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QDialog Class Reference

The QDialog class is the base class of dialog windows. More...

#include <qdialog.h>

Inherits QWidget.

Inherited by QColorDialog, QErrorMessage, QFileDialog, QFontDialog, QInputDialog, QMessageBox, QProgressDialog, QTabDialog and QWizard.

List of all member functions.

Public Members

• QDialog ( QWidget * parent = 0, const char * name = 0, bool modal = FALSE, WFlags f = 0 )
• ~QDialog ()
• enum DialogCode { Rejected, Accepted }
• int result () const
• virtual void show ()
• void setOrientation ( Orientation orientation )
• Orientation orientation () const
• void setExtension ( QWidget * extension )
• QWidget * extension () const
• void setSizeGripEnabled ( bool )
• bool isSizeGripEnabled () const

Public Slots

• int exec ()

Properties

• bool sizeGripEnabled - whether the size grip is enabled

Protected Members

• void setResult ( int i )

Protected Slots

• virtual void done ( int r )
• virtual void accept ()
• virtual void reject ()
• void showExtension ( bool showIt )

Detailed Description

A dialog window is a top-level window mostly used for short-term tasks and brief communications with the user. QDialogs may be modal or modeless. QDialogs can have default buttons, support extensibility and may provide a return value. QDialogs can have a QSizeGrip in their lower-right corner, using setSizeGripEnabled().

Note that QDialog uses the parent widget slightly differently from other classes in Qt. A dialog is always a top-level widget, but if it has a parent, its default location is centered on top of the parent. It will also share the parent's taskbar entry, for example.

There are three kinds of dialog that are useful:

1. A modal dialog is a dialog that blocks input to other visible windows in the same application: users must finish interacting with the dialog and close it before they can access any other window in the application. Modal dialogs have their own local event loop. Dialogs which are used to request a filename from the user or which are used to set application preferences are usually modal. Call exec() to display a modal dialog. When the user closes the dialog, exec() will provide a useful return value, and the flow of control will follow on from the exec() call at this time. Typically we connect a default button, e.g. "OK", to the accept() slot and a "Cancel" button to the reject() slot, to get the dialog to close and return the appropriate value. Alternatively you can connect to the done() slot, passing it Accepted or Rejected.

2. A non-modal dialog is a dialog that operates independently of other windows in the same application. Find and replace dialogs in word-processors are often modeless to allow the user to interact with both the application's main window and the dialog. Call show() to display a non-modal dialog. show() returns immediately so the flow of control will continue in the calling code. In practice you will often call show() and come to the end of the function in which show() is called with control returning to the main event loop.

3. A "semi-modal" dialog is a modal dialog that returns control to the caller immediately. Semi-modal dialogs do not have their own event loop, so you will need to call QApplication::processEvents() periodically to give the semi-modal dialog the opportunity to process its events. A progress dialog (e.g. QProgressDialog) is an example, where you only want the user to be able to interact with the progress dialog, e.g. to cancel a long running operation, but need to actually carry out the operation. Semi-modal dialogs are displayed by setting the modal flag to TRUE and calling the show() function.

Default button
A dialog's "default" button is the button that's pressed when the user presses Enter or Return. This button is used to signify that the user accepts the dialog's settings and wishes to close the dialog. Use QPushButton::setDefault(), QPushButton::isDefault() and QPushButton::autoDefault() to set and control the dialog's default button.

Extensibility
Extensibility is the ability to show the dialog in two ways: a partial dialog that shows the most commonly used options, and a full dialog that shows all the options. Typically an extensible dialog will initially appear as a partial dialog, but with a "More" button. If the user clicks the "More" button, the full dialog will appear. Extensibility is controlled with setExtension(), setOrientation() and showExtension().

Return value (modal dialogs)
Modal dialogs are often used in situations where a return value is required; for example to indicate whether the user pressed OK or Cancel. A dialog can be closed by calling the accept() or the reject() slots, and exec() will return Accepted or Rejected as appropriate. After the exec() call has returned the result is available from result(). Note that if the WDestructiveClose flag is set, then when accept() returns the dialog is deleted.

Examples

A modal dialog.

