QApplication(3qt)QApplication(3qt)NAME
QApplication - Manages the GUI application's control flow and main
settings
SYNOPSIS
#include <qapplication.h>
Inherits QObject.
Public Members
QApplication ( int & argc, char ** argv )
QApplication ( int & argc, char ** argv, bool GUIenabled )
enum Type { Tty, GuiClient, GuiServer }
QApplication ( int & argc, char ** argv, Type type )
QApplication ( Display * dpy, HANDLE visual = 0, HANDLE colormap = 0 )
QApplication ( Display * dpy, int argc, char ** argv, HANDLE visual =
0, HANDLE colormap = 0 )
virtual ~QApplication ()
int argc () const
char ** argv () const
Type type () const
enum ColorSpec { NormalColor = 0, CustomColor = 1, ManyColor = 2 }
QWidget * mainWidget () const
virtual void setMainWidget ( QWidget * mainWidget )
virtual void polish ( QWidget * w )
QWidget * focusWidget () const
QWidget * activeWindow () const
int exec ()
void processEvents ()
void processEvents ( int maxtime )
void processOneEvent () (obsolete)
bool hasPendingEvents ()
int enter_loop () (obsolete)
void exit_loop () (obsolete)
int loopLevel () const (obsolete)
virtual bool notify ( QObject * receiver, QEvent * e )
void setDefaultCodec ( QTextCodec * codec ) (obsolete)
QTextCodec * defaultCodec () const (obsolete)
void installTranslator ( QTranslator * mf )
void removeTranslator ( QTranslator * mf )
enum Encoding { DefaultCodec, UnicodeUTF8 }
QString translate ( const char * context, const char * sourceText,
const char * comment = 0, Encoding encoding = DefaultCodec ) const
QString applicationDirPath ()
QString applicationFilePath ()
virtual bool macEventFilter ( EventHandlerCallRef, EventRef )
virtual bool winEventFilter ( MSG * )
virtual bool x11EventFilter ( XEvent * )
int x11ProcessEvent ( XEvent * event )
virtual bool qwsEventFilter ( QWSEvent * )
void qwsSetCustomColors ( QRgb * colorTable, int start, int numColors )
void winFocus ( QWidget * widget, bool gotFocus )
bool isSessionRestored () const
QString sessionId () const
QString sessionKey () const
virtual void commitData ( QSessionManager & sm )
virtual void saveState ( QSessionManager & sm )
void wakeUpGuiThread ()
void lock ()
void unlock ( bool wakeUpGui = TRUE )
bool locked ()
bool tryLock ()
Public Slots
void quit ()
void closeAllWindows ()
void aboutQt ()
Signals
void lastWindowClosed ()
void aboutToQuit ()
void guiThreadAwake ()
Static Public Members
QStyle & style ()
void setStyle ( QStyle * style )
QStyle * setStyle ( const QString & style )
int colorSpec ()
void setColorSpec ( int spec )
QCursor * overrideCursor ()
void setOverrideCursor ( const QCursor & cursor, bool replace = FALSE )
void restoreOverrideCursor ()
bool hasGlobalMouseTracking ()
void setGlobalMouseTracking ( bool enable )
QPalette palette ( const QWidget * w = 0 )
void setPalette ( const QPalette & palette, bool informWidgets = FALSE,
const char * className = 0 )
QFont font ( const QWidget * w = 0 )
void setFont ( const QFont & font, bool informWidgets = FALSE, const
char * className = 0 )
QFontMetrics fontMetrics ()
QWidgetList * allWidgets ()
QWidgetList * topLevelWidgets ()
QDesktopWidget * desktop ()
QWidget * activePopupWidget ()
QWidget * activeModalWidget ()
QClipboard * clipboard ()
QWidget * widgetAt ( int x, int y, bool child = FALSE )
QWidget * widgetAt ( const QPoint & pos, bool child = FALSE )
QEventLoop * eventLoop ()
void exit ( int retcode = 0 )
bool sendEvent ( QObject * receiver, QEvent * event )
void postEvent ( QObject * receiver, QEvent * event )
void sendPostedEvents ( QObject * receiver, int event_type )
void sendPostedEvents ()
void removePostedEvents ( QObject * receiver )
bool startingUp ()
bool closingDown ()
void flushX ()
void flush ()
void syncX ()
void beep ()
void setWinStyleHighlightColor ( const QColor & c ) (obsolete)
const QColor & winStyleHighlightColor () (obsolete)
void setDesktopSettingsAware ( bool on )
bool desktopSettingsAware ()
void setCursorFlashTime ( int msecs )
int cursorFlashTime ()
void setDoubleClickInterval ( int ms )
int doubleClickInterval ()
void setWheelScrollLines ( int n )
int wheelScrollLines ()
void setGlobalStrut ( const QSize & strut )
QSize globalStrut ()
void setLibraryPaths ( const QStringList & paths )
QStringList libraryPaths ()
void addLibraryPath ( const QString & path )
void removeLibraryPath ( const QString & path )
void setStartDragTime ( int ms )
int startDragTime ()
void setStartDragDistance ( int l )
int startDragDistance ()
void setReverseLayout ( bool b )
bool reverseLayout ()
int horizontalAlignment ( int align )
bool isEffectEnabled ( Qt::UIEffect effect )
void setEffectEnabled ( Qt::UIEffect effect, bool enable = TRUE )
QWSDecoration & qwsDecoration ()
void qwsSetDecoration ( QWSDecoration * d )
RELATED FUNCTION DOCUMENTATION
void qAddPostRoutine ( QtCleanUpFunction p )
const char * qVersion ()
bool qSysInfo ( int * wordSize, bool * bigEndian )
void qDebug ( const char * msg, ... )
void qWarning ( const char * msg, ... )
void qFatal ( const char * msg, ... )
void qSystemWarning ( const char * msg, int code )
void Q_ASSERT ( bool test )
void Q_CHECK_PTR ( void * p )
QtMsgHandler qInstallMsgHandler ( QtMsgHandler h )
DESCRIPTION
The QApplication class manages the GUI application's control flow and
main settings.
It contains the main event loop, where all events from the window
system and other sources are processed and dispatched. It also handles
the application's initialization and finalization, and provides session
management. It also handles most system-wide and application-wide
settings.
For any GUI application that uses Qt, there is precisely one
QApplication object, no matter whether the application has 0, 1, 2 or
more windows at any time.
The QApplication object is accessible through the global pointer qApp.
Its main areas of responsibility are:
It initializes the application with the user's desktop settings such as
palette(), font() and doubleClickInterval(). It keeps track of these
properties in case the user changes the desktop globally, for example
through some kind of control panel.
It performs event handling, meaning that it receives events from the
underlying window system and dispatches them to the relevant widgets.
By using sendEvent() and postEvent() you can send your own events to
widgets.
It parses common command line arguments and sets its internal state
accordingly. See the constructor documentation below for more details
about this.
It defines the application's look and feel, which is encapsulated in a
QStyle object. This can be changed at runtime with setStyle().
It specifies how the application is to allocate colors. See
setColorSpec() for details.
It provides localization of strings that are visible to the user via
translate().
It provides some magical objects like the desktop() and the
clipboard().
