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# QWhatsThis Class Reference

The QWhatsThis class provides a simple description of any widget, i.e. answering the question "What's this?". More...

    #include <QWhatsThis>

- List of all members, including inherited members
- Obsolete members
- Compatibility members

### Static Public Members

- void enterWhatsThisMode ()
- void hideText ()
- bool inWhatsThisMode ()
- void leaveWhatsThisMode ()
- void showText ( const QPoint & pos, const QString & text, QWidget * w = 0 )

## Detailed Description

The QWhatsThis class provides a simple description of any widget, i.e. answering the question "What's this?".

"What's this?" help is part of an application's online help system, and provides users with information about the functionality and usage of a particular widget. "What's this?" help texts are typically longer and more detailed than tooltips, but generally provide less information than that supplied by separate help windows.

QWhatsThis provides a single window with an explanatory text that pops up when the user asks "What's this?". The default way for users to ask the question is to move the focus to the relevant widget and press Shift+F1. The help text appears immediately; it goes away as soon as the user does something else. (Note that if there is a shortcut for Shift+F1, this mechanism will not work.) Some dialogs provide a "?" button that users can click to enter "What's this?" mode; they then click the relevant widget to pop up the "What's this?" window. It is also possible to provide a a menu option or toolbar button to switch into "What's this?" mode.

To add "What's this?" text to a widget or an action, you simply call QWidget::setWhatsThis() or QAction::setWhatsThis().

The text can be either rich text or plain text. If you specify a rich text formatted string, it will be rendered using the default stylesheet, making it possible to embed images in the displayed text. To be as fast as possible, the default stylesheet uses a simple method to determine whether the text can be rendered as plain text. See QStyleSheet::defaultSheet() and QStyleSheet::mightBeRichText() for details.

            newAct = new QAction(tr("&New"), this);
            newAct->setShortcut(tr("Ctrl+N"));
            newAct->setStatusTip(tr("Create a new file"));
            newAct->setWhatsThis(tr("Click this option to create a new file."));

An alternative way to enter "What's this?" mode is to use the ready-made QWhatsThisAction, and add it to either a menu or a tool bar. By invoking this context help action (in the picture below the, buton with the arrow and question mark icon) the user switches into "What's this?" mode. If they now click on a widget the appropriate help text is shown. The mode is left when help is given or when the user presses Esc.

If you are using QMainWindow you can also use the QMainWindow::whatsThis() slot to enter the mode from a menu item.

You can enter "What's this?" mode programmatically with enterWhatsThisMode(), check the mode with inWhatsThisMode(), and return to normal mode with leaveWhatsThisMode().

If you want to control the "What's this?" behavior of a widget manually see `Qt::WA_CustomWhatsThis`.

It is also possible to show different help texts for different regions of a widget, by using a QHelpEvent of type QEvent::WhatsThis. Intercept the help event in your widget's QWidget::event() function and call QWhatsThis::showText() with the text you want to display for the position specified in QHelpEvent::pos(). If the text is rich text and the user clicks on a link, the widget also receives a QWhatsThisClickedEvent with the link's reference as QWhatsThisClickedEvent::href(). If a QWhatsThisClickedEvent is handled (i.e. QWidget::event() returns true), the help window remains visible. Call QWhatsThis::hideText() to hide it explicitly.

See also QToolTip.

## Member Function Documentation

### void QWhatsThis::enterWhatsThisMode () `[static]`

This function switches the user interface into "What's this?" mode. The user interface can be switched back into normal mode by the user (e.g. by them clicking or pressing Esc), or programmatically by calling leaveWhatsThisMode().

See also inWhatsThisMode().

### void QWhatsThis::hideText () `[static]`

If a "What's this?" window is showing, this destroys it.

See also showText().

### bool QWhatsThis::inWhatsThisMode () `[static]`

Returns true if the user interface is in "What's this?" mode; otherwise returns false.

See also enterWhatsThisMode().

### void QWhatsThis::leaveWhatsThisMode () `[static]`

If the user interface is in "What's this?" mode, this function switches back to normal mode; otherwise it does nothing.

See also enterWhatsThisMode() and inWhatsThisMode().

### void QWhatsThis::showText ( const QPoint & pos, const QString & text, QWidget * w = 0 ) `[static]`

Shows text as a "What's this?" window, at global position pos. The optional widget argument, w, is used to determine the appropriate screen on multi-head systems.

See also hideText().