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path: root/src/quick/handlers/qquicktaphandler.cpp
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/****************************************************************************
**
** Copyright (C) 2019 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 "qquicktaphandler_p.h"
#include "qquicksinglepointhandler_p_p.h"
#include <qpa/qplatformtheme.h>
#include <private/qguiapplication_p.h>
#include <QtGui/qstylehints.h>

QT_BEGIN_NAMESPACE

Q_LOGGING_CATEGORY(lcTapHandler, "qt.quick.handler.tap")

qreal QQuickTapHandler::m_multiTapInterval(0.0);
// single tap distance is the same as the drag threshold
int QQuickTapHandler::m_mouseMultiClickDistanceSquared(-1);
int QQuickTapHandler::m_touchMultiTapDistanceSquared(-1);

/*!
    \qmltype TapHandler
    \instantiates QQuickTapHandler
    \inherits SinglePointHandler
    \inqmlmodule QtQuick
    \ingroup qtquick-input-handlers
    \brief Handler for taps and clicks.

    TapHandler is a handler for taps on a touchscreen or clicks on a mouse.

    Detection of a valid tap gesture depends on \l gesturePolicy.  The default
    value is DragThreshold, which requires the press and release to be close
    together in both space and time.  In this case, DragHandler is able to
    function using only a passive grab, and therefore does not interfere with
    event delivery to any other Items or Input Handlers.  So the default
    gesturePolicy is useful when you want to modify behavior of an existing
    control or Item by adding a TapHandler with bindings and/or JavaScript
    callbacks.

    Note that buttons (such as QPushButton) are often implemented not to care
    whether the press and release occur close together: if you press the button
    and then change your mind, you need to drag all the way off the edge of the
    button in order to cancel the click.  For this use case, set the
    \l gesturePolicy to \c TapHandler.ReleaseWithinBounds.

    For multi-tap gestures (double-tap, triple-tap etc.), the distance moved
    must not exceed QPlatformTheme::MouseDoubleClickDistance with mouse and
    QPlatformTheme::TouchDoubleTapDistance with touch, and the time between
    taps must not exceed QStyleHints::mouseDoubleClickInterval().

    \sa MouseArea
*/

QQuickTapHandler::QQuickTapHandler(QQuickItem *parent)
    : QQuickSinglePointHandler(parent)
{
    if (m_mouseMultiClickDistanceSquared < 0) {
        m_multiTapInterval = qApp->styleHints()->mouseDoubleClickInterval() / 1000.0;
        m_mouseMultiClickDistanceSquared = QGuiApplicationPrivate::platformTheme()->
                    themeHint(QPlatformTheme::MouseDoubleClickDistance).toInt();
        m_mouseMultiClickDistanceSquared *= m_mouseMultiClickDistanceSquared;
        m_touchMultiTapDistanceSquared = QGuiApplicationPrivate::platformTheme()->
                    themeHint(QPlatformTheme::TouchDoubleTapDistance).toInt();
        m_touchMultiTapDistanceSquared *= m_touchMultiTapDistanceSquared;
    }
}

static bool dragOverThreshold(const QQuickEventPoint *point)
{
    QPointF delta = point->scenePosition() - point->scenePressPosition();
    return (QQuickWindowPrivate::dragOverThreshold(delta.x(), Qt::XAxis, point) ||
            QQuickWindowPrivate::dragOverThreshold(delta.y(), Qt::YAxis, point));
}