It knows about the application's windows. You can ask which widget is
at a certain position using widgetAt(), get a list of topLevelWidgets()
and closeAllWindows(), etc.
It manages the application's mouse cursor handling, see
setOverrideCursor() and setGlobalMouseTracking().
On the X window system, it provides functions to flush and sync the
communication stream, see flushX() and syncX().
It provides support for sophisticated session management. This makes it
possible for applications to terminate gracefully when the user logs
out, to cancel a shutdown process if termination isn't possible and
even to preserve the entire application's state for a future session.
See isSessionRestored(), sessionId() and commitData() and saveState()
for details.
The Application walk-through example contains a typical complete main()
that does the usual things with QApplication.
Since the QApplication object does so much initialization, it must be
created before any other objects related to the user interface are
created.
Since it also deals with common command line arguments, it is usually a
good idea to create it before any interpretation or modification of
argv is done in the application itself. (Note also that for X11,
setMainWidget() may change the main widget according to the -geometry
option. To preserve this functionality, you must set your defaults
before setMainWidget() and any overrides after.)
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Non-GUI programs: While Qt is not optimized or designed for writing
non-GUI programs, it's possible to use some of its classes without
creating a QApplication. This can be useful if you wish to share code
between a non-GUI server and a GUI client.
See also Main Window and Related Classes.
Member Type Documentation
QApplication::ColorSpec
QApplication::NormalColor - the default color allocation policy
QApplication::CustomColor - the same as NormalColor for X11; allocates
colors to a palette on demand under Windows
QApplication::ManyColor - the right choice for applications that use
thousands of colors
See setColorSpec() for full details.
QApplication::Encoding
This enum type defines the 8-bit encoding of character string arguments
to translate():
QApplication::DefaultCodec - the encoding specified by
QTextCodec::codecForTr() (Latin-1 if none has been set)
QApplication::UnicodeUTF8 - UTF-8
See also QObject::tr(), QObject::trUtf8(), and QString::fromUtf8().
QApplication::Type
QApplication::Tty - a console application
QApplication::GuiClient - a GUI client application
QApplication::GuiServer - a GUI server application
MEMBER FUNCTION DOCUMENTATIONQApplication::QApplication ( int & argc, char ** argv )
Initializes the window system and constructs an application object with
argc command line arguments in argv.
The global qApp pointer refers to this application object. Only one
application object should be created.
This application object must be constructed before any paint devices
(including widgets, pixmaps, bitmaps etc.).
Note that argc and argv might be changed. Qt removes command line
arguments that it recognizes. The modified argc and argv can also be
accessed later with qApp->argc() and qApp->argv(). The documentation
for argv() contains a detailed description of how to process command
line arguments.
Qt debugging options (not available if Qt was compiled with the
QT_NO_DEBUG flag defined):
-nograb, tells Qt that it must never grab the mouse or the keyboard.
-dograb (only under X11), running under a debugger can cause an
implicit -nograb, use -dograb to override.
-sync (only under X11), switches to synchronous mode for debugging.
See Debugging Techniques for a more detailed explanation.
All Qt programs automatically support the following command line
options:
-reverse causes text to be formatted for right-to-left languages rather
than in the usual left-to-right direction.
-style= style, sets the application GUI style. Possible values are
motif, windows, and platinum. If you compiled Qt with additional styles
or have additional styles as plugins these will be available to the
-style command line option.
-style style, is the same as listed above.
-session= session, restores the application from an earlier session.
-session session, is the same as listed above.
-widgetcount, prints debug message at the end about number of widgets
left undestroyed and maximum number of widgets existed at the same time
The X11 version of Qt also supports some traditional X11 command line
options:
-display display, sets the X display (default is $DISPLAY).
-geometry geometry, sets the client geometry of the main widget.
-fn or -font font, defines the application font. The font should be
specified using an X logical font description.
-bg or -background color, sets the default background color and an
application palette (light and dark shades are calculated).
-fg or -foreground color, sets the default foreground color.
-btn or -button color, sets the default button color.
-name name, sets the application name.
-title title, sets the application title (caption).
-visual TrueColor, forces the application to use a TrueColor visual on
an 8-bit display.
-ncols count, limits the number of colors allocated in the color cube
on an 8-bit display, if the application is using the
QApplication::ManyColor color specification. If count is 216 then a
6x6x6 color cube is used (i.e. 6 levels of red, 6 of green, and 6 of
blue); for other values, a cube approximately proportional to a 2x3x1
cube is used.
-cmap, causes the application to install a private color map on an
8-bit display.
See also argc() and argv().
QApplication::QApplication ( int & argc, char ** argv, bool GUIenabled )
Constructs an application object with argc command line arguments in
argv. If GUIenabled is TRUE, a GUI application is constructed,
otherwise a non-GUI (console) application is created.
Set GUIenabled to FALSE for programs without a graphical user interface
that should be able to run without a window system.
On X11, the window system is initialized if GUIenabled is TRUE. If
GUIenabled is FALSE, the application does not connect to the X-server.
On Windows and Macintosh, currently the window system is always
initialized, regardless of the value of GUIenabled. This may change in
future versions of Qt.
The following example shows how to create an application that uses a
graphical interface when available.
int main( int argc, char **argv )
{
#ifdef Q_WS_X11
bool useGUI = getenv( "DISPLAY" ) != 0;
#else
bool useGUI = TRUE;
#endif
QApplication app(argc, argv, useGUI);
if ( useGUI ) {
//start GUI version
...
} else {
//start non-GUI version
...
}
return app.exec();
}
QApplication::QApplication ( int & argc, char ** argv, Type type )
Constructs an application object with argc command line arguments in
argv.
For Qt/Embedded, passing QApplication::GuiServer for type makes this
application the server (equivalent to running with the -qws option).
QApplication::QApplication ( Display * dpy, HANDLE visual = 0, HANDLE colormap
= 0 )
Create an application, given an already open display dpy. If visual and
colormap are non-zero, the application will use those as the default
Visual and Colormap contexts.
Warning: Qt only supports TrueColor visuals at depths higher than 8
bits-per-pixel.
This is available only on X11.
QApplication::QApplication ( Display * dpy, int argc, char ** argv, HANDLE
visual = 0, HANDLE colormap = 0 )
Create an application, given an already open display dpy and using argc
command line arguments in argv. If visual and colormap are non-zero,
the application will use those as the default Visual and Colormap
contexts.
Warning: Qt only supports TrueColor visuals at depths higher than 8
bits-per-pixel.
This is available only on X11.
QApplication::~QApplication () [virtual]
Cleans up any window system resources that were allocated by this
application. Sets the global variable qApp to 0.
void QApplication::aboutQt () [slot]
Displays a simple message box about Qt. The message includes the
version number of Qt being used by the application.
This is useful for inclusion in the Help menu of an application. See
the examples/menu/menu.cpp example.
This function is a convenience slot for QMessageBox::aboutQt().
void QApplication::aboutToQuit () [signal]
This signal is emitted when the application is about to quit the main
event loop, e.g. when the event loop level drops to zero. This may
happen either after a call to quit() from inside the application or
when the users shuts down the entire desktop session.
