Contents

• Public Functions
• Detailed Description

Detailed Description

TheQWheelEvent class contains parameters that describe a wheel event.

Wheel events are sent to the widget under the mouse cursor, but if that widget does not handle the event they are sent to the focus widget. The rotation distance is provided bydelta(). The functionspos() andglobalPos() return the mouse cursor's location at the time of the event.

A wheel event contains a special accept flag that indicates whether the receiver wants the event. You should callignore() if you do not handle the wheel event; this ensures that it will be sent to the parent widget.

TheQWidget::setEnabled() function can be used to enable or disable mouse and keyboard events for a widget.

The event handlerQWidget::wheelEvent() receives wheel events.

Member Function Documentation

QWheelEvent::QWheelEvent(constQPoint & pos,int delta,Qt::MouseButtons buttons,Qt::KeyboardModifiers modifiers,Qt::Orientation orient = Qt::Vertical)

Constructs a wheel event object.

The position,pos, is the location of the mouse cursor within the widget. TheglobalPos() is initialized toQCursor::pos() which is usually, but not always, correct. Use the other constructor if you need to specify the global position explicitly.

Thebuttons describe the state of the mouse buttons at the time of the event,delta contains the rotation distance,modifiers holds the keyboard modifier flags at the time of the event, andorient holds the wheel's orientation.

See alsopos(),delta(), andstate().

QWheelEvent::QWheelEvent(constQPoint & pos, constQPoint & globalPos,int delta,Qt::MouseButtons buttons,Qt::KeyboardModifiers modifiers,Qt::Orientation orient = Qt::Vertical)

Constructs a wheel event object.

Thepos provides the location of the mouse cursor within the widget. The position in global coordinates is specified byglobalPos.delta contains the rotation distance,modifiers holds the keyboard modifier flags at the time of the event, andorient holds the wheel's orientation.

See alsopos(),globalPos(),delta(), andstate().

Qt::MouseButtons QWheelEvent::buttons() const

Returns the mouse state when the event occurred.

int QWheelEvent::delta() const

Returns the distance that the wheel is rotated, in eighths of a degree. A positive value indicates that the wheel was rotated forwards away from the user; a negative value indicates that the wheel was rotated backwards toward the user.

Most mouse types work in steps of 15 degrees, in which case the delta value is a multiple of 120; i.e., 120 units * 1/8 = 15 degrees.

However, some mice have finer-resolution wheels and send delta values that are less than 120 units (less than 15 degrees). To support this possibility, you can either cumulatively add the delta values from events until the value of 120 is reached, then scroll the widget, or you can partially scroll the widget in response to each wheel event.

Example:

void MyWidget::wheelEvent(QWheelEvent*event){int numDegrees= event->delta()/8;int numSteps= numDegrees/15;if (event->orientation()==Qt::Horizontal) {        scrollHorizontally(numSteps);    }else {        scrollVertically(numSteps);    }    event->accept();}

constQPoint & QWheelEvent::globalPos() const

Returns the global position of the mouse pointerat the time of the event. This is important on asynchronous window systems such as X11; whenever you move your widgets around in response to mouse events, globalPos() can differ a lot from the current cursor position returned byQCursor::pos().

See alsoglobalX() andglobalY().

int QWheelEvent::globalX() const

Returns the global x position of the mouse cursor at the time of the event.

See alsoglobalY() andglobalPos().

int QWheelEvent::globalY() const

Returns the global y position of the mouse cursor at the time of the event.

See alsoglobalX() andglobalPos().

Qt::Orientation QWheelEvent::orientation() const

Returns the wheel's orientation.

constQPoint & QWheelEvent::pos() const

Returns the position of the mouse cursor relative to the widget that received the event.

If you move your widgets around in response to mouse events, useglobalPos() instead of this function.

See alsox(),y(), andglobalPos().

int QWheelEvent::x() const

Returns the x position of the mouse cursor, relative to the widget that received the event.

See alsoy() andpos().

int QWheelEvent::y() const

Returns the y position of the mouse cursor, relative to the widget that received the event.

See alsox() andpos().