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1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" | |
3 | "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd"> | |
4 | <refentry id="glXGetConfig"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glXGetConfig</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glXGetConfig</refname> | |
17 | <refpurpose>return information about GLX visuals</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>int <function>glXGetConfig</function></funcdef> | |
23 | <paramdef>Display * <parameter>dpy</parameter></paramdef> | |
24 | <paramdef>XVisualInfo * <parameter>vis</parameter></paramdef> | |
25 | <paramdef>int <parameter>attrib</parameter></paramdef> | |
26 | <paramdef>int * <parameter>value</parameter></paramdef> | |
27 | </funcprototype> | |
28 | </funcsynopsis> | |
29 | </refsynopsisdiv> | |
30 | <!-- eqn: ignoring delim $$ --> | |
31 | <refsect1 id="parameters"><title>Parameters</title> | |
32 | <variablelist> | |
33 | <varlistentry> | |
34 | <term><parameter>dpy</parameter></term> | |
35 | <listitem> | |
36 | <para> | |
37 | Specifies the connection to the X server. | |
38 | </para> | |
39 | </listitem> | |
40 | </varlistentry> | |
41 | <varlistentry> | |
42 | <term><parameter>vis</parameter></term> | |
43 | <listitem> | |
44 | <para> | |
45 | Specifies the visual to be queried. | |
46 | It is a pointer to an <constant>XVisualInfo</constant> structure, | |
47 | not a visual ID or a pointer to a <constant>Visual</constant>. | |
48 | </para> | |
49 | </listitem> | |
50 | </varlistentry> | |
51 | <varlistentry> | |
52 | <term><parameter>attrib</parameter></term> | |
53 | <listitem> | |
54 | <para> | |
55 | Specifies the visual attribute to be returned. | |
56 | </para> | |
57 | </listitem> | |
58 | </varlistentry> | |
59 | <varlistentry> | |
60 | <term><parameter>value</parameter></term> | |
61 | <listitem> | |
62 | <para> | |
63 | Returns the requested value. | |
64 | </para> | |
65 | </listitem> | |
66 | </varlistentry> | |
67 | </variablelist> | |
68 | </refsect1> | |
69 | <refsect1 id="description"><title>Description</title> | |
70 | <para> | |
71 | <function>glXGetConfig</function> sets <parameter>value</parameter> to the <parameter>attrib</parameter> value of windows or GLX pixmaps | |
72 | created with respect to <parameter>vis</parameter>. | |
73 | <function>glXGetConfig</function> returns an error code if it fails for any reason. | |
74 | Otherwise, zero is returned. | |
75 | </para> | |
76 | <para> | |
77 | <parameter>attrib</parameter> is one of the following: | |
78 | </para> | |
79 | <para> | |
80 | </para> | |
81 | <variablelist> | |
82 | <varlistentry> | |
83 | <term><constant>GLX_USE_GL</constant></term> | |
84 | <listitem> | |
85 | <para> | |
86 | <constant>True</constant> if OpenGL rendering is supported by this visual, | |
87 | <constant>False</constant> otherwise. | |
88 | </para> | |
89 | </listitem> | |
90 | </varlistentry> | |
91 | <varlistentry> | |
92 | <term><constant>GLX_BUFFER_SIZE</constant></term> | |
93 | <listitem> | |
94 | <para> | |
95 | Number of bits per color buffer. | |
96 | For RGBA visuals, <constant>GLX_BUFFER_SIZE</constant> is the sum of | |
97 | <constant>GLX_RED_SIZE</constant>, | |
98 | <constant>GLX_GREEN_SIZE</constant>, | |
99 | <constant>GLX_BLUE_SIZE</constant>, and | |
100 | <constant>GLX_ALPHA_SIZE</constant>. | |
101 | For color index visuals, <constant>GLX_BUFFER_SIZE</constant> is the size of the | |
102 | color indexes. | |
103 | </para> | |
104 | </listitem> | |
105 | </varlistentry> | |
106 | <varlistentry> | |
107 | <term><constant>GLX_LEVEL</constant></term> | |
108 | <listitem> | |
109 | <para> | |
110 | Frame buffer level of the visual. | |
111 | Level zero is the default frame buffer. | |
112 | Positive levels correspond to frame buffers that overlay the default buffer, | |
113 | and negative levels correspond to frame buffers that underlay the default | |
114 | buffer. | |
115 | </para> | |
116 | </listitem> | |
117 | </varlistentry> | |
