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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta name="robots" content="noindex,noarchive">
<title>Qt Toolkit - QApplication Class</title><style type="text/css"><!--
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<a href=index.html><img width=122 height=65 src=qtlogo.jpg alt="Qt logo" align=left border=0></a>
<center><img src=dochead.gif width=472 height=27></center>
<br clear=all>
<h1 align=center>QApplication Class Reference</h1><br clear="all">
<p>
The QApplication class manages the application event queue.
<a href="#details">More...</a>
<p>
<code>#include <<a href="qapplication-h.html">qapplication.h</a>></code>
<p>
Inherits <a href="qobject.html">QObject</a>.
<p>Inherited by <a href="qxtapplication.html">QXtApplication</a>.
<p><a href="qapplication-members.html">List of all member functions.</a>
<h2>Public Members</h2>
<ul>
<li><span class="fn"><a href="qapplication.html#a0"><strong>QApplication</strong></a>(int&argc, char**argv)</span>
<li><span class="fn">virtual<a href="qapplication.html#a1"><strong>~QApplication</strong></a>()</span>
<li><span class="fn">int<a href="qapplication.html#a2"><strong>argc</strong></a>()const</span>
<li><span class="fn">char**<a href="qapplication.html#a3"><strong>argv</strong></a>()const</span>
<li><span class="fn">QWidget*<a href="qapplication.html#b8"><strong>mainWidget</strong></a>()const</span>
<li><span class="fn">void<a href="qapplication.html#b9"><strong>setMainWidget</strong></a>(QWidget*)</span>
<li><span class="fn">QWidget*<a href="qapplication.html#c6"><strong>focusWidget</strong></a>()const</span>
<li><span class="fn">int<a href="qapplication.html#c9"><strong>exec</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#d0"><strong>processEvents</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#d1"><strong>processEvents</strong></a>(intmaxtime)</span>
<li><span class="fn">void<a href="qapplication.html#d2"><strong>processOneEvent</strong></a>()</span>
<li><span class="fn">int<a href="qapplication.html#d3"><strong>enter_loop</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#d4"><strong>exit_loop</strong></a>()</span>
<li><span class="fn">virtualbool<a href="qapplication.html#d9"><strong>notify</strong></a>(QObject*, QEvent*)</span>
</ul>
<h2>Public Slots</h2>
<ul>
<li><span class="fn">void<a href="qapplication.html#f0"><strong>quit</strong></a>()</span>
</ul>
<h2>Signals</h2>
<ul>
<li><span class="fn">void<a href="qapplication.html#e9"><strong>lastWindowClosed</strong></a>()</span>
</ul>
<h2>Static Public Members</h2>
<ul>
<li><span class="fn">GUIStyle<a href="qapplication.html#f3"><strong>style</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#f4"><strong>setStyle</strong></a>(GUIStyle)</span>
<li><span class="fn">int<a href="qapplication.html#f5"><strong>colorSpec</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#f6"><strong>setColorSpec</strong></a>(int)</span>
<li><span class="fn">QCursor*<a href="qapplication.html#h5"><strong>overrideCursor</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#h6"><strong>setOverrideCursor</strong></a>(constQCursor&, boolreplace=FALSE)</span>
<li><span class="fn">void<a href="qapplication.html#h7"><strong>restoreOverrideCursor</strong></a>()</span>
<li><span class="fn">bool<a href="qapplication.html#h8"><strong>hasGlobalMouseTracking</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#h9"><strong>setGlobalMouseTracking</strong></a>(boolenable)</span>
<li><span class="fn">QPalette*<a href="qapplication.html#f7"><strong>palette</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#f8"><strong>setPalette</strong></a>(constQPalette&, boolupdateAllWidgets=FALSE)</span>
<li><span class="fn">QFont*<a href="qapplication.html#f9"><strong>font</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#g0"><strong>setFont</strong></a>(constQFont&, boolupdateAllWidgets=FALSE)</span>
<li><span class="fn">QFontMetrics<a href="qapplication.html#g3"><strong>fontMetrics</strong></a>()</span>
<li><span class="fn">QWidgetList*<a href="qapplication.html#g2"><strong>allWidgets</strong></a>()</span>
<li><span class="fn">QWidgetList*<a href="qapplication.html#g1"><strong>topLevelWidgets</strong></a>()</span>
<li><span class="fn">QWidget*<a href="qapplication.html#h4"><strong>desktop</strong></a>()</span>
<li><span class="fn">QWidget*<a href="qapplication.html#i9"><strong>activePopupWidget</strong></a>()</span>
<li><span class="fn">QWidget*<a href="qapplication.html#j0"><strong>activeModalWidget</strong></a>()</span>
<li><span class="fn">QClipboard*<a href="qapplication.html#j1"><strong>clipboard</strong></a>()</span>
<li><span class="fn">QWidget*<a href="qapplication.html#i0"><strong>widgetAt</strong></a>(intx, inty, boolchild=FALSE)</span>
<li><span class="fn">QWidget*<a href="qapplication.html#i1"><strong>widgetAt</strong></a>(constQPoint&, boolchild=FALSE)</span>
<li><span class="fn">void<a href="qapplication.html#g4"><strong>exit</strong></a>(intretcode=0)</span>
<li><span class="fn">bool<a href="qapplication.html#g5"><strong>sendEvent</strong></a>(QObject*receiver, QEvent*event)</span>
<li><span class="fn">void<a href="qapplication.html#i5"><strong>postEvent</strong></a>(QObject*receiver, QEvent*event)</span>
<li><span class="fn">void<a href="qapplication.html#i6"><strong>sendPostedEvents</strong></a>(QObject*receiver, intevent_type)</span>
<li><span class="fn">bool<a href="qapplication.html#g6"><strong>startingUp</strong></a>()</span>
<li><span class="fn">bool<a href="qapplication.html#g7"><strong>closingDown</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#i2"><strong>flushX</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#i3"><strong>syncX</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#i4"><strong>beep</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#g8"><strong>setWinStyleHighlightColor</strong></a>(constQColor&)</span>
<li><span class="fn">constQColor&<a href="qapplication.html#g9"><strong>winStyleHighlightColor</strong></a>()</span>
<li><span class="fn">void<a href="qapplication.html#h0"><strong>setDoubleClickInterval</strong></a>(int)</span>
<li><span class="fn">int<a href="qapplication.html#h1"><strong>doubleClickInterval</strong></a>()</span>
</ul>
<h2>Related Functions</h2>
(Note that these are not member functions.)
<ul>
<li>void <a href="qapplication.html#h3"><strong>qAddPostRoutine</strong></a> (CleanUpFunction p)
<li>Q_EXPORT const char * <a href="qapplication.html#j2"><strong>qVersion</strong></a> ()
<li>Q_EXPORT bool <a href="qapplication.html#j3"><strong>qSysInfo</strong></a> (int * wordSize, bool * bigEndian)
<li>Q_EXPORT void <a href="qapplication.html#j4"><strong>debug</strong></a> (const char * msg, ...)
