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/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtQuick module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qquickpointhandler_p.h"
#include <private/qquickwindow_p.h>
#include <QDebug>
QT_BEGIN_NAMESPACE
/*!
\qmltype PointHandler
\instantiates QQuickPointHandler
\inherits SinglePointHandler
\inqmlmodule QtQuick
\ingroup qtquick-input-handlers
\brief Handler for reacting to a single touchpoint.
PointHandler can be used to show feedback about a touchpoint or the mouse
position, or to otherwise react to pointer events.
When a press event occurs, each instance of PointHandler chooses a
single point which is not yet "taken" at that moment: if the press
occurs within the bounds of the \l {PointerHandler::parent}, and
no sibling PointHandler within the same \l {PointerHandler::parent}
has yet acquired a passive grab on that point, and if the other
constraints such as \l {PointerDeviceHandler::acceptedButtons}{acceptedButtons}, \l {PointerDeviceHandler::acceptedDevices}{acceptedDevices} etc.
are satisfied, it's
eligible, and the PointHandler then acquires a passive grab. In
this way, the \l {PointerHandler::parent} acts like an exclusive
group: there can be multiple instances of PointHandler, and the
set of pressed touchpoints will be distributed among them. Each
PointHandler which has chosen a point to track has its \l active
property \c true. It then continues to track its chosen point
until release: the properties of the \l point will be kept
up-to-date. Any Item can bind to these properties, and thereby
follow the point's movements.
By being only a passive grabber, it has the ability to keep independent
oversight of all movements. The passive grab cannot be stolen or overridden
even when other gestures are detected and exclusive grabs occur.
If your goal is orthogonal surveillance of eventpoints, an older
alternative was QObject::installEventFilter(), but that has never been a
built-in QtQuick feature: it requires some C++ code, such as a QQuickItem
subclass. PointHandler is more efficient than that, because only pointer
events will be delivered to it, during the course of normal event delivery
in QQuickWindow; whereas an event filter needs to filter all QEvents of all
types, and thus sets itself up as a potential event delivery bottleneck.
One possible use case is to add this handler to a transparent Item which is
on top of the rest of the scene (by having a high \l{Item::z} {z} value),
so that when a point is freshly pressed, it will be delivered to that Item
and its handlers first, providing the opportunity to take the passive grab
as early as possible. Such an item (like a pane of glass over the whole UI)
can be a convenient parent for other Items which visualize the kind of reactive
feedback which must always be on top; and likewise it can be the parent for
popups, popovers, dialogs and so on. If it will be used in that way, it can
be helpful for your main.cpp to use QQmlContext::setContextProperty() to
make the "glass pane" accessible by ID to the entire UI, so that other
Items and PointHandlers can be reparented to it.
\snippet pointerHandlers/pointHandler.qml 0
Like all input handlers, a PointHandler has a \l target property, which
may be used as a convenient place to put a point-tracking Item; but
PointHandler will not automatically manipulate the \c target item in any way.
You need to use bindings to make it react to the \l point.
\note On macOS, PointHandler does not react to the trackpad by default.
That is because macOS can provide either native gesture recognition, or raw
touchpoints, but not both. We prefer to use the native gesture event in
PinchHandler, so we do not want to disable it by enabling touch. However
MultiPointTouchArea does enable touch, thus disabling native gesture
recognition within the entire window; so it's an alternative if you only
want to react to all the touchpoints but do not require the smooth
native-gesture experience.
\sa MultiPointTouchArea
*/
QQuickPointHandler::QQuickPointHandler(QQuickItem *parent)
: QQuickSinglePointHandler(parent)
{
setIgnoreAdditionalPoints();
}
bool QQuickPointHandler::wantsEventPoint(const QPointerEvent *event, const QEventPoint &point)
{
// On press, we want it unless a sibling of the same type also does.
if (point.state() == QEventPoint::Pressed && QQuickSinglePointHandler::wantsEventPoint(event, point)) {
for (const QObject *grabber : event->passiveGrabbers(point)) {
if (grabber && grabber->parent() == parent() &&
grabber->metaObject()->className() == metaObject()->className())
return false;
}
return true;
}
// If we've already been interested in a point, stay interested, even if it has strayed outside bounds.
return (point.state() != QEventPoint::Pressed &&
QQuickSinglePointHandler::point().id() == point.id());
}
void QQuickPointHandler::handleEventPoint(QPointerEvent *event, QEventPoint &point)
{
switch (point.state()) {
case QEventPoint::Pressed:
if (QQuickWindowPrivate::isTouchEvent(event) ||
(static_cast<const QSinglePointEvent *>(event)->buttons() & acceptedButtons()) != Qt::NoButton) {
setPassiveGrab(event, point);
setActive(true);
}
break;
case QEventPoint::Released:
if (QQuickWindowPrivate::isTouchEvent(event) ||
(static_cast<const QSinglePointEvent *>(event)->buttons() & acceptedButtons()) == Qt::NoButton)
setActive(false);
break;
default:
break;
}
point.setAccepted(false); // Just lurking... don't interfere with propagation
emit translationChanged();
QQuickSinglePointHandler::handleEventPoint(event, point);
}
QVector2D QQuickPointHandler::translation() const
{
return QVector2D(point().position() - point().pressPosition());
}
QT_END_NAMESPACE
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