118 | <varlistentry> | |
119 | <term><constant>GLX_RGBA</constant></term> | |
120 | <listitem> | |
121 | <para> | |
122 | <constant>True</constant> if color buffers store red, green, blue, and alpha values. | |
123 | <constant>False</constant> if they store color indexes. | |
124 | </para> | |
125 | </listitem> | |
126 | </varlistentry> | |
127 | <varlistentry> | |
128 | <term><constant>GLX_DOUBLEBUFFER</constant></term> | |
129 | <listitem> | |
130 | <para> | |
131 | <constant>True</constant> if color buffers exist in front/back pairs that can be swapped, | |
132 | <constant>False</constant> otherwise. | |
133 | </para> | |
134 | </listitem> | |
135 | </varlistentry> | |
136 | <varlistentry> | |
137 | <term><constant>GLX_STEREO</constant></term> | |
138 | <listitem> | |
139 | <para> | |
140 | <constant>True</constant> if color buffers exist in left/right pairs, | |
141 | <constant>False</constant> otherwise. | |
142 | </para> | |
143 | </listitem> | |
144 | </varlistentry> | |
145 | <varlistentry> | |
146 | <term><constant>GLX_AUX_BUFFERS</constant></term> | |
147 | <listitem> | |
148 | <para> | |
149 | Number of auxiliary color buffers that are available. | |
150 | Zero indicates that no auxiliary color buffers exist. | |
151 | </para> | |
152 | </listitem> | |
153 | </varlistentry> | |
154 | <varlistentry> | |
155 | <term><constant>GLX_RED_SIZE</constant></term> | |
156 | <listitem> | |
157 | <para> | |
158 | Number of bits of red stored in each color buffer. | |
159 | Undefined if <constant>GLX_RGBA</constant> is <constant>False</constant>. | |
160 | </para> | |
161 | </listitem> | |
162 | </varlistentry> | |
163 | <varlistentry> | |
164 | <term><constant>GLX_GREEN_SIZE</constant></term> | |
165 | <listitem> | |
166 | <para> | |
167 | Number of bits of green stored in each color buffer. | |
168 | Undefined if <constant>GLX_RGBA</constant> is <constant>False</constant>. | |
169 | </para> | |
170 | </listitem> | |
171 | </varlistentry> | |
172 | <varlistentry> | |
173 | <term><constant>GLX_BLUE_SIZE</constant></term> | |
174 | <listitem> | |
175 | <para> | |
176 | Number of bits of blue stored in each color buffer. | |
177 | Undefined if <constant>GLX_RGBA</constant> is <constant>False</constant>. | |
178 | </para> | |
179 | </listitem> | |
180 | </varlistentry> | |
181 | <varlistentry> | |
182 | <term><constant>GLX_ALPHA_SIZE</constant></term> | |
183 | <listitem> | |
184 | <para> | |
185 | Number of bits of alpha stored in each color buffer. | |
186 | Undefined if <constant>GLX_RGBA</constant> is <constant>False</constant>. | |
187 | </para> | |
188 | </listitem> | |
189 | </varlistentry> | |
190 | <varlistentry> | |
191 | <term><constant>GLX_DEPTH_SIZE</constant></term> | |
192 | <listitem> | |
193 | <para> | |
194 | Number of bits in the depth buffer. | |
195 | </para> | |
196 | </listitem> | |
197 | </varlistentry> | |
198 | <varlistentry> | |
199 | <term><constant>GLX_STENCIL_SIZE</constant></term> | |
200 | <listitem> | |
201 | <para> | |
202 | Number of bits in the stencil buffer. | |
203 | </para> | |
204 | </listitem> | |
205 | </varlistentry> | |
206 | <varlistentry> | |
207 | <term><constant>GLX_ACCUM_RED_SIZE</constant></term> | |
208 | <listitem> | |
209 | <para> | |
210 | Number of bits of red stored in the accumulation buffer. | |
211 | </para> | |
212 | </listitem> | |
213 | </varlistentry> | |
214 | <varlistentry> | |
215 | <term><constant>GLX_ACCUM_GREEN_SIZE</constant></term> | |
216 | <listitem> | |
217 | <para> | |
218 | Number of bits of green stored in the accumulation buffer. | |
219 | </para> | |
220 | </listitem> | |
221 | </varlistentry> | |
222 | <varlistentry> | |
223 | <term><constant>GLX_ACCUM_BLUE_SIZE</constant></term> | |
224 | <listitem> | |
225 | <para> | |
226 | Number of bits of blue stored in the accumulation buffer. | |
227 | </para> | |
228 | </listitem> | |
229 | </varlistentry> | |
230 | <varlistentry> | |
231 | <term><constant>GLX_ACCUM_ALPHA_SIZE</constant></term> | |
232 | <listitem> | |
233 | <para> | |
