libcogl-doc 1.18.2-3 / usr / share / gtk-doc / html / cogl-2.0-experimental / cogl-2.0-experimental-Exception-handling.html

This file is indexed.

/usr/share/gtk-doc/html/cogl-2.0-experimental/cogl-2.0-experimental-Exception-handling.html is in libcogl-doc 1.18.2-3.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below. 

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Cogl 2.0 Reference Manual: Exception handling</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
<link rel="home" href="index.html" title="Cogl 2.0 Reference Manual">
<link rel="up" href="cogl-general-apis.html" title="General API concepts">
<link rel="prev" href="cogl-2.0-experimental-The-Object-Interface.html" title="The Object Interface">
<link rel="next" href="cogl-2.0-experimental-Common-Types.html" title="Common Types">
<meta name="generator" content="GTK-Doc V1.21 (XML mode)">
<link rel="stylesheet" href="style.css" type="text/css">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle">
<td width="100%" align="left" class="shortcuts">
<a href="#" class="shortcut">Top</a><span id="nav_description">  <span class="dim">|</span> 
                  <a href="#cogl-2.0-experimental-Exception-handling.description" class="shortcut">Description</a></span>
</td>
<td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td>
<td><a accesskey="u" href="cogl-general-apis.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td>
<td><a accesskey="p" href="cogl-2.0-experimental-The-Object-Interface.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td>
<td><a accesskey="n" href="cogl-2.0-experimental-Common-Types.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td>
</tr></table>
<div class="refentry">
<a name="cogl-2.0-experimental-Exception-handling"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2><span class="refentrytitle"><a name="cogl-2.0-experimental-Exception-handling.top_of_page"></a>Exception handling</span></h2>
<p>Exception handling — A way for Cogl to throw exceptions</p>
</td>
<td class="gallery_image" valign="top" align="right"></td>
</tr></table></div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Exception-handling.functions"></a><h2>Functions</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="functions_return">
<col class="functions_name">
</colgroup>
<tbody>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#cogl-error-matches" title="cogl_error_matches ()">cogl_error_matches</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<span class="returnvalue">void</span>
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#cogl-error-free" title="cogl_error_free ()">cogl_error_free</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="function_type">
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="returnvalue">CoglError</span></a> *
</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#cogl-error-copy" title="cogl_error_copy ()">cogl_error_copy</a> <span class="c_punctuation">()</span>
</td>
</tr>
<tr>
<td class="define_keyword">#define</td>
<td class="function_name">
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#COGL-GLIB-ERROR:CAPS" title="COGL_GLIB_ERROR()">COGL_GLIB_ERROR</a><span class="c_punctuation">()</span>
</td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Exception-handling.other"></a><h2>Types and Values</h2>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="name">
<col class="description">
</colgroup>
<tbody><tr>
<td class="define_keyword">#define</td>
<td class="function_name"><a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError">CoglError</a></td>
</tr></tbody>
</table></div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Exception-handling.description"></a><h2>Description</h2>
<p>As a general rule Cogl shields non-recoverable errors from
developers, such as most heap allocation failures (unless for
exceptionally large resources which we might reasonably expect to
fail) and this reduces the burden on developers.</p>
<p>There are some Cogl apis though that can fail for exceptional
reasons that can also potentially be recovered from at runtime
and for these apis we use a standard convention for reporting
runtime recoverable errors.</p>
<p>As an example if we look at the <a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#cogl-context-new" title="cogl_context_new ()"><code class="function">cogl_context_new()</code></a> api which
takes an error argument:</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2</pre></td>
        <td class="listing_code"><pre class="programlisting">CoglContext <span class="gtkdoc opt">*</span>
<span class="function"><a href="cogl-2.0-experimental-The-Top-Level-Context.html#cogl-context-new">cogl_context_new</a></span> <span class="gtkdoc opt">(</span>CoglDisplay <span class="gtkdoc opt">*</span>display<span class="gtkdoc opt">,</span> CoglError <span class="gtkdoc opt">**</span>error<span class="gtkdoc opt">);</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>A caller interested in catching any runtime error when creating a
new <a class="link" href="cogl-2.0-experimental-The-Top-Level-Context.html#CoglContext" title="CoglContext"><span class="type">CoglContext</span></a> would pass the address of a <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> pointer
that has first been initialized to <code class="literal">NULL</code> as follows:</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2
3
4</pre></td>
        <td class="listing_code"><pre class="programlisting">CoglError <span class="gtkdoc opt">*</span>error <span class="gtkdoc opt">=</span> NULL<span class="gtkdoc opt">;</span>
CoglContext <span class="gtkdoc opt">*</span>context<span class="gtkdoc opt">;</span>