<li>Q_EXPORT void <a href="qapplication.html#j5"><strong>warning</strong></a> (const char * msg, ...)
<li>Q_EXPORT void <a href="qapplication.html#j6"><strong>fatal</strong></a> (const char * msg, ...)
<li>void <a href="qapplication.html#j7"><strong>ASSERT</strong></a> (bool test)
<li>void <a href="qapplication.html#j8"><strong>CHECK_PTR</strong></a> (void * p)
<li>Q_EXPORT msg_handler <a href="qapplication.html#j9"><strong>qInstallMsgHandler</strong></a> (msg_handler h)
</ul>
<hr><h2><a name="details"></a>Detailed Description</h2>
The QApplication class manages the application event queue.
<p>
The QApplication class is central to Qt. It receives events from
the underlying window system and sends them to the destination widgets.
An application object must be created before any widgets can be created!
<p>Only one single QApplication object should be created. In fact Qt
complains if you create more than one, and this is normally done
in the main() function. Once a QApplication object has been
created, <code>qApp</code> (defined as <code>extern QApplication *qApp</code>)
refers to this object.
<p>Example (a complete Qt application):
<pre> #include <qapplication.h> // defines QApplication
#include <qpushbutton.h> // defines QPushButton
int main( int argc, char **argv )
{
<a href="qapplication.html">QApplication</a> app( argc, argv ); // create application object
<a href="qpushbutton.html">QPushButton</a> hello( "Hello, world!" ); // create a push button
app.<a href="qapplication.html#b9">setMainWidget</a>( &hello ); // define as main widget
connect( &hello, SIGNAL(clicked()), // clicking the button
&app, SLOT(quit()) ); // quits the application
hello.<a href="qwidget.html#k2">show</a>(); // show button
return app.<a href="qapplication.html#c9">exec</a>(); // run main event loop
}
</pre>
<p><strong>Important</strong><br> Notice that the QApplication object must
be created before any window-system functionality of Qt is used, this
includes widgets, colors, fonts etc.
<p>Note also that for X11, <a href="qapplication.html#b9">setMainWidget</a>() may change the main widget
according to the <em>-geometry</em> option. To preserve this functionality,
you must set your defaults before setMainWidget() and any overrides
after.
<p>While Qt is not optimized or designed for writing non-GUI programs,
it's possible to use <a href="tools.html">some of its classes</a>
without creating a QApplication. This can be very useful if you
wish to share code between a non-GUI server and a GUI client.
<p>Examples:
<a href="forever-forever-cpp.html#QApplication">forever/forever.cpp</a>
<a href="desktop-desktop-cpp.html#QApplication">desktop/desktop.cpp</a>
<a href="connect-connect-cpp.html#QApplication">connect/connect.cpp</a>
<a href="drawdemo-drawdemo-cpp.html#QApplication">drawdemo/drawdemo.cpp</a>
<a href="movies-main-cpp.html#QApplication">movies/main.cpp</a>
<a href="picture-picture-cpp.html#QApplication">picture/picture.cpp</a>
<a href="xform-xform-cpp.html#QApplication">xform/xform.cpp</a>
<a href="menu-menu-cpp.html#QApplication">menu/menu.cpp</a>
<a href="progress-progress-cpp.html#QApplication">progress/progress.cpp</a>
<a href="cursor-cursor-cpp.html#QApplication">cursor/cursor.cpp</a>
<a href="layout-layout-cpp.html#QApplication">layout/layout.cpp</a>
<a href="qmag-qmag-cpp.html#QApplication">qmag/qmag.cpp</a>
<a href="widgets-widgets-cpp.html#QApplication">widgets/widgets.cpp</a>
<hr><h2>Member Function Documentation</h2>
<h3 class="fn"><a name="a0"></a>QApplication::QApplication(int&argc, char**argv)</h3>
<p>Initializes the window system and onstructs an application object
with the command line arguments <em>argc</em> and <em>argv.</em>
<p>The global <code>qApp</code> pointer refers to this application object. Only
one application object should be created.
<p>This application object must be constructed before any <a href="qpaintdevice.html">paint devices</a> (includes widgets, pixmaps, bitmaps
etc.)
<p>Notice that <em>argc</em> and <em>argv</em> might be changed. Qt removes
command line arguments that it recognizes. <em>argc</em> and <em>argv</em> are
can be accessed later by <code>qApp-><a href="qapplication.html#a2">argc</a>()</code> and <code>qApp-><a href="qapplication.html#a3">argv</a>().</code> The
documentation for argv() contains a detailed description of how to
process command line arguments.
<p>Qt debugging options:
<ul>
<li> <code>-nograb,</code> tells Qt to never grab the mouse or the keyboard.
<li> <code>-sync</code> (only under X11), switches to synchronous mode for
debugging.
</ul>
<p>See <a href="debug.html">Debugging Techniques</a> for a more
detailed explanation.
<p>The X11 version of Qt supports a few more command line options:
<ul>
<li> <code>-display</code> <em>display,</em> sets the X display (default is $DISPLAY).
<li> <code>-geometry</code> <em>geometry,</em> sets the client geometry of the
<a href="qapplication.html#b9">main widget</a>.
<li> <code>-fn</code> or <code>-font</code> <em>font,</em> defines the application font.
<li> <code>-bg</code> or <code>-background</code> <em>color,</em> sets the default background color
and an application palette (light and dark shades are calculated).
<li> <code>-fg</code> or <code>-foreground</code> <em>color,</em> sets the default foreground color.
<li> <code>-name</code> <em>name,</em> sets the application name.
<li> <code>-title</code> <em>title,</em> sets the application title (caption).
<li> <code>-style=</code> <em>style,</em> sets the application GUI style. Possible values
are <code>motif</code> and <code>windows</code>
<li> <code>-visual TrueColor,</code> forces the application to use a TrueColor visual
on an 8-bit display.
<li> <code>-ncols</code> <em>count,</em> limits the number of colors allocated in the
color cube on a 8-bit display, if the application is using the
<code>QApplication::ManyColor</code> color specification. If <em>count</em> is
216 then a 6x6x6 color cube is used (ie. 6 levels of red, 6 of green,
and 6 of blue); for other values, a cube
approximately proportional to a 2x3x1 cube is used.
<li> <code>-cmap,</code> causes the application to install a private color map
on an 8-bit display.
</ul>
<p>See also: <a href="qapplication.html#a2">argc</a>() and <a href="qapplication.html#a3">argv</a>().
<h3 class="fn"><a name="a1"></a>QApplication::~QApplication() <code>[virtual]</code></h3>
<p>Deletes all remaining widgets and cleans up any window system
resources that were allocated by this application. Sets the global
variable <code>qApp</code> to null.
