1 /****************************************************************************
2 * Copyright 2020 Thomas E. Dickey *
3 * Copyright 1998-2015,2016 Free Software Foundation, Inc. *
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28 ****************************************************************************/
29
30 /****************************************************************************
31 * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
32 * and: Eric S. Raymond <esr@snark.thyrsus.com> *
33 * and: Thomas E. Dickey 1996-on *
34 * and: Alexander V Lukyanov 1997-1998 *
35 ****************************************************************************/
36
37 /******************************************************************************
38
39 NAME
40 hardscroll.c -- hardware-scrolling optimization for ncurses
41
42 SYNOPSIS
43 void _nc_scroll_optimize(void)
44
45 DESCRIPTION
46 OVERVIEW
47
48 This algorithm for computes optimum hardware scrolling to transform an
49 old screen (curscr) into a new screen (newscr) via vertical line moves.
50
51 Because the screen has a `grain' (there are insert/delete/scroll line
52 operations but no insert/delete/scroll column operations), it is efficient
53 break the update algorithm into two pieces: a first stage that does only line
54 moves, optimizing the end product of user-invoked insertions, deletions, and
55 scrolls; and a second phase (corresponding to the present doupdate code in
56 ncurses) that does only line transformations.
57
58 The common case we want hardware scrolling for is to handle line insertions
59 and deletions in screen-oriented text-editors. This two-stage approach will
60 accomplish that at a low computation and code-size cost.
61
62 LINE-MOVE COMPUTATION
63
64 Now, to a discussion of the line-move computation.
65
66 For expository purposes, consider the screen lines to be represented by
67 integers 0..23 (with the understanding that the value of 23 may vary).
68 Let a new line introduced by insertion, scrolling, or at the bottom of
69 the screen following a line delete be given the index -1.
70
71 Assume that the real screen starts with lines 0..23. Now, we have
72 the following possible line-oriented operations on the screen:
73
74 Insertion: inserts a line at a given screen row, forcing all lines below
75 to scroll forward. The last screen line is lost. For example, an insertion
76 at line 5 would produce: 0..4 -1 5..23.
77
78 Deletion: deletes a line at a given screen row, forcing all lines below
79 to scroll forward. The last screen line is made new. For example, a deletion
80 at line 7 would produce: 0..6 8..23 -1.
81
82 Scroll up: move a range of lines up 1. The bottom line of the range
83 becomes new. For example, scrolling up the region from 9 to 14 will
84 produce 0..8 10..14 -1 15..23.
85
86 Scroll down: move a range of lines down 1. The top line of the range
87 becomes new. For example, scrolling down the region from 12 to 16 will produce
88 0..11 -1 12..15 17..23.
89
90 Now, an obvious property of all these operations is that they preserve the
91 order of old lines, though not their position in the sequence.
92
93 The key trick of this algorithm is that the original line indices described
94 above are actually maintained as _line[].oldindex fields in the window
95 structure, and stick to each line through scroll and insert/delete operations.
96
97 Thus, it is possible at update time to look at the oldnum fields and compute
98 an optimal set of il/dl/scroll operations that will take the real screen
99 lines to the virtual screen lines. Once these vertical moves have been done,
100 we can hand off to the second stage of the update algorithm, which does line
101 transformations.
102
103 Note that the move computation does not need to have the full generality
104 of a diff algorithm (which it superficially resembles) because lines cannot
105 be moved out of order.
106
107 THE ALGORITHM
108
109 The scrolling is done in two passes. The first pass is from top to bottom
110 scroling hunks UP. The second one is from bottom to top scrolling hunks DOWN.
