
119: * (but not if the request is for exactly a screenful, since
120: * repainting itself involves scrolling forward a screenful).
121: */
122: do_repaint = (only_last && n > sc_height-1) ||
123: (forw_scroll >= 0 && n > forw_scroll && n != sc_height-1);
124:
125: if (!do_repaint)
126: {
1.5 millert 127: /*
128: * Forget any current line shift we might have
129: * (from the last line of the previous screenful).
130: */
131: extern int cshift;
132: cshift = 0;
133:
1.1 etheisen 134: if (top_scroll && n >= sc_height - 1 && pos != ch_length())
135: {
136: /*
137: * Start a new screen.
138: * {{ This is not really desirable if we happen
139: * to hit eof in the middle of this screen,
140: * but we don't yet know if that will happen. }}
141: */
1.5 millert 142: pos_clear();
143: add_forw_pos(pos);
144: force = 1;
1.1 etheisen 145: if (top_scroll == OPT_ONPLUS || first_time)
146: clear();
147: home();
148: } else
149: {
150: clear_bot();
151: }
152:
153: if (pos != position(BOTTOM_PLUS_ONE) || empty_screen())
154: {
155: /*
156: * This is not contiguous with what is
157: * currently displayed. Clear the screen image
158: * (position table) and start a new screen.
159: */
160: pos_clear();
161: add_forw_pos(pos);
162: force = 1;
163: if (top_scroll)
164: {
165: if (top_scroll == OPT_ONPLUS)
166: clear();
167: home();
168: } else if (!first_time)
169: {
170: putstr("...skipping...\n");
171: }
172: }
173: }
174:
175: while (--n >= 0)
176: {
177: /*
178: * Read the next line of input.
179: */
180: if (nblank > 0)
181: {
182: /*
183: * Still drawing blanks; don't get a line
184: * from the file yet.
185: * If this is the last blank line, get ready to
186: * read a line starting at ch_zero() next time.
187: */
188: if (--nblank == 0)
189: pos = ch_zero();
190: } else
191: {
192: /*
193: * Get the next line from the file.
194: */
195: pos = forw_line(pos);
196: if (pos == NULL_POSITION)
197: {
198: /*
199: * End of file: stop here unless the top line
200: * is still empty, or "force" is true.
1.5 millert 201: * Even if force is true, stop when the last
202: * line in the file reaches the top of screen.
1.1 etheisen 203: */
204: eof = 1;
205: if (!force && position(TOP) != NULL_POSITION)
206: break;
1.5 millert 207: if (!empty_lines(0, 0) &&
208: !empty_lines(1, 1) &&
209: empty_lines(2, sc_height-1))
210: break;
1.1 etheisen 211: }
212: }
213: /*
214: * Add the position of the next line to the position table.
215: * Display the current line on the screen.
216: */
217: add_forw_pos(pos);
218: nlines++;
219: if (do_repaint)
220: continue;
221: /*
222: * If this is the first screen displayed and
223: * we hit an early EOF (i.e. before the requested
224: * number of lines), we "squish" the display down
225: * at the bottom of the screen.
226: * But don't do this if a + option or a -t option
227: * was given. These options can cause us to
228: * start the display after the beginning of the file,
229: * and it is not appropriate to squish in that case.
230: */
231: if (first_time && pos == NULL_POSITION && !top_scroll &&
232: #if TAGS
233: tagoption == NULL &&
234: #endif
235: !plusoption)
236: {
237: squished = 1;
238: continue;
239: }
1.5 millert 240: if (top_scroll == OPT_ON)
1.1 etheisen 241: clear_eol();
242: put_line();
1.5 millert 243: if (clear_bg && final_attr != AT_NORMAL)
244: {
245: /*
246: * Writing the last character on the last line
247: * of the display may have scrolled the screen.
248: * If we were in standout mode, clear_bg terminals
249: * will fill the new line with the standout color.
250: * Now we're in normal mode again, so clear the line.