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="j0"></a>QApplication::activeModalWidget() <code>[static]</code></h3>
<p>Returns the active modal widget.
<p>A modal widget is a special top level widget which is a subclass of
<a href="qdialog.html">QDialog</a> that specifies the modal parameter of the constructor to TRUE.
A modal widget must be finished before the user can continue with other
parts of the program.
<p>The modal widgets are organized in a stack.
This function returns the active modal widget on top of the stack.
<p>See also: currentPopupWidget() and <a href="qapplication.html#g1">topLevelWidgets</a>().
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="i9"></a>QApplication::activePopupWidget() <code>[static]</code></h3>
<p>Returns the active popup widget.
<p>A popup widget is a special top level widget that sets the WType_Popup
widget flag, e.g. the <a href="qpopupmenu.html">QPopupMenu</a> widget. When the application opens a
popup widget, all events are sent to the popup and normal widgets and
modal widgets cannot be accessed before the popup widget is closed.
<p>Only other popup widgets may be opened when a popup widget is shown.
The popup widgets are organized in a stack.
This function returns the active popup widget on top of the stack.
<p>See also: currentModalWidget() and <a href="qapplication.html#g1">topLevelWidgets</a>().
<h3 class="fn">QWidgetList*<a name="g2"></a>QApplication::allWidgets() <code>[static]</code></h3>
<p>Returns a list of all the widgets in the application.
<p>The list is created using new and must be deleted by the caller.
<p>The list is <a href="qlist.html#a5">empty</a> if there are no
widgets.
<p>Note that some of the widgets may be hidden.
<p>Example:
<pre> //
// Updates all widgets.
//
QWidgetList *list = QApplication::allWidgets();
QWidgetListIt it( *list ); // iterate over the widgets
while ( it.current() ) { // for each top level widget...
it.current()->update();
++it;
}
delete list; // delete the list, not the widgets
</pre>
<p>The QWidgetList class is defined in the qwidcoll.h header file.<p><strong>Warning:</strong> Delete the list away as soon you have finished using it.
You can get in serious trouble if you for instance try to access
a widget that has been deleted.
<p>See also: <a href="qapplication.html#g1">topLevelWidgets</a>(), <a href="qwidget.html#k6">QWidget::isVisible</a>() and <a href="qlist.html#a5">QList::isEmpty</a>(),.
<h3 class="fn">int<a name="a2"></a>QApplication::argc()const</h3>
<p>Returns the number of command line arguments.
<p>The documentation for <a href="qapplication.html#a3">argv</a>() contains a detailed description of how to
process command line arguments.
<p>See also: <a href="qapplication.html#a3">argv</a>() and <a href="qapplication.html#a0">QApplication::QApplication</a>().
<h3 class="fn">char**<a name="a3"></a>QApplication::argv()const</h3>
<p>Returns the command line argument vector.
<p><code>argv()[0]</code> is the program name, <code>argv()[1]</code> is the first argument and
<code>argv()[<a href="qapplication.html#a2">argc</a>()-1]</code> is the last argument.
<p>A QApplication object is constructed by passing <em>argc</em> and <em>argv</em> from
the <code>main()</code> function. Some of the arguments may be recognized as Qt
options removed from the argument vector. For example, the X11
version of Qt knows about <code>-display, -font</code> and a few more options.
<p>Example:
<pre> // showargs.cpp - displays program arguments in a list box
#include <qapplication.h>
#include <qlistbox.h>
int main( int argc, char **argv )
{
<a href="qapplication.html">QApplication</a> a( argc, argv );
<a href="qlistbox.html">QListBox</a> b;
a.<a href="qapplication.html#b9">setMainWidget</a>( &b );
for ( int i=0; i<a.<a href="qapplication.html#a2">argc</a>(); i++ ) // a.<a href="qapplication.html#a2">argc</a>() == argc
b.<a href="qlistbox.html#a6">insertItem</a>( a.<a href="qapplication.html#a3">argv</a>()[i] ); // a.<a href="qapplication.html#a3">argv</a>()[i] == argv[i]
b.<a href="qtableview.html#a2">show</a>();
return a.<a href="qapplication.html#c9">exec</a>();
}
</pre>
<p>If you run <tt>showargs -display unix:0 -font 9x15bold hello
world</tt> under X11, the list box contains the three strings
"showargs", "hello" and "world".
<p>See also: <a href="qapplication.html#a2">argc</a>() and <a href="qapplication.html#a0">QApplication::QApplication</a>().
<h3 class="fn">void<a name="i4"></a>QApplication::beep() <code>[static]</code></h3>
<p>Sounds the bell, using the default volume and sound.
<h3 class="fn"><a href="qclipboard.html">QClipboard</a>*<a name="j1"></a>QApplication::clipboard() <code>[static]</code></h3>
<p>Returns a pointer to the application global clipboard.
<h3 class="fn">bool<a name="g7"></a>QApplication::closingDown() <code>[static]</code></h3>
<p>Returns TRUE if the application objects are being destroyed.
<p>See also: <a href="qapplication.html#g6">startingUp</a>().
<h3 class="fn">int<a name="f5"></a>QApplication::colorSpec() <code>[static]</code></h3>
<p>Returns the color specification.
<p>See also: <a href="qapplication.html#f6">QApplication::setColorSpec</a>().
<p>Examples:
<a href="showimg-showimg-cpp.html#QApplication::colorSpec">showimg/showimg.cpp</a>
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="h4"></a>QApplication::desktop() <code>[static]</code></h3>
<p>Returns the desktop widget (also called the root window).
<p>The desktop widget is useful for obtaining the size of the screen.
It can also be used to draw on the desktop.
<p><pre> <a href="qwidget.html">QWidget</a> *d = QApplication::desktop();
int w=d-><a href="qwidget.html#b9">width</a>(); // returns screen width
int h=d-><a href="qwidget.html#c0">height</a>(); // returns screen height
d-><a href="qwidget.html#f2">setBackgroundColor</a>( red ); // makes desktop red
</pre>
<p>Examples:
<a href="qmag-qmag-cpp.html#QApplication::desktop">qmag/qmag.cpp</a>
<h3 class="fn">int<a name="h1"></a>QApplication::doubleClickInterval() <code>[static]</code></h3>
<p>Returns the maximum duration for a double click.
<p>See also: <a href="qapplication.html#h0">setDoubleClickInterval</a>().
<h3 class="fn">int<a name="d3"></a>QApplication::enter_loop()</h3>
<p>This function enters the main event loop (recursively).
Do not call it unless you are an expert.
<p>See also: <a href="qapplication.html#d4">exit_loop</a>().
<h3 class="fn">int<a name="c9"></a>QApplication::exec()</h3>
<p>Enters the main event loop and waits until <a href="qapplication.html#g4">exit</a>() is called or
the <a href="qapplication.html#b9">main widget</a> is destroyed.
Returns the value that was specified to exit(), which is 0 if
exit() is called via <a href="qapplication.html#f0">quit</a>().
