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32<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>QThread Class Reference</h1>
33
34<p>The QThread class provides platform-independent threads.
35<a href="#details">More...</a>
36<p>All the functions in this class are <a href="threads.html#threadsafe">thread-safe</a> when Qt is built with thread support.</p>
37<p><tt>#include &lt;<a href="qthread-h.html">qthread.h</a>&gt;</tt>
38<p>Inherits <a href="qt.html">Qt</a>.
39<p><a href="qthread-members.html">List of all member functions.</a>
40<h2>Public Members</h2>
41<ul>
42<li class=fn><a href="#QThread"><b>QThread</b></a> ( unsigned&nbsp;int&nbsp;stackSize = 0 )</li>
43<li class=fn>virtual <a href="#~QThread"><b>~QThread</b></a> ()</li>
44<li class=fn>bool <a href="#wait"><b>wait</b></a> ( unsigned&nbsp;long&nbsp;time = ULONG_MAX )</li>
45<li class=fn>enum <a href="#Priority-enum"><b>Priority</b></a> { IdlePriority, LowestPriority, LowPriority, NormalPriority, HighPriority, HighestPriority, TimeCriticalPriority, InheritPriority }</li>
46<li class=fn>void <a href="#start"><b>start</b></a> ( Priority&nbsp;priority = InheritPriority )</li>
47<li class=fn>void <a href="#terminate"><b>terminate</b></a> ()</li>
48<li class=fn>bool <a href="#finished"><b>finished</b></a> () const</li>
49<li class=fn>bool <a href="#running"><b>running</b></a> () const</li>
50</ul>
51<h2>Static Public Members</h2>
52<ul>
53<li class=fn>Qt::HANDLE <a href="#currentThread"><b>currentThread</b></a> ()</li>
54<li class=fn>void postEvent ( QObject&nbsp;*&nbsp;receiver, QEvent&nbsp;*&nbsp;event ) &nbsp;<em>(obsolete)</em></li>
55<li class=fn>void <a href="#exit"><b>exit</b></a> ()</li>
56</ul>
57<h2>Protected Members</h2>
58<ul>
59<li class=fn>virtual void <a href="#run"><b>run</b></a> () = 0</li>
60</ul>
61<h2>Static Protected Members</h2>
62<ul>
63<li class=fn>void <a href="#sleep"><b>sleep</b></a> ( unsigned&nbsp;long&nbsp;secs )</li>
64<li class=fn>void <a href="#msleep"><b>msleep</b></a> ( unsigned&nbsp;long&nbsp;msecs )</li>
65<li class=fn>void <a href="#usleep"><b>usleep</b></a> ( unsigned&nbsp;long&nbsp;usecs )</li>
66</ul>
67<hr><a name="details"></a><h2>Detailed Description</h2>
68
69
70
71The QThread class provides platform-independent threads.
72<p>
73
74<p> A QThread represents a separate thread of control within the
75program; it shares data with all the other threads within the
76process but executes independently in the way that a separate
77program does on a multitasking operating system. Instead of
78starting in main(), QThreads begin executing in <a href="#run">run</a>(). You inherit
79run() to include your code. For example:
80<p> <pre>
81 class MyThread : public QThread {
82
83 public:
84
85 virtual void run();
86
87 };
88
89 void MyThread::<a href="#run">run</a>()
90 {
91 for( int count = 0; count &lt; 20; count++ ) {
92 <a href="#sleep">sleep</a>( 1 );
93 <a href="qapplication.html#qDebug">qDebug</a>( "Ping!" );
94 }
95 }
96
97 int main()
98 {
99 MyThread a;
100 MyThread b;
101 a.<a href="#start">start</a>();
102 b.<a href="#start">start</a>();
103 a.<a href="#wait">wait</a>();
104 b.<a href="#wait">wait</a>();
105 }
106 </pre>
107
108<p> This will start two threads, each of which writes Ping! 20 times
109to the screen and exits. The <a href="#wait">wait</a>() calls at the end of main() are
110necessary because exiting main() ends the program, unceremoniously
111killing all other threads. Each MyThread stops executing when it
112reaches the end of MyThread::run(), just as an application does
113when it leaves main().
114<p> <p>See also <a href="threads.html">Thread Support in Qt</a>, <a href="environment.html">Environment Classes</a>, and <a href="thread.html">Threading</a>.
115
116<hr><h2>Member Type Documentation</h2>
117<h3 class=fn><a name="Priority-enum"></a>QThread::Priority</h3>
118
119<p> This enum type indicates how the operating system should schedule
120newly created threads.
121<ul>
122<li><tt>QThread::IdlePriority</tt> - scheduled only when no other threads are
123running.
124<li><tt>QThread::LowestPriority</tt> - scheduled less often than LowPriority.
125<li><tt>QThread::LowPriority</tt> - scheduled less often than NormalPriority.
126<li><tt>QThread::NormalPriority</tt> - the default priority of the operating
127system.
128<li><tt>QThread::HighPriority</tt> - scheduled more often than NormalPriority.
129<li><tt>QThread::HighestPriority</tt> - scheduled more often then HighPriority.
130<li><tt>QThread::TimeCriticalPriority</tt> - scheduled as often as possible.
131<li><tt>QThread::InheritPriority</tt> - use the same priority as the creating
132thread. This is the default.
133</ul>
134<hr><h2>Member Function Documentation</h2>
135<h3 class=fn><a name="QThread"></a>QThread::QThread ( unsigned&nbsp;int&nbsp;stackSize = 0 )
136</h3>
137Constructs a new thread. The thread does not begin executing until
138<a href="#start">start</a>() is called.
