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27 ****************************************************************************/
28
29 /****************************************************************************
30 * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
31 * and: Eric S. Raymond <esr@snark.thyrsus.com> *
32 * and: Thomas E. Dickey 1996-on *
33 * and: Alexander V Lukyanov 1997-1998 *
34 ****************************************************************************/
35
36 /******************************************************************************
37
38 NAME
39 hardscroll.c -- hardware-scrolling optimization for ncurses
40
41 SYNOPSIS
42 void _nc_scroll_optimize(void)
43
44 DESCRIPTION
45 OVERVIEW
46
47 This algorithm for computes optimum hardware scrolling to transform an
48 old screen (curscr) into a new screen (newscr) via vertical line moves.
49
50 Because the screen has a `grain' (there are insert/delete/scroll line
51 operations but no insert/delete/scroll column operations), it is efficient
52 break the update algorithm into two pieces: a first stage that does only line
53 moves, optimizing the end product of user-invoked insertions, deletions, and
54 scrolls; and a second phase (corresponding to the present doupdate code in
55 ncurses) that does only line transformations.
56
57 The common case we want hardware scrolling for is to handle line insertions
58 and deletions in screen-oriented text-editors. This two-stage approach will
59 accomplish that at a low computation and code-size cost.
60
61 LINE-MOVE COMPUTATION
62
63 Now, to a discussion of the line-move computation.
64
65 For expository purposes, consider the screen lines to be represented by
66 integers 0..23 (with the understanding that the value of 23 may vary).
67 Let a new line introduced by insertion, scrolling, or at the bottom of
68 the screen following a line delete be given the index -1.
69
70 Assume that the real screen starts with lines 0..23. Now, we have
71 the following possible line-oriented operations on the screen:
72
73 Insertion: inserts a line at a given screen row, forcing all lines below
74 to scroll forward. The last screen line is lost. For example, an insertion
75 at line 5 would produce: 0..4 -1 5..23.
76
77 Deletion: deletes a line at a given screen row, forcing all lines below
78 to scroll forward. The last screen line is made new. For example, a deletion
79 at line 7 would produce: 0..6 8..23 -1.
80
81 Scroll up: move a range of lines up 1. The bottom line of the range
82 becomes new. For example, scrolling up the region from 9 to 14 will
83 produce 0..8 10..14 -1 15..23.
84
85 Scroll down: move a range of lines down 1. The top line of the range
86 becomes new. For example, scrolling down the region from 12 to 16 will produce
87 0..11 -1 12..15 17..23.
88
89 Now, an obvious property of all these operations is that they preserve the
90 order of old lines, though not their position in the sequence.
91
92 The key trick of this algorithm is that the original line indices described
93 above are actually maintained as _line[].oldindex fields in the window
94 structure, and stick to each line through scroll and insert/delete operations.
95
96 Thus, it is possible at update time to look at the oldnum fields and compute
97 an optimal set of il/dl/scroll operations that will take the real screen
98 lines to the virtual screen lines. Once these vertical moves have been done,
99 we can hand off to the second stage of the update algorithm, which does line
100 transformations.
101
102 Note that the move computation does not need to have the full generality
103 of a diff algorithm (which it superficially resembles) because lines cannot
104 be moved out of order.
105
106 THE ALGORITHM
107
108 The scrolling is done in two passes. The first pass is from top to bottom
109 scroling hunks UP. The second one is from bottom to top scrolling hunks DOWN.
110 Obviously enough, no lines to be scrolled will be destroyed. (lav)
111
112 HOW TO TEST THIS:
113
114 Use the following production:
115
116 hardscroll: hardscroll.c
117 $(CC) -g -DSCROLLDEBUG hardscroll.c -o hardscroll
118
119 Then just type scramble vectors and watch. The following test loads are
120 a representative sample of cases:
121
122 ----------------------------- CUT HERE ------------------------------------
123 # No lines moved
124 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
125 #
126 # A scroll up
127 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
128 #
129 # A scroll down
130 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
131 #
132 # An insertion (after line 12)
133 0 1 2 3 4 5 6 7 8 9 10 11 12 -1 13 14 15 16 17 18 19 20 21 22
134 #
135 # A simple deletion (line 10)
136 0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
137 #
138 # A more complex case
139 -1 -1 -1 -1 -1 3 4 5 6 7 -1 -1 8 9 10 11 12 13 14 15 16 17 -1 -1
140 ----------------------------- CUT HERE ------------------------------------
141
142 AUTHOR
143 Eric S. Raymond <esr@snark.thyrsus.com>, November 1994
144 New algorithm by Alexander V. Lukyanov <lav@yars.free.net>, Aug 1997
145
146 *****************************************************************************/
147
148 #include <curses.priv.h>
149
150 MODULE_ID("$Id: hardscroll.c,v 1.42 2008/08/03 23:49:30 tom Exp $")
151
152 #if defined(SCROLLDEBUG) || defined(HASHDEBUG)
153
154 # undef screen_lines
155 # define screen_lines MAXLINES
156 NCURSES_EXPORT_VAR(int)
157 oldnums[MAXLINES];
158 # define OLDNUM(n) oldnums[n]
159 # define _tracef printf
160 # undef TR
161 # define TR(n, a) if (_nc_tracing & (n)) { _tracef a ; putchar('\n'); }
162
163 extern NCURSES_EXPORT_VAR(unsigned) _nc_tracing;
164
165 #else /* no debug */
166
167 /* OLDNUM(n) indicates which line will be shifted to the position n.
