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comparison src/xgccache.c @ 428:3ecd8885ac67 r21-2-22

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Import from CVS: tag r21-2-22
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date Mon, 13 Aug 2007 11:28:15 +0200
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427:0a0253eac470 428:3ecd8885ac67
1 /* Efficient caching of X GCs (graphics contexts).
2 Copyright (C) 1993 Free Software Foundation, Inc.
3 Copyright (C) 1994, 1995 Board of Trustees, University of Illinois.
4
5 This file is part of XEmacs.
6
7 XEmacs is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 2, or (at your option) any
10 later version.
11
12 XEmacs is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with XEmacs; see the file COPYING. If not, write to
19 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
21
22 /* Synched up with: Not in FSF. */
23
24 /* Emacs uses a lot of different display attributes; for example, assume
25 that only four fonts are in use (normal, bold, italic, and bold-italic).
26 Then assume that one stipple or background is used for text selections,
27 and another is used for highlighting mousable regions. That makes 16
28 GCs already. Add in the fact that another GC may be needed to display
29 the text cursor in any of those regions, and you've got 32. Add in
30 more fonts, and it keeps increasing exponentially.
31
32 We used to keep these GCs in a cache of merged (fully qualified) faces.
33 However, a lot of other code in xterm.c used XChangeGC of existing GCs,
34 which is kind of slow and kind of random. Also, managing the face cache
35 was tricky because it was hard to know when a face was no longer visible
36 on the frame -- we had to mark all frames as garbaged whenever a face
37 was changed, which caused an unpleasant amount of flicker (since faces are
38 created/destroyed (= changed) whenever a frame is created/destroyed.
39
40 So this code maintains a cache at the GC level instead of at the face
41 level. There is an upper limit on the size of the cache, after which we
42 will stop creating GCs and start reusing them (reusing the least-recently-
43 used ones first). So if faces get changed, their GCs will eventually be
44 recycled. Also more sharing of GCs is possible.
45
46 This code uses hash tables. It could be that, if the cache size is small
47 enough, a linear search might be faster; but I doubt it, since we need
48 `equal' comparisons, not `eq', and I expect that the optimal cache size
49 will be ~100.
50
51 Written by jwz, 14 jun 93
52 */
53
54 #include <config.h>
55 #include <X11/Xlib.h>
56 #include "xgccache.h"
57
58
59 #define GC_CACHE_SIZE 100
60
61 #define GCCACHE_HASH
62
63
64 #ifdef GCCACHE_HASH
65 #include "lisp.h"
66 #include "hash.h"
67 #endif
68
69 struct gcv_and_mask {
70 XGCValues gcv;
71 unsigned long mask;
72 };
73
74 struct gc_cache_cell {
75 GC gc;
76 struct gcv_and_mask gcvm;
77 struct gc_cache_cell *prev, *next;
78 };
79
80 struct gc_cache {
81 Display *dpy; /* used only as arg to XCreateGC/XFreeGC */
82 Window window; /* used only as arg to XCreateGC */
83 int size;
84 struct gc_cache_cell *head;
85 struct gc_cache_cell *tail;
86 #ifdef GCCACHE_HASH
87 struct hash_table *table;
88 #endif
89
90 int create_count;
91 int delete_count;
92 };
93
94 #ifdef GCCACHE_HASH
95 static unsigned long
96 gc_cache_hash (CONST void *arg)