139<p> If <em>stackSize</em> is greater than zero, the maximum stack size is
140set to <em>stackSize</em> bytes, otherwise the maximum stack size is
141automatically determined by the operating system.
142<p> <b>Warning:</b> Most operating systems place minimum and maximum limits
143on thread stack sizes. The thread will fail to start if the stack
144size is outside these limits.
145
146<h3 class=fn><a name="~QThread"></a>QThread::~QThread ()<tt> [virtual]</tt>
147</h3>
148QThread destructor.
149<p> Note that deleting a QThread object will not stop the execution of
150the thread it represents. Deleting a running QThread (i.e.
151<a href="#finished">finished</a>() returns FALSE) will probably result in a program crash.
152You can <a href="#wait">wait</a>() on a thread to make sure that it has finished.
153
154<h3 class=fn>Qt::HANDLE <a name="currentThread"></a>QThread::currentThread ()<tt> [static]</tt>
155</h3>
156This returns the thread handle of the currently executing thread.
157<p> <b>Warning:</b> The handle returned by this function is used for internal
158purposes and should <em>not</em> be used in any application code. On
159Windows, the returned value is a pseudo handle for the current
160thread, and it cannot be used for numerical comparison.
161
162<h3 class=fn>void <a name="exit"></a>QThread::exit ()<tt> [static]</tt>
163</h3>
164Ends the execution of the calling thread and wakes up any threads
165waiting for its termination.
166
167<h3 class=fn>bool <a name="finished"></a>QThread::finished () const
168</h3>
169Returns TRUE if the thread is finished; otherwise returns FALSE.
170
171<h3 class=fn>void <a name="msleep"></a>QThread::msleep ( unsigned&nbsp;long&nbsp;msecs )<tt> [static protected]</tt>
172</h3>
173System independent sleep. This causes the current thread to sleep
174for <em>msecs</em> milliseconds
175
176<h3 class=fn>void <a name="postEvent"></a>QThread::postEvent ( <a href="qobject.html">QObject</a>&nbsp;*&nbsp;receiver, <a href="qevent.html">QEvent</a>&nbsp;*&nbsp;event )<tt> [static]</tt>
177</h3> <b>This function is obsolete.</b> It is provided to keep old source working. We strongly advise against using it in new code.
178<p> Use <a href="qapplication.html#postEvent">QApplication::postEvent</a>() instead.
179
180<h3 class=fn>void <a name="run"></a>QThread::run ()<tt> [pure virtual protected]</tt>
181</h3>
182
183<p> This method is pure virtual, and must be implemented in derived
184classes in order to do useful work. Returning from this method
185will end the execution of the thread.
186<p> <p>See also <a href="#wait">wait</a>().
187
188<h3 class=fn>bool <a name="running"></a>QThread::running () const
189</h3>
190Returns TRUE if the thread is running; otherwise returns FALSE.
191
192<h3 class=fn>void <a name="sleep"></a>QThread::sleep ( unsigned&nbsp;long&nbsp;secs )<tt> [static protected]</tt>
193</h3>
194System independent sleep. This causes the current thread to sleep
195for <em>secs</em> seconds.
196
197<h3 class=fn>void <a name="start"></a>QThread::start ( <a href="qthread.html#Priority-enum">Priority</a>&nbsp;priority = InheritPriority )
198</h3>
199Begins execution of the thread by calling <a href="#run">run</a>(), which should be
200reimplemented in a QThread subclass to contain your code. The
201operating system will schedule the thread according to the <em>priority</em> argument.
202<p> If you try to start a thread that is already running, this
203function will wait until the the thread has finished and then
204restart the thread.
205<p> <p>See also <a href="#Priority-enum">Priority</a>.
206
207<h3 class=fn>void <a name="terminate"></a>QThread::terminate ()
208</h3>
209This function terminates the execution of the thread. The thread
210may or may not be terminated immediately, depending on the
211operating system's scheduling policies. Use <a href="#wait">QThread::wait</a>()
212after <a href="#terminate">terminate</a>() for synchronous termination.
213<p> When the thread is terminated, all threads waiting for the
214the thread to finish will be woken up.
215<p> <b>Warning:</b> This function is dangerous, and its use is discouraged.
216The thread can be terminated at any point in its code path. Threads
217can be terminated while modifying data. There is no chance for
218the thread to cleanup after itself, unlock any held mutexes, etc.
219In short, use this function only if <em>absolutely</em> necessary.
220
221<h3 class=fn>void <a name="usleep"></a>QThread::usleep ( unsigned&nbsp;long&nbsp;usecs )<tt> [static protected]</tt>
222</h3>
223System independent sleep. This causes the current thread to sleep
224for <em>usecs</em> microseconds
225
226<h3 class=fn>bool <a name="wait"></a>QThread::wait ( unsigned&nbsp;long&nbsp;time = ULONG_MAX )
227</h3>
228A thread calling this function will block until either of these
229conditions is met:
230<p> <ul>
231<li> The thread associated with this QThread object has finished
232execution (i.e. when it returns from <a href="#run">run</a>()). This function
233will return TRUE if the thread has finished. It also returns
234TRUE if the thread has not been started yet.
235<li> <em>time</em> milliseconds has elapsed. If <em>time</em> is ULONG_MAX (the
236default), then the wait will never timeout (the thread must
237return from <a href="#run">run</a>()). This function will return FALSE if the
238wait timed out.
239</ul>
240<p> This provides similar functionality to the POSIX <tt>pthread_join()</tt> function.
241
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