|
|
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
|
|
|
|
|
<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/object.doc:86 -->
|
|
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
|
|
|
|
|
<title>Timers</title>
|
|
|
|
|
<style type="text/css"><!--
|
|
|
|
|
fn { margin-left: 1cm; text-indent: -1cm; }
|
|
|
|
|
a:link { color: #004faf; text-decoration: none }
|
|
|
|
|
a:visited { color: #672967; text-decoration: none }
|
|
|
|
|
body { background: #ffffff; color: black; }
|
|
|
|
|
--></style>
|
|
|
|
|
</head>
|
|
|
|
|
<body>
|
|
|
|
|
|
|
|
|
|
<table border="0" cellpadding="0" cellspacing="0" width="100%">
|
|
|
|
|
<tr bgcolor="#E5E5E5">
|
|
|
|
|
<td valign=center>
|
|
|
|
|
<a href="index.html">
|
|
|
|
|
<font color="#004faf">Home</font></a>
|
|
|
|
|
| <a href="classes.html">
|
|
|
|
|
<font color="#004faf">All Classes</font></a>
|
|
|
|
|
| <a href="mainclasses.html">
|
|
|
|
|
<font color="#004faf">Main Classes</font></a>
|
|
|
|
|
| <a href="annotated.html">
|
|
|
|
|
<font color="#004faf">Annotated</font></a>
|
|
|
|
|
| <a href="groups.html">
|
|
|
|
|
<font color="#004faf">Grouped Classes</font></a>
|
|
|
|
|
| <a href="functions.html">
|
|
|
|
|
<font color="#004faf">Functions</font></a>
|
|
|
|
|
</td>
|
|
|
|
|
<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Timers</h1>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<p> <a href="ntqobject.html">TQObject</a>, the base class of all TQt objects, provides the basic timer
|
|
|
|
|
support in TQt. With <a href="ntqobject.html#startTimer">TQObject::startTimer</a>(), you start a timer with
|
|
|
|
|
an <em>interval</em> in milliseconds as argument. The function returns a
|
|
|
|
|
unique integer timer id. The timer will now "fire" every <em>interval</em>
|
|
|
|
|
milliseconds, until you explicitly call <a href="ntqobject.html#killTimer">TQObject::killTimer</a>() with
|
|
|
|
|
the timer id.
|
|
|
|
|
<p> For this mechanism to work, the application must run in an event
|
|
|
|
|
loop. You start an event loop with <a href="ntqapplication.html#exec">TQApplication::exec</a>(). When a
|
|
|
|
|
timer fires, the application sends a <a href="qtimerevent.html">TQTimerEvent</a>, and the flow of
|
|
|
|
|
control leaves the event loop until the timer event is processed. This
|
|
|
|
|
implies that a timer cannot fire while your application is busy doing
|
|
|
|
|
something else. In other words: the accuracy of timers depends on the
|
|
|
|
|
granularity of your application.
|
|
|
|
|
<p> There is practically no upper limit for the interval value (more than
|
|
|
|
|
one year is possible). The accuracy depends on the underlying operating
|
|
|
|
|
system. Windows 95/98 has 55 millisecond (18.2 times per second)
|
|
|
|
|
accuracy; other systems that we have tested (UNIX X11 and Windows NT)
|
|
|
|
|
can handle 1 millisecond intervals.
|
|
|
|
|
<p> The main API for the timer functionality is <a href="ntqtimer.html">TQTimer</a>. That class
|
|
|
|
|
provides regular timers that emit a signal when the timer fires, and
|
|
|
|
|
inherits <a href="ntqobject.html">TQObject</a> so that it fits well into the ownership structure
|
|
|
|
|
of most GUI programs. The normal way of using it is like this:
|
|
|
|
|
<pre>
|
|
|
|
|
<a href="ntqtimer.html">TQTimer</a> * counter = new <a href="ntqtimer.html">TQTimer</a>( this );
|
|
|
|
|
connect( counter, SIGNAL(<a href="ntqtimer.html#timeout">timeout</a>()),
|
|
|
|
|
this, SLOT(updateCaption()) );
|
|
|
|
|
counter-><a href="ntqtimer.html#start">start</a>( 1000 );
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p> The counter timer is made into a child of this widget, so that when
|
|
|
|
|
this widget is deleted, the timer is deleted too. Next, its timeout
|
|
|
|
|
signal is connected to the slot that will do the work, and finally
|
|
|
|
|
it's started.