The signal is particularly useful if your application has to do some
last-second cleanup. Note that no user interaction is possible in this
state.
See also quit().
QWidget * QApplication::activeModalWidget () [static]
Returns the active modal widget.
A modal widget is a special top level widget which is a subclass of
QDialog that specifies the modal parameter of the constructor as TRUE.
A modal widget must be closed before the user can continue with other
parts of the program.
Modal widgets are organized in a stack. This function returns the
active modal widget at the top of the stack.
See also activePopupWidget() and topLevelWidgets().
QWidget * QApplication::activePopupWidget () [static]
Returns the active popup widget.
A popup widget is a special top level widget that sets the WType_Popup
widget flag, e.g. the QPopupMenu widget. When the application opens a
popup widget, all events are sent to the popup. Normal widgets and
modal widgets cannot be accessed before the popup widget is closed.
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 at the top of the stack.
See also activeModalWidget() and topLevelWidgets().
QWidget * QApplication::activeWindow () const
Returns the application top-level window that has the keyboard input
focus, or 0 if no application window has the focus. Note that there
might be an activeWindow() even if there is no focusWidget(), for
example if no widget in that window accepts key events.
See also QWidget::setFocus(), QWidget::focus, and focusWidget().
Example: network/mail/smtp.cpp.
void QApplication::addLibraryPath ( const QString & path ) [static]
Append path to the end of the library path list. If path is empty or
already in the path list, the path list is not changed.
The default path list consists of a single entry, the installation
directory for plugins. The default installation directory for plugins
is INSTALL/plugins, where INSTALL is the directory where Qt was
installed.
See also removeLibraryPath(), libraryPaths(), and setLibraryPaths().
QWidgetList * QApplication::allWidgets () [static]
Returns a list of all the widgets in the application.
The list is created using new and must be deleted by the caller.
The list is empty (QPtrList::isEmpty()) if there are no widgets.
Note that some of the widgets may be hidden.
Example that updates all widgets:
QWidgetList *list = QApplication::allWidgets();
QWidgetListIt it( *list ); // iterate over the widgets
QWidget * w;
while ( (w=it.current()) != 0 ) { // for each widget...
++it;
w->update();
}
delete list; // delete the list, not the widgets
The QWidgetList class is defined in the qwidgetlist.h header file.
Warning: Delete the list as soon as you have finished using it. The
widgets in the list may be deleted by someone else at any time.
See also topLevelWidgets(), QWidget::visible, and QPtrList::isEmpty().
QString QApplication::applicationDirPath ()
Returns the directory that contains the application executable.
For example, if you have installed Qt in the C:\Trolltech\Qt
directory, and you run the demo example, this function will return
"C:/Trolltech/Qt/examples/demo".
On Mac OS X this will point to the directory actually containing the
executable, which may be inside of an application bundle (if the
application is bundled).
Warning: On Unix, this function assumes that argv[0] contains the file
name of the executable (which it normally does). It also assumes that
the current directory hasn't been changed by the application.
See also applicationFilePath().
QString QApplication::applicationFilePath ()
Returns the file path of the application executable.
For example, if you have installed Qt in the C:\Trolltech\Qt
directory, and you run the demo example, this function will return
"C:/Trolltech/Qt/examples/demo/demo.exe".
Warning: On Unix, this function assumes that argv[0] contains the file
name of the executable (which it normally does). It also assumes that
the current directory hasn't been changed by the application.
See also applicationDirPath().
int QApplication::argc () const
Returns the number of command line arguments.
The documentation for argv() describes how to process command line
arguments.
See also argv() and QApplication::QApplication().
Examples:
char ** QApplication::argv () const
Returns the command line argument vector.
argv()[0] is the program name, argv()[1] is the first argument and
argv()[argc()-1] is the last argument.
A QApplication object is constructed by passing argc and argv from the
main() function. Some of the arguments may be recognized as Qt options
and removed from the argument vector. For example, the X11 version of
Qt knows about -display, -font and a few more options.
Example:
// showargs.cpp - displays program arguments in a list box
#include <qapplication.h>
#include <qlistbox.h>
int main( int argc, char **argv )
{
QApplication a( argc, argv );
QListBox b;
a.setMainWidget( &b );
for ( int i = 0; i < a.argc(); i++ ) // a.argc() == argc
b.insertItem( a.argv()[i] ); // a.argv()[i] == argv[i]
b.show();
return a.exec();
}
If you run showargs -display unix:0 -font 9x15bold hello world under
X11, the list box contains the three strings "showargs"," hello" and
"world".
Qt provides a global pointer, qApp, that points to the QApplication
object, and through which you can access argc() and argv() in functions
other than main().
See also argc() and QApplication::QApplication().
Examples:
void QApplication::beep () [static]
Sounds the bell, using the default volume and sound.
QClipboard * QApplication::clipboard () [static]
Returns a pointer to the application global clipboard.
Examples:
void QApplication::closeAllWindows () [slot]
Closes all top-level windows.
This function is particularly useful for applications with many top-
level windows. It could, for example, be connected to a "Quit" entry in
the file menu as shown in the following code example:
// the "Quit" menu entry should try to close all windows
QPopupMenu* file = new QPopupMenu( this );
file->insertItem( "&Quit", qApp, SLOT(closeAllWindows()), CTRL+Key_Q );
// when the last window is closed, the application should quit
connect( qApp, SIGNAL( lastWindowClosed() ), qApp, SLOT( quit() ) );
The windows are closed in random order, until one window does not
accept the close event.
See also QWidget::close(), QWidget::closeEvent(), lastWindowClosed(),
quit(), topLevelWidgets(), and QWidget::isTopLevel.
Examples:
bool QApplication::closingDown () [static]
Returns TRUE if the application objects are being destroyed; otherwise
returns FALSE.
See also startingUp().
int QApplication::colorSpec () [static]
Returns the color specification.
See also QApplication::setColorSpec().
Example: showimg/showimg.cpp.
void QApplication::commitData ( QSessionManager & sm ) [virtual]
This function deals with session management. It is invoked when the
QSessionManager wants the application to commit all its data.
Usually this means saving all open files, after getting permission from
the user. Furthermore you may want to provide a means by which the user
can cancel the shutdown.
Note that you should not exit the application within this function.
Instead, the session manager may or may not do this afterwards,
depending on the context.
Warning: Within this function, no user interaction is possible, unless
you ask the session manager sm for explicit permission. See
QSessionManager::allowsInteraction() and
QSessionManager::allowsErrorInteraction() for details and example
usage.
The default implementation requests interaction and sends a close event
to all visible top level widgets. If any event was rejected, the
shutdown is canceled.
See also isSessionRestored(), sessionId(), saveState(), and the Session
Management overview.
int QApplication::cursorFlashTime () [static]
Returns the text cursor's flash (blink) time in milliseconds. The flash
time is the time required to display, invert and restore the caret
display.
The default value on X11 is 1000 milliseconds. On Windows, the control
panel value is used.
Widgets should not cache this value since it may be changed at any time
by the user changing the global desktop settings.
See also setCursorFlashTime().
QTextCodec * QApplication::defaultCodec () const
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Returns QTextCodec::codecForTr().
QDesktopWidget * QApplication::desktop () [static]
Returns the desktop widget (also called the root window).
