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462
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1 /* Efficient caching of Gtk 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 hashtables. 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 Hacked by William Perry, apr 2000
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53 */
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54
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55 #include <config.h>
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56 #include <gtk/gtk.h>
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57 #include "lisp.h"
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58 #include "gccache-gtk.h"
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59
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60 #define GC_CACHE_SIZE 100
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61
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62 #define GCCACHE_HASH
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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 GdkGCValues gcv;
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2054
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71 unsigned long mask; /* contains a GdkGCValuesMask bitmask. */
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462
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72 };
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73
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74 struct gc_cache_cell {
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75 GdkGC *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 GdkWindow *window; /* used only as arg to XCreateGC */
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82 int size;
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83 struct gc_cache_cell *head;
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84 struct gc_cache_cell *tail;
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85 #ifdef GCCACHE_HASH
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86 struct hash_table * table;
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87 #endif
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88
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89 int create_count;
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90 int delete_count;
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91 };
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92
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93 #ifdef GCCACHE_HASH
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94 static unsigned long
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95 gc_cache_hash (const void *arg)
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96 {
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97 const struct gcv_and_mask *gcvm = (const struct gcv_and_mask *) arg;
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98 unsigned long *longs = (unsigned long *) &gcvm->gcv;
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99 unsigned long hash = gcvm->mask;
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778
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100 unsigned int i;
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462
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101 /* This could look at the mask and only use the used slots in the
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102 hash code. That would win in that we wouldn't have to initialize
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103 every slot of the gcv when calling gc_cache_lookup. But we need
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104 the hash function to be as fast as possible; some timings should
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105 be done. */
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106 for (i = 0; i < (sizeof (GdkGCValues) / sizeof (unsigned long)); i++)
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107 hash = (hash<<1) ^ *longs++;
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108 return hash;
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109 }
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110
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111 #endif /* GCCACHE_HASH */
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112
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113 static int
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114 gc_cache_eql (const void *arg1, const void *arg2)
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115 {
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116 /* See comment in gc_cache_hash */
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117 const struct gcv_and_mask *gcvm1 = (const struct gcv_and_mask *) arg1;
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118 const struct gcv_and_mask *gcvm2 = (const struct gcv_and_mask *) arg2;
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119
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120 return !memcmp(&gcvm1->gcv, &gcvm2->gcv, sizeof(gcvm1->gcv))
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121 && gcvm1->mask == gcvm2->mask;
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122 }
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123
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124 struct gc_cache *
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125 make_gc_cache (GtkWidget *widget)
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126 {
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127 struct gc_cache *cache = xnew (struct gc_cache);
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128 cache->window = widget->window;
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129 cache->size = 0;
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130 cache->head = cache->tail = 0;
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131 cache->create_count = cache->delete_count = 0;
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132 #ifdef GCCACHE_HASH
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133 cache->table =
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134 make_general_hash_table (GC_CACHE_SIZE, gc_cache_hash, gc_cache_eql);
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135 #endif
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136 return cache;
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137 }
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138
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139 void
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140 free_gc_cache (struct gc_cache *cache)
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141 {
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142 struct gc_cache_cell *rest, *next;
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143 rest = cache->head;
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144 while (rest)
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145 {
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146 gdk_gc_destroy(rest->gc);
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147 next = rest->next;
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1726
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148 xfree (rest, struct gc_cache_cell *);
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462
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149 rest = next;
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150 }
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151 #ifdef GCCACHE_HASH
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152 free_hash_table (cache->table);
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153 #endif
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1726
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154 xfree (cache, struct gc_cache *);
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462
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155 }
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156
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157 GdkGC *
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2054
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158 gc_cache_lookup (struct gc_cache *cache, GdkGCValues *gcv, unsigned long mask)
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462
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159 {
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160 struct gc_cache_cell *cell, *next, *prev;
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161 struct gcv_and_mask gcvm;
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162
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163 if ((!!cache->head) != (!!cache->tail)) abort ();
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164 if (cache->head && (cache->head->prev || cache->tail->next)) abort ();
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165
