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QAccel Class Reference

The QAccel class handles keyboard accelerator and shortcut keys. More...

#include <qaccel.h>

Inherits QObject.

List of all member functions.

Public Members


Static Public Members

Protected Members

Detailed Description

The QAccel class handles keyboard accelerator and shortcut keys.

A keyboard accelerator triggers an action when a certain key combination is pressed. The accelerator handles all keyboard activity for all children of one top level widget, so it is not affected by the keyboard focus.

In most cases, you will not need to use this class directly. Use QMenuData::insertItem() or QMenuData::setAccel() to make accelerators for operations that are also available on menus. Many widgets automatically generate accelerators, such as QButton, QGroupBox, QLabel(with QLabel::setBuddy()), QMenuBar and QTabBar. Example:

     QPushButton p( "&Exit", parent ); //automatic shortcut ALT+Key_E
     QPopupMenu *fileMenu = new fileMenu( parent );
     fileMenu->insertItem( "Undo", parent, SLOT(undo()), CTRL+Key_Z );

A QAccel contains a list of accelerator items. The following functions manipulate the list: insertItem(), removeItem(), clear(), key(), findKey().

Each accelerator item consists of an identifier and a keyboard code combined with modifiers (SHIFT, CTRL, ALT or UNICODE_ACCEL). For example, CTRL + Key_P could be a shortcut for printing a document. The key codes are listed in qnamespace.h. As an alternative, use UNICODE_ACCEL with the unicode code point of the character. For example, UNICODE_ACCEL + 'A' gives the same accelerator as Key_A.

When an accelerator key is pressed, the accelerator sends out the signal activated() with a number that identifies this particular accelerator item. Accelerator items can also be individually connected, so that two different keys will activate two different slots (see connectItem() and disconnectItem()).

Use setEnabled() to enable/disable all items in the accelerator, or setItemEnabled() to enable/disable individual items. An item is active only when the QAccel is enabled and the item itself is.

The function setWhatsThis() specifies the What's This text for an accelerator item.

A QAccel object handles key events to the QWidget::topLevelWidget() containing parent, and hence to any child widgets of that window. The accelerator will be deleted when parent is deleted, and will consume relevant key events until then.


     QAccel *a = new QAccel( myWindow );        // create accels for myWindow
     a->connectItem( a->insertItem(Key_P+CTRL), // adds Ctrl+P accelerator
                     myWindow,                  // connected to myWindow's
                     SLOT(printDoc()) );        // printDoc() slot

See also QKeyEvent, QWidget::keyPressEvent(), QMenuData::setAccel(), QButton::setAccel(), QLabel::setBuddy() and GUI Design Handbook: Keyboard Shortcuts

Member Function Documentation

QAccel::QAccel ( QWidget * parent, const char * name=0 )

Constructs a QAccel object with parent parent and name name. The accelerator operates on parent.

QAccel::QAccel ( QWidget * watch, QObject * parent, const char * name=0 )

Constructs a QAccel object that operates on watch, but is a child of parent.

This constructor is not needed for normal application programming.

QAccel::~QAccel ()

Destructs the accelerator object and frees all allocated resources.

void QAccel::activated ( int id ) [signal]

This signal is emitted when an accelerator key is pressed. id is a number that identifies this particular accelerator item.

void QAccel::clear ()

Removes all accelerator items.

bool QAccel::connectItem ( int id, const QObject * receiver, const char * member )

Connects the accelerator item id to the slot member of receiver.

    a->connectItem( 201, mainView, SLOT(quit()) );

Of course, you can also send a signal as member.

See also disconnectItem().

uint QAccel::count () const

Returns the number of accelerator items in this accelerator.

bool QAccel::disconnectItem ( int id, const QObject * receiver, const char * member )

Disconnects an accelerator item from a function in another object.

See also connectItem().

bool QAccel::eventFilter ( QObject * o, QEvent * e ) [virtual protected]

Processes accelerator events intended for the top level widget.

Reimplemented from QObject.

int QAccel::findKey ( int key ) const

Returns the identifier of the accelerator item with the key code key, or -1 if the item cannot be found.

int QAccel::insertItem ( int key, int id=-1 )

Inserts an accelerator item and returns the item's identifier.

key is a key code plus a combination of SHIFT, CTRL and ALT. id is the accelerator item id.