bool QQuickTapHandler::wantsEventPoint(QQuickEventPoint *point)
{
    if (!point->pointerEvent()->asPointerMouseEvent() &&
            !point->pointerEvent()->asPointerTouchEvent() &&
            !point->pointerEvent()->asPointerTabletEvent() )
        return false;
    // If the user has not violated any constraint, it could be a tap.
    // Otherwise we want to give up the grab so that a competing handler
    // (e.g. DragHandler) gets a chance to take over.
    // Don't forget to emit released in case of a cancel.
    bool ret = false;
    bool overThreshold = dragOverThreshold(point);
    if (overThreshold) {
        m_longPressTimer.stop();
        m_holdTimer.invalidate();
    }
    switch (point->state()) {
    case QQuickEventPoint::Pressed:
    case QQuickEventPoint::Released:
        ret = parentContains(point);
        break;
    case QQuickEventPoint::Updated:
        switch (m_gesturePolicy) {
        case DragThreshold:
            ret = !overThreshold && parentContains(point);
            break;
        case WithinBounds:
            ret = parentContains(point);
            break;
        case ReleaseWithinBounds:
            ret = point->pointId() == this->point().id();
            break;
        }
        break;
    case QQuickEventPoint::Stationary:
        // Never react in any way when the point hasn't moved.
        // In autotests, the point's position may not even be correct, because
        // QTest::touchEvent(window, touchDevice).stationary(1)
        // provides no opportunity to give a position, so it ends up being random.
        break;
    }
    // If this is the grabber, returning false from this function will cancel the grab,
    // so onGrabChanged(this, CancelGrabExclusive, point) and setPressed(false) will be called.
    // But when m_gesturePolicy is DragThreshold, we don't get an exclusive grab, but
    // we still don't want to be pressed anymore.
    if (!ret && point->pointId() == this->point().id() && point->state() != QQuickEventPoint::Stationary)
        setPressed(false, true, point);
    return ret;
}

void QQuickTapHandler::handleEventPoint(QQuickEventPoint *point)
{
    switch (point->state()) {
    case QQuickEventPoint::Pressed:
        setPressed(true, false, point);
        break;
    case QQuickEventPoint::Released:
        if ((point->pointerEvent()->buttons() & acceptedButtons()) == Qt::NoButton)
            setPressed(false, false, point);
        break;
    default:
        break;
    }
}

/*!
    \qmlproperty real QtQuick::TapHandler::longPressThreshold

    The time in seconds that an event point must be pressed in order to
    trigger a long press gesture and emit the \l longPressed() signal.
    If the point is released before this time limit, a tap can be detected
    if the \l gesturePolicy constraint is satisfied. The default value is
    QStyleHints::mousePressAndHoldInterval() converted to seconds.
*/
qreal QQuickTapHandler::longPressThreshold() const
{
    return longPressThresholdMilliseconds() / 1000.0;
}

void QQuickTapHandler::setLongPressThreshold(qreal longPressThreshold)
{
    int ms = qRound(longPressThreshold * 1000);
    if (m_longPressThreshold == ms)
        return;

    m_longPressThreshold = ms;
    emit longPressThresholdChanged();
}

int QQuickTapHandler::longPressThresholdMilliseconds() const
{
    return (m_longPressThreshold < 0 ? QGuiApplication::styleHints()->mousePressAndHoldInterval() : m_longPressThreshold);
}

void QQuickTapHandler::timerEvent(QTimerEvent *event)
{
    if (event->timerId() == m_longPressTimer.timerId()) {
        m_longPressTimer.stop();
        qCDebug(lcTapHandler) << objectName() << "longPressed";
        emit longPressed();
    }
}

/*!
    \qmlproperty enumeration QtQuick::TapHandler::gesturePolicy

    The spatial constraint for a tap or long press gesture to be recognized,
    in addition to the constraint that the release must occur before
    \l longPressThreshold has elapsed. If these constraints are not satisfied,
    the \l tapped signal is not emitted, and \l tapCount is not incremented.
    If the spatial constraint is violated, \l pressed transitions immediately
    from true to false, regardless of the time held.