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166 /* Gdk does not have the equivalent of 'None' for the clip_mask, so
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167 we need to check it carefully, or gdk_gc_new_with_values will
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168 coredump */
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169 if ((mask & GDK_GC_CLIP_MASK) && !gcv->clip_mask)
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170 {
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171 mask &= ~GDK_GC_CLIP_MASK;
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172 }
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173
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174 gcvm.mask = mask;
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175 gcvm.gcv = *gcv; /* this copies... */
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176
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177 #ifdef GCCACHE_HASH
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178
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179 if (gethash (&gcvm, cache->table, (const void **) &cell))
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180
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181 #else /* !GCCACHE_HASH */
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182
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183 cell = cache->tail; /* start at the end (most recently used) */
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184 while (cell)
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185 {
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186 if (gc_cache_eql (&gcvm, &cell->gcvm))
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187 break;
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188 else
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189 cell = cell->prev;
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190 }
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191
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192 /* #### This whole file needs some serious overhauling. */
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193 if (!(mask | GDK_GC_TILE) && cell->gcvm.gcv.tile)
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194 cell = 0;
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195 else if (!(mask | GDK_GC_STIPPLE) && cell->gcvm.gcv.stipple)
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196 cell = 0;
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197
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198 if (cell)
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199
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200 #endif /* !GCCACHE_HASH */
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201
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202 {
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203 /* Found a cell. Move this cell to the end of the list, so that it
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204 will be less likely to be collected than a cell that was accessed
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205 less recently.
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206 */
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207 if (cell == cache->tail)
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208 return cell->gc;
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209
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210 next = cell->next;
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211 prev = cell->prev;
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212 if (prev) prev->next = next;
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213 if (next) next->prev = prev;
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214 if (cache->head == cell) cache->head = next;
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215 cell->next = 0;
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216 cell->prev = cache->tail;
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217 cache->tail->next = cell;
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218 cache->tail = cell;
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219 if (cache->head == cell) abort ();
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220 if (cell->next) abort ();
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221 if (cache->head->prev) abort ();
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222 if (cache->tail->next) abort ();
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223 return cell->gc;
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224 }
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225
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226 /* else, cache miss. */
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227
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228 if (cache->size == GC_CACHE_SIZE)
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229 /* Reuse the first cell on the list (least-recently-used).
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230 Remove it from the list, and unhash it from the table.
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231 */
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232 {
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233 cell = cache->head;
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234 cache->head = cell->next;
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235 cache->head->prev = 0;
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236 if (cache->tail == cell) cache->tail = 0; /* only one */
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237 gdk_gc_destroy (cell->gc);
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238 cache->delete_count++;
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239 #ifdef GCCACHE_HASH
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240 remhash (&cell->gcvm, cache->table);
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241 #endif
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242 }
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243 else if (cache->size > GC_CACHE_SIZE)
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244 abort ();
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245 else
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246 {
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247 /* Allocate a new cell (don't put it in the list or table yet). */
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248 cell = xnew (struct gc_cache_cell);
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249 cache->size++;
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250 }
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251
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252 /* Now we've got a cell (new or reused). Fill it in. */
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253 memcpy (&cell->gcvm.gcv, gcv, sizeof (GdkGCValues));
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254 cell->gcvm.mask = mask;
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255
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256 /* Put the cell on the end of the list. */
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257 cell->next = 0;
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258 cell->prev = cache->tail;
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259 if (cache->tail) cache->tail->next = cell;
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260 cache->tail = cell;
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261 if (! cache->head) cache->head = cell;
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262
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263 cache->create_count++;
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264 #ifdef GCCACHE_HASH
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265 /* Hash it in the table */
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266 puthash (&cell->gcvm, cell, cache->table);
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267 #endif
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268
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269 /* Now make and return the GC. */
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2054
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270 cell->gc = gdk_gc_new_with_values (cache->window, gcv, (GdkGCValuesMask) mask);
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462
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271
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272 /* debug */
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273 assert (cell->gc == gc_cache_lookup (cache, gcv, mask));
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274
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275 return cell->gc;
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276 }
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