QPushButton Class Reference

#include <qpushbutton.h>

Inheritance diagram for QPushButton:

[legend]Collaboration diagram for QPushButton:

[legend]List of all members.

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Detailed Description

The QPushButton widget provides a command button.

The push button, or command button, is perhaps the most commonly used widget in any graphical user interface. Push (click) a button to command the computer to perform some action, or to answer a question. Typical buttons are OK, Apply, Cancel, Close, Yes, No and Help.

A command button is rectangular and typically displays a text label describing its action. A shortcut key can be specified by preceding the preferred character with an ampersand in the text. For example:

        QPushButton *button = new QPushButton("&Download", this);

In this example the shortcut is {Alt+D}. See the {QShortcut::mnemonic}{QShortcut} documentation for details (to display an actual ampersand, use '&&').

Push buttons display a textual label, and optionally a small icon. These can be set using the constructors and changed later using setText() and setIcon(). If the button is disabled the appearance of the text and icon will be manipulated with respect to the GUI style to make the button look "disabled".

A push button emits the signal clicked() when it is activated by the mouse, the Spacebar or by a keyboard shortcut. Connect to this signal to perform the button's action. Push buttons also provide less commonly used signals, for example, pressed() and released().

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 push button that is activated when the user presses the Enter or Return key in a dialog. You can change this with setAutoDefault(). Note that auto-default buttons reserve a little extra space which is necessary to draw a default-button indicator. If you do not want this space around your buttons, call setAutoDefault(false).

Being so central, the button widget has grown to accommodate a great many variations in the past decade. The Microsoft style guide now 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: Available or not (grayed out, disabled). Standard push button, toggling push button or menu button. On or off (only for toggling push buttons). Default or normal. The default button in a dialog can generally be "clicked" using the Enter or Return key. Auto-repeat or not. Pressed down or not.

As a general rule, use a push button when the application or dialog window performs an action when the user clicks on it (such as Apply, Cancel, Close and 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 (such as 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 buttons.

If you need toggle behavior (see setCheckable()) or a button that auto-repeats the activation signal when being pushed down like the arrows in a scroll bar (see setAutoRepeat()), a command button is probably not what you want. When in doubt, use a tool button.

A variation of a command button is a menu button. These provide not just one command, but several, since when they are clicked they pop up a menu of options. Use the method setMenu() to associate a popup menu with a push button.

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

100% macintosh-pushbutton.png Screenshot of a Macintosh style push button A push button shown in the {Macintosh Style Widget Gallery}{Macintosh widget style}. windowsxp-pushbutton.png Screenshot of a Windows XP style push button A push button shown in the {Windows XP Style Widget Gallery}{Windows XP widget style}. plastique-pushbutton.png Screenshot of a Plastique style push button A push button shown in the {Plastique Style Widget Gallery}{Plastique widget style}.

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

See also:

QToolButton, QRadioButton, QCheckBox, {fowler}{GUI Design Handbook: Push Button}

Definition at line 36 of file qpushbutton.h.

Public Slots
void	showMenu ()
Public Member Functions
	QPushButton (QWidget *parent=0)
	QPushButton (const QString &text, QWidget *parent=0)
	QPushButton (const QIcon &icon, const QString &text, QWidget *parent=0)
	~QPushButton ()
QSize	sizeHint () const
bool	autoDefault () const
void	setAutoDefault (bool)
bool	isDefault () const
void	setDefault (bool)
void	setMenu (QMenu *menu)
QMenu *	menu () const
void	setFlat (bool)
bool	isFlat () const
Protected Member Functions
bool	event (QEvent *e)
void	paintEvent (QPaintEvent *)
void	keyPressEvent (QKeyEvent *)
void	focusInEvent (QFocusEvent *)
void	focusOutEvent (QFocusEvent *)

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Constructor & Destructor Documentation

QPushButton::QPushButton

(

QWidget *

parent = 0

)

[explicit]

Constructs a push button with no text and a parent.

Definition at line 227 of file qpushbutton.cpp.

References d.