The desktop widget is useful for obtaining the size of the screen. It
may also be possible to draw on the desktop. We recommend against
assuming that it's possible to draw on the desktop, since this does not
work on all operating systems.
QDesktopWidget *d = QApplication::desktop();
int w = d->width(); // returns desktop width
int h = d->height(); // returns desktop height
Examples:
bool QApplication::desktopSettingsAware () [static]
Returns the value set by setDesktopSettingsAware(); by default TRUE.
See also setDesktopSettingsAware().
int QApplication::doubleClickInterval () [static]
Returns the maximum duration for a double click.
The default value on X11 is 400 milliseconds. On Windows, the control
panel value is used.
See also setDoubleClickInterval().
int QApplication::enter_loop ()
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
This function enters the main event loop (recursively). Do not call it
unless you really know what you are doing.
Use QApplication::eventLoop()->enterLoop() instead.
QEventLoop * QApplication::eventLoop () [static]
Returns the application event loop. This function will return zero if
called during and after destroying QApplication.
To create your own instance of QEventLoop or QEventLoop subclass create
it before you create the QApplication object.
See also QEventLoop.
Example: distributor/distributor.ui.h.
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()).
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.
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.
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().
See also quit(), exit(), processEvents(), and setMainWidget().
Examples:
void QApplication::exit ( int retcode = 0 ) [static]
Tells the application to exit with a return code.
After this function has been called, the application leaves the main
event loop and returns from the call to exec(). The exec() function
returns retcode.
By convention, a retcode of 0 means success, and any non-zero value
indicates an error.
Note that unlike the C library function of the same name, this function
does return to the caller -- it is event processing that stops.
See also quit() and exec().
Examples:
void QApplication::exit_loop ()
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
This function exits from a recursive call to the main event loop. Do
not call it unless you are an expert.
Use QApplication::eventLoop()->exitLoop() instead.
void QApplication::flush () [static]
Flushes the window system specific event queues.
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.
See also flushX(), sendPostedEvents(), and QPainter::flush().
void QApplication::flushX () [static]
Flushes the X event queue in the X11 implementation. This normally
returns almost immediately. Does nothing on other platforms.
See also syncX().
Example: xform/xform.cpp.
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.
See also QWidget::setFocus(), QWidget::focus, and activeWindow().
QFont QApplication::font ( const QWidget * w = 0 ) [static]
Returns the default font for the widget w, or the default application
font if w is 0.
See also setFont(), fontMetrics(), and QWidget::font.
Examples:
QFontMetrics QApplication::fontMetrics () [static]
Returns display (screen) font metrics for the application font.
See also font(), setFont(), QWidget::fontMetrics(), and
QPainter::fontMetrics().
QSize QApplication::globalStrut () [static]
Returns the application's global strut.
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.
See also setGlobalStrut().
void QApplication::guiThreadAwake () [signal]
This signal is emitted after the event loop returns from a function
that could block.
See also wakeUpGuiThread().
bool QApplication::hasGlobalMouseTracking () [static]
Returns TRUE if global mouse tracking is enabled; otherwise returns
FALSE.
See also setGlobalMouseTracking().
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().
int QApplication::horizontalAlignment ( int align ) [static]
Strips out vertical alignment flags and transforms an alignment align
of AlignAuto into AlignLeft or AlignRight according to the language
used. The other horizontal alignment flags are left untouched.
void QApplication::installTranslator ( QTranslator * mf )
Adds the message file mf to the list of message files to be used for
translations.
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.
See also removeTranslator(), translate(), and QTranslator::load().
Example: i18n/main.cpp.
bool QApplication::isEffectEnabled ( Qt::UIEffect effect ) [static]
Returns TRUE if effect is enabled; otherwise returns FALSE.
By default, Qt will try to use the desktop settings. Call
setDesktopSettingsAware(FALSE) to prevent this.
Note: All effects are disabled on screens running at less than 16-bit
color depth.
See also setEffectEnabled() and Qt::UIEffect.
bool QApplication::isSessionRestored () const
Returns TRUE if the application has been restored from an earlier
session; otherwise returns FALSE.
See also sessionId(), commitData(), and saveState().
void QApplication::lastWindowClosed () [signal]
This signal is emitted when the user has closed the last top level
window.
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.
For convenience, this signal is not emitted for transient top level
widgets such as popup menus and dialogs.
See also mainWidget(), topLevelWidgets(), QWidget::isTopLevel, and
QWidget::close().
Examples:
QStringList QApplication::libraryPaths () [static]
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 INSTALL/plugins, where INSTALL is the
directory where Qt was installed. The directory of the application
executable (NOT the working directory) is also added to the plugin
paths.
If you want to iterate over the list, you should iterate over a copy,
e.g.
QStringList list = app.libraryPaths();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See the plugins documentation for a description of how the library
paths are used.
See also setLibraryPaths(), addLibraryPath(), removeLibraryPath(), and
QLibrary.
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.
See also unlock(), locked(), and Thread Support in Qt.
bool QApplication::locked ()
Returns TRUE if the Qt Library Mutex is locked by a different thread;
otherwise returns FALSE.
Warning: 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.
See also lock(), unlock(), and Thread Support in Qt.
int QApplication::loopLevel () const
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Returns the current loop level.
Use QApplication::eventLoop()->loopLevel() instead.
bool QApplication::macEventFilter ( EventHandlerCallRef, EventRef ) [virtual]
This virtual function is only implemented under Macintosh.
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.
Return TRUE if you want to stop the event from being processed. Return
FALSE for normal event dispatching.
QWidget * QApplication::mainWidget () const
Returns the main application widget, or 0 if there is no main widget.
See also setMainWidget().
bool QApplication::notify ( QObject * receiver, QEvent * e ) [virtual]
Sends event e to receiver: receiver->event(e). Returns the value that
is returned from the receiver's event handler.
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).
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>
Reimplementing this function. This is very powerful, providing complete
control; but only one subclass can be qApp.
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.
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.
Installing an event filter on the object. Such an event filter gets all
the events except Tab and Shift-Tab key presses.
Reimplementing paintEvent(), mousePressEvent() and so on. This is the
commonest, easiest and least powerful way.
See also QObject::event() and installEventFilter().
QCursor * QApplication::overrideCursor () [static]
Returns the active application override cursor.
This function returns 0 if no application cursor has been defined (i.e.
the internal cursor stack is empty).
See also setOverrideCursor() and restoreOverrideCursor().
QPalette QApplication::palette ( const QWidget * w = 0 ) [static]
Returns the application palette.
If a widget is passed in w, 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.
See also setPalette() and QWidget::palette.
Examples:
void QApplication::polish ( QWidget * w ) [virtual]
Initialization of the appearance of the widget w before it is first
shown.
Usually widgets call this automatically when they are polished. It may
be used to do some style-based central customization of widgets.
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.
See also QStyle::polish(), QWidget::polish(), setPalette(), and
setFont().
void QApplication::postEvent ( QObject * receiver, QEvent * event ) [static]
Note: This function is thread-safe when Qt is built withthread
support.</p> Adds the event event with the object receiver as the
receiver of the event, to an event queue and returns immediately.
