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2587
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1 /* Efficient caching of X GCs (graphics contexts).
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2 Copyright (C) 1993 Free Software Foundation, Inc.
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3 Copyright (C) 1994, 1995 Board of Trustees, University of Illinois.
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4
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5 This file is part of XEmacs.
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6
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7 XEmacs is free software; you can redistribute it and/or modify it
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8 under the terms of the GNU General Public License as published by the
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9 Free Software Foundation; either version 2, or (at your option) any
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10 later version.
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11
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12 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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15 for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with XEmacs; see the file COPYING. If not, write to
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19 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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20 Boston, MA 02111-1307, USA. */
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21
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22 /* Synched up with: Not in FSF. */
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23
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24 /* Emacs uses a lot of different display attributes; for example, assume
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25 that only four fonts are in use (normal, bold, italic, and bold-italic).
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26 Then assume that one stipple or background is used for text selections,
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27 and another is used for highlighting mousable regions. That makes 16
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28 GCs already. Add in the fact that another GC may be needed to display
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29 the text cursor in any of those regions, and you've got 32. Add in
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30 more fonts, and it keeps increasing exponentially.
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31
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32 We used to keep these GCs in a cache of merged (fully qualified) faces.
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33 However, a lot of other code in xterm.c used XChangeGC of existing GCs,
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34 which is kind of slow and kind of random. Also, managing the face cache
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35 was tricky because it was hard to know when a face was no longer visible
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36 on the frame -- we had to mark all frames as garbaged whenever a face
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37 was changed, which caused an unpleasant amount of flicker (since faces are
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38 created/destroyed (= changed) whenever a frame is created/destroyed.
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39
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40 So this code maintains a cache at the GC level instead of at the face
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41 level. There is an upper limit on the size of the cache, after which we
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42 will stop creating GCs and start reusing them (reusing the least-recently-
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43 used ones first). So if faces get changed, their GCs will eventually be
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44 recycled. Also more sharing of GCs is possible.
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45
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46 This code uses hash tables. It could be that, if the cache size is small
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47 enough, a linear search might be faster; but I doubt it, since we need
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48 `equal' comparisons, not `eq', and I expect that the optimal cache size
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49 will be ~100.
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50
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51 Written by jwz, 14 jun 93
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52 */
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53
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54 #include <config.h>
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55 #include <X11/Xlib.h>
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56 #include "xgccache.h"
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57
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58
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59 #define GC_CACHE_SIZE 100
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60
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61 #define GCCACHE_HASH
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62
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63
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64 #ifdef GCCACHE_HASH
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65 #include "lisp.h"
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66 #include "hash.h"
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67 #endif
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68
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69 struct gcv_and_mask {
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70 XGCValues gcv;
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71 unsigned long mask;
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72 };
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73
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74 struct gc_cache_cell {
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75 GC gc;
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76 struct gcv_and_mask gcvm;
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77 struct gc_cache_cell *prev, *next;
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78 };
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79
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80 struct gc_cache {
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81 Display *dpy; /* used only as arg to XCreateGC/XFreeGC */
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82 Window window; /* used only as arg to XCreateGC */
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83 int size;
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84 struct gc_cache_cell *head;
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85 struct gc_cache_cell *tail;
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86 #ifdef GCCACHE_HASH
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87 struct hash_table *table;
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88 #endif
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89
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90 int create_count;
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91 int delete_count;
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92 };
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93
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94 #ifdef GCCACHE_HASH
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95 static Hashcode
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96 gc_cache_hash (const void *arg)
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97 {
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98 const struct gcv_and_mask *gcvm = (const struct gcv_and_mask *) arg;
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99 unsigned long *longs = (unsigned long *) &gcvm->gcv;
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100 Hashcode hash = gcvm->mask;
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101 int i;
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102 /* This could look at the mask and only use the used slots in the
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103 hash code. That would win in that we wouldn't have to initialize
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104 every slot of the gcv when calling gc_cache_lookup. But we need
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105 the hash function to be as fast as possible; some timings should
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106 be done. */
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107 for (i = 0; i < (int) (sizeof (XGCValues) / sizeof (unsigned long)); i++)