    : QAbstractButton(*new QPushButtonPrivate, parent)
{
    Q_D(QPushButton);
    d->init();
}

QPushButton::QPushButton	(	const QString &	text,
		QWidget *	parent = 0
	)			[explicit]

Constructs a push button with the parent parent and the text text.

Definition at line 239 of file qpushbutton.cpp.

References d, QAbstractButton::setText(), and QAbstractButton::text().

    : QAbstractButton(*new QPushButtonPrivate, parent)
{
    Q_D(QPushButton);
    d->init();
    setText(text);
}

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QPushButton::QPushButton	(	const QIcon &	icon,
		const QString &	text,
		QWidget *	parent = 0
	)

Constructs a push button with an icon and a text, and a parent.

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

Definition at line 255 of file qpushbutton.cpp.

References d, QAbstractButton::icon(), QAbstractButton::setIcon(), QAbstractButton::setText(), and QAbstractButton::text().

    : QAbstractButton(*new QPushButtonPrivate, parent)
{
    Q_D(QPushButton);
    d->init();
    setText(text);
    setIcon(icon);
}

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QPushButton::~QPushButton

(

)

Destroys the push button.

Definition at line 268 of file qpushbutton.cpp.

{
}

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Member Function Documentation

QSize QPushButton::sizeHint

(

)

const [virtual]

Reimplemented from QWidget.

Definition at line 362 of file qpushbutton.cpp.

References QStyle::CT_PushButton, d, QWidget::ensurePolished(), QWidget::fontMetrics(), QString::fromLatin1(), QApplication::globalStrut(), h, QSize::height(), QAbstractButton::icon(), QStyleOptionButton::iconSize, isNull(), menu(), QStyle::pixelMetric(), QStyle::PM_MenuButtonIndicator, qMax(), s, QFontMetrics::size(), QWidget::style(), QAbstractButton::text(), Qt::TextShowMnemonic, w, and QSize::width().

Referenced by QProgressDialogPrivate::layout(), Q3ProgressDialog::layout(), Q3TabDialog::setSizes(), Q3ProgressDialog::sizeHint(), and Q3FileDialog::updateGeometries().

{
    Q_D(const QPushButton);
    ensurePolished();

    int w = 0, h = 0;

    QStyleOptionButton opt = d->getStyleOption();

    // calculate contents size...
#ifndef QT_NO_ICON
    if (!icon().isNull()) {
        int ih = opt.iconSize.height();
        int iw = opt.iconSize.width() + 4;
        w += iw;
        h = qMax(h, ih);
    }
#endif
#ifndef QT_NO_MENU
    if (menu())
        w += style()->pixelMetric(QStyle::PM_MenuButtonIndicator, &opt, this);
#endif
    QString s(text());
    bool empty = s.isEmpty();
    if (empty)
        s = QString::fromLatin1("XXXX");
    QFontMetrics fm = fontMetrics();
    QSize sz = fm.size(Qt::TextShowMnemonic, s);
    if(!empty || !w)
        w += sz.width();
    if(!empty || !h)
        h = qMax(h, sz.height());
    return (style()->sizeFromContents(QStyle::CT_PushButton, &opt, QSize(w, h), this).
            expandedTo(QApplication::globalStrut()));
}

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bool QPushButton::autoDefault

(

)

const

Definition at line 329 of file qpushbutton.cpp.

References QPushButtonPrivate::Auto, and d.

Referenced by focusInEvent(), focusOutEvent(), keyPressEvent(), and QDialog::setVisible().

{
    Q_D(const QPushButton);
    if(d->autoDefault == QPushButtonPrivate::Auto)
        return ( d->dialogParent() != 0 );
    return d->autoDefault;
}

void QPushButton::setAutoDefault

(

bool

)

Definition at line 318 of file qpushbutton.cpp.

References QPushButtonPrivate::Auto, d, QPushButtonPrivate::Off, QPushButtonPrivate::On, QWidget::update(), and QWidget::updateGeometry().

Referenced by qdesigner_internal::QtGradientDialog::QtGradientDialog(), and Server::Server().