97 {
98 CONST struct gcv_and_mask *gcvm = (CONST struct gcv_and_mask *) arg;
99 unsigned long *longs = (unsigned long *) &gcvm->gcv;
100 unsigned long hash = gcvm->mask;
101 int i;
102 /* This could look at the mask and only use the used slots in the
103 hash code. That would win in that we wouldn't have to initialize
104 every slot of the gcv when calling gc_cache_lookup. But we need
105 the hash function to be as fast as possible; some timings should
106 be done. */
107 for (i = 0; i < (sizeof (XGCValues) / sizeof (unsigned long)); i++)
108 hash = (hash<<1) ^ *longs++;
109 return hash;
110 }
111
112 #endif /* GCCACHE_HASH */
113
114 static int
115 gc_cache_eql (CONST void *arg1, CONST void *arg2)
116 {
117 /* See comment in gc_cache_hash */
118 return !memcmp (arg1, arg2, sizeof (struct gcv_and_mask));
119 }
120
121 struct gc_cache *
122 make_gc_cache (Display *dpy, Window window)
123 {
124 struct gc_cache *cache = xnew (struct gc_cache);
125 cache->dpy = dpy;
126 cache->window = window;
127 cache->size = 0;
128 cache->head = cache->tail = 0;
129 cache->create_count = cache->delete_count = 0;
130 #ifdef GCCACHE_HASH
131 cache->table =
132 make_general_hash_table (GC_CACHE_SIZE, gc_cache_hash, gc_cache_eql);
133 #endif
134 return cache;
135 }
136
137 void
138 free_gc_cache (struct gc_cache *cache)
139 {
140 struct gc_cache_cell *rest, *next;
141 rest = cache->head;
142 while (rest)
143 {
144 XFreeGC (cache->dpy, rest->gc);
145 next = rest->next;
146 xfree (rest);
147 rest = next;
148 }
149 #ifdef GCCACHE_HASH
150 free_hash_table (cache->table);
151 #endif
152 xfree (cache);
153 }
154
155 GC
156 gc_cache_lookup (struct gc_cache *cache, XGCValues *gcv, unsigned long mask)
157 {
158 struct gc_cache_cell *cell, *next, *prev;
159 struct gcv_and_mask gcvm;
160
161 if ((!!cache->head) != (!!cache->tail)) abort ();
162 if (cache->head && (cache->head->prev || cache->tail->next)) abort ();
163
164 gcvm.mask = mask;
165 gcvm.gcv = *gcv; /* this copies... */
166
167 #ifdef GCCACHE_HASH
168
169 if (gethash (&gcvm, cache->table, (CONST void **) &cell))
170
171 #else /* !GCCACHE_HASH */
172
173 cell = cache->tail; /* start at the end (most recently used) */
174 while (cell)
175 {
176 if (gc_cache_eql (&gcvm, &cell->gcvm))
177 break;
178 else
179 cell = cell->prev;
180 }
181
182 /* #### This whole file needs some serious overhauling. */
183 if (!(mask | GCTile) && cell->gc->values.tile)
184 cell = 0;
185 else if (!(mask | GCStipple) && cell->gc->values.stipple)
186 cell = 0;
187
188 if (cell)
189
190 #endif /* !GCCACHE_HASH */
191
192 {
193 /* Found a cell. Move this cell to the end of the list, so that it
194 will be less likely to be collected than a cell that was accessed
195 less recently.
196 */
197 if (cell == cache->tail)
198 return cell->gc;
199
200 next = cell->next;
201 prev = cell->prev;
202 if (prev) prev->next = next;
203 if (next) next->prev = prev;
204 if (cache->head == cell) cache->head = next;
205 cell->next = 0;
206 cell->prev = cache->tail;
207 cache->tail->next = cell;
208 cache->tail = cell;
209 if (cache->head == cell) abort ();
210 if (cell->next) abort ();
211 if (cache->head->prev) abort ();
212 if (cache->tail->next) abort ();
213 return cell->gc;
214 }
215
216 /* else, cache miss. */
217
218 if (cache->size == GC_CACHE_SIZE)
219 /* Reuse the first cell on the list (least-recently-used).