        QFileDialog *dlg = new QFileDialog( workingDirectory,
                QString::null, 0, 0, TRUE );
        dlg->setCaption( QFileDialog::tr( "Open" ) );
        dlg->setMode( QFileDialog::ExistingFile );
        QString result;
        if ( dlg->exec() == QDialog::Accepted ) {
            result = dlg->selectedFile();
            workingDirectory = dlg->url();
        }
        delete dlg;
        return result;

A modeless dialog. After the show() call, control returns to the main event loop.

    int main( int argc, char **argv )
    {
        QApplication a( argc, argv );

        int scale = 10;

        LifeDialog *life = new LifeDialog( scale );
        a.setMainWidget( life );
        life->setCaption("Qt Example - Life");
        life->show();

        return a.exec();
    }

See the QProgressDialog documentation for an example of a semi-modal dialog.

See also QTabDialog, QWidget, QProgressDialog, GUI Design Handbook: Dialogs, Standard, Abstract Widget Classes and Dialog Classes.

Member Type Documentation

QDialog::DialogCode

The value returned by a modal dialog.

• QDialog::Accepted
• QDialog::Rejected

Member Function Documentation

QDialog::QDialog ( QWidget * parent = 0, const char * name = 0, bool modal = FALSE, WFlags f = 0 )

If modal is FALSE (the default), the dialog is modeless and should be displayed with show(). If modal is TRUE and the dialog is displayed with exec(), the dialog is modal, i.e. blocks input to other windows. If modal is TRUE and the dialog is displayed show(), the dialog is semi-modal.

The widget flags f are passed on to the QWidget constructor.

If, for example, you don't want a What's this button in the titlebar of the dialog, pass WStyle_Customize | WStyle_NormalBorder | WStyle_Title | WStyle_SysMenu in f.

We recommend that you always pass a non-null parent.

See also QWidget::setWFlags() and Qt::WidgetFlags.

QDialog::~QDialog ()

void QDialog::accept () [virtual protected slot]

See also reject() and done().

void QDialog::done ( int r ) [virtual protected slot]

If the dialog has the WDestructiveClose flag set, done() also deletes the dialog. If the dialog is the applications's main widget, the application terminates.

See also accept(), reject(), QApplication::mainWidget() and QApplication::quit().

Example: movies/main.cpp.

int QDialog::exec () [slot]

See also show() and result().

Examples: i18n/main.cpp, network/networkprotocol/view.cpp, qdir/qdir.cpp, showimg/showimg.cpp and wizard/main.cpp.

QWidget * QDialog::extension () const

See also setExtension().

bool QDialog::isSizeGripEnabled () const

Returns TRUE if the size grip is enabled; otherwise returns FALSE. See the "sizeGripEnabled" property for details.

Orientation QDialog::orientation () const

See also setOrientation().

void QDialog::reject () [virtual protected slot]

See also accept() and done().

int QDialog::result () const

Returns the modal dialog's result code, Accepted or Rejected.

void QDialog::setExtension ( QWidget * extension )

This function must only be called while the dialog is hidden.

See also showExtension(), setOrientation() and extension().

void QDialog::setOrientation ( Orientation orientation )

See also orientation() and setExtension().

void QDialog::setResult ( int i ) [protected]

Sets the modal dialog's result code to i.

void QDialog::setSizeGripEnabled ( bool )

Sets whether the size grip is enabled. See the "sizeGripEnabled" property for details.

void QDialog::show () [virtual]

The dialog does not have a local event loop so you must call QApplication::processEvents() periodically to give the dialog the opportunity to process its events.

The dialog will be semi-modal if the modal flag was set to TRUE in the constructor.

Warning:

In Qt 2.x, calling show() on a modal dialog enters a local event loop, and works like exec(), but doesn't return the result code exec() returns. Trolltech has always warned that doing this is unwise.

See also exec().

Examples: movies/main.cpp, showimg/showimg.cpp, sql/overview/form1/main.cpp and tabdialog/main.cpp.

Reimplemented from QWidget.

void QDialog::showExtension ( bool showIt ) [protected slot]

This slot is usually connected to the QButton::toggled() signal of a QPushButton.

If the dialog is not visible, or has no extension, nothing happens.

See also show(), setExtension() and setOrientation().

Property Documentation

bool sizeGripEnabled

This property holds whether the size grip is enabled.

A QSizeGrip is placed in the bottom right corner of the dialog when this property is enabled. By default, the size grip is disabled.

Set this property's value with setSizeGripEnabled() and get this property's value with isSizeGripEnabled().

This file is part of the Qt toolkit. Copyright © 1995-2002 Trolltech. All Rights Reserved.