QDialog Class

A modal dialog is a dialog that blocks input to other visible windows in the same application. Dialogs that are used to request a file name from the user or that are used to set application preferences are usually modal. Dialogs can be application modal (the default) or window modal.

When an application modal dialog is opened, the user must finish interacting with the dialog and close it before they can access any other window in the application. Window modal dialogs only block access to the window associated with the dialog, allowing the user to continue to use other windows in an application.

The most common way to display a modal dialog is to call its exec() function. When the user closes the dialog, exec() will provide a useful return value. To close the dialog and return the appropriate value, you must connect a default button, e.g. an OK button to the accept() slot and a Cancel button to the reject() slot. Alternatively, you can call the done() slot with Accepted or Rejected.

An alternative is to call setModal(true) or setWindowModality(), then show(). Unlike exec(), show() returns control to the caller immediately. Calling setModal(true) is especially useful for progress dialogs, where the user must have the ability to interact with the dialog, e.g. to cancel a long running operation. If you use show() and setModal(true) together to perform a long operation, you must call QCoreApplication::processEvents() periodically during processing to enable the user to interact with the dialog. (See QProgressDialog.)

A modeless 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 with the dialog.

Modeless dialogs are displayed using show(), which returns control to the caller immediately.

If you invoke the show() function after hiding a dialog, the dialog will be displayed in its original position. This is because the window manager decides the position for windows that have not been explicitly placed by the programmer. To preserve the position of a dialog that has been moved by the user, save its position in your closeEvent() handler and then move the dialog to that position, before showing it again.

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

If the user presses the Esc key in a dialog, QDialog::reject() will be called. This will cause the window to close: The close event cannot be ignored.

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 toggle button. If the user presses the More button down, the dialog is expanded. The Extension Example shows how to achieve extensible dialogs using Qt.

Modal dialogs are often used in situations where a return value is required, e.g. 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. The exec() call returns the result of the dialog. The result is also available from result() if the dialog has not been destroyed.

In order to modify your dialog's close behavior, you can reimplement the functions accept(), reject() or done(). The closeEvent() function should only be reimplemented to preserve the dialog's position or to override the standard close or reject behavior.

A modal dialog:

void EditorWindow::countWords()
{
    WordCountDialog dialog(this);
    dialog.setWordCount(document().wordCount());
    dialog.exec();
}

A modeless dialog:

void EditorWindow::find()
{
    if (!findDialog) {
        findDialog = new FindDialog(this);
        connect(findDialog, &FindDialog::findNext,
                this, &EditorWindow::findNext);
    }

    findDialog->show();
    findDialog->raise();
    findDialog->activateWindow();
}

See also QDialogButtonBox, QTabWidget, QWidget, QProgressDialog, Extension Example, Standard Dialogs Example

The value returned by a modal dialog.

This property holds whether show() should pop up the dialog as modal or modeless

By default, this property is false and show() pops up the dialog as modeless. Setting this property to true is equivalent to setting QWidget::windowModality to Qt::ApplicationModal.

exec() ignores the value of this property and always pops up the dialog as modal.

Access functions:

• bool isModal() const

• void setModal(bool modal)

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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.

Access functions:

• bool isSizeGripEnabled() const

• void setSizeGripEnabled(bool)

Constructs a dialog with parent parent.

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.

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 title bar of the dialog, pass Qt::WindowTitleHint | Qt::WindowSystemMenuHint in f.

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Destroys the QDialog, deleting all its children.

Hides the modal dialog and sets the result code to Accepted.

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This signal is emitted when the dialog has been accepted either by the user or by calling accept() or done() with the QDialog::Accepted argument.

Note that this signal is not emitted when hiding the dialog with hide() or setVisible(false). This includes deleting the dialog while it is visible.

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Reimplements: QWidget::closeEvent(QCloseEvent *event).

Reimplements: QWidget::contextMenuEvent(QContextMenuEvent *event).

Closes the dialog and sets its result code to r. The finished() signal will emit r; if r is QDialog::Accepted or QDialog::Rejected, the accepted() or the rejected() signals will also be emitted, respectively.

If this dialog is shown with exec(), done() also causes the local event loop to finish, and exec() to return r.

As with QWidget::close(), done() deletes the dialog if the Qt::WA_DeleteOnClose flag is set. If the dialog is the application's main widget, the application terminates. If the dialog is the last window closed, the QGuiApplication::lastWindowClosed() signal is emitted.

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Reimplements: QObject::eventFilter(QObject *watched, QEvent *event).

Shows the dialog as a modal dialog, blocking until the user closes it. The function returns a DialogCode result.

If the dialog is application modal, users cannot interact with any other window in the same application until they close the dialog. If the dialog is window modal, only interaction with the parent window is blocked while the dialog is open. By default, the dialog is application modal.

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This signal is emitted when the dialog's result code has been set, either by the user or by calling done(), accept(), or reject().

Note that this signal is not emitted when hiding the dialog with hide() or setVisible(false). This includes deleting the dialog while it is visible.

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Reimplements: QWidget::keyPressEvent(QKeyEvent *event).

Reimplements an access function for property: QWidget::minimumSizeHint.

Shows the dialog as a window modal dialog, returning immediately.

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Hides the modal dialog and sets the result code to Rejected.

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This signal is emitted when the dialog has been rejected either by the user or by calling reject() or done() with the QDialog::Rejected argument.

Note that this signal is not emitted when hiding the dialog with hide() or setVisible(false). This includes deleting the dialog while it is visible.

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Reimplements: QWidget::resizeEvent(QResizeEvent *event).

In general returns the modal dialog's result code, Accepted or Rejected.

Do not call this function if the dialog was constructed with the Qt::WA_DeleteOnClose attribute.

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Sets the modal dialog's result code to i.

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Reimplements an access function for property: QWidget::visible.

Reimplements: QWidget::showEvent(QShowEvent *event).

Reimplements an access function for property: QWidget::sizeHint.