context <span class="gtkdoc opt">=</span> <span class="function"><a href="cogl-2.0-experimental-The-Top-Level-Context.html#cogl-context-new">cogl_context_new</a></span> <span class="gtkdoc opt">(</span>NULL<span class="gtkdoc opt">, &amp;</span>error<span class="gtkdoc opt">);</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>The return status should usually be enough to determine if there
was an error set (in this example we can check if context == <code class="literal">NULL</code>)
but if it's not possible to tell from the function's return status
you can instead look directly at the error pointer which you
initialized to <code class="literal">NULL</code>. In this example we now check the error,
report any error to the user, free the error and then simply
abort without attempting to recover.</p>
<div class="informalexample">
  <table class="listing_frame" border="0" cellpadding="0" cellspacing="0">
    <tbody>
      <tr>
        <td class="listing_lines" align="right"><pre>1
2
3
4
5
6
7</pre></td>
        <td class="listing_code"><pre class="programlisting"><span class="keyword">if</span> <span class="gtkdoc opt">(</span>context <span class="gtkdoc opt">==</span> NULL<span class="gtkdoc opt">)</span>
  <span class="gtkdoc opt">{</span>
    <span class="function">fprintf</span> <span class="gtkdoc opt">(</span>stderr<span class="gtkdoc opt">,</span> <span class="string">&quot;Failed to create a Cogl context: %s</span><span class="gtkdoc esc">\n</span><span class="string">&quot;</span><span class="gtkdoc opt">,</span>
             error<span class="gtkdoc opt">-&gt;</span>message<span class="gtkdoc opt">);</span>
    <span class="function"><a href="cogl-2.0-experimental-Exception-handling.html#cogl-error-free">cogl_error_free</a></span> <span class="gtkdoc opt">(</span>error<span class="gtkdoc opt">);</span>
    <span class="function">abort</span> <span class="gtkdoc opt">();</span>
  <span class="gtkdoc opt">}</span></pre></td>
      </tr>
    </tbody>
  </table>
</div>

