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QPushButton Class Reference

The QPushButton widget provides a command button. More...

#include <qpushbutton.h>

Inherits QButton.

Inherited by QPEDateEdit and MenuButton.

List of all member functions.

Public Members

Public Slots

Important Inherited Members

Properties

Detailed Description

The QPushButton widget provides a command button.

The push button, also referred to as command button, is perhaps the most central widget in any graphical user interface: Push it to command the computer to perform some action. Typical actions are Ok, Apply, Cancel, Close or Help.

A command button is rectangular (ca. 80x22 pixel) and typically displays a text label describing its action. An underscored character in the label, marked with an ampersand in the text, signals an accelerator key.

This code creates a push button labelled "Rock & Roll". Due to the first ampersand, the c displays underscored and the button gets the automatic accelerator key, Alt-C: 

    QPushButton *p = new QPushButton( "Ro&ck && Roll", this );

The text can be changed anytime later with setText(). You can also define a pixmap with setPixmap(). The text/pixmap is manipulated as necessary to create "disabled" appearance according to the respective GUI style when the button is disabled. A command button can, in addition to the text or pixmap label, also display a little icon. Use the extended constructor or setIconSet() to define this icon.

A push button emits the signal clicked() when it is activated, either with the mouse, the spacebar or a keyboard accelerator. Connect to this signal to perform the button's action. Other signals of less importance are pressed() when the button is pressed down and released() when it is released, respectively.

Command buttons in dialogs are by default auto-default buttons, i.e. they become the default push button automatically when they receive the keyboard input focus. A default button is a command button that is activated when the users hits the Enter or Return key in a dialog. Adjust this behaviour with setAutoDefault(). Note that auto-default buttons reserve a little extra space necessary to draw a default-button indicator. If you do not want this space around your buttons, call setAutoDefault( FALSE ).

Being so central, the widget has grown to accomodate a great many variations in the past decade, and by now the Microsoft style guide shows about ten different states of Windows push buttons, and the text implies that there are dozens more when all the combinations of features are taken into consideration.

The most important modes or states are, sorted roughly by importance:

As a general rule, use a push button when the application or dialog window performs an action when the user clicks on it (like Apply, Cancel, Close, Help, ...) and when the widget is supposed to have a wide, rectangular shape with a text label. Small, typically square buttons that change the state of the window rather than performing an action (like for example the buttons in the top/right corner of the QFileDialog), are not command buttons, but tool buttons. Qt provides a special class QToolButton for these.

Also, if you need toggle behaviour (see setToggleButton()) or a button that auto-repeats the activation signal when being pushed down like the arrows in a scrollbar (see setAutoRepeat()), a command button is probably not what you want. In case of doubt, go with a tool button.

A variation of a command button is a menu button. It provides not just one command, but several. Use the method setPopup() to associate a popup menu with a push button.

Other classes of buttons are option buttons (see QRadioButton) and check boxes (see QCheckBox).

In Qt, the QButton class provides most of the modes and other API, and QPushButton provides GUI logic. See QButton for more information about the API.

See also QToolButton, QRadioButton, QCheckBox, and GUI Design Handbook: Push Button.

Member Function Documentation

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

Constructs a push button with no text.

The parent and name arguments are sent to the QWidget constructor.

QPushButton::QPushButton ( const QString & text, QWidget * parent, const char * name = 0 )

Constructs a push button with a text.

The parent and name arguments are sent to the QWidget constructor.

QPushButton::QPushButton ( const QIconSet & icon, const QString & text, QWidget * parent, const char * name = 0 )

Constructs a push button with an icon and a text.

Note that you can also pass a QPixmap object as icon (thanks to C++' implicit type conversion).

The parent and name arguments are sent to the QWidget constructor.

QPushButton::~QPushButton ()

Destructs the push button

int QButton::accel () const

Returns the accelerator key currently set for the button, or 0 if no accelerator key has been set.

See also setAccel().

bool QPushButton::autoDefault () const

Returns TRUE if the button is an auto-default button.

See also setAutoDefault().

bool QButton::autoRepeat () const

Returns TRUE if the button is auto-repeating, else FALSE.

The default is FALSE.

See also setAutoRepeat().

QButtonGroup * QButton::group () const

Returns a pointer to the group of which this button is a member.

If the button is not a member of any QButtonGroup, this function returns 0.

See also setGroup() and QButtonGroup.

QIconSet * QPushButton::iconSet () const

Returns the button's icon or 0 if no icon has been defined.

See also setIconSet().

bool QPushButton::isDefault () const

Returns TRUE if the button is currently default.

See also setDefault().

bool QButton::isDown () const

Returns TRUE if the button pressed down, or FALSE if it is standing up.

See also setDown().

bool QButton::isExclusiveToggle () const

Returns TRUE if this button behaves exclusively inside a QButtonGroup. In that case, this button can only be toggled off by another button being toggled on.

bool QPushButton::isFlat () const

Returns whether the border is disabled.

See also setFlat().

bool QPushButton::isMenuButton () const

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

Returns TRUE if this button indicates to the user that pressing it will pop up a menu, and FALSE otherwise. The default is FALSE.

See also setIsMenuButton().

bool QButton::isOn () const

Returns TRUE if this toggle button is switched on, or FALSE if it is switched off.

See also setOn() and isToggleButton().

bool QButton::isToggleButton () const

Returns TRUE if the button is a toggle button.

See also setToggleButton().

const QPixmap * QButton::pixmap () const

Returns the button pixmap, or 0 if the button has no pixmap.