168 if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from
169 somewhere. */
170 NCURSES_EXPORT_VAR(int *)
171 _nc_oldnums = 0; /* obsolete: keep for ABI compat */
172
173 # if USE_HASHMAP
174 # define oldnums SP->_oldnum_list
175 # define OLDNUM(n) oldnums[n]
176 # else /* !USE_HASHMAP */
177 # define OLDNUM(n) newscr->_line[n].oldindex
178 # endif /* !USE_HASHMAP */
179
180 #define OLDNUM_SIZE SP->_oldnum_size
181
182 #endif /* defined(SCROLLDEBUG) || defined(HASHDEBUG) */
183
184 NCURSES_EXPORT(void)
_nc_scroll_optimize(void)185 _nc_scroll_optimize(void)
186 /* scroll optimization to transform curscr to newscr */
187 {
188 int i;
189 int start, end, shift;
190
191 TR(TRACE_ICALLS, (T_CALLED("_nc_scroll_optimize")));
192
193 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
194 #if USE_HASHMAP
195 /* get enough storage */
196 if (OLDNUM_SIZE < screen_lines) {
197 int *new_oldnums = typeRealloc(int, screen_lines, oldnums);
198 if (!new_oldnums)
199 return;
200 oldnums = new_oldnums;
201 OLDNUM_SIZE = screen_lines;
202 }
203 /* calculate the indices */
204 _nc_hash_map();
205 #endif
206 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
207
208 #ifdef TRACE
209 if (USE_TRACEF(TRACE_UPDATE | TRACE_MOVE)) {
210 _nc_linedump();
211 _nc_unlock_global(tracef);
212 }
213 #endif /* TRACE */
214
215 /* pass 1 - from top to bottom scrolling up */
216 for (i = 0; i < screen_lines;) {
217 while (i < screen_lines && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) <= i))
218 i++;
219 if (i >= screen_lines)
220 break;
221
222 shift = OLDNUM(i) - i; /* shift > 0 */
223 start = i;
224
225 i++;
226 while (i < screen_lines && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i
227 == shift)
228 i++;
229 end = i - 1 + shift;
230
231 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
232 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
233 if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR) {
234 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
235 continue;
236 }
237 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
238 }
239
240 /* pass 2 - from bottom to top scrolling down */
241 for (i = screen_lines - 1; i >= 0;) {
242 while (i >= 0 && (OLDNUM(i) == _NEWINDEX || OLDNUM(i) >= i))
243 i--;
244 if (i < 0)
245 break;
246
247 shift = OLDNUM(i) - i; /* shift < 0 */
248 end = i;
249
250 i--;
251 while (i >= 0 && OLDNUM(i) != _NEWINDEX && OLDNUM(i) - i == shift)
252 i--;
253 start = i + 1 - (-shift);
254
255 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
256 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
257 if (_nc_scrolln(shift, start, end, screen_lines - 1) == ERR) {
258 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
259 continue;
260 }
261 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
262 }
263 TR(TRACE_ICALLS, (T_RETURN("")));
264 }
265
266 #if defined(TRACE) || defined(SCROLLDEBUG) || defined(HASHDEBUG)
267 NCURSES_EXPORT(void)
_nc_linedump(void)268 _nc_linedump(void)
269 /* dump the state of the real and virtual oldnum fields */
270 {
271 int n;
272 char *buf = 0;
273 size_t want = (screen_lines + 1) * 4;
274
275 if ((buf = typeMalloc(char, want)) != 0) {
276
277 (void) strcpy(buf, "virt");
278 for (n = 0; n < screen_lines; n++)
279 (void) sprintf(buf + strlen(buf), " %02d", OLDNUM(n));
280 TR(TRACE_UPDATE | TRACE_MOVE, (buf));
281 free(buf);
282 }
283 }
284 #endif /* defined(TRACE) || defined(SCROLLDEBUG) */
285
286 #ifdef SCROLLDEBUG
287
288 int
main(int argc GCC_UNUSED,char * argv[]GCC_UNUSED)289 main(int argc GCC_UNUSED, char *argv[]GCC_UNUSED)
290 {
291 char line[BUFSIZ], *st;
292
293 #ifdef TRACE
294 _nc_tracing = TRACE_MOVE;
295 #endif
296 for (;;) {
297 int n;
298
299 for (n = 0; n < screen_lines; n++)
300 oldnums[n] = _NEWINDEX;
301
302 /* grab the test vector */
303 if (fgets(line, sizeof(line), stdin) == (char *) NULL)
304 exit(EXIT_SUCCESS);
305
306 /* parse it */
307 n = 0;
308 if (line[0] == '#') {
309 (void) fputs(line, stderr);
310 continue;
311 }
312 st = strtok(line, " ");
313 do {
314 oldnums[n++] = atoi(st);
315 } while
316 ((st = strtok((char *) NULL, " ")) != 0);
317
318 /* display it */
319 (void) fputs("Initial input:\n", stderr);
320 _nc_linedump();
321
322 _nc_scroll_optimize();
323 }
324 }
325
326 #endif /* SCROLLDEBUG */
327
328 /* hardscroll.c ends here */
329