diff options
Diffstat (limited to 'src/gui/kernel/qevent.cpp')
| -rw-r--r-- | src/gui/kernel/qevent.cpp | 158 |
1 files changed, 115 insertions, 43 deletions
diff --git a/src/gui/kernel/qevent.cpp b/src/gui/kernel/qevent.cpp index 7365820..3e1d12d 100644 --- a/src/gui/kernel/qevent.cpp +++ b/src/gui/kernel/qevent.cpp @@ -3538,38 +3538,108 @@ QMenubarUpdatedEvent::QMenubarUpdatedEvent(QMenuBar * const menuBar) \since 4.6 \ingroup events - Touch events occur when pressing, releasing, or moving one or more - touch points on a touch device (such as a touch-screen or - track-pad). To receive touch events, widgets have to have the - Qt::WA_AcceptTouchEvents attribute set and graphics items need to have - the \l{QGraphicsItem::setAcceptTouchEvents()}{acceptTouchEvents} - attribute set to true. - - All touch events are of type QEvent::TouchBegin, - QEvent::TouchUpdate, or QEvent::TouchEnd. The touchPoints() - function returns a list of all touch points contained in the event. - Information about each touch point can be retrieved using the - QTouchEvent::TouchPoint class. The Qt::TouchPointState enum - describes the different states that a touch point may have. - - Similar to QMouseEvent, Qt automatically grabs each touch point on - the first press inside a widget; the widget will receive all - updates for the touch point until it is released. Note that it is - possible for a widget to receive events for multiple touch points, - and that multiple widgets may be receiving touch events at the same - time. - - A touch event contains a special accept flag that indicates - whether the receiver wants the event. By default, the event is - accepted. You should call ignore() if the touch event is not handled by - your widget. A QEvent::TouchBegin event is propagated up the parent widget - chain until a widget accepts it with accept(), or an event filter - consumes it. If the QEvent::TouchBegin event is neither accepted nor consumed, - then mouse events are simulated from the state of the first touch - point. - - Reimplement QWidget::event() for widgets and QGraphicsItem::sceneEvent() - for items in a graphics view to receive touch events. + \section1 Enabling Touch Events + + Touch events occur when pressing, releasing, or moving one or more touch points on a touch + device (such as a touch-screen or track-pad). To receive touch events, widgets have to have the + Qt::WA_AcceptTouchEvents attribute set and graphics items need to have the + \l{QGraphicsItem::setAcceptTouchEvents()}{acceptTouchEvents} attribute set to true. + + Note: when using QAbstractScrollArea based widgets, you should enabled the + Qt::WA_AcceptTouchEvents attribute on the scroll area's + \l{QAbstractScrollArea::viewport()}{viewport}. + + \section1 Event Delivery and Propagation + + All touch events are of type QEvent::TouchBegin, QEvent::TouchUpdate, or QEvent::TouchEnd. + Reimplement QWidget::event() or QAbstractScrollArea::viewportEvent() for widgets and + QGraphicsItem::sceneEvent() for items in a graphics view to receive touch events. By default, + QWidget::event() translates the first non-primary touch point in a QTouchEvent into a + QMouseEvent. This makes it possible to enable touch events on existing widgets that do not + normally handle QTouchEvent. See below for information on some special considerations needed + when doing this. + + QEvent::TouchBegin is the first touch event sent to a widget. The QEvent::TouchBegin event + contains a special accept flag that indicates whether the receiver wants the event. By default, + the event is accepted. You should call ignore() if the touch event is not handled by your + widget. The QEvent::TouchBegin event is propagated up the parent widget chain until a widget + accepts it with accept(), or an event filter consumes it. For QGraphicsItems, the + QEvent::TouchBegin event is propagated to items under the mouse (similar to mouse event + propagation for QGraphicsItems). + + The QEvent::TouchUpdate and QEvent::TouchEnd events are sent to the widget or item that + accepted the QEvent::TouchBegin event. If the QEvent::TouchBegin event is not accepted and not + filtered by an event filter, then no further touch events are sent until the next + QEvent::TouchBegin. + + The touchPoints() function returns a list of all touch points contained in the event. + Information about each touch point can be retrieved using the QTouchEvent::TouchPoint class. + The Qt::TouchPointState enum describes the different states that a touch point may have. + + Similar to QMouseEvent, Qt automatically grabs each touch point on the first press inside a + widget; the widget will receive all updates for the