220 Remove it from the list, and unhash it from the table.
221 */
222 {
223 cell = cache->head;
224 cache->head = cell->next;
225 cache->head->prev = 0;
226 if (cache->tail == cell) cache->tail = 0; /* only one */
227 XFreeGC (cache->dpy, cell->gc);
228 cache->delete_count++;
229 #ifdef GCCACHE_HASH
230 remhash (&cell->gcvm, cache->table);
231 #endif
232 }
233 else if (cache->size > GC_CACHE_SIZE)
234 abort ();
235 else
236 {
237 /* Allocate a new cell (don't put it in the list or table yet). */
238 cell = xnew (struct gc_cache_cell);
239 cache->size++;
240 }
241
242 /* Now we've got a cell (new or reused). Fill it in. */
243 memcpy (&cell->gcvm.gcv, gcv, sizeof (XGCValues));
244 cell->gcvm.mask = mask;
245
246 /* Put the cell on the end of the list. */
247 cell->next = 0;
248 cell->prev = cache->tail;
249 if (cache->tail) cache->tail->next = cell;
250 cache->tail = cell;
251 if (! cache->head) cache->head = cell;
252
253 cache->create_count++;
254 #ifdef GCCACHE_HASH
255 /* Hash it in the table */
256 puthash (&cell->gcvm, cell, cache->table);
257 #endif
258
259 /* Now make and return the GC. */
260 cell->gc = XCreateGC (cache->dpy, cache->window, mask, gcv);
261
262 /* debug */
263 assert (cell->gc == gc_cache_lookup (cache, gcv, mask));
264
265 return cell->gc;
266 }
267
268
269 #ifdef DEBUG_XEMACS
270
271 void describe_gc_cache (struct gc_cache *cache);
272 void
273 describe_gc_cache (struct gc_cache *cache)
274 {
275 int count = 0;
276 struct gc_cache_cell *cell = cache->head;
277 stderr_out ("\nsize: %d", cache->size);
278 stderr_out ("\ncreated: %d", cache->create_count);
279 stderr_out ("\ndeleted: %d", cache->delete_count);
280 while (cell)
281 {
282 struct gc_cache_cell *cell2;
283 int i = 0;
284 stderr_out ("\n%d:\t0x%lx GC: 0x%08lx hash: 0x%08lx\n",
285 count, (long) cell, (long) cell->gc, gc_cache_hash (&cell->gcvm));
286 for (cell2 = cache->head; cell2; cell2 = cell2->next, i++)
287 if (count != i &&
288 gc_cache_hash (&cell->gcvm) == gc_cache_hash (&cell2->gcvm))
289 stderr_out ("\tHASH COLLISION with cell %d\n", i);
290 stderr_out ("\tmask: %8lx\n", cell->gcvm.mask);
291
292 #define FROB(field) do { \
293 if ((int)cell->gcvm.gcv.field != (~0)) \
294 stderr_out ("\t%-12s%8x\n", #field ":", (int)cell->gcvm.gcv.field); \
295 } while (0)
296 FROB (function);
297 FROB (plane_mask);
298 FROB (foreground);
299 FROB (background);
300 FROB (line_width);
301 FROB (line_style);
302 FROB (cap_style);
303 FROB (join_style);
304 FROB (fill_style);
305 FROB (fill_rule);
306 FROB (arc_mode);
307 FROB (tile);
308 FROB (stipple);
309 FROB (ts_x_origin);
310 FROB (ts_y_origin);
311 FROB (font);
312 FROB (subwindow_mode);
313 FROB (graphics_exposures);
314 FROB (clip_x_origin);
315 FROB (clip_y_origin);
316 FROB (clip_mask);
317 FROB (dash_offset);
318 #undef FROB
319
320 count++;
321 if (cell->next && cell == cache->tail)
322 stderr_out ("\nERROR! tail is here!\n\n");
323 else if (!cell->next && cell != cache->tail)
324 stderr_out ("\nERROR! tail is not at the end\n\n");
325 cell = cell->next;
326 }
327 if (count != cache->size)
328 stderr_out ("\nERROR! count should be %d\n\n", cache->size);
329 }
330
331 #endif /* DEBUG_XEMACS */