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108 hash = (hash << 1) ^ *longs++;
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109 return hash;
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110 }
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111
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112 #endif /* GCCACHE_HASH */
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113
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114 static int
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115 gc_cache_eql (const void *arg1, const void *arg2)
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116 {
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117 /* See comment in gc_cache_hash */
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118 return !memcmp (arg1, arg2, sizeof (struct gcv_and_mask));
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119 }
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120
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121 struct gc_cache *
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122 make_gc_cache (Display *dpy, Window window)
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123 {
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124 struct gc_cache *cache = xnew (struct gc_cache);
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125 cache->dpy = dpy;
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126 cache->window = window;
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127 cache->size = 0;
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128 cache->head = cache->tail = 0;
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129 cache->create_count = cache->delete_count = 0;
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130 #ifdef GCCACHE_HASH
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131 cache->table =
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132 make_general_hash_table (GC_CACHE_SIZE, gc_cache_hash, gc_cache_eql);
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133 #endif
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134 return cache;
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135 }
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136
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137 void
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138 free_gc_cache (struct gc_cache *cache)
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139 {
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140 struct gc_cache_cell *rest, *next;
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141 rest = cache->head;
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142 while (rest)
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143 {
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144 XFreeGC (cache->dpy, rest->gc);
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145 next = rest->next;
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146 xfree (rest, struct gc_cache_cell *);
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147 rest = next;
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148 }
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149 #ifdef GCCACHE_HASH
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150 free_hash_table (cache->table);
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151 #endif
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152 xfree (cache, struct gc_cache *);
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153 }
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154
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155 GC
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156 gc_cache_lookup (struct gc_cache *cache, XGCValues *gcv, unsigned long mask)
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157 {
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158 struct gc_cache_cell *cell, *next, *prev;
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159 struct gcv_and_mask gcvm;
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160
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161 if ((!!cache->head) != (!!cache->tail)) ABORT ();
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162 if (cache->head && (cache->head->prev || cache->tail->next)) ABORT ();
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163
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164 gcvm.mask = mask;
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165 gcvm.gcv = *gcv; /* this copies... */
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166
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167 #ifdef GCCACHE_HASH
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168
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169 /* The intermediate cast fools gcc into not outputting strict-aliasing
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170 complaints */
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171 if (gethash (&gcvm, cache->table, (const void **) (void *) &cell))
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172
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173 #else /* !GCCACHE_HASH */
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174
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175 cell = cache->tail; /* start at the end (most recently used) */
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176 while (cell)
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177 {
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178 if (gc_cache_eql (&gcvm, &cell->gcvm))
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179 break;
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180 else
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181 cell = cell->prev;
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182 }
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183
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184 /* #### This whole file needs some serious overhauling. */
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185 if (!(mask | GCTile) && cell->gc->values.tile)
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186 cell = 0;
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187 else if (!(mask | GCStipple) && cell->gc->values.stipple)
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188 cell = 0;
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189
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190 if (cell)
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191
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192 #endif /* !GCCACHE_HASH */
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193
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194 {
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195 /* Found a cell. Move this cell to the end of the list, so that it
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196 will be less likely to be collected than a cell that was accessed
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197 less recently.
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198 */
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199 if (cell == cache->tail)
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200 return cell->gc;
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201
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202 next = cell->next;
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203 prev = cell->prev;
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204 if (prev) prev->next = next;
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205 if (next) next->prev = prev;
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206 if (cache->head == cell) cache->head = next;
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207 cell->next = 0;
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208 cell->prev = cache->tail;
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209 cache->tail->next = cell;
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210 cache->tail = cell;
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211 if (cache->head == cell) ABORT ();
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212 if (cell->next) ABORT ();
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213 if (cache->head->prev) ABORT ();
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214 if (cache->tail->next) ABORT ();
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215 return cell->gc;
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216 }
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217
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218 /* else, cache miss. */
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219
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220 if (cache->size == GC_CACHE_SIZE)
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221 /* Reuse the first cell on the list (least-recently-used).
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222 Remove it from the list, and unhash it from the table.