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.
When control returns to the main event loop, all events that are stored
in the queue will be sent using the notify() function.
See also sendEvent() and notify().
void QApplication::processEvents ()
Processes pending events, for 3 seconds or until there are no more
events to process, whichever is shorter.
You can call this function occasionally when your program is busy
performing a long operation (e.g. copying a file).
See also exec(), QTimer, and QEventLoop::processEvents().
Examples:
void QApplication::processEvents ( int maxtime )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Processes pending events for maxtime milliseconds or until there are no
more events to process, whichever is shorter.
You can call this function occasionally when you program is busy doing
a long operation (e.g. copying a file).
See also exec(), QTimer, and QEventLoop::processEvents().
void QApplication::processOneEvent ()
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Waits for an event to occur, processes it, then returns.
This function is useful for adapting Qt to situations where the event
processing must be grafted onto existing program loops.
Using this function in new applications may be an indication of design
problems.
See also processEvents(), exec(), and QTimer.
void QApplication::quit () [slot]
Tells the application to exit with return code 0 (success). Equivalent
to calling QApplication::exit( 0 ).
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.
Example:
QPushButton *quitButton = new QPushButton( "Quit" );
connect( quitButton, SIGNAL(clicked()), qApp, SLOT(quit()) );
See also exit(), aboutToQuit(), lastWindowClosed(), and QAction.
Examples:
QWSDecoration & QApplication::qwsDecoration () [static]
Return the QWSDecoration used for decorating windows.
This method is non-portable. It is available only in Qt/Embedded.
See also QWSDecoration.
bool QApplication::qwsEventFilter ( QWSEvent * ) [virtual]
This virtual function is only implemented under Qt/Embedded.
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.
Return TRUE if you want to stop the event from being processed. Return
FALSE for normal event dispatching.
void QApplication::qwsSetCustomColors ( QRgb * colorTable, int start, int
numColors )
Set Qt/Embedded custom color table.
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.
colorTable is an array of up to 40 custom colors. start is the starting
index (0-39) and numColors is the number of colors to be set (1-40).
This method is non-portable. It is available only in Qt/Embedded.
void QApplication::qwsSetDecoration ( QWSDecoration * d ) [static]
Set the QWSDecoration derived class to use for decorating the
Qt/Embedded windows to d.
This method is non-portable. It is available only in Qt/Embedded.
See also QWSDecoration.
void QApplication::removeLibraryPath ( const QString & path ) [static]
Removes path from the library path list. If path is empty or not in the
path list, the list is not changed.
See also addLibraryPath(), libraryPaths(), and setLibraryPaths().
void QApplication::removePostedEvents ( QObject * receiver ) [static]
Note: This function is thread-safe when Qt is built withthread
support.</p> Removes all events posted using postEvent() for receiver.
The events are not dispatched, instead they are removed from the queue.
You should never need to call this function. If you do call it, be
aware that killing events may cause receiver to break one or more
invariants.
void QApplication::removeTranslator ( QTranslator * mf )
Removes the message file mf from the list of message files used by this
application. (It does not delete the message file from the file
system.)
See also installTranslator(), translate(), and QObject::tr().
Example: i18n/main.cpp.
void QApplication::restoreOverrideCursor () [static]
Undoes the last setOverrideCursor().
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.
See also setOverrideCursor() and overrideCursor().
Examples:
bool QApplication::reverseLayout () [static]
Returns TRUE if all dialogs and widgets will be laid out in a mirrored
(right to left) fashion. Returns FALSE if dialogs and widgets will be
laid out left to right.
See also setReverseLayout().
void QApplication::saveState ( QSessionManager & sm ) [virtual]
This function deals with session management. It is invoked when the
session manager wants the application to preserve its state for a
future session.
For example, a text editor would create a temporary file that includes
the current contents of its edit buffers, the location of the cursor
and other aspects of the current editing session.
Note that you should never exit the application within this function.
Instead, the session manager may or may not do this afterwards,
depending on the context. Futhermore, most session managers will very
likely request a saved state immediately after the application has been
started. This permits the session manager to learn about the
application's restart policy.
Warning: Within this function, no user interaction is possible, unless
you ask the session manager sm for explicit permission. See
QSessionManager::allowsInteraction() and
QSessionManager::allowsErrorInteraction() for details.
See also isSessionRestored(), sessionId(), commitData(), and the
Session Management overview.
bool QApplication::sendEvent ( QObject * receiver, QEvent * event ) [static]
Sends event event directly to receiver receiver, using the notify()
function. Returns the value that was returned from the event handler.
The event is not deleted when the event has been sent. The normal
approach is to create the event on the stack, e.g.
QMouseEvent me( QEvent::MouseButtonPress, pos, 0, 0 );
QApplication::sendEvent( mainWindow, &me );
If you create the event on the heap you must delete it.
See also postEvent() and notify().
Example: popup/popup.cpp.
void QApplication::sendPostedEvents ( QObject * receiver, int event_type )
[static]
Immediately dispatches all events which have been previously queued
with QApplication::postEvent() and which are for the object receiver
and have the event type event_type.
Note that events from the window system are not dispatched by this
function, but by processEvents().
If receiver is null, the events of event_type are sent for all objects.
If event_type is 0, all the events are sent for receiver.
void QApplication::sendPostedEvents () [static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Dispatches all posted events, i.e. empties the event queue.
QString QApplication::sessionId () const
Returns the current session's identifier.
If the application has been restored from an earlier session, this
identifier is the same as it was in that previous session.
The session identifier is guaranteed to be unique both for different
applications and for different instances of the same application.
See also isSessionRestored(), sessionKey(), commitData(), and
saveState().
QString QApplication::sessionKey () const
Returns the session key in the current session.
If the application has been restored from an earlier session, this key
is the same as it was when the previous session ended.
The session key changes with every call of commitData() or saveState().
See also isSessionRestored(), sessionId(), commitData(), and
saveState().
void QApplication::setColorSpec ( int spec ) [static]
Sets the color specification for the application to spec.
The color specification controls how the application allocates colors
when run on a display with a limited amount of colors, e.g. 8 bit / 256
color displays.
The color specification must be set before you create the QApplication
object.
The options are:
QApplication::NormalColor. This is the default color allocation
strategy. Use this option if your application uses buttons, menus,
texts and pixmaps with few colors. With this option, the application
uses system global colors. This works fine for most applications under
X11, but on Windows machines it may cause dithering of non-standard
colors.
QApplication::CustomColor. Use this option if your application needs a
small number of custom colors. On X11, this option is the same as
NormalColor. On Windows, Qt creates a Windows palette, and allocates
colors to it on demand.
QApplication::ManyColor. Use this option if your application is very
color hungry (e.g. it requires thousands of colors). Under X11 the
effect is:
For 256-color displays which have at best a 256 color true color
visual, the default visual is used, and colors are allocated from a
color cube. The color cube is the 6x6x6 (216 color) "Web
palette"<sup>*</sup>, but the number of colors can be changed by the
-ncols option. The user can force the application to use the true color
visual with the -visual option.
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, for example. They provide an 8 bit visual by default but can
deliver true color when asked. On Windows, Qt creates a Windows
palette, and fills it with a color cube.