251: */
252: clear_eol();
253: }
1.1 etheisen 254: }
255:
256: if (ignore_eoi)
257: hit_eof = 0;
258: else if (eof && !ABORT_SIGS())
259: hit_eof++;
260: else
261: eof_check();
262: if (nlines == 0)
263: eof_bell();
264: else if (do_repaint)
265: repaint();
266: first_time = 0;
267: (void) currline(BOTTOM);
268: }
269:
270: /*
271: * Display n lines, scrolling backward.
272: */
273: public void
274: back(n, pos, force, only_last)
1.5 millert 275: register int n;
1.1 etheisen 276: POSITION pos;
277: int force;
278: int only_last;
279: {
280: int nlines = 0;
281: int do_repaint;
282:
283: squish_check();
284: do_repaint = (n > get_back_scroll() || (only_last && n > sc_height-1));
285: hit_eof = 0;
286: while (--n >= 0)
287: {
288: /*
289: * Get the previous line of input.
290: */
291: pos = back_line(pos);
292: if (pos == NULL_POSITION)
293: {
294: /*
295: * Beginning of file: stop here unless "force" is true.
296: */
297: if (!force)
298: break;
299: }
300: /*
301: * Add the position of the previous line to the position table.
302: * Display the line on the screen.
303: */
304: add_back_pos(pos);
305: nlines++;
306: if (!do_repaint)
307: {
308: home();
309: add_line();
310: put_line();
311: }
312: }
313:
314: eof_check();
315: if (nlines == 0)
316: eof_bell();
317: else if (do_repaint)
318: repaint();
319: (void) currline(BOTTOM);
320: }
321:
322: /*
323: * Display n more lines, forward.
324: * Start just after the line currently displayed at the bottom of the screen.
325: */
326: public void
327: forward(n, force, only_last)
328: int n;
329: int force;
330: int only_last;
331: {
332: POSITION pos;
333:
1.6 ! millert 334: if (quit_at_eof && hit_eof)
1.1 etheisen 335: {
336: /*
337: * If the -e flag is set and we're trying to go
338: * forward from end-of-file, go on to the next file.
339: */
340: if (edit_next(1))
341: quit(QUIT_OK);
342: return;
343: }
344:
345: pos = position(BOTTOM_PLUS_ONE);
346: if (pos == NULL_POSITION && (!force || empty_lines(2, sc_height-1)))
347: {
348: if (ignore_eoi)
349: {
350: /*
351: * ignore_eoi is to support A_F_FOREVER.
352: * Back up until there is a line at the bottom
353: * of the screen.
354: */
355: if (empty_screen())
356: pos = ch_zero();
357: else
358: {
359: do
360: {
361: back(1, position(TOP), 1, 0);
362: pos = position(BOTTOM_PLUS_ONE);
363: } while (pos == NULL_POSITION);
364: }
1.5 millert 365: } else
366: {
1.1 etheisen 367: eof_bell();
368: hit_eof++;
369: return;
370: }
371: }
372: forw(n, pos, force, only_last, 0);
373: }
374:
375: /*
376: * Display n more lines, backward.
377: * Start just before the line currently displayed at the top of the screen.
378: */
379: public void
380: backward(n, force, only_last)
381: int n;
382: int force;
383: int only_last;
384: {
385: POSITION pos;
386:
387: pos = position(TOP);
388: if (pos == NULL_POSITION && (!force || position(BOTTOM) == 0))
389: {
390: eof_bell();
391: return;
392: }
393: back(n, pos, force, only_last);
394: }
395:
396: /*
397: * Get the backwards scroll limit.
398: * Must call this function instead of just using the value of
399: * back_scroll, because the default case depends on sc_height and
400: * top_scroll, as well as back_scroll.
401: */
402: public int
403: get_back_scroll()
404: {
1.5 millert 405: if (no_back_scroll)
406: return (0);
1.1 etheisen 407: if (back_scroll >= 0)
408: return (back_scroll);
409: if (top_scroll)
410: return (sc_height - 2);
411: return (10000); /* infinity */
412: }