<p></p>
<p>All Cogl APIs that accept an error argument can also be passed a
<code class="literal">NULL</code> pointer. In this case if an exceptional error condition is hit
then Cogl will simply log the error message and abort the
application. This can be compared to language execeptions where the
developer has not attempted to catch the exception. This means the
above example is essentially redundant because it's what Cogl would
have done automatically and so, similarly, if your application has
no way to recover from a particular error you might just as well
pass a <code class="literal">NULL</code> <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> pointer to save a bit of typing.</p>
<div class="note">If you are used to using the GLib API you will probably
recognize that <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> is just like a <span class="type">GError</span>. In fact if Cogl
has been built with --enable-glib then it is safe to cast a
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> to a <span class="type">GError</span>.</div>
<div class="note">An important detail to be aware of if you are used to using
GLib's GError API is that Cogl deviates from the GLib GError
conventions in one noteable way which is that a <code class="literal">NULL</code> error pointer
does not mean you want to ignore the details of an error, it means
you are not trying to catch any exceptional errors the function might
throw which will result in the program aborting with a log message
if an error is thrown.</div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Exception-handling.functions_details"></a><h2>Functions</h2>
<div class="refsect2">
<a name="cogl-error-matches"></a><h3>cogl_error_matches ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Common-Types.html#CoglBool" title="CoglBool"><span class="returnvalue">CoglBool</span></a>
cogl_error_matches (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> *error</code></em>,
                    <em class="parameter"><code><span class="type">uint32_t</span> domain</code></em>,
                    <em class="parameter"><code><span class="type">int</span> code</code></em>);</pre>
<p>Returns <code class="literal">TRUE</code> if error matches <em class="parameter"><code>domain</code></em>
 and <em class="parameter"><code>code</code></em>
, <code class="literal">FALSE</code> otherwise.
In particular, when error is <code class="literal">NULL</code>, FALSE will be returned.</p>
<div class="refsect3">
<a name="id-1.2.3.3.6.2.5"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>error</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> thrown by the Cogl api or <code class="literal">NULL</code></p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>domain</p></td>
<td class="parameter_description"><p>The error domain</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>code</p></td>
<td class="parameter_description"><p>The error code</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.2.3.3.6.2.6"></a><h4>Returns</h4>
<p> whether the <em class="parameter"><code>error</code></em>
corresponds to the given <em class="parameter"><code>domain</code></em>
and <em class="parameter"><code>code</code></em>
.</p>
<p></p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-error-free"></a><h3>cogl_error_free ()</h3>
<pre class="programlisting"><span class="returnvalue">void</span>
cogl_error_free (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> *error</code></em>);</pre>
<p>Frees a <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> and associated resources.</p>
<div class="refsect3">
<a name="id-1.2.3.3.6.3.5"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>error</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> thrown by the Cogl api</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
<hr>
<div class="refsect2">
<a name="cogl-error-copy"></a><h3>cogl_error_copy ()</h3>
<pre class="programlisting"><a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="returnvalue">CoglError</span></a> *
cogl_error_copy (<em class="parameter"><code><a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> *error</code></em>);</pre>
<p>Makes a copy of <em class="parameter"><code>error</code></em>
 which can later be freed using
<a class="link" href="cogl-2.0-experimental-Exception-handling.html#cogl-error-free" title="cogl_error_free ()"><code class="function">cogl_error_free()</code></a>.</p>
<div class="refsect3">
<a name="id-1.2.3.3.6.4.5"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>error</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> thrown by the Cogl api</p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
<div class="refsect3">
<a name="id-1.2.3.3.6.4.6"></a><h4>Returns</h4>
<p> A newly allocated <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> initialized to match the
contents of <em class="parameter"><code>error</code></em>
.</p>
<p></p>
</div>
</div>
<hr>
<div class="refsect2">
<a name="COGL-GLIB-ERROR:CAPS"></a><h3>COGL_GLIB_ERROR()</h3>
<pre class="programlisting">#define COGL_GLIB_ERROR(COGL_ERROR) ((CoglError *)COGL_ERROR)
</pre>
<p>Simply casts a <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> to a <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a></p>
<p>If Cogl is built with GLib support then it can safely be assumed
that a CoglError is a GError and can be used directly with the
GError api.</p>
<div class="refsect3">
<a name="id-1.2.3.3.6.5.6"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody><tr>
<td class="parameter_name"><p>COGL_ERROR</p></td>
<td class="parameter_description"><p>A <a class="link" href="cogl-2.0-experimental-Exception-handling.html#CoglError" title="CoglError"><span class="type">CoglError</span></a> thrown by the Cogl api or <code class="literal">NULL</code></p></td>
<td class="parameter_annotations"> </td>
</tr></tbody>
</table></div>
</div>
</div>
</div>
<div class="refsect1">
<a name="cogl-2.0-experimental-Exception-handling.other_details"></a><h2>Types and Values</h2>
<div class="refsect2">
<a name="CoglError"></a><h3>CoglError</h3>
<pre class="programlisting">#define CoglError GError
</pre>
<div class="refsect3">
<a name="id-1.2.3.3.7.2.4"></a><h4>Parameters</h4>
<div class="informaltable"><table width="100%" border="0">
<colgroup>
<col width="150px" class="parameters_name">
<col class="parameters_description">
<col width="200px" class="parameters_annotations">
</colgroup>
<tbody>
<tr>
<td class="parameter_name"><p>domain</p></td>
<td class="parameter_description"><p>A high-level domain identifier for the error</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>code</p></td>
<td class="parameter_description"><p>A specific error code within a specified domain</p></td>
<td class="parameter_annotations"> </td>
</tr>
<tr>
<td class="parameter_name"><p>message</p></td>
<td class="parameter_description"><p>A human readable error message</p></td>
<td class="parameter_annotations"> </td>
</tr>
</tbody>
</table></div>
</div>
</div>
</div>
</div>
<div class="footer">
<hr>
          Generated by GTK-Doc V1.21</div>
</body>
</html>

APT Browse - Built by Thomas Orozco.