qapplication.3qt

Trolltech公司发布的基于C++图形开发环境

This function enters the main event loop (recursively). Do not call it unless you really know what you are doing.
.SH "QEventLoop * QApplication::eventLoop ()\fC [static]\fR"
Returns the application event loop. This function will return zero if called during and after destroying QApplication.
.PP
To create your own instance of QEventLoop or QEventLoop subclass create it before you create the QApplication object.
.PP
See also QEventLoop.
.PP
Example: distributor/distributor.ui.h.
.SH "int QApplication::exec ()"
Enters the main event loop and waits until exit() is called or the main widget is destroyed, and returns the value that was set to exit() (which is 0 if exit() is called via quit()).
.PP
It is necessary to call this function to start event handling. The main event loop receives events from the window system and dispatches these to the application widgets.
.PP
Generally speaking, no user interaction can take place before calling exec(). As a special case, modal widgets like QMessageBox can be used before calling exec(), because modal widgets call exec() to start a local event loop.
.PP
To make your application perform idle processing, i.e. executing a special function whenever there are no pending events, use a QTimer with 0 timeout. More advanced idle processing schemes can be achieved using processEvents().
.PP
See also quit(), exit(), processEvents(), and setMainWidget().
.PP
Examples:
.)l helpsystem/main.cpp, life/main.cpp, network/archivesearch/main.cpp, network/ftpclient/main.cpp, opengl/main.cpp, t1/main.cpp, and t4/main.cpp.
.SH "void QApplication::exit ( int retcode = 0 )\fC [static]\fR"
Tells the application to exit with a return code.
.PP
After this function has been called, the application leaves the main event loop and returns from the call to exec(). The exec() function returns \fIretcode\fR.
.PP
By convention, a \fIretcode\fR of 0 means success, and any non-zero value indicates an error.
.PP
Note that unlike the C library function of the same name, this function \fIdoes\fR return to the caller -- it is event processing that stops.
.PP
See also quit() and exec().
.PP
Examples:
.)l chart/chartform.cpp, extension/mainform.ui.h, and picture/picture.cpp.
.SH "void QApplication::exit_loop ()"
\fBThis function is obsolete.\fR It is provided to keep old source working. We strongly advise against using it in new code.
.PP
This function exits from a recursive call to the main event loop. Do not call it unless you are an expert.
.SH "void QApplication::flush ()\fC [static]\fR"
Flushes the window system specific event queues.
.PP
If you are doing graphical changes inside a loop that does not return to the event loop on asynchronous window systems like X11 or double buffered window systems like MacOS X, and you want to visualize these changes immediately (e.g. Splash Screens), call this function.
.PP
See also flushX(), sendPostedEvents(), and QPainter::flush().
.SH "void QApplication::flushX ()\fC [static]\fR"
Flushes the X event queue in the X11 implementation. This normally returns almost immediately. Does nothing on other platforms.
.PP
See also syncX().
.PP
Example: xform/xform.cpp.
.SH "QWidget * QApplication::focusWidget () const"
Returns the application widget that has the keyboard input focus, or 0 if no widget in this application has the focus.
.PP
See also QWidget::setFocus(), QWidget::focus, and activeWindow().
.SH "QFont QApplication::font ( const QWidget * w = 0 )\fC [static]\fR"
Returns the default font for the widget \fIw\fR, or the default application font if \fIw\fR is 0.
.PP
See also setFont(), fontMetrics(), and QWidget::font.
.PP
Examples:
.)l qfd/fontdisplayer.cpp, themes/metal.cpp, and themes/themes.cpp.
.SH "QFontMetrics QApplication::fontMetrics ()\fC [static]\fR"
Returns display (screen) font metrics for the application font.
.PP
See also font(), setFont(), QWidget::fontMetrics(), and QPainter::fontMetrics().
.SH "QSize QApplication::globalStrut ()\fC [static]\fR"
Returns the application's global strut.
.PP
The strut is a size object whose dimensions are the minimum that any GUI element that the user can interact with should have. For example no button should be resized to be smaller than the global strut size.