    \value TapHandler.DragThreshold
           (the default value) The event point must not move significantly.
           If the mouse, finger or stylus moves past the system-wide drag
           threshold (QStyleHints::startDragDistance), the tap gesture is
           canceled, even if the button or finger is still pressed. This policy
           can be useful whenever TapHandler needs to cooperate with other
           input handlers (for example \l DragHandler) or event-handling Items
           (for example QtQuick Controls), because in this case TapHandler
           will not take the exclusive grab, but merely a passive grab.

    \value TapHandler.WithinBounds
           If the event point leaves the bounds of the \c parent Item, the tap
           gesture is canceled. The TapHandler will take the exclusive grab on
           press, but will release the grab as soon as the boundary constraint
           is no longer satisfied.

    \value TapHandler.ReleaseWithinBounds
           At the time of release (the mouse button is released or the finger
           is lifted), if the event point is outside the bounds of the
           \c parent Item, a tap gesture is not recognized. This corresponds to
           typical behavior for button widgets: you can cancel a click by
           dragging outside the button, and you can also change your mind by
           dragging back inside the button before release. Note that it's
           necessary for TapHandler take the exclusive grab on press and retain
           it until release in order to detect this gesture.
*/
void QQuickTapHandler::setGesturePolicy(QQuickTapHandler::GesturePolicy gesturePolicy)
{
    if (m_gesturePolicy == gesturePolicy)
        return;

    m_gesturePolicy = gesturePolicy;
    emit gesturePolicyChanged();
}

/*!
    \qmlproperty bool QtQuick::TapHandler::pressed
    \readonly

    Holds true whenever the mouse or touch point is pressed,
    and any movement since the press is compliant with the current
    \l gesturePolicy. When the event point is released or the policy is
    violated, \e pressed will change to false.
*/
void QQuickTapHandler::setPressed(bool press, bool cancel, QQuickEventPoint *point)
{
    if (m_pressed != press) {
        qCDebug(lcTapHandler) << objectName() << "pressed" << m_pressed << "->" << press << (cancel ? "CANCEL" : "") << point;
        m_pressed = press;
        connectPreRenderSignal(press);
        updateTimeHeld();
        if (press) {
            m_longPressTimer.start(longPressThresholdMilliseconds(), this);
            m_holdTimer.start();
        } else {
            m_longPressTimer.stop();
            m_holdTimer.invalidate();
        }
        if (press) {
            // on press, grab before emitting changed signals
            if (m_gesturePolicy == DragThreshold)
                setPassiveGrab(point, press);
            else
                setExclusiveGrab(point, press);
        }
        if (!cancel && !press && parentContains(point)) {
            if (point->timeHeld() < longPressThreshold()) {
                // Assuming here that pointerEvent()->timestamp() is in ms.
                qreal ts = point->pointerEvent()->timestamp() / 1000.0;
                if (ts - m_lastTapTimestamp < m_multiTapInterval &&
                        QVector2D(point->scenePosition() - m_lastTapPos).lengthSquared() <
                        (point->pointerEvent()->device()->type() == QQuickPointerDevice::Mouse ?
                         m_mouseMultiClickDistanceSquared : m_touchMultiTapDistanceSquared))
                    ++m_tapCount;
                else
                    m_tapCount = 1;
                qCDebug(lcTapHandler) << objectName() << "tapped" << m_tapCount << "times";
                emit tapped(point);
                emit tapCountChanged();
                if (m_tapCount == 1)
                    emit singleTapped(point);
                else if (m_tapCount == 2)
                    emit doubleTapped(point);
                m_lastTapTimestamp = ts;
                m_lastTapPos = point->scenePosition();
            } else {
                qCDebug(lcTapHandler) << objectName() << "tap threshold" << longPressThreshold() << "exceeded:" << point->timeHeld();
            }
        }
        emit pressedChanged();
        if (!press && m_gesturePolicy != DragThreshold) {
            // on release, ungrab after emitting changed signals
            setExclusiveGrab(point, press);
        }
        if (cancel) {
            emit canceled(point);
            setExclusiveGrab(point, false);
            // In case there is a filtering parent (Flickable), we should not give up the passive grab,
            // so that it can continue to filter future events.
            d_func()->reset();
            emit pointChanged();
        }
    }
}

