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Diffstat (limited to 'src/quick/handlers/qquickpointhandler.cpp')
| -rw-r--r-- | src/quick/handlers/qquickpointhandler.cpp | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/src/quick/handlers/qquickpointhandler.cpp b/src/quick/handlers/qquickpointhandler.cpp new file mode 100644 index 0000000000..ed03685252 --- /dev/null +++ b/src/quick/handlers/qquickpointhandler.cpp @@ -0,0 +1,161 @@ +/**************************************************************************** +** +** 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 Qt.labs.handlers + \ingroup qtquick-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 parent, and no sibling PointHandler within the same + \l parent has yet acquired a passive grab on that point, and if the other + constraints such as \l acceptedMouseButtons, \l acceptedDevices etc. are + satisfied, it's eligible, and the PointHandler then acquires a passive + grab. In this way, the \l 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 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 pointer 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(QObject *parent) + : QQuickSinglePointHandler(parent) +{ + setIgnoreAdditionalPoints(); +} + +QQuickPointHandler::~QQuickPointHandler() +{ +} + +bool QQuickPointHandler::wantsEventPoint(QQuickEventPoint *pt) +{ + // On press, we want it unless a sibling of the same type also does. + if (pt->state() == QQuickEventPoint::Pressed && QQuickSinglePointHandler::wantsEventPoint(pt)) { + for (const QQuickPointerHandler *grabber : pt->passiveGrabbers()) { + 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 (pt->state() != QQuickEventPoint::Pressed && point().id() == pt->pointId()); +} + +void QQuickPointHandler::handleEventPoint(QQuickEventPoint *point) +{ + switch (point->state()) { + case QQuickEventPoint::Pressed: + setPassiveGrab(point); + setActive(true); + break; + case QQuickEventPoint::Released: + setActive(false); + break; + default: + break; + } + point->setAccepted(false); // Just lurking... don't interfere with propagation + emit translationChanged(); +} + +QVector2D QQuickPointHandler::translation() const +{ + return QVector2D(point().position() - point().pressPosition()); +} + +QT_END_NAMESPACE |