.PP
See also setGlobalStrut().
.SH "void QApplication::guiThreadAwake ()\fC [signal]\fR"
This signal is emitted after the event loop returns from a function that could block.
.PP
See also wakeUpGuiThread().
.SH "bool QApplication::hasGlobalMouseTracking ()\fC [static]\fR"
Returns TRUE if global mouse tracking is enabled; otherwise returns FALSE.
.PP
See also setGlobalMouseTracking().
.SH "bool QApplication::hasPendingEvents ()"
This function returns TRUE if there are pending events; otherwise returns FALSE. Pending events can be either from the window system or posted events using QApplication::postEvent().
.SH "int QApplication::horizontalAlignment ( int align )\fC [static]\fR"
Strips out vertical alignment flags and transforms an alignment \fIalign\fR of AlignAuto into AlignLeft or AlignRight according to the language used. The other horizontal alignment flags are left untouched.
.SH "void QApplication::installTranslator ( QTranslator * mf )"
Adds the message file \fImf\fR to the list of message files to be used for translations.
.PP
Multiple message files can be installed. Translations are searched for in the last installed message file, then the one from last, and so on, back to the first installed message file. The search stops as soon as a matching translation is found.
.PP
See also removeTranslator(), translate(), and QTranslator::load().
.PP
Example: i18n/main.cpp.
.SH "bool QApplication::isEffectEnabled ( Qt::UIEffect effect )\fC [static]\fR"
Returns TRUE if \fIeffect\fR is enabled; otherwise returns FALSE.
.PP
By default, Qt will try to use the desktop settings. Call setDesktopSettingsAware(FALSE) to prevent this.
.PP
Note: All effects are disabled on screens running at less than 16-bit color depth.
.PP
See also setEffectEnabled() and Qt::UIEffect.
.SH "bool QApplication::isSessionRestored () const"
Returns TRUE if the application has been restored from an earlier session; otherwise returns FALSE.
.PP
See also sessionId(), commitData(), and saveState().
.SH "void QApplication::lastWindowClosed ()\fC [signal]\fR"
This signal is emitted when the user has closed the last top level window.
.PP
The signal is very useful when your application has many top level widgets but no main widget. You can then connect it to the quit() slot.
.PP
For convenience, this signal is \fInot\fR emitted for transient top level widgets such as popup menus and dialogs.
.PP
See also mainWidget(), topLevelWidgets(), QWidget::isTopLevel, and QWidget::close().
.PP
Examples:
.)l addressbook/main.cpp, extension/main.cpp, helpviewer/main.cpp, mdi/main.cpp, network/archivesearch/main.cpp, qwerty/main.cpp, and regexptester/main.cpp.
.SH "QStringList QApplication::libraryPaths ()\fC [static]\fR"
Returns a list of paths that the application will search when dynamically loading libraries. The installation directory for plugins is the only entry if no paths have been set. The default installation directory for plugins is \fCINSTALL/plugins\fR, where \fCINSTALL\fR is the directory where Qt was installed. The directory of the application executable (NOT the working directory) is also added to the plugin paths.
.PP
If you want to iterate over the list, you should iterate over a copy, e.g.
.PP
.nf
.br
    QStringList list = app.libraryPaths();
.br
    QStringList::Iterator it = list.begin();
.br
    while( it != list.end() ) {
.br
        myProcessing( *it );
.br
        ++it;
.br
    }
.br
.fi
.PP
See the plugins documentation for a description of how the library paths are used.
.PP
See also setLibraryPaths(), addLibraryPath(), removeLibraryPath(), and QLibrary.
.SH "void QApplication::lock ()"
Lock the Qt Library Mutex. If another thread has already locked the mutex, the calling thread will block until the other thread has unlocked the mutex.
.PP
See also unlock(), locked(), and Thread Support in Qt.
.SH "bool QApplication::locked ()"
Returns TRUE if the Qt Library Mutex is locked by a different thread; otherwise returns FALSE.