<p>It is necessary to call this function to start event handling.
The main event loop receives <a href="qwidget.html#n3">events</a> from
the window system and dispatches these to the application widgets.
<p>Generally, no user interaction can take place before calling exec().
As a special case, modal widgets like <a href="qmessagebox.html">QMessageBox</a> can be used before
calling exec(), because modal widget have a local event loop.
<p>To make your application perform idle processing, i.e. executing a
special function whenever there are no pending events, use a <a href="qtimer.html">QTimer</a>
with 0 timeout. More advanced idle processing schemes can be
achieved by using <a href="qapplication.html#d0">processEvents</a>() and <a href="qapplication.html#d2">processOneEvent</a>().
<p>See also: <a href="qapplication.html#f0">quit</a>(), <a href="qapplication.html#g4">exit</a>(), <a href="qapplication.html#d0">processEvents</a>(), <a href="qapplication.html#b9">setMainWidget</a>() and <a href="qtimer.html">QTimer</a>.
<p>Examples:
<a href="forever-forever-cpp.html#exec">forever/forever.cpp</a>
<a href="connect-connect-cpp.html#exec">connect/connect.cpp</a>
<a href="mainlyQt-editor-cpp.html#exec">mainlyQt/editor.cpp</a>
<a href="drawdemo-drawdemo-cpp.html#exec">drawdemo/drawdemo.cpp</a>
<a href="movies-main-cpp.html#exec">movies/main.cpp</a>
<a href="picture-picture-cpp.html#exec">picture/picture.cpp</a>
<a href="xform-xform-cpp.html#exec">xform/xform.cpp</a>
<a href="menu-menu-cpp.html#exec">menu/menu.cpp</a>
<a href="progress-progress-cpp.html#exec">progress/progress.cpp</a>
<a href="cursor-cursor-cpp.html#exec">cursor/cursor.cpp</a>
<a href="layout-layout-cpp.html#exec">layout/layout.cpp</a>
<a href="qmag-qmag-cpp.html#exec">qmag/qmag.cpp</a>
<a href="widgets-widgets-cpp.html#exec">widgets/widgets.cpp</a>
<h3 class="fn">void<a name="g4"></a>QApplication::exit(intretcode=0) <code>[static]</code></h3>
<p>Tells the application to exit with a return code.
<p>After this function has been called, the application leaves the main
event loop and returns from the call to <a href="qapplication.html#c9">exec</a>(). The exec() function
returns <em>retcode.</em>
<p>By convention, <em>retcode</em> 0 means success, any non-zero value indicates
an error.
<p>Note that unlike the C library exit function, this function <em>does</em>
returns to the caller - it is event processing that stops.
<p>See also: <a href="qapplication.html#f0">quit</a>() and <a href="qapplication.html#c9">exec</a>().
<p>Examples:
<a href="picture-picture-cpp.html#QApplication::exit">picture/picture.cpp</a>
<h3 class="fn">void<a name="d4"></a>QApplication::exit_loop()</h3>
<p>This function leaves from a recursive call to the main event loop.
Do not call it unless you are an expert.
<p>See also: <a href="qapplication.html#d3">enter_loop</a>().
<h3 class="fn">void<a name="i2"></a>QApplication::flushX() <code>[static]</code></h3>
<p>Flushes the X event queue in the X11 implementation.
Does nothing on other platforms.
<p>See also: <a href="qapplication.html#i3">syncX</a>().
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="c6"></a>QApplication::focusWidget()const</h3>
<p>Returns the application widget that has the keyboard input focus, or null
if no application widget has the focus.
<p>See also: <a href="qwidget.html#i2">QWidget::setFocus</a>() and <a href="qwidget.html#i1">QWidget::hasFocus</a>().
<h3 class="fn"><a href="qfont.html">QFont</a>*<a name="f9"></a>QApplication::font() <code>[static]</code></h3>
<p>Returns the default application font. There is always an application
font, i.e. the returned pointer is guaranteed to be non-null.
<p>See also: <a href="qapplication.html#g0">setFont</a>(), <a href="qapplication.html#g3">fontMetrics</a>() and <a href="qwidget.html#f8">QWidget::font</a>().
<h3 class="fn"><a href="qfontmetrics.html">QFontMetrics</a><a name="g3"></a>QApplication::fontMetrics() <code>[static]</code></h3>
<p>Returns display (screen) font metrics for the application font.
<p>See also: <a href="qapplication.html#f9">font</a>(), <a href="qapplication.html#g0">setFont</a>(), <a href="qwidget.html#g0">QWidget::fontMetrics</a>() and <a href="qpainter.html#b9">QPainter::fontMetrics</a>().
<h3 class="fn">bool<a name="h8"></a>QApplication::hasGlobalMouseTracking() <code>[static]</code></h3>
<p>Returns TRUE if global mouse tracking is enabled, otherwise FALSE.
<p>See also: <a href="qapplication.html#h9">setGlobalMouseTracking</a>().
<h3 class="fn">void<a name="e9"></a>QApplication::lastWindowClosed() <code>[signal]</code></h3>
<p>This signal is emitted when the user has closed a top level widget
and there are no more visible top level widgets left.
<p>The signal is very useful when your application has many top level
widgets but no main widget. You can then connect it to the <a href="qapplication.html#f0">quit</a>() slot.
<p>See also: <a href="qapplication.html#b8">mainWidget</a>(), <a href="qapplication.html#g1">topLevelWidgets</a>() and <a href="qwidget.html#a5">QWidget::isTopLevel</a>().
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="b8"></a>QApplication::mainWidget()const</h3>
<p>Returns the main application widget, or 0 if there is not a defined
main widget.
<p>See also: <a href="qapplication.html#b9">setMainWidget</a>().
<h3 class="fn">bool<a name="d9"></a>QApplication::notify(<a href="qobject.html">QObject</a>*receiver, <a href="qevent.html">QEvent</a>*event) <code>[virtual]</code></h3>
<p>Sends <em>event</em> to <em>receiver:</em> <code>receiver-><a href="qobject.html#a2">event</a>( event )</code>
Returns the value that is returned from the receiver's event handler.
<p>Reimplementing this virtual function is one of five ways to process
an event: <ol> <li> Reimplementing this function. Very powerful,
you get <em>complete</em> control, but of course only one subclass can be
qApp.
<p><li> Installing an event filter on qApp. Such an event filter gets
to process all events for all widgets, so it's just as powerful as
reimplementing notify(), and in this way it's possible to have more
than one application-global event filter. Global event filter get
to see even mouse events for <a href="qwidget.html#a9">disabled
widgets,</a> and if <a href="qapplication.html#h9">global mouse
tracking</a> is enabled, mouse move events for all widgets.
<p><li> Reimplementing <a href="qobject.html#a2">QObject::event</a>() (as <a href="qwidget.html">QWidget</a> does). If you do
this you get tab key-presses, and you get to see the events before
any widget-specific event filters.
