path: root/src/quick/handlers/qquicktaphandler.cpp

// Copyright (C) 2019 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

#include "qquicktaphandler_p.h"
#include "qquicksinglepointhandler_p_p.h"
#include <QtQuick/private/qquickdeliveryagent_p_p.h>
#include <QtQuick/qquickwindow.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.

    \snippet pointerHandlers/tapHandlerButton.qml 0

    For multi-tap gestures (double-tap, triple-tap etc.), the distance moved
    must not exceed QStyleHints::mouseDoubleClickDistance() with mouse and
    QStyleHints::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 = qApp->styleHints()->mouseDoubleClickDistance();
        m_mouseMultiClickDistanceSquared *= m_mouseMultiClickDistanceSquared;
        m_touchMultiTapDistanceSquared = qApp->styleHints()->touchDoubleTapDistance();
        m_touchMultiTapDistanceSquared *= m_touchMultiTapDistanceSquared;
    }
}

bool QQuickTapHandler::wantsEventPoint(const QPointerEvent *event, const QEventPoint &point)
{
    if (!QQuickDeliveryAgentPrivate::isMouseEvent(event) &&
            !QQuickDeliveryAgentPrivate::isTouchEvent(event) &&
            !QQuickDeliveryAgentPrivate::isTabletEvent(event))
        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 = d_func()->dragOverThreshold(point);
    if (overThreshold && m_gesturePolicy != DragWithinBounds) {
        m_longPressTimer.stop();
        m_holdTimer.invalidate();
    }
    switch (point.state()) {
    case QEventPoint::Pressed:
    case QEventPoint::Released:
        ret = parentContains(point);
        break;
    case QEventPoint::Updated:
        switch (m_gesturePolicy) {
        case DragThreshold:
            ret = !overThreshold && parentContains(point);
            break;
        case WithinBounds:
        case DragWithinBounds:
            ret = parentContains(point);
            break;
        case ReleaseWithinBounds:
            ret = point.id() == this->point().id();
            break;
        }
        break;
    case QEventPoint::Stationary:
        // If the point hasn't moved since last time, the return value should be the same as last time.
        // If we return false here, QQuickPointerHandler::handlePointerEvent() will call setActive(false).
        ret = point.id() == this->point().id();
        break;
    case QEventPoint::Unknown:
        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.id() == this->point().id())
        setPressed(false, true, const_cast<QPointerEvent *>(event), const_cast<QEventPoint &>(point));
    return ret;
}

void QQuickTapHandler::handleEventPoint(QPointerEvent *event, QEventPoint &point)
{
    const bool isTouch = QQuickDeliveryAgentPrivate::isTouchEvent(event);
    switch (point.state()) {
    case QEventPoint::Pressed:
        setPressed(true, false, event, point);
        break;
    case QEventPoint::Released: {
        if (isTouch || (static_cast<const QSinglePointEvent *>(event)->buttons() & acceptedButtons()) == Qt::NoButton)
            setPressed(false, false, event, point);
        break;
    }
    default:
        break;
    }

    QQuickSinglePointHandler::handleEventPoint(event, point);

    // If TapHandler only needs a passive grab, it should not block other items and handlers from reacting.
    // If the point is accepted, QQuickItemPrivate::localizedTouchEvent() would skip it.
    if (isTouch && m_gesturePolicy == DragThreshold)
        point.setAccepted(false);
}

/*!
    \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();
    } else if (event->timerId() == m_doubleTapTimer.timerId()) {
        m_doubleTapTimer.stop();
        qCDebug(lcTapHandler) << objectName() << "double-tap timer expired; taps:" << m_tapCount;
        Q_ASSERT(m_exclusiveSignals == (SingleTap | DoubleTap));
        if (m_tapCount == 1)
            emit singleTapped(m_singleTapReleasedPoint, m_singleTapReleasedButton);
        else if (m_tapCount == 2)
            emit doubleTapped(m_singleTapReleasedPoint, m_singleTapReleasedButton);
    }
}

/*!
    \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.

    The \c gesturePolicy also affects grab behavior as described below.