{
    Q_D(QPushButton);
    uint state = enable ? QPushButtonPrivate::On : QPushButtonPrivate::Off;
    if (d->autoDefault != QPushButtonPrivate::Auto && d->autoDefault == state)
        return;
    d->autoDefault = state;
    update();
    updateGeometry();
}

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bool QPushButton::isDefault

(

)

const

Definition at line 353 of file qpushbutton.cpp.

References d.

Referenced by QAccessibleButton::state(), and QAccessibleButton::text().

{
    Q_D(const QPushButton);
    return d->defaultButton;
}

void QPushButton::setDefault

(

bool

)

Definition at line 337 of file qpushbutton.cpp.

References d, QAccessible::StateChanged, QWidget::update(), and QAccessible::updateAccessibility().

Referenced by BlockingClient::BlockingClient(), Client::Client(), Window::createMessageGroupBox(), WidgetGallery::createTopRightGroupBox(), FtpWindow::ftpCommandFinished(), FtpWindow::FtpWindow(), QDialogPrivate::hideDefault(), HttpWindow::HttpWindow(), QColorDialogPrivate::init(), QInputDialogPrivate::init(), Q3FileDialog::init(), ItemDialog::ItemDialog(), qdesigner_internal::OldSignalSlotDialog::OldSignalSlotDialog(), NewForm::on_treeWidget_currentItemChanged(), PluginDialog::PluginDialog(), Q3TabDialog::Q3TabDialog(), Q3Wizard::Q3Wizard(), QFontDialog::QFontDialog(), qdesigner_internal::RichTextEditorDialog::RichTextEditorDialog(), SpreadSheet::runInputDialog(), QDialogPrivate::setDefault(), QDialog::setVisible(), Oubliette::showInventory(), TableEditor::TableEditor(), and VersionDialog::VersionDialog().

{
    Q_D(QPushButton);
    if (d->defaultButton == enable)
        return;
    d->defaultButton = enable;
    if (d->defaultButton) {
        if (QDialog *dlg = d->dialogParent())
            dlg->d_func()->setMainDefault(this);
    }
    update();
#ifndef QT_NO_ACCESSIBILITY
    QAccessible::updateAccessibility(this, 0, QAccessible::StateChanged);
#endif
}

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void QPushButton::setMenu

(

QMenu *

menu

)

Associates the popup menu menu with this push button. This turns the button into a menu button, which in some styles will produce a small triangle to the right of the button's text.

Ownership of the menu is not transferred to the push button.

See also:

menu()

Definition at line 473 of file qpushbutton.cpp.

References QWidget::addAction(), QObject::connect(), d, QObject::disconnect(), menu(), QAbstractButton::pressed(), QWidget::removeAction(), SIGNAL, SLOT, QWidget::update(), and QWidget::updateGeometry().

Referenced by Window::createPushButtonGroup().

{
    Q_D(QPushButton);
    if (menu == d->menu)
        return;

    if (menu && !d->menu) {
        disconnect(this, SIGNAL(pressed()), this, SLOT(_q_popupPressed()));
        connect(this, SIGNAL(pressed()), this, SLOT(_q_popupPressed()));
    }
    if (d->menu)
        removeAction(d->menu->menuAction());
    d->menu = menu;
    if (d->menu)
        addAction(d->menu->menuAction());
    update();
    updateGeometry();
}

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QMenu * QPushButton::menu

(

)

const

Returns the button's associated popup menu or 0 if no popup menu has been set.

See also:

setMenu()

Definition at line 498 of file qpushbutton.cpp.

References d.

Referenced by AccessibleFactory::create(), QAccessibleButton::doAction(), setMenu(), sizeHint(), and QAccessibleButton::state().

{
    Q_D(const QPushButton);
    return d->menu;
}

void QPushButton::setFlat

(

bool

)

Definition at line 563 of file qpushbutton.cpp.

References d, QWidget::update(), and QWidget::updateGeometry().