<p><li> Installing an event filter on the object. Such an even filter
gets all the events except Tab and Shift-Tab key presses.
<p><li> Finally, reimplementing paintEvent(), mousePressEvent() and so
on. This is the normal, easist and least powerful way. </ol>
<p>See also: <a href="qobject.html#a2">QObject::event</a>() and <a href="qobject.html#c3">installEventFilter</a>().
<h3 class="fn"><a href="qcursor.html">QCursor</a>*<a name="h5"></a>QApplication::overrideCursor() <code>[static]</code></h3>
<p>Returns the active application override cursor.
<p>This function returns 0 if no application cursor has been defined (i.e. the
internal cursor stack is empty).
<p>See also: <a href="qapplication.html#h6">setOverrideCursor</a>() and <a href="qapplication.html#h7">restoreOverrideCursor</a>().
<h3 class="fn"><a href="qpalette.html">QPalette</a>*<a name="f7"></a>QApplication::palette() <code>[static]</code></h3>
<p>Returns a pointer to the default application palette. There is
always an application palette, i.e. the returned pointer is
guaranteed to be non-null.
<p>See also: <a href="qapplication.html#f8">setPalette</a>() and <a href="qwidget.html#f6">QWidget::palette</a>().
<h3 class="fn">void<a name="i5"></a>QApplication::postEvent(<a href="qobject.html">QObject</a>*receiver, <a href="qevent.html">QEvent</a>*event) <code>[static]</code></h3>
<p>Stores the event in a queue and returns immediatly.
<p>The event must be allocated on the heap, as it is deleted when the event
has been posted.
<p>When control returns to the main event loop, all events that are
stored in the queue will be sent using the <a href="qapplication.html#d9">notify</a>() function.
<p>See also: <a href="qapplication.html#g5">sendEvent</a>().
<h3 class="fn">void<a name="d0"></a>QApplication::processEvents()</h3>
<p>Processes pending events, for 3 seconds or until there
are no more events to process, then return.
<p>You can call this function occasionally when your program is busy doing a
long operation (e.g. copying a file).
<p>See also: processEvents(), <a href="qapplication.html#c9">exec</a>() and <a href="qtimer.html">QTimer</a>.
<h3 class="fn">void<a name="d1"></a>QApplication::processEvents(intmaxtime)</h3>
<p>Processes pending events, for <em>maxtime</em> milliseconds or until there
are no more events to process, then return.
<p>You can call this function occasionally when you program is busy doing a
long operation (e.g. copying a file).
<p>See also: <a href="qapplication.html#d2">processOneEvent</a>(), <a href="qapplication.html#c9">exec</a>() and <a href="qtimer.html">QTimer</a>.
<h3 class="fn">void<a name="d2"></a>QApplication::processOneEvent()</h3>
<p>Waits for an event to occur, processes it, then returns.
<p>This function is useful for adapting Qt to situations where the event
processing must be grafted into existing program loops. Beware
that using this function in new applications may be an indication
of design problems.
<p>See also: <a href="qapplication.html#d0">processEvents</a>(), <a href="qapplication.html#c9">exec</a>() and <a href="qtimer.html">QTimer</a>.
<h3 class="fn">void<a name="f0"></a>QApplication::quit() <code>[slot]</code></h3>
<p>Tells the application to exit with return code 0 (success).
Equivalent to calling <a href="qapplication.html#g4">QApplication::exit</a>( 0 ).
<p>This function is a <a href="metaobjects.html">slot</a>, i.e. you
may connect any signal to activate quit().
<p>Example:
<pre> <a href="qpushbutton.html">QPushButton</a> *quitButton = new <a href="qpushbutton.html">QPushButton</a>( "Quit" );
connect( quitButton, SIGNAL(clicked()), qApp, SLOT(quit()) );
</pre>
<p>See also: <a href="qapplication.html#g4">exit</a>().
<h3 class="fn">void<a name="h7"></a>QApplication::restoreOverrideCursor() <code>[static]</code></h3>
<p>Restores the effect of <a href="qapplication.html#h6">setOverrideCursor</a>().
<p>If setOverrideCursor() has been called twice, calling
restoreOverrideCursor() will activate the first cursor set. Calling
this function a second time restores the original widgets cursors.
<p>Application cursors are stored on an internal stack. setOverrideCursor()
pushes the cursor onto the stack, and restoreOverrideCursor() pops the
active cursor off the stack. Every setOverrideCursor() must have an
corresponding restoreOverrideCursor(), otherwise the stack will get out
of sync. <a href="qapplication.html#h5">overrideCursor</a>() returns 0 if the cursor stack is empty.
<p>See also: <a href="qapplication.html#h6">setOverrideCursor</a>() and <a href="qapplication.html#h5">overrideCursor</a>().
<p>Examples:
<a href="showimg-showimg-cpp.html#QApplication::restoreOverrideCursor">showimg/showimg.cpp</a>
<h3 class="fn">bool<a name="g5"></a>QApplication::sendEvent(<a href="qobject.html">QObject</a>*receiver, <a href="qevent.html">QEvent</a>*event) <code>[static]</code></h3>
<p>Sends an event directly to a receiver, using the <a href="qapplication.html#d9">notify</a>() function.
Returns the value that was returned from the event handler.
<p>See also: <a href="qapplication.html#i5">postEvent</a>() and <a href="qapplication.html#d9">notify</a>().
<h3 class="fn">void<a name="i6"></a>QApplication::sendPostedEvents(<a href="qobject.html">QObject</a>*receiver, intevent_type) <code>[static]</code></h3>
<p>Immediately dispatches all events which have been previously enqueued
with <a href="qapplication.html#i5">QApplication::postEvent</a>() and which are for the object <em>receiver</em>
and have the <em>event_type.</em>
<p>Some event compression may occur. Note that events from the
window system are <em>not</em> dispatched by this function.
<h3 class="fn">void<a name="f6"></a>QApplication::setColorSpec(intspec) <code>[static]</code></h3>
<p>Sets the color specification for the application to <em>spec.</em>
<p>The color specification controls how your application allocates
colors. You must set the color specification before you create the
QApplication object.
<p>The choices are:
<ul>
<li> <code>QApplication::NormalColor.</code>
This is the default color allocation strategy.
Use this choice if your application uses buttons, menus,
texts and pixmaps with few colors.
With this choice, the application allocates system global colors.
This work fine for most applications under X11, but Windows dithers to
the 20 standard colors unless the display has true color support (more
than 256 colors).
<p><li> <code>QApplication::CustomColor.</code>
Use this choice if your application needs a small number of
custom colors. This choice only makes a difference on Windows
- the application gets more colors when it is active, but the
background windows look less good.
Under X11 this is the same as <code>NormalColor.</code> Under Windows, Qt creates a Windows palette if the display
supports 256 colors.