Be aware that the CustomColor and ManyColor choices may lead to
colormap flashing: The foreground application gets (most) of the
available colors, while the background windows will look less
attractive.
Example:
int main( int argc, char **argv )
{
QApplication::setColorSpec( QApplication::ManyColor );
QApplication a( argc, argv );
...
}
QColor provides more functionality for controlling color allocation and
freeing up certain colors. See QColor::enterAllocContext() for more
information.
To check what mode you end up with, call QColor::numBitPlanes() once
the QApplication object exists. A value greater than 8 (typically 16,
24 or 32) means true color.
<sup>*</sup> The color cube used by Qt has 216 colors whose red, green,
and blue components always have one of the following values: 0x00,
0x33, 0x66, 0x99, 0xCC, or 0xFF.
See also colorSpec(), QColor::numBitPlanes(), and
QColor::enterAllocContext().
Examples:
void QApplication::setCursorFlashTime ( int msecs ) [static]
Sets the text cursor's flash (blink) time to msecs milliseconds. The
flash time is the time required to display, invert and restore the
caret display. Usually the text cursor is displayed for msecs/2
milliseconds, then hidden for msecs/2 milliseconds, but this may vary.
Note that on Microsoft Windows, calling this function sets the cursor
flash time for all windows.
See also cursorFlashTime().
void QApplication::setDefaultCodec ( QTextCodec * codec )
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
This is the same as QTextCodec::setCodecForTr().
void QApplication::setDesktopSettingsAware ( bool on ) [static]
By default, Qt will try to use the current standard colors, fonts etc.,
from the underlying window system's desktop settings, and use them for
all relevant widgets. This behavior can be switched off by calling this
function with on set to FALSE.
This static function must be called before creating the QApplication
object, like this:
int main( int argc, char** argv ) {
QApplication::setDesktopSettingsAware( FALSE ); // I know better than the user
QApplication myApp( argc, argv ); // Use default fonts & colors
...
}
See also desktopSettingsAware().
void QApplication::setDoubleClickInterval ( int ms ) [static]
Sets the time limit that distinguishes a double click from two
consecutive mouse clicks to ms milliseconds.
Note that on Microsoft Windows, calling this function sets the double
click interval for all windows.
See also doubleClickInterval().
void QApplication::setEffectEnabled ( Qt::UIEffect effect, bool enable = TRUE
) [static]
Enables the UI effect effect if enable is TRUE, otherwise the effect
will not be used.
Note: All effects are disabled on screens running at less than 16-bit
color depth.
See also isEffectEnabled(), Qt::UIEffect, and
setDesktopSettingsAware().
void QApplication::setFont ( const QFont & font, bool informWidgets = FALSE,
const char * className = 0 ) [static]
Changes the default application font to font. If informWidgets is TRUE,
then existing widgets are informed about the change and may adjust
themselves to the new application setting. If informWidgets is FALSE,
the change only affects newly created widgets. If className is passed,
the change applies only to classes that inherit className (as reported
by QObject::inherits()).
On application start-up, the default font depends on the window system.
It can vary depending on both the window system version and the locale.
This function lets you override the default font; but overriding may be
a bad idea because, for example, some locales need extra-large fonts to
support their special characters.
See also font(), fontMetrics(), and QWidget::font.
Examples:
void QApplication::setGlobalMouseTracking ( bool enable ) [static]
Enables global mouse tracking if enable is TRUE, or disables it if
enable is FALSE.
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. tooltips.
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 QWidget::setMouseTracking(TRUE).
This function uses an internal counter. Each
setGlobalMouseTracking(TRUE) must have a corresponding
setGlobalMouseTracking(FALSE):
// at this point global mouse tracking is off
QApplication::setGlobalMouseTracking( TRUE );
QApplication::setGlobalMouseTracking( TRUE );
QApplication::setGlobalMouseTracking( FALSE );
// at this point it's still on
QApplication::setGlobalMouseTracking( FALSE );
// but now it's off
See also hasGlobalMouseTracking() and QWidget::mouseTracking.
void QApplication::setGlobalStrut ( const QSize & strut ) [static]
Sets the application's global strut to strut.
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.
The strut size should be considered when reimplementing GUI controls
that may be used on touch-screens or similar IO-devices.
Example:
QSize& WidgetClass::sizeHint() const
{
return QSize( 80, 25 ).expandedTo( QApplication::globalStrut() );
}
See also globalStrut().
void QApplication::setLibraryPaths ( const QStringList & paths ) [static]
Sets the list of directories to search when loading libraries to paths.
All existing paths will be deleted and the path list will consist of
the paths given in paths.
See also libraryPaths(), addLibraryPath(), removeLibraryPath(), and
QLibrary.
void QApplication::setMainWidget ( QWidget * mainWidget ) [virtual]
Sets the application's main widget to mainWidget.
In most respects the main widget is like any other widget, except that
if it is closed, the application exits. Note that QApplication does not
take ownership of the mainWidget, so if you create your main widget on
the heap you must delete it yourself.
You need not have a main widget; connecting lastWindowClosed() to
quit() is an alternative.
For X11, this function also resizes and moves the main widget according
to the -geometry command-line option, so you should set the default
geometry (using QWidget::setGeometry()) before calling setMainWidget().
See also mainWidget(), exec(), and quit().
Examples:
void QApplication::setOverrideCursor ( const QCursor & cursor, bool replace =
FALSE ) [static]
Sets the application override cursor to cursor.
Application override cursors are intended for showing the user that the
application is in a special state, for example during an operation that
might take some time.
This cursor will be displayed in all the application's widgets until
restoreOverrideCursor() or another setOverrideCursor() is called.
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 eventually be followed by a corresponding
restoreOverrideCursor(), otherwise the stack will never be emptied.
If replace is TRUE, the new cursor will replace the last override
cursor (the stack keeps its depth). If replace is FALSE, the new stack
is pushed onto the top of the stack.
Example:
QApplication::setOverrideCursor( QCursor(Qt::WaitCursor) );
calculateHugeMandelbrot(); // lunch time...
QApplication::restoreOverrideCursor();
See also overrideCursor(), restoreOverrideCursor(), and
QWidget::cursor.
Examples:
void QApplication::setPalette ( const QPalette & palette, bool informWidgets =
FALSE, const char * className = 0 ) [static]
Changes the default application palette to palette. If informWidgets is
TRUE, then existing widgets are informed about the change and may
adjust themselves to the new application setting. If informWidgets is
FALSE, the change only affects newly created widgets.
If className is passed, the change applies only to widgets that inherit
className (as reported by QObject::inherits()). If className is left 0,
the change affects all widgets, thus overriding any previously set
class specific palettes.
The palette may be changed according to the current GUI style in
QStyle::polish().
See also QWidget::palette, palette(), and QStyle::polish().
Examples:
void QApplication::setReverseLayout ( bool b ) [static]
If b is TRUE, all dialogs and widgets will be laid out in a mirrored
fashion, as required by right to left languages such as Arabic and
Hebrew. If b is FALSE, dialogs and widgets are laid out left to right.
Changing this flag in runtime does not cause a relayout of already
instantiated widgets.