QPopupMenu * QPushButton::popup () const

Returns the associated popup menu or 0 if no popup menu has been defined.

See also setPopup().

void QButton::pressed () [signal]

This signal is emitted when the button is pressed down.

See also released() and clicked().

void QButton::released () [signal]

This signal is emitted when the button is released.

See also pressed(), clicked(), and toggled().

void QButton::setAccel ( int key ) [virtual]

Specifies an accelerator key for the button, or removes the accelerator if key is 0.

Setting a button text containing a shortcut character (for example the 'x' in E&xit) automatically defines an ALT+letter accelerator for the button. You only need to call this function in order to specify a custom accelerator.

Example: 

    QPushButton *b1 = new QPushButton;
    b1->setText( "&OK" );               // sets accel ALT+'O'

    QPushButton *b2 = new QPushButton;
    b2->setPixmap( printIcon );         // pixmap instead of text
    b2->setAccel( CTRL+'P' );           // custom accel

See also accel(), setText(), and QAccel.

void QPushButton::setAutoDefault ( bool enable ) [virtual]

Sets the push buttons to an auto-default button if enable is TRUE, or to a normal button if enable is FALSE.

An auto-default button becomes automatically the default push button in a dialog when it receives the keyboard input focus.

In some GUI styles, a default button is drawn with an extra frame around it, up to 3 pixels or more. Qt automatically keeps this space free around auto-default buttons, i.e. auto-default buttons may have a slightly larger size hint.

See also autoDefault() and setDefault().

void QButton::setAutoRepeat ( bool enable ) [virtual]

Turns on auto-repeat for the button if enable is TRUE, or turns it off if enable is FALSE.

When auto-repeat is enabled, the clicked() signal is emitted at regular intervals while the buttons is down.

setAutoRepeat() has no effect for toggle buttons.

See also isDown(), autoRepeat(), and clicked().

void QPushButton::setDefault ( bool enable ) [virtual]

Sets this button to be the current default button of a dialog if enable is TRUE, or to be a normal button if enable is FALSE.

The current default button gets clicked when the user presses the "Enter" key, independently of which widget in the dialog currently has the keyboard input focus. Only one push button can at any time be the default button. This button is then displayed with an additional frame ( depending on the GUI style ).

The default button behaviour is only provided in dialogs. Buttons can always be clicked from the keyboard by pressing return or the spacebar when the button has focus.

See also isDefault(), setAutoDefault(), and QDialog.

void QButton::setDown ( bool enable ) [virtual]

Sets the state of the button to pressed down if enable is TRUE or to standing up if enable is FALSE.

If the button is a toggle button, it is not toggled. Call toggle() as well if you need to do that. The pressed() and released() signals are not emitted by this function.

This method is provided in case you need to reimplement the mouse event handlers.

See also isDown(), setOn(), toggle(), and toggled().

void QPushButton::setFlat ( bool f )

Disable the border.

See also flat().

void QPushButton::setIconSet ( const QIconSet & icon )

Sets the button to display the icon icon in addition to its text or pixmap

See also iconSet().

void QPushButton::setIsMenuButton ( bool enable ) [virtual]

This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.

Tells this button to draw a menu indication triangle if enable is TRUE, and to not draw one if enable is FALSE (the default).

setIsMenuButton() does not cause the button to do anything other than draw the menu indication.

See also isMenuButton().

void QPushButton::setOn ( bool enable ) [virtual slot]

Switches a toggle button on if enable is TRUE or off if enable is FALSE.

See also isOn(), toggle(), toggled(), and isToggleButton().

void QButton::setPixmap ( const QPixmap & pixmap ) [virtual]

Sets the button to display pixmap

If pixmap is monochrome (i.e. it is a QBitmap or its depth is 1) and it does not have a mask, this function sets the pixmap to be its own mask. The purpose of this is to draw transparent bitmaps, which is important for e.g. toggle buttons.

See also pixmap(), setText(), setAccel(), and QPixmap::mask().

void QPushButton::setPopup ( QPopupMenu * popup )

Associates the popup menu popup with this push button and thus turns it into a menu button.

Ownership of the popup menu is not transferred.

See also popup().

void QButton::setText ( const QString & text ) [virtual]

Sets the button to display text.

If the text contains an ampersand, QButton creates an automatic accelerator for it, such as Alt-c for "&Cancel".

See also text(), setPixmap(), setAccel(), and QPixmap::mask().

void QPushButton::setToggleButton ( bool enable ) [virtual]

Makes the push button a toggle button if enable is TRUE, or a normal push button if enable is FALSE.

Toggle buttons have an on/off state similar to check boxes. A push button is initially not a toggle button.

See also setOn(), toggle(), isToggleButton(), and toggled().

ToggleState QButton::state () const

Returns the state of the button.

See also ToggleState, ToggleType, and setState().

void QButton::stateChanged ( int state ) [signal]

This signal is emitted whenever a toggle button changes status. state is 2 if the button is on, 1 if it is in the "no change" state or 0 if the button is off.

This may be the result of a user action, toggle() slot activation, setState(), or because setOn() was called.

See also clicked().

QString QButton::text () const

Returns the button text, or null string if the button has no text.

See also setText().

void QPushButton::toggle () [slot]

Toggles the state of a toggle button.

See also isOn(), setOn(), toggled(), and isToggleButton().

void QButton::toggled ( bool on ) [signal]

This signal is emitted whenever a toggle button changes status. on is TRUE if the button is on, or FALSE if the button is off.

This may be the result of a user action, toggle() slot activation, or because setOn() was called.

See also clicked().

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Qtopia version 2.2.0