<p><li> <code>QApplication::ManyColor.</code>
Use this choice if your application is very color hungry
(e.g. it wants thousands of colors).
Under Windows, this is equal to <code>CustomColor.</code>
Under X11 the effect is:
<ul>
<li> For 256-color displays which have at best a 256 color true color
visual, the default visual is used, and a colors are allocated
from a color cube.
The color cube is the 6x6x6 (216 color) "Web palette", but the
number of colors can be changed by the <em>-ncols</em> option.
The user can force the application to use the true color visual by
the <a href="qapplication.html#a0">-visual</a>
option.
<li> For 256-color displays which have a true color visual with more
than 256 colors, use that visual. Silicon Graphics X servers
have this feature. They provide an 8 bit visual as default but
can deliver true color when asked.
</ul>
</ul>
<p>Example:
<pre> int main( int argc, char **argv )
{
<a href="qapplication.html#f6">QApplication::setColorSpec</a>( QApplication::ManyColor );
<a href="qapplication.html">QApplication</a> a( argc, argv );
...
}
</pre>
<p><a href="qcolor.html">QColor</a> provides more functionality for controlling color allocation and
freeing up certains colors. See <a href="qcolor.html#f2">QColor::enterAllocContext</a>() for more
information.
<p>To see what mode you end up with, you can call <a href="qcolor.html#e9">QColor::numBitPlanes</a>()
once the QApplication object exists. A value greater than 8 (typically
16, 24 or 32) means true color.
<p>The color cube used by Qt are all those colors with red, green, and blue
components of either 0x00, 0x33, 0x66, 0x99, 0xCC, or 0xFF.
<p>See also: <a href="qapplication.html#f5">colorSpec</a>(), <a href="qcolor.html#e9">QColor::numBitPlanes</a>() and <a href="qcolor.html#f2">QColor::enterAllocContext</a>().
<p>Examples:
<a href="widgets-widgets-cpp.html#QApplication::setColorSpec">widgets/widgets.cpp</a>
<h3 class="fn">void<a name="h0"></a>QApplication::setDoubleClickInterval(intms) <code>[static]</code></h3>
<p>Sets the time limit that distinguishes a double click from two
consecutive mouse clicks to <em>ms</em> milliseconds. This value is
ignored under Windows (the control panel value is used.)
<p>The default value is 400 milliseconds.
<p>See also: <a href="qapplication.html#h1">doubleClickInterval</a>().
<h3 class="fn">void<a name="g0"></a>QApplication::setFont(const<a href="qfont.html">QFont</a>&font, boolupdateAllWidgets=FALSE) <code>[static]</code></h3>
<p>Changes the default application font to <em>font.</em>
<p>The default font depends on the X server in use.
<p>If <em>updateAllWidgets</em> is TRUE, then the font of all existing
widgets is set to <em>font.</em>
<p>Widgets created after this call get <em>font</em> as their <a href="qwidget.html#f8">font</a>.
<p>See also: <a href="qapplication.html#f9">font</a>(), <a href="qapplication.html#g3">fontMetrics</a>() and <a href="qwidget.html#f9">QWidget::setFont</a>().
<p>Examples:
<a href="desktop-desktop-cpp.html#setFont">desktop/desktop.cpp</a>
<a href="movies-main-cpp.html#QApplication::setFont">movies/main.cpp</a>
<h3 class="fn">void<a name="h9"></a>QApplication::setGlobalMouseTracking(boolenable) <code>[static]</code></h3>
<p>Enables global mouse tracking if <em>enable</em> is TRUE or disables it
if <em>enable</em> is FALSE.
<p>Enabling global mouse tracking makes it possible for widget event
filters or application event filters to get all mouse move events, even
when no button is depressed. This is useful for special GUI elements,
e.g. tool tips.
<p>Global mouse tracking does not affect widgets and their
mouseMoveEvent(). For a widget to get mouse move events when no button
is depressed, it must do <a href="qwidget.html#h5">QWidget::setMouseTracking</a>(TRUE).
<p>This function has an internal counter. Each
setGlobalMouseTracking(TRUE) must have a corresponding
setGlobalMouseTracking(FALSE).
<p>See also: <a href="qapplication.html#h8">hasGlobalMouseTracking</a>() and <a href="qwidget.html#h1">QWidget::hasMouseTracking</a>().
<h3 class="fn">void<a name="b9"></a>QApplication::setMainWidget(<a href="qwidget.html">QWidget</a>*mainWidget)</h3>
<p>Sets the main widget of the application.
<p>The special thing about the main widget is that destroying the main
widget (i.e. the program calls <a href="qwidget.html#k5">QWidget::close</a>() or the user
double-clicks the window close box) will leave the main event loop and
<a href="qapplication.html#f0">exit the application</a>.
<p>For X11, this function also resizes and moves the main widget
according to the <em>-geometry</em> command-line option, so you should
<a href="qwidget.html#l5">set the default geometry</a> before
calling setMainWidget().
<p>See also: <a href="qapplication.html#b8">mainWidget</a>(), <a href="qapplication.html#c9">exec</a>() and <a href="qapplication.html#f0">quit</a>().
<p>Examples:
<a href="forever-forever-cpp.html#setMainWidget">forever/forever.cpp</a>
<a href="connect-connect-cpp.html#setMainWidget">connect/connect.cpp</a>
<a href="mainlyQt-editor-cpp.html#setMainWidget">mainlyQt/editor.cpp</a>
<a href="drawdemo-drawdemo-cpp.html#setMainWidget">drawdemo/drawdemo.cpp</a>
<a href="picture-picture-cpp.html#setMainWidget">picture/picture.cpp</a>
<a href="xform-xform-cpp.html#setMainWidget">xform/xform.cpp</a>
<a href="menu-menu-cpp.html#setMainWidget">menu/menu.cpp</a>
<a href="progress-progress-cpp.html#setMainWidget">progress/progress.cpp</a>
<a href="cursor-cursor-cpp.html#setMainWidget">cursor/cursor.cpp</a>
<a href="layout-layout-cpp.html#setMainWidget">layout/layout.cpp</a>
<a href="qmag-qmag-cpp.html#setMainWidget">qmag/qmag.cpp</a>
<a href="widgets-widgets-cpp.html#setMainWidget">widgets/widgets.cpp</a>
<h3 class="fn">void<a name="h6"></a>QApplication::setOverrideCursor(const<a href="qcursor.html">QCursor</a>&cursor, boolreplace=FALSE) <code>[static]</code></h3>
<p>Sets the application override cursor to <em>cursor.</em>
<p>Application override cursor are intended for showing the user that the
application is in a special state, for example during an operation that
might take some time.
<p>This cursor will be displayed in all application widgets until
<a href="qapplication.html#h7">restoreOverrideCursor</a>() or another setOverrideCursor() is called.
