Home · All Classes · Main Classes · Annotated · Grouped Classes · Functions

QEvent Class Reference

The QEvent class is the base class of all event classes. Event objects contain event parameters. More...

#include <QEvent>

Part of the QtCore module.

Inherited by QChildEvent, QCloseEvent, QCustomEvent, QDragLeaveEvent, QDropEvent, QFileOpenEvent, QFocusEvent, QHideEvent, QHoverEvent, QIconDragEvent, QInputEvent, QInputMethodEvent, QMoveEvent, QPaintEvent, QResizeEvent, QShowEvent, QTimerEvent, and QToolBarChangeEvent.

Public Types

Properties

Public Functions


Detailed Description

The QEvent class is the base class of all event classes. Event objects contain event parameters.

Qt's main event loop (QApplication::exec()) fetches native window system events from the event queue, translates them into QEvents, and sends the translated events to QObjects.

In general, events come from the underlying window system (spontaneous() returns true), but it is also possible to manually send events using QApplication::sendEvent() and QApplication::postEvent() (spontaneous() returns false).

QObjects receive events by having their QObject::event() function called. The function can be reimplemented in subclasses to customize event handling and add additional event types; QWidget::event() is a notable example. By default, events are dispatched to event handlers like QObject::timerEvent() and QWidget::mouseMoveEvent(). QObject::installEventFilter() allows an object to intercept events destined for another object.

The basic QEvent contains only an event type parameter and an accept flag. The accept flag set with accept(), and cleared with ignore(). It is set by default, but don't rely on this as subclasses may choose to clear it in their constructor.

Subclasses of QEvent contain additional parameters that describe the particular event.

QWidget::event() QApplication::sendEvent() QApplication::postEvent() QApplication::processEvents()

See also QObject::event() and QObject::installEventFilter().


Member Type Documentation

enum QEvent::Type

This enum type defines the valid event types in Qt. The event types and the specialized classes for each type are as follows:

