Q3WhatsThis Class Reference

#include <q3whatsthis.h>

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List of all members.

Detailed Description

Definition at line 37 of file q3whatsthis.h.

Public Member Functions

 Q3WhatsThis (QWidget *)
 ~Q3WhatsThis ()
bool eventFilter (QObject *, QEvent *)
virtual QString text (const QPoint &)
virtual bool clicked (const QString &href)

Static Public Member Functions

static void enterWhatsThisMode ()
static bool inWhatsThisMode ()
static void add (QWidget *w, const QString &s)
static void remove (QWidget *w)
static QToolButton * whatsThisButton (QWidget *parent)
static void leaveWhatsThisMode (const QString &text=QString(), const QPoint &pos=QCursor::pos(), QWidget *w=0)
static void display (const QString &text, const QPoint &pos=QCursor::pos(), QWidget *w=0)

Constructor & Destructor Documentation

Q3WhatsThis::Q3WhatsThis ( QWidget *  widget  ) 

Constructs a new "What's This?" object for widget.

Definition at line 36 of file q3whatsthis.cpp.

References QObject::installEventFilter(), and QLayoutItem::widget().

00037     : QObject(widget)
00038 {
00039     if (widget)
00040         widget->installEventFilter(this);
00041 }

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Q3WhatsThis::~Q3WhatsThis (  ) 

Destroys the "What's This?" object.

Definition at line 46 of file q3whatsthis.cpp.

00047 {
00048 }

Member Function Documentation

bool Q3WhatsThis::eventFilter ( QObject *  o,
QEvent *  e 
) [virtual]

Filters events if this object has been installed as an event filter for the watched object.

In your reimplementation of this function, if you want to filter the event out, i.e. stop it being handled further, return true; otherwise return false.

Example: 

        class MainWindow : public QMainWindow
        {
        public:
            MainWindow();

        protected:
            bool eventFilter(QObject *obj, QEvent *ev);

        private:
            QTextEdit *textEdit;
        };

        MainWindow::MainWindow()
        {
            textEdit = new QTextEdit;
            setCentralWidget(textEdit);

            textEdit->installEventFilter(this);
        }

        bool MainWindow::eventFilter(QObject *obj, QEvent *event)
        {
            if (obj == textEdit) {
                if (event->type() == QEvent::KeyPress) {
                    QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
                    qDebug() << "Ate key press" << keyEvent->key();
                    return true;
                } else {
                    return false;
                }
            } else {
                // pass the event on to the parent class
                return QMainWindow::eventFilter(obj, event);
            }
        }

Notice in the example above that unhandled events are passed to the base class's eventFilter() function, since the base class might have reimplemented eventFilter() for its own internal purposes.

Warning:
If you delete the receiver object in this function, be sure to return true. Otherwise, Qt will forward the event to the deleted object and the program might crash.
See also:
installEventFilter()

Reimplemented from QObject.

Definition at line 55 of file q3whatsthis.cpp.

References clicked(), QWhatsThis::hideText(), o, QObject::parent(), QEvent::QueryWhatsThis, s, QWhatsThis::showText(), text(), QEvent::type(), QEvent::WhatsThis, and QEvent::WhatsThisClicked.

00056 {
00057     if (o != parent() || !o->isWidgetType())
00058         return false;
00059 
00060     if (e->type() == QEvent::WhatsThis) {
00061         QString s = text(static_cast<QHelpEvent*>(e)->pos());
00062         if (!s.isEmpty())
00063             QWhatsThis::showText(static_cast<QHelpEvent*>(e)->globalPos(), s, static_cast<QWidget*>(o));
00064     } else if (e->type() == QEvent::QueryWhatsThis) {
00065         QString s = text(static_cast<QHelpEvent*>(e)->pos());
00066         if (s.isEmpty())
00067             return false;
00068     } else if (e->type() == QEvent::WhatsThisClicked) {
00069         QString href = static_cast<QWhatsThisClickedEvent*>(e)->href();
00070         if (clicked(href))
00071             QWhatsThis::hideText();
00072     } else {
00073         return false;
00074     }
00075     return true;
00076 }

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void Q3WhatsThis::enterWhatsThisMode (  )  [inline, static]

Enters "What's This?" mode and returns immediately.

Qt will install a special cursor and take over mouse input until the user clicks somewhere. It then shows any help available and ends "What's This?" mode. Finally, Qt removes the special cursor and help window and then restores ordinary event processing, at which point the left mouse button is no longer pressed.