<p>Application cursors are stored on an internal stack. setOverrideCursor()
pushes the cursor onto the stack, and restoreOverrideCursor() pops the
active cursor off the stack. Every setOverrideCursor() must have an
corresponding restoreOverrideCursor(), otherwise the stack will get out
of sync. <a href="qapplication.html#h5">overrideCursor</a>() returns 0 if the cursor stack is empty.
<p>If <em>replace</em> is TRUE, the new cursor will replace the last override
cursor.
<p>Example:
<pre> <a href="qapplication.html#h6">QApplication::setOverrideCursor</a>( waitCursor );
calculateHugeMandelbrot(); // lunch time...
<a href="qapplication.html#h7">QApplication::restoreOverrideCursor</a>();
</pre>
<p>See also: <a href="qapplication.html#h5">overrideCursor</a>(), <a href="qapplication.html#h7">restoreOverrideCursor</a>() and <a href="qwidget.html#g7">QWidget::setCursor</a>().
<p>Examples:
<a href="showimg-showimg-cpp.html#QApplication::setOverrideCursor">showimg/showimg.cpp</a>
<h3 class="fn">void<a name="f8"></a>QApplication::setPalette(const<a href="qpalette.html">QPalette</a>&palette, boolupdateAllWidgets=FALSE) <code>[static]</code></h3>
<p>Changes the default application palette to <em>palette.</em>
<p>If <em>updateAllWidgets</em> is TRUE, then the palette of all existing
widgets is set to <em>palette.</em>
<p>Widgets created after this call get <em>palette</em> as their <a href="qwidget.html#f6">palette</a>.
<p>See also: <a href="qwidget.html#f7">QWidget::setPalette</a>() and <a href="qapplication.html#f7">palette</a>().
<p>Examples:
<a href="xform-xform-cpp.html#setPalette">xform/xform.cpp</a>
<h3 class="fn">void<a name="f4"></a>QApplication::setStyle(GUIStylestyle) <code>[static]</code></h3>
<p>Sets the application GUI style to <em>style.</em>
<p>The style parameter can be <code>WindowsStyle</code> or <code>MotifStyle.</code>
<p>See also: <a href="qapplication.html#f3">style</a>() and <a href="qwidget.html#a4">QWidget::setStyle</a>().
<h3 class="fn">void<a name="g8"></a>QApplication::setWinStyleHighlightColor(const<a href="qcolor.html">QColor</a>&c) <code>[static]</code></h3>
<p>Sets the color used to mark selections in windows style for all widgets
in the application. Will repaint all widgets if the color is changed.
<p>The default color is <code>darkBlue.</code>
<p>See also: <a href="qapplication.html#g9">winStyleHighlightColor</a>().
<p>Examples:
<a href="widgets-widgets-cpp.html#QApplication::setWinStyleHighlightColor">widgets/widgets.cpp</a>
<h3 class="fn">bool<a name="g6"></a>QApplication::startingUp() <code>[static]</code></h3>
<p>Returns TRUE if an application object has not been created yet.
<p>See also: <a href="qapplication.html#g7">closingDown</a>().
<h3 class="fn">GUIStyle<a name="f3"></a>QApplication::style() <code>[static]</code></h3>
<p>Returns the GUI style of the application.
<p>See also: <a href="qapplication.html#f4">setStyle</a>().
<h3 class="fn">void<a name="i3"></a>QApplication::syncX() <code>[static]</code></h3>
<p>Synchronizes with the X server in the X11 implementation.
Does nothing on other platforms.
<p>See also: <a href="qapplication.html#i2">flushX</a>().
<h3 class="fn">QWidgetList*<a name="g1"></a>QApplication::topLevelWidgets() <code>[static]</code></h3>
<p>Returns a list of the top level widgets in the application.
<p>The list is created using new and must be deleted by the caller.
<p>The list is <a href="qlist.html#a5">empty</a> if there are no
top level widgets.
<p>Note that some of the top level widgets may be hidden.
<p>Example:
<pre> //
// Shows all hidden top level widgets.
//
QWidgetList *list = QApplication::topLevelWidgets();
QWidgetListIt it( *list ); // iterate over the widgets
while ( it.current() ) { // for each top level widget...
if ( !it.current()->isVisible() )
it.current()->show();
++it;
}
delete list; // delete the list, not the widgets
</pre>
<p>The QWidgetList class is defined in the qwidcoll.h header file.<p><strong>Warning:</strong> Delete the list away as soon you have finished using it.
You can get in serious trouble if you for instance try to access
a widget that has been deleted.
<p>See also: <a href="qapplication.html#g2">allWidgets</a>(), <a href="qwidget.html#a5">QWidget::isTopLevel</a>(), <a href="qwidget.html#k6">QWidget::isVisible</a>() and <a href="qlist.html#a5">QList::isEmpty</a>().
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="i0"></a>QApplication::widgetAt(intx, inty, boolchild=FALSE) <code>[static]</code></h3>
<p>Returns a pointer to the widget at global screen position <em>(x,y),</em> or a
null pointer if there is no Qt widget there.
<p>If <em>child</em> is FALSE and there is a child widget at position <em>(x,y),</em>
the top-level widget containing it is returned. If <em>child</em> is TRUE
the child widget at position <em>(x,y)</em> is returned.
<p>See also: <a href="qcursor.html#c2">QCursor::pos</a>(), <a href="qwidget.html#i7">QWidget::grabMouse</a>() and <a href="qwidget.html#j0">QWidget::grabKeyboard</a>().
<h3 class="fn"><a href="qwidget.html">QWidget</a>*<a name="i1"></a>QApplication::widgetAt(const<a href="qpoint.html">QPoint</a>&pos, boolchild=FALSE) <code>[static]</code></h3>
<p>This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
<h3 class="fn">const<a href="qcolor.html">QColor</a>&<a name="g9"></a>QApplication::winStyleHighlightColor() <code>[static]</code></h3>
<p>Returns the color used to mark selections in windows style.
<p>See also: <a href="qapplication.html#g8">setWinStyleHighlightColor</a>().
<hr><h2>Related Functions</h2>
<h3>void <a name="h3"></a>qAddPostRoutine (CleanUpFunction p)</h3>
<p>Adds a global routine that will be called from the QApplication destructor.
This function is normally used to add cleanup routines.
<p>CleanUpFunctions is defined as <code> typedef void
(*CleanUpFunction)(); </code>, i.e. a pointer to a function that
takes no arguments and returns nothing.
<p>Example of use:
<pre> static int *global_ptr = 0;
void cleanup_ptr()
{
delete [] global_ptr;
}
void init_ptr()
{
global_ptr = new int[100]; // allocate data
<a href="qapplication.html#h3">qAddPostRoutine</a>( cleanup_ptr ); // delete later
}
</pre>
<h3>Q_EXPORT const char * <a name="j2"></a>qVersion ()</h3>
<p>Returns the Qt version number for the library, typically "1.30"
or "1.31".