touch point until it is released. Note that + it is possible for a widget to receive events for multiple touch points, and that multiple + widgets may be receiving touch events at the same time. + + \section1 Touch Point Grouping + + As mentioned above, it is possible that several widgets can be receiving QTouchEvents at the + same time. However, Qt makes sure to never send duplicate QEvent::TouchBegin events to the same + widget, which could theoretically happen during propagation if, for example, the user touched 2 + separate widgets in a QGroupBox and both widgets ignored the QEvent::TouchBegin event. + + To avoid this, Qt will group new touch points together using the following rules: + + \list + + \i When the first touch point is detected, the destination widget is determined firstly by the + location on screen first and secondly by the propagation rules. + + \i When additional touch points are detected, Qt first looks to see if there are any active + touch points on any ancestor or descendent of the widget under the new touch point. If there + are, the new touch point is grouped with the first, and the new touch point will be sent in a + single QTouchEvent to the widget that handled the first touch point. (The widget under the new + touch point will not receive an event). + + \endlist + + This makes it possible for sibling widgets to handle touch events independently while making + sure that the sequence of QTouchEvents is always correct. + + \section1 Mouse Events and the Primary Touch Point + + QTouchEvent delivery is independent from that of QMouseEvent. On some windowing systems, mouse + events are also sent for the \l{QTouchEvent::TouchPoint::isPrimary()}{primary touch point}. + This means it is possible for your widget to receive both QTouchEvent and QMouseEvent for the + same user interaction point. You can use the QTouchEvent::TouchPoint::isPrimary() function to + identify the primary touch point. + + Note that on some systems, it is possible to receive touch events without a primary touch + point. All this means is that there will be no mouse event generated for the touch points in + the QTouchEvent. + + \section1 Caveats + + \list + + \i As mentioned above, enabling touch events means multiple widgets can be receiving touch + events simultaneously. Combined with the default QWidget::event() handling for QTouchEvents, + this gives you great flexibility in designing multi-touch user interfaces. Be aware of the + implications. For example, is is possible that the user is moving a QSlider with one finger and + pressing a QPushButton with another. The signals are emitted from these widgets will be + interleaved. + + \i Recursion into the event loop using one of the exec() methods (e.g. QDialog::exec() or + QMenu::exec()) in a QTouchEvent event handler is not supported. Since there are multiple event + recipients, unexpected recursion may cause problems, including but not limited to lost events + and unexpected infinite recursion. + + \i QTouchEvents are not affected by a \l{QWidget::grabMouse()}{mouse grab} or an + \l{QApplication::activePopupWidget()}{active popup widget}. The behavior of QTouchEvents is + undefined when opening a popup or grabbing the mouse while there are multiple active touch + points. + + \endlist \sa QTouchEvent::TouchPoint, Qt::TouchPointState, Qt::WA_AcceptTouchEvents, QGraphicsItem::acceptTouchEvents() @@ -3648,6 +3718,11 @@ QTouchEvent::~QTouchEvent() Returns the list of touch points contained in the touch event. */ +/*! \fn QTouchEvent::DeviceType QTouchEvent::deviceType() const + + Returns the touch device Type, which is of type \l {QTouchEvent::DeviceType} {DeviceType}. +*/ + /*! \fn void QTouchEvent::setWidget(QWidget *widget) \internal @@ -3669,6 +3744,14 @@ QTouchEvent::~QTouchEvent() Sets the list of touch points for this event. */ +/*! \fn void QTouchEvent::setDeviceType(DeviceType deviceType) + + \internal + + Sets the device type to \a deviceType, which is of type \l {QTouchEvent::DeviceType} + {DeviceType}. +*/ + /*! \class QTouchEvent::TouchPoint \brief The QTouchEvent::TouchPoint class provides information about a touch point in a QTouchEvent. \since 4.6 @@ -4080,15 +4163,4 @@ QTouchEvent::TouchPoint &QTouchEvent::TouchPoint::operator=(const QTouchEvent::T return *this; } -/*! \fn QTouchEvent::DeviceType QTouchEvent::deviceType() const - Returns the touch device Type, which is of type - \l {QTouchEvent::DeviceType} {DeviceType}. - */ - -/*! \fn void QTouchEvent::setDeviceType(DeviceType deviceType) - Sets the device type to \a deviceType, which is of type - \l {QTouchEvent::DeviceType} {DeviceType}. - */ - - QT_END_NAMESPACE |