111 Obviously enough, no lines to be scrolled will be destroyed. (lav)
112
113 HOW TO TEST THIS:
114
115 Use the following production:
116
117 hardscroll: hardscroll.c
118 $(CC) -g -DSCROLLDEBUG hardscroll.c -o hardscroll
119
120 Then just type scramble vectors and watch. The following test loads are
121 a representative sample of cases:
122
123 ----------------------------- CUT HERE ------------------------------------
124 # No lines moved
125 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
126 #
127 # A scroll up
128 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
129 #
130 # A scroll down
131 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
132 #
133 # An insertion (after line 12)
134 0 1 2 3 4 5 6 7 8 9 10 11 12 -1 13 14 15 16 17 18 19 20 21 22
135 #
136 # A simple deletion (line 10)
137 0 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 -1
138 #
139 # A more complex case
140 -1 -1 -1 -1 -1 3 4 5 6 7 -1 -1 8 9 10 11 12 13 14 15 16 17 -1 -1
141 ----------------------------- CUT HERE ------------------------------------
142
143 AUTHOR
144 Eric S. Raymond <esr@snark.thyrsus.com>, November 1994
145 New algorithm by Alexander V. Lukyanov <lav@yars.free.net>, Aug 1997
146
147 *****************************************************************************/
148
149 #include <curses.priv.h>
150
151 MODULE_ID("$Id: hardscroll.c,v 1.54 2020/02/02 23:34:34 tom Exp $")
152
153 #if defined(SCROLLDEBUG) || defined(HASHDEBUG)
154
155 # undef screen_lines
156 # define screen_lines(sp) MAXLINES
157 NCURSES_EXPORT_VAR (int)
158 oldnums[MAXLINES];
159 # define OLDNUM(sp,n) oldnums[n]
160 # define _tracef printf
161 # undef TR
162 # define TR(n, a) if (_nc_tracing & (n)) { _tracef a ; putchar('\n'); }
163
164 extern NCURSES_EXPORT_VAR(unsigned) _nc_tracing;
165
166 #else /* no debug */
167
168 /* OLDNUM(n) indicates which line will be shifted to the position n.
169 if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from
170 somewhere. */
171 NCURSES_EXPORT_VAR (int *)
172 _nc_oldnums = 0; /* obsolete: keep for ABI compat */
173
174 # if USE_HASHMAP
175 # define oldnums(sp) (sp)->_oldnum_list
176 # define OLDNUM(sp,n) oldnums(sp)[n]
177 # else /* !USE_HASHMAP */
178 # define OLDNUM(sp,n) NewScreen(sp)->_line[n].oldindex
179 # endif /* !USE_HASHMAP */
180
181 #define OLDNUM_SIZE(sp) (sp)->_oldnum_size
182
183 #endif /* defined(SCROLLDEBUG) || defined(HASHDEBUG) */
184
185 NCURSES_EXPORT(void)
NCURSES_SP_NAME(_nc_scroll_optimize)186 NCURSES_SP_NAME(_nc_scroll_optimize) (NCURSES_SP_DCL0)
187 /* scroll optimization to transform curscr to newscr */
188 {
189 int i;
190 int start, end, shift;
191
192 TR(TRACE_ICALLS, (T_CALLED("_nc_scroll_optimize(%p)"), (void *) SP_PARM));
193
194 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
195 #if USE_HASHMAP
196 /* get enough storage */
197 assert(OLDNUM_SIZE(SP_PARM) >= 0);
198 assert(screen_lines(SP_PARM) > 0);
199 if ((oldnums(SP_PARM) == 0)
200 || (OLDNUM_SIZE(SP_PARM) < screen_lines(SP_PARM))) {
201 int need_lines = ((OLDNUM_SIZE(SP_PARM) < screen_lines(SP_PARM))
202 ? screen_lines(SP_PARM)
203 : OLDNUM_SIZE(SP_PARM));
204 int *new_oldnums = typeRealloc(int,
205 (size_t) need_lines,
206 oldnums(SP_PARM));
207 if (!new_oldnums)
208 return;
209 oldnums(SP_PARM) = new_oldnums;
210 OLDNUM_SIZE(SP_PARM) = need_lines;
211 }
212 /* calculate the indices */
213 NCURSES_SP_NAME(_nc_hash_map) (NCURSES_SP_ARG);
214 #endif
215 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
216
217 #ifdef TRACE
218 if (USE_TRACEF(TRACE_UPDATE | TRACE_MOVE)) {
219 NCURSES_SP_NAME(_nc_linedump) (NCURSES_SP_ARG);
220 _nc_unlock_global(tracef);
221 }
222 #endif /* TRACE */
223
224 /* pass 1 - from top to bottom scrolling up */