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223 */
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224 {
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225 cell = cache->head;
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226 cache->head = cell->next;
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227 cache->head->prev = 0;
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228 if (cache->tail == cell) cache->tail = 0; /* only one */
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229 XFreeGC (cache->dpy, cell->gc);
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230 cache->delete_count++;
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231 #ifdef GCCACHE_HASH
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232 remhash (&cell->gcvm, cache->table);
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233 #endif
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234 }
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235 else if (cache->size > GC_CACHE_SIZE)
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236 ABORT ();
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237 else
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238 {
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239 /* Allocate a new cell (don't put it in the list or table yet). */
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240 cell = xnew (struct gc_cache_cell);
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241 cache->size++;
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242 }
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243
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244 /* Now we've got a cell (new or reused). Fill it in. */
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245 memcpy (&cell->gcvm.gcv, gcv, sizeof (XGCValues));
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246 cell->gcvm.mask = mask;
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247
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248 /* Put the cell on the end of the list. */
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249 cell->next = 0;
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250 cell->prev = cache->tail;
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251 if (cache->tail) cache->tail->next = cell;
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252 cache->tail = cell;
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253 if (! cache->head) cache->head = cell;
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254
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255 cache->create_count++;
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256 #ifdef GCCACHE_HASH
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257 /* Hash it in the table */
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258 puthash (&cell->gcvm, cell, cache->table);
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259 #endif
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260
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261 /* Now make and return the GC. */
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262 cell->gc = XCreateGC (cache->dpy, cache->window, mask, gcv);
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263
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264 /* debug */
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265 assert (cell->gc == gc_cache_lookup (cache, gcv, mask));
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266
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267 return cell->gc;
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268 }
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269
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270
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271 #ifdef DEBUG_XEMACS
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272
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273 void describe_gc_cache (struct gc_cache *cache);
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274 void
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275 describe_gc_cache (struct gc_cache *cache)
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276 {
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277 int count = 0;
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278 struct gc_cache_cell *cell = cache->head;
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279 stderr_out ("\nsize: %d", cache->size);
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280 stderr_out ("\ncreated: %d", cache->create_count);
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281 stderr_out ("\ndeleted: %d", cache->delete_count);
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282 while (cell)
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283 {
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284 struct gc_cache_cell *cell2;
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285 int i = 0;
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286 stderr_out ("\n%d:\t0x%lx GC: 0x%08lx hash: 0x%08lx\n",
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287 count, (long) cell, (long) cell->gc, gc_cache_hash (&cell->gcvm));
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288 for (cell2 = cache->head; cell2; cell2 = cell2->next, i++)
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289 if (count != i &&
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290 gc_cache_hash (&cell->gcvm) == gc_cache_hash (&cell2->gcvm))
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291 stderr_out ("\tHASH COLLISION with cell %d\n", i);
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292 stderr_out ("\tmask: %8lx\n", cell->gcvm.mask);
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293
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294 #define FROB(field) do { \
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295 if ((int)cell->gcvm.gcv.field != (~0)) \
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296 stderr_out ("\t%-12s%8x\n", #field ":", (int)cell->gcvm.gcv.field); \
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297 } while (0)
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298 FROB (function);
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299 FROB (plane_mask);
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300 FROB (foreground);
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301 FROB (background);
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302 FROB (line_width);
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303 FROB (line_style);
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304 FROB (cap_style);
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305 FROB (join_style);
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306 FROB (fill_style);
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307 FROB (fill_rule);
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308 FROB (arc_mode);
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309 FROB (tile);
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310 FROB (stipple);
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311 FROB (ts_x_origin);
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312 FROB (ts_y_origin);
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313 FROB (font);
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314 FROB (subwindow_mode);
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315 FROB (graphics_exposures);
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316 FROB (clip_x_origin);
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317 FROB (clip_y_origin);
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318 FROB (clip_mask);
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319 FROB (dash_offset);
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320 #undef FROB
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321
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322 count++;
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323 if (cell->next && cell == cache->tail)
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324 stderr_out ("\nERROR! tail is here!\n\n");
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325 else if (!cell->next && cell != cache->tail)
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326 stderr_out ("\nERROR! tail is not at the end\n\n");
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327 cell = cell->next;
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328 }
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329 if (count != cache->size)
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330 stderr_out ("\nERROR! count should be %d\n\n", cache->size);
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331 }
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332
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333 #endif /* DEBUG_XEMACS */
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