|
|
|
|
|
<p> <a href="ntqtimer.html">TQTimer</a> also provides a simple one-shot timer API. <a href="ntqbutton.html">TQButton</a> uses this
|
|
|
|
|
to show the button being pressed down and then (0.1 seconds later) be
|
|
|
|
|
released when the keyboard is used to "press" a button, for example:
|
|
|
|
|
<p> <pre>
|
|
|
|
|
TQTimer::<a href="ntqtimer.html#singleShot">singleShot</a>( 100, this, SLOT(animateTimeout()) );
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p> 0.1 seconds after this line of code is executed, the same button's
|
|
|
|
|
animateTimeout() slot is called.
|
|
|
|
|
<p> Here is an outline of a slightly longer example that combines object
|
|
|
|
|
communication via signals and slots with a TQTimer object. It
|
|
|
|
|
demonstrates how to use timers to perform intensive calculations in a
|
|
|
|
|
single-threaded application without blocking the user interface.
|
|
|
|
|
<p> <pre>
|
|
|
|
|
// The Mandelbrot class uses a TQTimer to calculate the mandelbrot
|
|
|
|
|
// set one scanline at a time without blocking the CPU. It
|
|
|
|
|
// inherits TQObject to use signals and slots. Calling start()
|
|
|
|
|
// starts the calculation. The done() signal is emitted when it
|
|
|
|
|
// has finished. Note that this example is not complete, just an
|
|
|
|
|
// outline.
|
|
|
|
|
|
|
|
|
|
class Mandelbrot : public <a href="ntqobject.html">TQObject</a>
|
|
|
|
|
{
|
|
|
|
|
<a href="metaobjects.html#Q_OBJECT">Q_OBJECT</a> // required for signals/slots
|
|
|
|
|
public:
|
|
|
|
|
Mandelbrot( <a href="ntqobject.html">TQObject</a> *parent=0, const char *name );
|
|
|
|
|
...
|
|
|
|
|
public slots:
|
|
|
|
|
void start();
|
|
|
|
|
signals:
|
|
|
|
|
void done();
|
|
|
|
|
private slots:
|
|
|
|
|
void calculate();
|
|
|
|
|
private:
|
|
|
|
|
<a href="ntqtimer.html">TQTimer</a> timer;
|
|
|
|
|
...
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
//
|
|
|
|
|
// Constructs and initializes a Mandelbrot object.
|
|
|
|
|
//
|
|
|
|
|
|
|
|
|
|
Mandelbrot::Mandelbrot( <a href="ntqobject.html">TQObject</a> *parent=0, const char *name )
|
|
|
|
|
: <a href="ntqobject.html">TQObject</a>( parent, name )
|
|
|
|
|
{
|
|
|
|
|
<a href="ntqobject.html#connect">connect</a>( &timer, SIGNAL(<a href="ntqtimer.html#timeout">timeout</a>()), SLOT(calculate()) );
|
|
|
|
|
...
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
//
|
|
|
|
|
// Starts the calculation task. The internal calculate() slot
|
|
|
|
|
// will be activated every 10 milliseconds.
|
|
|
|
|
//
|
|
|
|
|
|
|
|
|
|
void Mandelbrot::start()
|
|
|
|
|
{
|
|
|
|
|
if ( !timer.<a href="ntqtimer.html#isActive">isActive</a>() ) // not already running
|
|
|
|
|
timer.<a href="ntqtimer.html#start">start</a>( 10 ); // timeout every 10 ms
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
//
|
|
|
|
|
// Calculates one scanline at a time.
|
|
|
|
|
// Emits the done() signal when finished.
|
|
|
|
|
//
|
|
|
|
|
|
|
|
|
|
void Mandelbrot::calculate()
|
|
|
|
|
{
|
|
|
|
|
... // perform the calculation for a scanline
|
|
|
|
|
if ( finished ) { // no more scanlines
|
|
|
|
|
timer.<a href="ntqtimer.html#stop">stop</a>();
|
|
|
|
|
emit done();
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
</pre>
|
|
|
|
|
|
|
|
|
|
<p>
|
|
|
|
|
<!-- eof -->
|
|
|
|
|
<p><address><hr><div align=center>
|
|
|
|
|
<table width=100% cellspacing=0 border=0><tr>
|
|
|
|
|
<td>Copyright © 2007
|
|
|
|
|
<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
|
|
|
|
|
<td align=right><div align=right>TQt 3.3.8</div>
|
|
|
|
|
</table></div></address></body>
|
|
|
|
|
</html>
|