234 | Number of bits of alpha stored in the accumulation buffer. | |
235 | </para> | |
236 | </listitem> | |
237 | </varlistentry> | |
238 | </variablelist> | |
239 | <para> | |
240 | The X protocol allows a single visual ID to be instantiated with | |
241 | different numbers of bits per pixel. | |
242 | Windows or GLX pixmaps that will be rendered with OpenGL, however, | |
243 | must be instantiated with a color buffer depth of <constant>GLX_BUFFER_SIZE</constant>. | |
244 | </para> | |
245 | <para> | |
246 | Although a GLX implementation can export many visuals that support GL | |
247 | rendering, | |
248 | it must support | |
249 | at least one RGBA visual. This visual must have at | |
250 | least one color buffer, | |
251 | a stencil buffer of at least 1 bit, | |
252 | a depth buffer of at least 12 bits, | |
253 | and an accumulation buffer. | |
254 | Alpha bitplanes are optional in this visual. | |
255 | However, | |
256 | its color buffer size must be as great as that of the | |
257 | deepest <constant>TrueColor</constant>, <constant>DirectColor</constant>, | |
258 | <constant>PseudoColor</constant>, or <constant>StaticColor</constant> visual supported on level zero, | |
259 | and it must itself be made available on level zero. | |
260 | </para> | |
261 | <para> | |
262 | In addition, if the X server exports a <constant>PseudoColor</constant> | |
263 | or <constant>StaticColor</constant> visual on framebuffer level 0, a color index | |
264 | visual is also required on that level. | |
265 | It must have | |
266 | at least one color buffer, | |
267 | a stencil buffer of at least 1 bit, | |
268 | and a depth buffer of at least 12 bits. | |
269 | This visual must | |
270 | have as many | |
271 | color bitplanes as the deepest | |
272 | <constant>PseudoColor</constant> or <constant>StaticColor</constant> visual supported on level 0. | |
273 | </para> | |
274 | <para> | |
275 | Applications are best written to select the visual that most closely | |
276 | meets their requirements. | |
277 | Creating windows or GLX pixmaps with unnecessary buffers can result in | |
278 | reduced rendering performance as well as poor resource allocation. | |
279 | </para> | |
280 | </refsect1> | |
281 | <refsect1 id="notes"><title>Notes</title> | |
282 | <para> | |
283 | <constant>XVisualInfo</constant> is defined in <emphasis>Xutil.h.</emphasis> | |
284 | It is a structure that includes <emphasis>visual</emphasis>, <emphasis>visualID</emphasis>, <emphasis>screen</emphasis>, and | |
285 | <emphasis>depth</emphasis> elements. | |
286 | </para> | |
287 | </refsect1> | |
288 | <refsect1 id="errors"><title>Errors</title> | |
289 | <para> | |
290 | <constant>GLX_NO_EXTENSION</constant> is returned if <parameter>dpy</parameter> does not support the GLX | |
291 | extension. | |
292 | </para> | |
293 | <para> | |
294 | <constant>GLX_BAD_SCREEN</constant> is returned if the screen of <parameter>vis</parameter> does not correspond | |
295 | to a screen. | |
296 | </para> | |
297 | <para> | |
298 | <constant>GLX_BAD_ATTRIBUTE</constant> is returned if <parameter>attrib</parameter> is not a valid GLX attribute. | |
299 | </para> | |
300 | <para> | |
301 | <constant>GLX_BAD_VISUAL</constant> is returned if <parameter>vis</parameter> doesn't support GLX and an | |
302 | attribute other than <constant>GLX_USE_GL</constant> is requested. | |
303 | </para> | |
304 | </refsect1> | |
305 | <refsect1 id="seealso"><title>See Also</title> | |
306 | <para> | |
307 | <citerefentry><refentrytitle>glXChooseVisual</refentrytitle></citerefentry>, | |
308 | <citerefentry><refentrytitle>glXCreateContext</refentrytitle></citerefentry> | |
309 | </para> | |
310 | </refsect1> | |
311 | <refsect1 id="Copyright"><title>Copyright</title> | |
312 | <para> | |
313 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
314 | Silicon Graphics, Inc. This document is licensed under the SGI | |
315 | Free Software B License. For details, see | |
316 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
317 | </para> | |
318 | </refsect1> | |
319 | </refentry> |