See also reverseLayout().
void QApplication::setStartDragDistance ( int l ) [static]
Sets the distance after which a drag should start to l pixels.
See also startDragDistance().
void QApplication::setStartDragTime ( int ms ) [static]
Sets the time after which a drag should start to ms ms.
See also startDragTime().
void QApplication::setStyle ( QStyle * style ) [static]
Sets the application's GUI style to style. Ownership of the style
object is transferred to QApplication, so QApplication will delete the
style object on application exit or when a new style is set.
Example usage:
QApplication::setStyle( new QWindowsStyle );
When switching application styles, the color palette is set back to the
initial colors or the system defaults. This is necessary since certain
styles have to adapt the color palette to be fully style-guide
compliant.
See also style(), QStyle, setPalette(), and desktopSettingsAware().
Example: themes/themes.cpp.
QStyle * QApplication::setStyle ( const QString & style ) [static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Requests a QStyle object for style from the QStyleFactory.
The string must be one of the QStyleFactory::keys(), typically one of
"windows", "motif", "cde", "motifplus", "platinum", "sgi" and"
compact". Depending on the platform, "windowsxp", "aqua" or" macintosh"
may be available.
A later call to the QApplication constructor will override the
requested style when a "-style" option is passed in as a commandline
parameter.
Returns 0 if an unknown style is passed, otherwise the QStyle object
returned is set as the application's GUI style.
void QApplication::setWheelScrollLines ( int n ) [static]
Sets the number of lines to scroll when the mouse wheel is rotated to
n.
If this number exceeds the number of visible lines in a certain widget,
the widget should interpret the scroll operation as a single page up /
page down operation instead.
See also wheelScrollLines().
void QApplication::setWinStyleHighlightColor ( const QColor & c ) [static]
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
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.
The default color is darkBlue.
See also winStyleHighlightColor().
int QApplication::startDragDistance () [static]
If you support drag and drop in you application and a drag should start
after a mouse click and after moving the mouse a certain distance, you
should use the value which this method returns as the distance.
For example, if the mouse position of the click is stored in startPos
and the current position (e.g. in the mouse move event) is currPos, you
can find out if a drag should be started with code like this:
if ( ( startPos - currPos ).manhattanLength() >
QApplication::startDragDistance() )
startTheDrag();
Qt uses this value internally, e.g. in QFileDialog.
The default value is 4 pixels.
See also setStartDragDistance(), startDragTime(), and
QPoint::manhattanLength().
int QApplication::startDragTime () [static]
If you support drag and drop in you application and a drag should start
after a mouse click and after a certain time elapsed, you should use
the value which this method returns as the delay (in ms).
Qt also uses this delay internally, e.g. in QTextEdit and QLineEdit,
for starting a drag.
The default value is 500 ms.
See also setStartDragTime() and startDragDistance().
bool QApplication::startingUp () [static]
Returns TRUE if an application object has not been created yet;
otherwise returns FALSE.
See also closingDown().
QStyle & QApplication::style () [static]
Returns the application's style object.
See also setStyle() and QStyle.
void QApplication::syncX () [static]
Synchronizes with the X server in the X11 implementation. This normally
takes some time. Does nothing on other platforms.
See also flushX().
QWidgetList * QApplication::topLevelWidgets () [static]
Returns a list of the top level widgets in the application.
The list is created using new and must be deleted by the caller.
The list is empty (QPtrList::isEmpty()) if there are no top level
widgets.
Note that some of the top level widgets may be hidden, for example the
tooltip if no tooltip is currently shown.
Example:
// Show all hidden top level widgets.
QWidgetList *list = QApplication::topLevelWidgets();
QWidgetListIt it( *list ); // iterate over the widgets
QWidget * w;
while ( (w=it.current()) != 0 ) { // for each top level widget...
++it;
if ( !w->isVisible() )
w->show();
}
delete list; // delete the list, not the widgets
Warning: Delete the list as soon you have finished using it. The
widgets in the list may be deleted by someone else at any time.
See also allWidgets(), QWidget::isTopLevel, QWidget::visible, and
QPtrList::isEmpty().
QString QApplication::translate ( const char * context, const char *
sourceText, const char * comment = 0, Encoding encoding = DefaultCodec
) const
Note: This function is reentrant when Qt is built with thread
support.</p> Returns the translation text for sourceText, by querying
the installed messages files. The message files are searched from the
most recently installed message file back to the first installed
message file.
QObject::tr() and QObject::trUtf8() provide this functionality more
conveniently.
context is typically a class name (e.g., "MyDialog") and sourceText is
either English text or a short identifying text, if the output text
will be very long (as for help texts).
comment is a disambiguating comment, for when the same sourceText is
used in different roles within the same context. By default, it is
null. encoding indicates the 8-bit encoding of character stings
See the QTranslator documentation for more information about contexts
and comments.
If none of the message files contain a translation for sourceText in
context, this function returns a QString equivalent of sourceText. The
encoding of sourceText is specified by encoding; it defaults to
DefaultCodec.
This function is not virtual. You can use alternative translation
techniques by subclassing QTranslator.
Warning: This method is reentrant only if all translators are installed
before calling this method. Installing or removing translators while
performing translations is not supported. Doing so will most likely
result in crashes or other undesirable behavior.
See also QObject::tr(), installTranslator(), and defaultCodec().
bool QApplication::tryLock ()
Attempts to lock the Qt Library Mutex, and returns immediately. If the
lock was obtained, this function returns TRUE. If another thread has
locked the mutex, this function returns FALSE, instead of waiting for
the lock to become available.
The mutex must be unlocked with unlock() before another thread can
successfully lock it.
See also lock(), unlock(), and Thread Support in Qt.
Type QApplication::type () const
Returns the type of application, Tty, GuiClient or GuiServer.
void QApplication::unlock ( bool wakeUpGui = TRUE )
Unlock the Qt Library Mutex. If wakeUpGui is TRUE (the default), then
the GUI thread will be woken with QApplication::wakeUpGuiThread().
See also lock(), locked(), and Thread Support in Qt.
void QApplication::wakeUpGuiThread ()
Wakes up the GUI thread.
See also guiThreadAwake() and Thread Support in Qt.
int QApplication::wheelScrollLines () [static]
Returns the number of lines to scroll when the mouse wheel is rotated.
See also setWheelScrollLines().
QWidget * QApplication::widgetAt ( int x, int y, bool child = FALSE ) [static]
Returns a pointer to the widget at global screen position (x, y), or 0
if there is no Qt widget there.
If child is FALSE and there is a child widget at position (x, y), the
top-level widget containing it is returned. If child is TRUE the child
widget at position (x, y) is returned.
This function is normally rather slow.
See also QCursor::pos(), QWidget::grabMouse(), and
QWidget::grabKeyboard().
QWidget * QApplication::widgetAt ( const QPoint & pos, bool child = FALSE )
[static]
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns a pointer to the widget at global screen position pos, or 0 if
there is no Qt widget there.
If child is FALSE and there is a child widget at position pos, the top-
level widget containing it is returned. If child is TRUE the child
widget at position pos is returned.
bool QApplication::winEventFilter ( MSG * ) [virtual]
This virtual function is only implemented under Windows.
The message procedure calls this function for every message received.