The user can also use the Esc key to leave "What's This?" mode.

See also:
inWhatsThisMode(), leaveWhatsThisMode()

Definition at line 45 of file q3whatsthis.h.

References QWhatsThis::enterWhatsThisMode().

00045 { QWhatsThis::enterWhatsThisMode(); }

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bool Q3WhatsThis::inWhatsThisMode (  )  [inline, static]

Returns true if the application is in "What's This?" mode; otherwise returns false.

See also:
enterWhatsThisMode(), leaveWhatsThisMode()

Definition at line 46 of file q3whatsthis.h.

References QWhatsThis::inWhatsThisMode().

00046 { return QWhatsThis::inWhatsThisMode(); }

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void Q3WhatsThis::add ( QWidget *  widget,
const QString &  text 
) [inline, static]

Adds text as "What's This?" help for widget. If the text is rich text formatted (i.e. it contains markup) it will be rendered with the default stylesheet QStyleSheet::defaultSheet().

The text is destroyed if the widget is later destroyed, so it need not be explicitly removed.

See also:
remove()

Definition at line 48 of file q3whatsthis.h.

References s, and w.

00048 { w->setWhatsThis(s); }

void Q3WhatsThis::remove ( QWidget *  widget  )  [inline, static]

Removes the "What's This?" help associated with the widget. This happens automatically if the widget is destroyed.

See also:
add()

Definition at line 49 of file q3whatsthis.h.

References w.

00049 { w->setWhatsThis(QString()); }

QToolButton * Q3WhatsThis::whatsThisButton ( QWidget *  parent  )  [static]

Creates a QToolButton preconfigured to enter "What's This?" mode when clicked. You will often use this with a tool bar as parent: 

  (void)QWhatsThis::whatsThisButton( my_help_tool_bar );

Definition at line 194 of file q3whatsthis.cpp.

References QObject::parent().

00195 {
00196     return QWhatsThis::whatsThisButton(parent);
00197 }

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void Q3WhatsThis::leaveWhatsThisMode ( const QString &  text = QString(),
const QPoint &  pos = QCursor::pos(),
QWidget *  widget = 0 
) [inline, static]

This function is used internally by widgets that support QWidget::customWhatsThis(); applications do not usually call it. An example of such a widget is Q3PopupMenu: menus still work normally in "What's This?" mode but also provide help texts for individual menu items.

If text is not empty, a "What's This?" help window is displayed at the global screen position pos. If widget widget is not 0 and has its own dedicated QWhatsThis object, this object will receive clicked() messages when the user clicks on hyperlinks inside the help text.

See also:
inWhatsThisMode(), enterWhatsThisMode(), clicked()

Definition at line 51 of file q3whatsthis.h.

References QWhatsThis::showText(), and w.

00052         { QWhatsThis::showText(pos, text, w); }

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void Q3WhatsThis::display ( const QString &  text,
const QPoint &  pos = QCursor::pos(),
QWidget *  widget = 0 
) [inline, static]

Display text in a help window at the global screen position pos.

If widget widget is not 0 and has its own dedicated QWhatsThis object, this object will receive clicked() messages when the user clicks on hyperlinks inside the help text.

See also:
clicked()

Definition at line 53 of file q3whatsthis.h.

References QWhatsThis::showText(), and w.

00054         { QWhatsThis::showText(pos, text, w); }

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QString Q3WhatsThis::text ( const QPoint &   )  [virtual]

This virtual function returns the text for position pos in the widget that this "What's This?" object documents. If there is no "What's This?" text for the position, an empty string is returned.

The default implementation returns an empty string.

Definition at line 85 of file q3whatsthis.cpp.

References QObject::isWidgetType(), and QObject::parent().

Referenced by eventFilter().

00086 {
00087     if (parent() && parent()->isWidgetType())
00088         return static_cast<QWidget*>(parent())->whatsThis();
00089     return QString();
00090 }

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bool Q3WhatsThis::clicked ( const QString &  href  )  [virtual]

This virtual function is called when the user clicks inside the "What's this?" window. href is the link the user clicked on, or an empty string if there was no link.

If the function returns true (the default), the "What's this?" window is closed, otherwise it remains visible.

The default implementation ignores href and returns true.

Definition at line 102 of file q3whatsthis.cpp.

Referenced by eventFilter().

00103 {
00104     return true;
00105 }

The documentation for this class was generated from the following files:
Generated on Thu Mar 15 16:37:38 2007 for Qt 4.2 User's Guide by  doxygen 1.5.1