<h3>Q_EXPORT bool <a name="j3"></a>qSysInfo (int * wordSize, bool * bigEndian)</h3>
<p>Obtains information about the system.
<p>The system's word size in bits (typically 32) is returned in <em>*wordSize.</em>
The <em>*bigEndian</em> is set to TRUE if this is a big-endian machine,
or to FALSE if this is a little-endian machine.
<p>This function calls <a href="qapplication.html#j6">fatal</a>() with a message if the computer is truely weird
(i.e. different endianness for 16 bit and 32 bit integers).
<h3>Q_EXPORT void <a name="j4"></a>debug (const char * msg, ...)</h3>
<p>Prints a debug message, or calls the message handler (if it has been
installed).
<p>This function takes a format string and a stack arguments, similar to
the C printf() function.
<p>Example:
<pre> <a href="qapplication.html#j4">debug</a>( "my window handle = %x", myWidget->id() );
</pre>
<p>Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.<p><strong>Warning:</strong> The internal buffer is limited to 512 bytes (including the
0-terminator.
<p>See also: <a href="qapplication.html#j5">warning</a>(), <a href="qapplication.html#j6">fatal</a>(), <a href="qapplication.html#j9">qInstallMsgHandler</a>() and <a href="debug.html">Debugging</a>
<h3>Q_EXPORT void <a name="j5"></a>warning (const char * msg, ...)</h3>
<p>Prints a warning message, or calls the message handler (if it has been
installed).
<p>This function takes a format string and a stack arguments, similar to
the C printf() function.
<p>Example:
<pre> void f( int c )
{
if ( c > 200 )
<a href="qapplication.html#j5">warning</a>( "f: bad argument, c == %d", c );
}
</pre>
<p>Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.<p><strong>Warning:</strong> The internal buffer is limited to 512 bytes (including the
0-terminator.
<p>See also: <a href="qapplication.html#j4">debug</a>(), <a href="qapplication.html#j6">fatal</a>(), <a href="qapplication.html#j9">qInstallMsgHandler</a>() and <a href="debug.html">Debugging</a>
<p>Examples:
<a href="progress-progress-cpp.html#warning">progress/progress.cpp</a>
<h3>Q_EXPORT void <a name="j6"></a>fatal (const char * msg, ...)</h3>
<p>Prints a fatal error message and exits, or calls the message handler (if it
has been installed).
<p>This function takes a format string and a stack arguments, similar to
the C printf() function.
<p>Example:
<pre> int divide( int a, int b )
{
if ( b == 0 ) // program error
<a href="qapplication.html#j6">fatal</a>( "divide: cannot divide by zero" );
return a/b;
}
</pre>
<p>Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.<p><strong>Warning:</strong> The internal buffer is limited to 512 bytes (including the
0-terminator.
<p>See also: <a href="qapplication.html#j4">debug</a>(), <a href="qapplication.html#j5">warning</a>(), <a href="qapplication.html#j9">qInstallMsgHandler</a>() and <a href="debug.html">Debugging</a>
<h3>void <a name="j7"></a>ASSERT (bool test)</h3>
<p>Prints a warning message containing the source code file name and line number
if <em>test</em> is FALSE.
<p>This is really a macro defined in <a href="qglobal-h.html">qglobal.h</a>.
<p>ASSERT is useful for testing required conditions in your program.
<p>Example:
<pre> //
// File: div.cpp
//
#include <qglobal.h>
int divide( int a, int b )
{
ASSERT( b != 0 ); // this is line 9
return a/b;
}
</pre>
<p>If <code>b</code> is zero, the ASSERT statement will output the following message
using the <a href="qapplication.html#j5">warning</a>() function:
<pre> ASSERT: "b == 0" in div.cpp (9)
</pre>
<p>See also: <a href="qapplication.html#j5">warning</a>() and <a href="debug.html">Debugging</a>
<h3>void <a name="j8"></a>CHECK_PTR (void * p)</h3>
<p>If <em>p</em> is null, a fatal messages says that the program ran out of memory
and exits. If <em>p</em> is not null, nothing happens.
<p>This is really a macro defined in <a href="qglobal-h.html">qglobal.h</a>.<p><strong>Warning:</strong> CHECK_PTR only works for the development release of the Qt
library. In the release library, CHECK_PTR will be substituted with
nothing.
<p>Example:
<pre> int *a;
CHECK_PTR( a = new int[80] ); // never do this!
// do this instead:
a = new int[80];
CHECK_PTR( a ); // this is fine
</pre>
<p>See also: <a href="qapplication.html#j6">fatal</a>() and <a href="debug.html">Debugging</a>
<h3>Q_EXPORT msg_handler <a name="j9"></a>qInstallMsgHandler (msg_handler h)</h3>
<p>Installs a Qt message handler. Returns a pointer to the message handler
previously defined.
<p>The message handler is a function that prints out debug messages,
warnings and fatal error messages. The Qt library (debug version)
contains hundreds of warning messages that are printed when internal
errors (usually invalid function arguments) occur. If you implement
your own message handler, you get total control of these messages.
<p>The default message handler prints the message to the standard output
under X11 or to the debugger under Windows. If it is a fatal message,
the application aborts immediately.
<p>Only one message handler can be defined, since this is usually done on
an application-wide basis to control debug output.
<p>To restore the message handler, call <code>qInstallMsgHandler(0).</code>
<p>Example:
<pre> #include <qapplication.h>
#include <stdio.h>
#include <stdlib.h>
void myMessageOutput( QtMsgType type, const char *msg )
{
switch ( type ) {
case QtDebugMsg:
fprintf( stderr, "Debug: %s\n", msg );
break;
case QtWarningMsg:
fprintf( stderr, "Warning: %s\n", msg );
break;
case QtFatalMsg:
fprintf( stderr, "Fatal: %s\n", msg );
abort(); // dump core on purpose
}
}
int main( int argc, char **argv )
{
<a href="qapplication.html#j9">qInstallMsgHandler</a>( myMessageOutput );
<a href="qapplication.html">QApplication</a> a( argc, argv );
...
return a.<a href="qapplication.html#c9">exec</a>();
}
</pre>
<p>See also: <a href="qapplication.html#j4">debug</a>(), <a href="qapplication.html#j5">warning</a>(), <a href="qapplication.html#j6">fatal</a>() and <a href="debug.html">Debugging</a>
<hr><p>
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This file is part of the <a href="index.html">Qt toolkit</a>,
copyright © 1995-99
<a href="troll.html">Troll Tech</a>, all rights reserved.
<p>
It was generated from the following files:
<ul>
<li>qapplication.h: 1998/10/07
<li>qapplication.cpp: 1999/01/25
</ul>
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<table width="100%" cellspacing="0" border="0"><tr>
<td>Copyright 1999 Troll Tech<td><a href="trademarks.html">Trademarks</a>
<td align="right"><div align="right">Qt version 1.45</div>
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