If id is negative, then the item will be assigned a unique negative identifier.

    QAccel *a = new QAccel( myWindow );         // create accels for myWindow
    a->insertItem( Key_P + CTRL, 200 );         // Ctrl+P to print document
    a->insertItem( Key_X + ALT , 201 );         // Alt+X  to quit
    a->insertItem( UNICODE_ACCEL + 'q', 202 );  // Unicode 'q' to quit
    a->insertItem( Key_D );                     // gets a unique negative id
    a->insertItem( Key_P + CTRL + SHIFT );      // gets a unique negative id

bool QAccel::isEnabled () const

Returns TRUE if the accelerator is enabled, or FALSE if it is disabled.

See also setEnabled() and isItemEnabled().

bool QAccel::isItemEnabled ( int id ) const

Returns TRUE if the accelerator item with the identifier id is enabled. Returns FALSE if the item is disabled or cannot be found.

See also setItemEnabled() and isEnabled().

int QAccel::key ( int id )

Returns the key code of the accelerator item with the identifier id, or zero if the id cannot be found.

QString QAccel::keyToString ( int k ) [static]

Creates an accelerator string for the key k. For instance CTRL+Key_O gives "Ctrl+O". The "Ctrl" etc. are translated (using QObject::tr()) in the "QAccel" scope.

See also stringToKey().

void QAccel::removeItem ( int id )

Removes the accelerator item with the identifier id.

void QAccel::repairEventFilter ()

Makes sure that the accelerator is watching the correct event filter. This function is called automatically; you should not need to call it in application code.

void QAccel::setEnabled ( bool enable )

Enables the accelerator if enable is TRUE, or disables it if enable is FALSE.

Individual keys can also be enabled or disabled using setItemEnabled(). To work, a key must be an enabled item in an enabled QAccel.

See also isEnabled() and setItemEnabled().

void QAccel::setItemEnabled ( int id, bool enable )

Enables the accelerator key item if enable is TRUE, and disables item if enable is FALSE.

To work, a key must be an enabled item in an enabled QAccel.

See also isItemEnabled() and isEnabled().

void QAccel::setWhatsThis ( int id, const QString & text )

Sets a Whats This help for the accelerator item id to text.

The text will be shown when the application is in What's This mode and the user hits the accelerator key.

To set Whats This help on a menu item (with or without an accelerator key) use QMenuData::setWhatsThis().

See also whatsThis(), QWhatsThis::inWhatsThisMode() and QMenuData::setWhatsThis().

int QAccel::shortcutKey ( const QString & str ) [static]

Returns the shortcut key for string, or 0 if string has no shortcut sequence.

For example, shortcutKey("E&xit") returns ALT+Key_X, shortcutKey("&Exit") returns ALT+Key_E and shortcutKey("Exit") returns 0. (In code that does not inherit the Qt namespace class, you need to write e.g. Qt::ALT+Qt::Key_X.)

We provide a list of common accelerators in English. At the time of writing the Microsoft and The Open Group appear to not have issued such recommendations for other languages.

int QAccel::stringToKey ( const QString & s ) [static]

Returns an accelerator code for the string s. For example "Ctrl+O" gives CTRL+UNICODE_ACCEL+'O'. The strings "Ctrl", "Shift", "Alt" are recognized, as well as their translated equivalents in the "QAccel" scope (using QObject::tr()). Returns 0 if s is not recognized.

A common usage of this function is to provide translatable accelerator values for menus:

        QPopupMenu* file = new QPopupMenu(this);
        file->insertItem( p1, tr("&Open..."), this, SLOT(open()),
            QAccel::stringToKey(tr("Ctrl+O")) );

QString QAccel::whatsThis ( int id ) const

Returns the Whats This help text for the specified item id or QString::null if no text has been defined yet.

See also setWhatsThis().

bool QAccel::ignoreWhatsThis () const

For internal use only.

void QAccel::setIgnoreWhatsThis ( bool b )

For internal use only.

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