void QQuickTapHandler::onGrabChanged(QQuickPointerHandler *grabber, QQuickEventPoint::GrabTransition transition, QQuickEventPoint *point)
{
    QQuickSinglePointHandler::onGrabChanged(grabber, transition, point);
    bool isCanceled = transition == QQuickEventPoint::CancelGrabExclusive || transition == QQuickEventPoint::CancelGrabPassive;
    if (grabber == this && (isCanceled || point->state() == QQuickEventPoint::Released))
        setPressed(false, isCanceled, point);
}

void QQuickTapHandler::connectPreRenderSignal(bool conn)
{
    if (conn)
        connect(parentItem()->window(), &QQuickWindow::beforeSynchronizing, this, &QQuickTapHandler::updateTimeHeld);
    else
        disconnect(parentItem()->window(), &QQuickWindow::beforeSynchronizing, this, &QQuickTapHandler::updateTimeHeld);
}

void QQuickTapHandler::updateTimeHeld()
{
    emit timeHeldChanged();
}

/*!
    \qmlproperty int QtQuick::TapHandler::tapCount
    \readonly

    The number of taps which have occurred within the time and space
    constraints to be considered a single gesture.  For example, to detect
    a triple-tap, you can write:

    \qml
    Rectangle {
        width: 100; height: 30
        signal tripleTap
        TapHandler {
            acceptedButtons: Qt.AllButtons
            onTapped: if (tapCount == 3) tripleTap()
        }
    }
    \endqml
*/

/*!
    \qmlproperty real QtQuick::TapHandler::timeHeld
    \readonly

    The amount of time in seconds that a pressed point has been held, without
    moving beyond the drag threshold. It will be updated at least once per
    frame rendered, which enables rendering an animation showing the progress
    towards an action which will be triggered by a long-press. It is also
    possible to trigger one of a series of actions depending on how long the
    press is held.

    A value of less than zero means no point is being held within this
    handler's \l [QML] Item.
*/

/*!
    \qmlsignal QtQuick::TapHandler::tapped

    This signal is emitted each time the \c parent Item is tapped.

    That is, if you press and release a touchpoint or button within a time
    period less than \l longPressThreshold, while any movement does not exceed
    the drag threshold, then the \c tapped signal will be emitted at the time
    of release.
*/

/*!
    \qmlsignal QtQuick::TapHandler::singleTapped
    \since 5.11

    This signal is emitted when the \c parent Item is tapped once.
    After an amount of time greater than QStyleHints::mouseDoubleClickInterval,
    it can be tapped again; but if the time until the next tap is less,
    \l tapCount will increase.
*/

/*!
    \qmlsignal QtQuick::TapHandler::doubleTapped
    \since 5.11

    This signal is emitted when the \c parent Item is tapped twice within a
    short span of time (QStyleHints::mouseDoubleClickInterval) and distance
    (QPlatformTheme::MouseDoubleClickDistance or
    QPlatformTheme::TouchDoubleTapDistance). This signal always occurs after
    \l singleTapped, \l tapped, and \l tapCountChanged.
*/

/*!
    \qmlsignal QtQuick::TapHandler::longPressed

    This signal is emitted when the \c parent Item is pressed and held for a
    time period greater than \l longPressThreshold. That is, if you press and
    hold a touchpoint or button, while any movement does not exceed the drag
    threshold, then the \c longPressed signal will be emitted at the time that
    \l timeHeld exceeds \l longPressThreshold.
*/

/*!
    \qmlsignal QtQuick::TapHandler::tapCountChanged

    This signal is emitted when the \c parent Item is tapped once or more (within
    a specified time and distance span) and when the present \c tapCount differs
    from the previous \c tapCount.
*/
QT_END_NAMESPACE