225 for (i = 0; i < screen_lines(SP_PARM);) {
226 while (i < screen_lines(SP_PARM)
227 && (OLDNUM(SP_PARM, i) == _NEWINDEX || OLDNUM(SP_PARM, i) <= i))
228 i++;
229 if (i >= screen_lines(SP_PARM))
230 break;
231
232 shift = OLDNUM(SP_PARM, i) - i; /* shift > 0 */
233 start = i;
234
235 i++;
236 while (i < screen_lines(SP_PARM)
237 && OLDNUM(SP_PARM, i) != _NEWINDEX
238 && OLDNUM(SP_PARM, i) - i == shift)
239 i++;
240 end = i - 1 + shift;
241
242 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
243 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
244 if (NCURSES_SP_NAME(_nc_scrolln) (NCURSES_SP_ARGx
245 shift,
246 start,
247 end,
248 screen_lines(SP_PARM) - 1) == ERR) {
249 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
250 continue;
251 }
252 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
253 }
254
255 /* pass 2 - from bottom to top scrolling down */
256 for (i = screen_lines(SP_PARM) - 1; i >= 0;) {
257 while (i >= 0
258 && (OLDNUM(SP_PARM, i) == _NEWINDEX
259 || OLDNUM(SP_PARM, i) >= i)) {
260 i--;
261 }
262 if (i < 0)
263 break;
264
265 shift = OLDNUM(SP_PARM, i) - i; /* shift < 0 */
266 end = i;
267
268 i--;
269 while (i >= 0
270 && OLDNUM(SP_PARM, i) != _NEWINDEX
271 && OLDNUM(SP_PARM, i) - i == shift) {
272 i--;
273 }
274 start = i + 1 - (-shift);
275
276 TR(TRACE_UPDATE | TRACE_MOVE, ("scroll [%d, %d] by %d", start, end, shift));
277 #if !defined(SCROLLDEBUG) && !defined(HASHDEBUG)
278 if (NCURSES_SP_NAME(_nc_scrolln) (NCURSES_SP_ARGx
279 shift,
280 start,
281 end,
282 screen_lines(SP_PARM) - 1) == ERR) {
283 TR(TRACE_UPDATE | TRACE_MOVE, ("unable to scroll"));
284 continue;
285 }
286 #endif /* !defined(SCROLLDEBUG) && !defined(HASHDEBUG) */
287 }
288 TR(TRACE_ICALLS, (T_RETURN("")));
289 }
290
291 #if NCURSES_SP_FUNCS
292 NCURSES_EXPORT(void)
_nc_scroll_optimize(void)293 _nc_scroll_optimize(void)
294 {
295 NCURSES_SP_NAME(_nc_scroll_optimize) (CURRENT_SCREEN);
296 }
297 #endif
298
299 #if defined(TRACE) || defined(SCROLLDEBUG) || defined(HASHDEBUG)
300 NCURSES_EXPORT(void)
NCURSES_SP_NAME(_nc_linedump)301 NCURSES_SP_NAME(_nc_linedump) (NCURSES_SP_DCL0)
302 /* dump the state of the real and virtual oldnum fields */
303 {
304 char *buf = 0;
305 size_t want = ((size_t) screen_lines(SP_PARM) + 1) * 4;
306 (void) SP_PARM;
307
308 if ((buf = typeMalloc(char, want)) != 0) {
309 int n;
310
311 *buf = '\0';
312 for (n = 0; n < screen_lines(SP_PARM); n++)
313 _nc_SPRINTF(buf + strlen(buf),
314 _nc_SLIMIT(want - strlen(buf))
315 " %02d", OLDNUM(SP_PARM, n));
316 TR(TRACE_UPDATE | TRACE_MOVE, ("virt %s", buf));
317 free(buf);
318 }
319 }
320
321 #if NCURSES_SP_FUNCS
322 NCURSES_EXPORT(void)
_nc_linedump(void)323 _nc_linedump(void)
324 {
325 NCURSES_SP_NAME(_nc_linedump) (CURRENT_SCREEN);
326 }
327 #endif
328
329 #endif /* defined(TRACE) || defined(SCROLLDEBUG) */
330
331 #ifdef SCROLLDEBUG
332
333 int
main(int argc GCC_UNUSED,char * argv[]GCC_UNUSED)334 main(int argc GCC_UNUSED, char *argv[]GCC_UNUSED)
335 {
336 char line[BUFSIZ], *st;
337
338 #ifdef TRACE
339 _nc_tracing = TRACE_MOVE;
340 #endif
341 for (;;) {
342 int n;
343
344 for (n = 0; n < screen_lines(sp); n++)
345 oldnums[n] = _NEWINDEX;
346
347 /* grab the test vector */
348 if (fgets(line, sizeof(line), stdin) == (char *) NULL)
349 exit(EXIT_SUCCESS);
350
351 /* parse it */
352 n = 0;
353 if (line[0] == '#') {
354 (void) fputs(line, stderr);
355 continue;
356 }
357 st = strtok(line, " ");
358 do {
359 oldnums[n++] = atoi(st);
360 } while
361 ((st = strtok((char *) NULL, " ")) != 0);
362
363 /* display it */
364 (void) fputs("Initial input:\n", stderr);
365 _nc_linedump();
366
367 _nc_scroll_optimize();
368 }
369 }
370
371 #endif /* SCROLLDEBUG */
372
373 /* hardscroll.c ends here */
374