Reimplement this function if you want to process window messages that
are not processed by Qt. If you don't want the event to be processed by
Qt, then return TRUE; otherwise return FALSE.
void QApplication::winFocus ( QWidget * widget, bool gotFocus )
This function is available only on Windows.
If gotFocus is TRUE, widget will become the active window. Otherwise
the active window is reset to NULL.
const QColor & QApplication::winStyleHighlightColor () [static]
This function is obsolete. It is provided to keep old source working.
We strongly advise against using it in new code.
Returns the color used to mark selections in windows style.
See also setWinStyleHighlightColor().
bool QApplication::x11EventFilter ( XEvent * ) [virtual]
This virtual function is only implemented under X11.
If you create an application that inherits QApplication and reimplement
this function, you get direct access to all X events that the are
received from the X server.
Return TRUE if you want to stop the event from being processed. Return
FALSE for normal event dispatching.
See also x11ProcessEvent().
int QApplication::x11ProcessEvent ( XEvent * event )
This function does the core processing of individual X events, normally
by dispatching Qt events to the right destination.
It returns 1 if the event was consumed by special handling, 0 if the
event was consumed by normal handling, and -1 if the event was for an
unrecognized widget.
See also x11EventFilter().
RELATED FUNCTION DOCUMENTATIONvoid Q_ASSERT ( bool test )
Prints a warning message containing the source code file name and line
number if test is FALSE.
This is really a macro defined in qglobal.h.
Q_ASSERT is useful for testing pre- and post-conditions.
Example:
//
// File: div.cpp
//
#include <qglobal.h>
int divide( int a, int b )
{
Q_ASSERT( b != 0 ); // this is line 9
return a/b;
}
If b is zero, the Q_ASSERT statement will output the following message
using the qWarning() function:
ASSERT: "b != 0" in div.cpp (9)
See also qWarning() and Debugging.
void Q_CHECK_PTR ( void * p )
If p is 0, prints a warning message containing the source code file
name and line number, saying that the program ran out of memory.
This is really a macro defined in qglobal.h.
Example:
int *a;
Q_CHECK_PTR( a = new int[80] ); // WRONG!
a = new (nothrow) int[80]; // Right
Q_CHECK_PTR( a );
See also qWarning() and Debugging.
void qAddPostRoutine ( QtCleanUpFunction p )
Adds a global routine that will be called from the QApplication
destructor. This function is normally used to add cleanup routines for
program-wide functionality.
The function given by p should take no arguments and return nothing,
like this:
static int *global_ptr = 0;
static void cleanup_ptr()
{
delete [] global_ptr;
global_ptr = 0;
}
void init_ptr()
{
global_ptr = new int[100]; // allocate data
qAddPostRoutine( cleanup_ptr ); // delete later
}
Note that for an application- or module-wide cleanup, qAddPostRoutine()
is often not suitable. People have a tendency to make such modules
dynamically loaded, and then unload those modules long before the
QApplication destructor is called, for example.
For modules and libraries, using a reference-counted initialization
manager or Qt' parent-child delete mechanism may be better. Here is an
example of a private class which uses the parent-child mechanism to
call a cleanup function at the right time:
class MyPrivateInitStuff: public QObject {
private:
MyPrivateInitStuff( QObject * parent ): QObject( parent) {
// initialization goes here
}
MyPrivateInitStuff * p;
public:
static MyPrivateInitStuff * initStuff( QObject * parent ) {
if ( !p )
p = new MyPrivateInitStuff( parent );
return p;
}
~MyPrivateInitStuff() {
// cleanup (the "post routine") goes here
}
}
By selecting the right parent widget/object, this can often be made to
clean up the module's data at the exact right moment.
void qDebug ( const char * msg, ... )
Prints a debug message msg, or calls the message handler (if it has
been installed).
This function takes a format string and a list of arguments, similar to
the C printf() function.
Example:
qDebug( "my window handle = %x", myWidget->id() );
Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.
Warning: The internal buffer is limited to 8196 bytes (including the
'\0'-terminator).
Warning: Passing (const char *)0 as argument to qDebug might lead to
crashes on certain platforms due to the platforms printf
implementation.
See also qWarning(), qFatal(), qInstallMsgHandler(), and Debugging.
void qFatal ( const char * msg, ... )
Prints a fatal error message msg and exits, or calls the message
handler (if it has been installed).
This function takes a format string and a list of arguments, similar to
the C printf() function.
Example:
int divide( int a, int b )
{
if ( b == 0 ) // program error
qFatal( "divide: cannot divide by zero" );
return a/b;
}
Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.
Warning: The internal buffer is limited to 8196 bytes (including the
'\0'-terminator).
Warning: Passing (const char *)0 as argument to qFatal might lead to
crashes on certain platforms due to the platforms printf
implementation.
See also qDebug(), qWarning(), qInstallMsgHandler(), and Debugging.
QtMsgHandler qInstallMsgHandler ( QtMsgHandler h )
Installs a Qt message handler h. Returns a pointer to the message
handler previously defined.
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.
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.
Only one message handler can be defined, since this is usually done on
an application-wide basis to control debug output.
To restore the message handler, call qInstallMsgHandler(0).
Example:
#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(); // deliberately core dump
}
}
int main( int argc, char **argv )
{
qInstallMsgHandler( myMessageOutput );
QApplication a( argc, argv );
...
return a.exec();
}
See also qDebug(), qWarning(), qFatal(), and Debugging.
bool qSysInfo ( int * wordSize, bool * bigEndian )
Obtains information about the system.
The system's word size in bits (typically 32) is returned in *wordSize.
The *bigEndian is set to TRUE if this is a big-endian machine, or to
FALSE if this is a little-endian machine.
In debug mode, this function calls qFatal() with a message if the
computer is truly weird (i.e. different endianness for 16 bit and 32
bit integers); in release mode it returns FALSE.
void qSystemWarning ( const char * msg, int code )
Prints the message msg and uses code to get a system specific error
message. When code is -1 (the default), the system's last error code
will be used if possible. Use this method to handle failures in
platform specific API calls.
This function does nothing when Qt is built with QT_NO_DEBUG defined.
const char * qVersion ()
Returns the Qt version number as a string, for example, "2.3.0" or"
3.0.5".
The QT_VERSION define has the numeric value in the form: 0xmmiibb (m =
major, i = minor, b = bugfix). For example, Qt 3.0.5's QT_VERSION is
0x030005.
void qWarning ( const char * msg, ... )
Prints a warning message msg, or calls the message handler (if it has
been installed).
This function takes a format string and a list of arguments, similar to
the C printf() function.
Example:
void f( int c )
{
if ( c > 200 )
qWarning( "f: bad argument, c == %d", c );
}
Under X11, the text is printed to stderr. Under Windows, the text is
sent to the debugger.
Warning: The internal buffer is limited to 8196 bytes (including the
'\0'-terminator).
Warning: Passing (const char *)0 as argument to qWarning might lead to
crashes on certain platforms due to the platforms printf
implementation.
See also qDebug(), qFatal(), qInstallMsgHandler(), and Debugging.
SEE ALSO
http://doc.trolltech.com/qapplication.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qapplication.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QApplication(3qt)