Qt Toolkit - QKeyEvent Class

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# QKeyEvent Class Reference

The QKeyEvent class contains parameters that describe a key event. More...

`#include <qevent.h>`

Inherits QEvent.

List of all member functions.

## Public Members

- QKeyEvent ( Type type, int key, int ascii, int state, const QString & text=QString::null, bool autorep=FALSE, ushort count=1 )
- int key () const
- int ascii () const
- ButtonState state () const
- ButtonState stateAfter () const
- bool isAccepted () const
- QString text () const
- bool isAutoRepeat () const
- int count () const
- void accept ()
- void ignore ()

## Detailed Description

The QKeyEvent class contains parameters that describe a key event.

Key events occur when a key is pressed or released when a widget has keyboard input focus.

A key event contains a special accept flag which tells whether the receiver wants the key. You should call QKeyEvent::ignore() if the key press or release event is not handled by your widget.

The QWidget::setEnable() function can be used to enable or disable mouse and keyboard events for a widget.

The event handlers QWidget::keyPressEvent() and QWidget::keyReleaseEvent() receive key events.

See also QFocusEvent and QWidget::grabKeyboard().

Examples: picture/picture.cpp

## Member Function Documentation

### QKeyEvent::QKeyEvent ( Type type, int key, int ascii, int state, const QString & text=QString::null, bool autorep=FALSE, ushort count=1 )

Constructs a key event object.

The type parameter must be `QEvent::KeyPress` or `QEvent::KeyRelease.`

If key is 0, the event is not a result of a known key (e.g. it may be the result of a compose sequence or keyboard macro).

text will be returned by text().

If autorep is TRUE then isAutoRepeat() will be TRUE.

count is the number of single keys.

The accept flag is set to TRUE.

### void QKeyEvent::accept ()

Sets the accept flag of the key event object.

Setting the accept parameter indicates that the receiver of the event wants the key event. Unwanted key events are sent to the parent widget.

The accept flag is set by default.

See also ignore().

### int QKeyEvent::ascii () const

Returns the ASCII code of the key that was pressed or released. We recommend using text() instead.

See also text().

Examples: picture/picture.cpp

### int QKeyEvent::count () const

Returns the number of single keys for this event. If text() is not empty, this is simply the length of the string.

However, Qt also compresses invisible keycodes, such as BackSpace. For those, count() returns the number of key presses/repeats this event represents.

See also QWidget::setKeyCompression().

### void QKeyEvent::ignore ()

Clears the accept flag parameter of the key event object.

Clearing the accept parameter indicates that the event receiver does not want the key event. Unwanted key events are sent to the parent widget.

The accept flag is set by default.

See also accept().

### bool QKeyEvent::isAccepted () const

Returns TRUE if the receiver of the event wants to keep the key.

### bool QKeyEvent::isAutoRepeat () const

Returns TRUE if this event comes from an auto-repeating key and FALSE if it comes from an initial press.

Note that if the event is a multiple-key compressed event which partly is due to autorepeat, this function returns an indeterminate value.

### int QKeyEvent::key () const

Returns the code of the key that was pressed or released.

The header file qnamespace.h lists the possible keyboard codes. These codes are independent of the underlying window system.

Key code 0 means that the event is not a result of a known key (e.g. it may be the result of a compose sequence or keyboard macro).

### ButtonState QKeyEvent::state () const

Returns the keyboard modifier flags that existed immediately before the event occurred.

The returned value is `ShiftButton, ControlButton` and `AltButton` OR'ed together.

See also stateAfter().

### ButtonState QKeyEvent::stateAfter () const

Returns the keyboard modifier flags that existed immediately after the event occurred.

Warning: This function cannot be trusted.

See also state().

### QString QKeyEvent::text () const

Returns the Unicode text which this key generated.

See also QWidget::setKeyCompression().

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