    \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
           \l {QPointerEvent::addPassiveGrabber()}{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
           \l {QPointerEvent::setExclusiveGrabber}{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 to take the
           \l {QPointerEvent::setExclusiveGrabber}{exclusive grab} on press
           and retain it until release in order to detect this gesture.

    \value TapHandler.DragWithinBounds
           On press, TapHandler takes the
           \l {QPointerEvent::setExclusiveGrabber}{exclusive grab}; after that,
           the event point can be dragged within the bounds of the \c parent
           item, while the \l timeHeld property keeps counting, and the
           \l longPressed() signal will be emitted regardless of drag distance.
           However, like \c WithinBounds, if the point leaves the bounds,
           the tap gesture is \l {PointerHandler::}{canceled()}, \l active()
           becomes \c false, and \l timeHeld stops counting. This is suitable
           for implementing press-drag-release components, such as menus, in
           which a single TapHandler detects press, \c timeHeld drives an
           "opening" animation, and then the user can drag to a menu item and
           release, while never leaving the bounds of the parent scene containing
           the menu. This value was added in Qt 6.3.
*/
void QQuickTapHandler::setGesturePolicy(QQuickTapHandler::GesturePolicy gesturePolicy)
{
    if (m_gesturePolicy == gesturePolicy)
        return;

    m_gesturePolicy = gesturePolicy;
    emit gesturePolicyChanged();
}

/*!
    \qmlproperty enumeration QtQuick::TapHandler::exclusiveSignals
    \since 6.5

    Determines the exclusivity of the singleTapped() and doubleTapped() signals.

    \value NotExclusive (the default) singleTapped() and doubleTapped() are
    emitted immediately when the user taps once or twice, respectively.

    \value SingleTap singleTapped() is emitted immediately when the user taps
    once, and doubleTapped() is never emitted.

    \value DoubleTap doubleTapped() is emitted immediately when the user taps
    twice, and singleTapped() is never emitted.

    \value (SingleTap | DoubleTap) Both signals are delayed until
    QStyleHints::mouseDoubleClickInterval(), such that either singleTapped()
    or doubleTapped() can be emitted, but not both. But if 3 or more taps
    occur within \c mouseDoubleClickInterval, neither signal is emitted.

    \note The remaining signals such as tapped() and tapCountChanged() are
    always emitted immediately, regardless of this property.
*/
void QQuickTapHandler::setExclusiveSignals(QQuickTapHandler::ExclusiveSignals exc)
{
    if (m_exclusiveSignals == exc)
        return;