Referenced by Window::createPushButtonGroup(), and WidgetGallery::createTopRightGroupBox().

{
    Q_D(QPushButton);
    if (d->flat == flat)
        return;
    d->flat = flat;
    update();
    updateGeometry();
}

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bool QPushButton::isFlat

(

)

const

Definition at line 573 of file qpushbutton.cpp.

References d.

{
    Q_D(const QPushButton);
    return d->flat;
}

void QPushButton::showMenu

(

)

[slot]

Shows (pops up) the associated popup menu. If there is no such menu, this function does nothing. This function does not return until the popup menu has been closed by the user.

Definition at line 509 of file qpushbutton.cpp.

References d, and QAbstractButton::setDown().

Referenced by QAccessibleButton::doAction().

{
    Q_D(QPushButton);
    if (!d || !d->menu)
        return;
    setDown(true);
    d->_q_popupPressed();
}

bool QPushButton::event

(

QEvent *

e

)

[protected, virtual]

Reimplemented from QAbstractButton.

Definition at line 580 of file qpushbutton.cpp.

References QAbstractButton::event().

Referenced by qdesigner_internal::StyledButton::paintEvent().

{
    return QAbstractButton::event(e);
}

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void QPushButton::paintEvent

(

QPaintEvent *

)

[protected, virtual]

Implements QAbstractButton.

Definition at line 402 of file qpushbutton.cpp.

References QStyle::CE_PushButton, d, and p.

Referenced by qdesigner_internal::StyledButton::paintEvent().

{
    Q_D(QPushButton);
    QStylePainter p(this);
    p.drawControl(QStyle::CE_PushButton, d->getStyleOption());
}

void QPushButton::keyPressEvent

(

QKeyEvent *

e

)

[protected, virtual]

Reimplemented from QAbstractButton.

Definition at line 411 of file qpushbutton.cpp.

References autoDefault(), QAbstractButton::click(), d, QKeyEvent::key(), Qt::Key_Enter, Qt::Key_Return, and QAbstractButton::keyPressEvent().

{
    Q_D(QPushButton);
    switch (e->key()) {
    case Qt::Key_Enter:
    case Qt::Key_Return:
        if (autoDefault() || d->defaultButton) {
            click();
            break;
        }
        // fall through
    default:
        QAbstractButton::keyPressEvent(e);
    }
}

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void QPushButton::focusInEvent

(

QFocusEvent *

e

)

[protected, virtual]

Reimplemented from QAbstractButton.

Definition at line 430 of file qpushbutton.cpp.

References autoDefault(), d, QAbstractButton::focusInEvent(), Qt::PopupFocusReason, QFocusEvent::reason(), and QWidget::window().

{
    Q_D(QPushButton);
    if (e->reason() != Qt::PopupFocusReason && autoDefault() && !d->defaultButton) {
        d->defaultButton = true;
        QDialog *dlg = qobject_cast<QDialog*>(window());
        if (dlg)
            dlg->d_func()->setDefault(this);
    }
    QAbstractButton::focusInEvent(e);
}

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void QPushButton::focusOutEvent

(

QFocusEvent *

e

)

[protected, virtual]

Reimplemented from QAbstractButton.

Definition at line 445 of file qpushbutton.cpp.

References autoDefault(), d, QAbstractButton::focusOutEvent(), Qt::PopupFocusReason, QFocusEvent::reason(), QAbstractButton::setDown(), and QWidget::window().

{
    Q_D(QPushButton);
    if (e->reason() != Qt::PopupFocusReason && autoDefault() && d->defaultButton) {
        QDialog *dlg = qobject_cast<QDialog*>(window());
        if (dlg)
            dlg->d_func()->setDefault(0);
        else
            d->defaultButton = false;
    }

    QAbstractButton::focusOutEvent(e);
#ifndef QT_NO_MENU
    if (d->menu && d->menu->isVisible())        // restore pressed status
        setDown(true);
#endif
}

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The documentation for this class was generated from the following files:

• src/gui/widgets/qpushbutton.h
• src/gui/widgets/qpushbutton.cpp

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