ConstantValueDescription
QEvent::None0Not an event.
QEvent::Accessibility86Accessibility information is requested.
QEvent::AccessibilityHelp119Used to query for additional information about complex widgets. QAccessibleEvent
QEvent::ActionChanged113An action has been changed.
QEvent::ActionAdded114A new action has been added.
QEvent::ActionRemoved115An action has been removed.
QEvent::ActivationChange99A widget's top-level window activation state has changed.
QEvent::ApplicationActivated121The application has been made available to the user.
QEvent::ApplicationDeactivated122The application has been suspended, and is unavailable to the user.
QEvent::ApplicationFontChange36The default application font has changed.
QEvent::ApplicationLayoutDirectionChange37The default application layout direction has changed.
QEvent::ApplicationPaletteChange38The default application palette has changed.
QEvent::ApplicationWindowIconChange35The application's icon has changed.
QEvent::ChildAdded68An object gets a child, QChildEvent.
QEvent::ChildPolished69A widget child gets polished, QChildEvent.
QEvent::ChildRemoved71An object loses a child, QChildEvent.
QEvent::Clipboard40The clipboard contents have changed.
QEvent::Close19Widget was closed (permanently), QCloseEvent.
QEvent::ContextMenu82Context popup menu, QContextMenuEvent
QEvent::Create15Reserved.
QEvent::DeferredDelete52The object will be deleted after it has cleaned up.
QEvent::Destroy16Reserved.
QEvent::DragEnter60The cursor enters a widget during a drag and drop action, QDragEnterEvent.
QEvent::DragLeave62The cursor leaves a widget during a drag and drop action, QDragLeaveEvent.
QEvent::DragMove61A drag and drop action is in progress, QDragMoveEvent.
QEvent::Drop63A drag and drop action is completed, QDropEvent.
QEvent::EnabledChange98Widget's enabled state has changed
QEvent::Enter10Mouse enters widget's boundaries.
QEvent::FileOpen116File open request.
QEvent::FocusIn8Widget gains keyboard focus, QFocusEvent.
QEvent::FocusOut9Widget loses keyboard focus, QFocusEvent.
QEvent::FontChange97Widget's font has changed
QEvent::Hide18Widget was hidden, QHideEvent.
QEvent::HideToParent27A child widget has been hidden.
QEvent::IconTextChange101Widget's icon text has been changed
QEvent::KeyPress6Key press (including Shift, for example), QKeyEvent.
QEvent::KeyRelease7Key release, QKeyEvent.
QEvent::LanguageChange89The application translation changed, QTranslator
QEvent::LayoutDirectionChange90The direction of layouts changed
QEvent::LayoutRequest76Widget layout needs to be redone.
QEvent::Leave11Mouse leaves widget's boundaries.
QEvent::LocaleChange88The system locale changed
QEvent::MetaCall43 
QEvent::ModifiedChange102Widgets modification state has been changed
QEvent::MouseButtonDblClick4Mouse press again, QMouseEvent.
QEvent::MouseButtonPress2Mouse press, QMouseEvent.
QEvent::MouseButtonRelease3Mouse release, QMouseEvent.
QEvent::MouseMove5Mouse move, QMouseEvent.
QEvent::MouseTrackingChange109The mouse tracking state has changed.
QEvent::Move13Widget's position changed, QMoveEvent.
QEvent::Paint12Screen update necessary, QPaintEvent.
QEvent::PaletteChange39Palette of the widget changed.
QEvent::Polish75The widget is polished.
QEvent::PolishRequest74The widget should be polished.
QEvent::Quit20Reserved.
QEvent::ParentChange21Reserved.
QEvent::Resize14Widget's size changed, QResizeEvent.
QEvent::Shortcut117Key press in child for shortcut key handling, QKeyEvent.
QEvent::ShortcutOverride51Key press in child, for overriding shortcut key handling, QKeyEvent.
QEvent::Show17Widget was shown on screen, QShowEvent.
QEvent::ShowToParent26A child widget has been shown.
QEvent::ShowWindowRequest73Widget's window should be shown (obsolete).
QEvent::SockAct50Socket activated, used to implement QSocketNotifier.
QEvent::Speech42Reserved for speech input.
QEvent::StatusTip112 
QEvent::StyleChange100Widget's style has been changed
QEvent::TabletMove87A Wacom Tablet Move Event.
QEvent::TabletPress92A Wacom Tablet Press Event
QEvent::TabletRelease93A Wacom Tablet Release Event
QEvent::Timer1Regular timer events, QTimerEvent.
QEvent::ToolBarChange120The toolbar button is toggled on Mac.
QEvent::ToolTip110 
QEvent::UpdateRequest77The widget should be repainted.
QEvent::WhatsThis111The widget should reveal What'sThis help
QEvent::WhatsThisClicked118A link in a widget's What's This help was clicked
QEvent::QueryWhatsThis123The widget should accept the event if it has What's This help
QEvent::EnterWhatsThisMode124Send to toplevel widgets when the application enters What's This mode
QEvent::LeaveWhatsThisMode125Send to toplevel widgets when the application leaves What's This mode
QEvent::Wheel31Mouse wheel rolled, QWheelEvent.
QEvent::WindowActivate24Window was activated.
QEvent::WindowBlocked103 
QEvent::WindowDeactivate25Window was deactivated.
QEvent::WindowIconChange34 
QEvent::WindowStateChange105The window's state, i.e. minimized, maximized or full-screen, has changed. See QWidget::windowState().
QEvent::WindowTitleChange33 
QEvent::WindowUnblocked104 
QEvent::ZOrderChange126The widget's z-order has changed. This event is never sent to top level windows.
QEvent::User1000User-defined event.
QEvent::MaxUser65535Last user event id.

User events should have values between User and MaxUser inclusive.


Property Documentation

accepted : bool

the accept flag of the event object

Setting the accept parameter indicates that the event receiver wants the event. Unwanted events might be propagated to the parent widget. By default, isAccepted() is set to true, but don't rely on this as subclasses may choose to clear it in their constructor.

For convenience, the accept flag can also be set with accept(), and cleared with ignore().

Access functions:


Member Function Documentation

QEvent::QEvent ( Type type )

Contructs an event object of type type.

QEvent::~QEvent ()   [virtual]

Destroys the event. If it was posted, it will be removed from the list of events to be posted.

void QEvent::accept ()

Sets the accept flag of the event object, the equivalent of callign setAccepted(true).

Setting the accept parameter indicates that the event receiver wants the event. Unwanted events might be propagated to the parent widget.

See also ignore().

void QEvent::ignore ()

Clears the accept flag parameter of the event object, the equivalent of calling setAccepted(false).

Clearing the accept parameter indicates that the event receiver does not want the event. Unwanted events might be propgated to the parent widget.

See also accept().

bool QEvent::spontaneous () const

Returns true if the event originated outside the application (a system event); otherwise returns false.

Type QEvent::type () const

Returns the event type.


Copyright © 2005 Trolltech Trademarks
Qt 4.0.0-b2