.PP
\fBWarning:\fR Due to different implementations of recursive mutexes on the supported platforms, calling this function from the same thread that previously locked the mutex will give undefined results.
.PP
See also lock(), unlock(), and Thread Support in Qt.
.SH "int QApplication::loopLevel () const"
\fBThis function is obsolete.\fR It is provided to keep old source working. We strongly advise against using it in new code.
.PP
Returns the current loop level.
.SH "bool QApplication::macEventFilter ( EventHandlerCallRef, EventRef )\fC [virtual]\fR"
This virtual function is only implemented under Macintosh.
.PP
If you create an application that inherits QApplication and reimplement this function, you get direct access to all Carbon Events that are received from the MacOS.
.PP
Return TRUE if you want to stop the event from being processed. Return FALSE for normal event dispatching.
.SH "QWidget * QApplication::mainWidget () const"
Returns the main application widget, or 0 if there is no main widget.
.PP
See also setMainWidget().
.SH "bool QApplication::notify ( QObject * receiver, QEvent * e )\fC [virtual]\fR"
Sends event \fIe\fR to \fIreceiver\fR: \fIreceiver\fR->event(\fIe\fR). Returns the value that is returned from the receiver's event handler.
.PP
For certain types of events (e.g. mouse and key events), the event will be propagated to the receiver's parent and so on up to the top-level object if the receiver is not interested in the event (i.e., it returns FALSE).
.PP
There are five different ways that events can be processed; reimplementing this virtual function is just one of them. All five approaches are listed below: <ol type=1>
.TP
Reimplementing this function. This is very powerful, providing complete control; but only one subclass can be qApp.
.IP
.TP
Installing an event filter on qApp. Such an event filter is able to process all events for all widgets, so it's just as powerful as reimplementing notify(); furthermore, it's possible to have more than one application-global event filter. Global event filters even see mouse events for disabled widgets, and if global mouse tracking is enabled, as well as mouse move events for all widgets.
.IP
.TP
Reimplementing QObject::event() (as QWidget does). If you do this you get Tab key presses, and you get to see the events before any widget-specific event filters.
.IP
.TP
Installing an event filter on the object. Such an event filter gets all the events except Tab and Shift-Tab key presses.
.IP
.TP
Reimplementing paintEvent(), mousePressEvent() and so on. This is the commonest, easiest and least powerful way.
.PP
See also QObject::event() and installEventFilter().
.SH "QCursor * QApplication::overrideCursor ()\fC [static]\fR"
Returns the active application override cursor.
.PP
This function returns 0 if no application cursor has been defined (i.e. the internal cursor stack is empty).
.PP
See also setOverrideCursor() and restoreOverrideCursor().
.SH "QPalette QApplication::palette ( const QWidget * w = 0 )\fC [static]\fR"
Returns the application palette.
.PP
If a widget is passed in \fIw\fR, the default palette for the widget's class is returned. This may or may not be the application palette. In most cases there isn't a special palette for certain types of widgets, but one notable exception is the popup menu under Windows, if the user has defined a special background color for menus in the display settings.
.PP
See also setPalette() and QWidget::palette.
.PP
Examples:
.)l desktop/desktop.cpp, themes/metal.cpp, and themes/wood.cpp.
.SH "void QApplication::polish ( QWidget * w )\fC [virtual]\fR"
Initialization of the appearance of the widget \fIw\fR \fIbefore\fR it is first shown.
.PP
Usually widgets call this automatically when they are polished. It may be used to do some style-based central customization of widgets.
.PP
Note that you are not limited to the public functions of QWidget. Instead, based on meta information like QObject::className() you are able to customize any kind of widget.
.PP
See also QStyle::polish(), QWidget::polish(), setPalette(), and setFont().
.SH "void QApplication::postEvent ( QObject * receiver, QEvent * event )\fC [static]\fR"
\fBNote:\fR This function is thread-safe when Qt is built withthread support.</p> Adds the event \fIevent\fR with the object \fIreceiver\fR as the receiver of the event, to an event queue and returns immediately.