    m_exclusiveSignals = exc;
    emit exclusiveSignalsChanged();
}

/*!
    \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, QPointerEvent *event, QEventPoint &point)
{
    if (m_pressed != press) {
        qCDebug(lcTapHandler) << objectName() << "pressed" << m_pressed << "->" << press
                              << (cancel ? "CANCEL" : "") << point << "gp" << m_gesturePolicy;
        m_pressed = press;
        connectPreRenderSignal(press);
        updateTimeHeld();
        if (press) {
            m_longPressTimer.start(longPressThresholdMilliseconds(), this);
            m_holdTimer.start();
        } else {
            m_longPressTimer.stop();
            m_holdTimer.invalidate();
            if (m_exclusiveSignals == (SingleTap | DoubleTap)) {
                if (m_tapCount == 0) {
                    m_singleTapReleasedPoint = point;
                    m_singleTapReleasedButton = event->isSinglePointEvent() ? static_cast<QSinglePointEvent *>(event)->button() : Qt::NoButton;
                    qCDebug(lcTapHandler) << objectName() << "waiting to emit singleTapped:" << qApp->styleHints()->mouseDoubleClickInterval() << "ms";
                    m_doubleTapTimer.start(qApp->styleHints()->mouseDoubleClickInterval(), this);
                } else if (m_doubleTapTimer.isActive()) {
                    qCDebug(lcTapHandler) << objectName() << "tap" << (m_tapCount + 1) << "after" << event->timestamp() / 1000.0 - m_lastTapTimestamp << "sec";
                }
            }
        }
        if (press) {
            // on press, grab before emitting changed signals
            if (m_gesturePolicy == DragThreshold)
                setPassiveGrab(event, point, press);
            else
                setExclusiveGrab(event, point, press);
        }
        if (!cancel && !press && parentContains(point)) {
            if (point.timeHeld() < longPressThreshold()) {
                // Assuming here that pointerEvent()->timestamp() is in ms.
                const qreal ts = event->timestamp() / 1000.0;
                const qreal interval = ts - m_lastTapTimestamp;
                const auto distanceSquared = QVector2D(point.scenePosition() - m_lastTapPos).lengthSquared();
                if (interval < m_multiTapInterval && distanceSquared <
                        (event->device()->type() == QInputDevice::DeviceType::Mouse ?
                         m_mouseMultiClickDistanceSquared : m_touchMultiTapDistanceSquared))
                    ++m_tapCount;
                else
                    m_tapCount = 1;
                qCDebug(lcTapHandler) << objectName() << "tapped" << m_tapCount << "times; interval since last:" << interval
                                      << "sec; distance since last:" << qSqrt(distanceSquared);
                auto button = event->isSinglePointEvent() ? static_cast<QSinglePointEvent *>(event)->button() : Qt::NoButton;
                emit tapped(point, button);
                emit tapCountChanged();
                if (m_tapCount == 1 && !m_exclusiveSignals.testFlag(DoubleTap))
                    emit singleTapped(point, button);
                else if (m_tapCount == 2 && !m_exclusiveSignals.testFlag(SingleTap)) {
                    emit doubleTapped(point, button);
                }
                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(event, point, press);
        }
        if (cancel) {
            emit canceled(point);
            setExclusiveGrab(event, 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, QPointingDevice::GrabTransition transition,
                                     QPointerEvent *ev, QEventPoint &point)
{
    QQuickSinglePointHandler::onGrabChanged(grabber, transition, ev, point);
    bool isCanceled = transition == QPointingDevice::CancelGrabExclusive || transition == QPointingDevice::CancelGrabPassive;
    if (grabber == this && (isCanceled || point.state() == QEventPoint::Released))
        setPressed(false, isCanceled, ev, point);
}

void QQuickTapHandler::connectPreRenderSignal(bool conn)
{
    auto par = parentItem();
    if (!par)
        return;
    if (conn)
        connect(par->window(), &QQuickWindow::beforeSynchronizing, this, &QQuickTapHandler::updateTimeHeld);
    else
        disconnect(par->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.

    \note If \l gesturePolicy is set to \c TapHandler.DragWithinBounds,
    \c timeHeld does not stop counting even when the pressed point is moved
    beyond the drag threshold, but only when the point leaves the \l {Item::}
    {parent} item's \l {QtQuick::Item::contains()}{bounds}.
*/

/*!
    \qmlsignal QtQuick::TapHandler::tapped(eventPoint eventPoint, Qt::MouseButton button)

    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.  The \a eventPoint signal parameter contains information
    from the release event about the point that was tapped, and \a button
    is the \l {Qt::MouseButton}{mouse button} that was clicked, or \c NoButton
    on a touchscreen.

    \snippet pointerHandlers/tapHandlerOnTapped.qml 0
*/

/*!
    \qmlsignal QtQuick::TapHandler::singleTapped(eventPoint eventPoint, Qt::MouseButton button)
    \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. The \a eventPoint signal parameter contains
    information from the release event about the point that was tapped, and
    \a button is the \l {Qt::MouseButton}{mouse button} that was clicked, or
    \c NoButton on a touchscreen.
*/

/*!
    \qmlsignal QtQuick::TapHandler::doubleTapped(eventPoint eventPoint, Qt::MouseButton button)
    \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
    (QStyleHints::mouseDoubleClickDistance() or
    QStyleHints::touchDoubleTapDistance()). This signal always occurs after
    \l singleTapped, \l tapped, and \l tapCountChanged. The \a eventPoint
    signal parameter contains information from the release event about the
    point that was tapped, and \a button is the
    \l {Qt::MouseButton}{mouse button} that was clicked, or \c NoButton
    on a touchscreen.
*/

/*!
    \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

#include "moc_qquicktaphandler_p.cpp"