.PP
The event must be allocated on the heap since the post event queue will take ownership of the event and delete it once it has been posted.
.PP
When control returns to the main event loop, all events that are stored in the queue will be sent using the notify() function.
.PP
See also sendEvent() and notify().
.SH "void QApplication::processEvents ()"
Processes pending events, for 3 seconds or until there are no more events to process, whichever is shorter.
.PP
You can call this function occasionally when your program is busy performing a long operation (e.g. copying a file).
.PP
See also exec(), QTimer, and QEventLoop::processEvents().
.PP
Examples:
.)l fileiconview/qfileiconview.cpp and network/ftpclient/main.cpp.
.SH "void QApplication::processEvents ( int maxtime )"
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
.PP
Processes pending events for \fImaxtime\fR milliseconds or until there are no more events to process, whichever is shorter.
.PP
You can call this function occasionally when you program is busy doing a long operation (e.g. copying a file).
.PP
See also exec(), QTimer, and QEventLoop::processEvents().
.SH "void QApplication::processOneEvent ()"
\fBThis function is obsolete.\fR It is provided to keep old source working. We strongly advise against using it in new code.
.PP
Waits for an event to occur, processes it, then returns.
.PP
This function is useful for adapting Qt to situations where the event processing must be grafted onto existing program loops.
.PP
Using this function in new applications may be an indication of design problems.
.PP
See also processEvents(), exec(), and QTimer.
.SH "void QApplication::quit ()\fC [slot]\fR"
Tells the application to exit with return code 0 (success). Equivalent to calling QApplication::exit( 0 ).
.PP
It's common to connect the lastWindowClosed() signal to quit(), and you also often connect e.g. QButton::clicked() or signals in QAction, QPopupMenu or QMenuBar to it.
.PP
Example:
.PP
.nf
.br
    QPushButton *quitButton = new QPushButton( "Quit" );
.br
    connect( quitButton, SIGNAL(clicked()), qApp, SLOT(quit()) );
.br
.fi
.PP
See also exit(), aboutToQuit(), lastWindowClosed(), and QAction.
.PP
Examples:
.)l addressbook/main.cpp, mdi/main.cpp, network/archivesearch/main.cpp, regexptester/main.cpp, t2/main.cpp, t4/main.cpp, and t6/main.cpp.
.SH "QWSDecoration & QApplication::qwsDecoration ()\fC [static]\fR"
Return the QWSDecoration used for decorating windows.
.PP
This method is non-portable. It is available \fIonly\fR in Qt/Embedded.
.PP
See also QWSDecoration.
.SH "bool QApplication::qwsEventFilter ( QWSEvent * )\fC [virtual]\fR"
This virtual function is only implemented under Qt/Embedded.
.PP
If you create an application that inherits QApplication and reimplement this function, you get direct access to all QWS (Q Window System) events that the are received from the QWS master process.
.PP
Return TRUE if you want to stop the event from being processed. Return FALSE for normal event dispatching.
.SH "void QApplication::qwsSetCustomColors ( QRgb * colorTable, int start, int numColors )"
Set Qt/Embedded custom color table.
.PP
Qt/Embedded on 8-bpp displays allocates a standard 216 color cube. The remaining 40 colors may be used by setting a custom color table in the QWS master process before any clients connect.
.PP
\fIcolorTable\fR is an array of up to 40 custom colors. \fIstart\fR is the starting index (0-39) and \fInumColors\fR is the number of colors to be set (1-40).
.PP
This method is non-portable. It is available \fIonly\fR in Qt/Embedded.
.SH "void QApplication::qwsSetDecoration ( QWSDecoration * d )\fC [static]\fR"
Set the QWSDecoration derived class to use for decorating the Qt/Embedded windows to \fId\fR.
.PP
This method is non-portable. It is available \fIonly\fR in Qt/Embedded.
.PP
See also QWSDecoration.
.SH "void QApplication::removeLibraryPath ( const QString & path )\fC [static]\fR"
Removes \fIpath\fR from the library path list. If \fIpath\fR is empty or not in the path list, the list is not changed.
.PP