1// Copyright (C) 2017 The Qt Company Ltd.
2// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
3
4#include "qquickpointhandler_p.h"
5#include <private/qquickdeliveryagent_p_p.h>
6#include <private/qquickwindow_p.h>
7#include <QDebug>
8#include <QtCore/qpointer.h>
9
10QT_BEGIN_NAMESPACE
11
12/*!
13 \qmltype PointHandler
14 \nativetype QQuickPointHandler
15 \inherits SinglePointHandler
16 \inqmlmodule QtQuick
17 \ingroup qtquick-input-handlers
18 \brief Handler for reacting to a single touchpoint.
19
20 PointHandler can be used to show feedback about a touchpoint or the mouse
21 position, or to otherwise react to pointer events.
22
23 When a press event occurs, each instance of PointHandler chooses a
24 single point which is not yet "taken" at that moment: if the press
25 occurs within the bounds of the \l {PointerHandler::parent}, and
26 no sibling PointHandler within the same \l {PointerHandler::parent}
27 has yet acquired a passive grab on that point, and if the other
28 constraints such as \l {PointerDeviceHandler::acceptedButtons}{acceptedButtons}, \l {PointerDeviceHandler::acceptedDevices}{acceptedDevices} etc.
29 are satisfied, it's
30 eligible, and the PointHandler then acquires a passive grab. In
31 this way, the \l {PointerHandler::parent} acts like an exclusive
32 group: there can be multiple instances of PointHandler, and the
33 set of pressed touchpoints will be distributed among them. Each
34 PointHandler which has chosen a point to track has its \l active
35 property \c true. It then continues to track its chosen point
36 until release: the properties of the \l point will be kept
37 up-to-date. Any Item can bind to these properties, and thereby
38 follow the point's movements.
39
40 By being only a passive grabber, it has the ability to keep independent
41 oversight of all movements. The passive grab cannot be stolen or overridden
42 even when other gestures are detected and exclusive grabs occur.
43
44 If your goal is orthogonal surveillance of eventpoints, an older
45 alternative was QObject::installEventFilter(), but that has never been a
46 built-in QtQuick feature: it requires some C++ code, such as a QQuickItem
47 subclass. PointHandler is more efficient than that, because only pointer
48 events will be delivered to it, during the course of normal event delivery
49 in QQuickWindow; whereas an event filter needs to filter all QEvents of all
50 types, and thus sets itself up as a potential event delivery bottleneck.
51
52 One possible use case is to add this handler to a transparent Item which is
53 on top of the rest of the scene (by having a high \l{Item::z} {z} value),
54 so that when a point is freshly pressed, it will be delivered to that Item
55 and its handlers first, providing the opportunity to take the passive grab
56 as early as possible. Such an item (like a pane of glass over the whole UI)
57 can be a convenient parent for other Items which visualize the kind of reactive
58 feedback which must always be on top; and likewise it can be the parent for
59 popups, popovers, dialogs and so on. If it will be used in that way, it can
60 be helpful for your main.cpp to use QQmlContext::setContextProperty() to
61 make the "glass pane" accessible by ID to the entire UI, so that other
62 Items and PointHandlers can be reparented to it.
63
64 \snippet pointerHandlers/pointHandler.qml 0
65
66 Like all input handlers, a PointHandler has a \l target property, which
67 may be used as a convenient place to put a point-tracking Item; but
68 PointHandler will not automatically manipulate the \c target item in any way.
69 You need to use bindings to make it react to the \l point.
70
71 \note On macOS, PointHandler does not react to multiple fingers on the
72 trackpad by default, although it does react to a pressed point (mouse position).
73 That is because macOS can provide either native gesture recognition, or raw
74 touchpoints, but not both. We prefer to use the native gesture event in
75 PinchHandler, so we do not want to disable it by enabling touch. However
76 MultiPointTouchArea does enable touch, thus disabling native gesture
77 recognition within the entire window; so it's an alternative if you only
78 want to react to all the touchpoints but do not require the smooth
79 native-gesture experience.
80
81 \sa MultiPointTouchArea, HoverHandler, {Qt Quick Examples - Pointer Handlers}
82*/
83
84QQuickPointHandler::QQuickPointHandler(QQuickItem *parent)
85 : QQuickSinglePointHandler(parent)
86{
87 setIgnoreAdditionalPoints();
88}
89
90bool QQuickPointHandler::wantsEventPoint(const QPointerEvent *event, const QEventPoint &point)
91{
92 // On press, we want it unless a sibling of the same type also does.
93 // If a synth-mouse press occurs, and we've already been interested in the original point, stay interested.
94 const bool trackedPointId = QQuickSinglePointHandler::point().id() == point.id() &&
95 QQuickSinglePointHandler::point().device() == point.device();
96 if ((point.state() == QEventPoint::Pressed && QQuickSinglePointHandler::wantsEventPoint(event, point))
97 || (QQuickDeliveryAgentPrivate::isSynthMouse(ev: event) && trackedPointId)) {
98 for (const QObject *grabber : event->passiveGrabbers(point)) {
99 if (grabber && grabber != this && grabber->parent() == parent() &&
100 grabber->metaObject()->className() == metaObject()->className())
101 return false;
102 }
103 return true;
104 }
105 // If we've already been interested in a point, stay interested, even if it has strayed outside bounds.
106 return (point.state() != QEventPoint::Pressed && trackedPointId);
107}
108
109void QQuickPointHandler::handleEventPoint(QPointerEvent *event, QEventPoint &point)
110{
111 switch (point.state()) {
112 case QEventPoint::Pressed:
113 if (acceptedButtons() == Qt::NoButton || !event->isSinglePointEvent() ||
114 (static_cast<const QSinglePointEvent *>(event)->buttons() & acceptedButtons()) != Qt::NoButton) {
115 setPassiveGrab(event, point);
116 setActive(true);
117 }
118 break;
119 case QEventPoint::Released:
120 if (acceptedButtons() == Qt::NoButton || !event->isSinglePointEvent() ||
121 (static_cast<const QSinglePointEvent *>(event)->buttons() & acceptedButtons()) == Qt::NoButton)
122 setActive(false);
123 break;
124 default:
125 break;
126 }
127 point.setAccepted(false); // Just lurking... don't interfere with propagation
128 emit translationChanged();
129 if (!QQuickDeliveryAgentPrivate::isSynthMouse(ev: event))
130 QQuickSinglePointHandler::handleEventPoint(event, point);
131}
132
133QVector2D QQuickPointHandler::translation() const
134{
135 return QVector2D(point().position() - point().pressPosition());
136}
137
138/*!
139 \qmlproperty flags PointHandler::acceptedButtons
140
141 The mouse buttons that can activate this PointHandler.
142
143 By default, this property is set to \l {QtQuick::MouseEvent::button} {Qt.LeftButton}.
144 It can be set to an OR combination of mouse buttons, and will ignore events
145 in which other buttons are pressed or held. If it is set to \c Qt.NoButton,
146 it means it does not care about buttons at all, and ignores synthetic
147 mouse events that come from any device for which it's already handling
148 an authentic \l eventPoint.
149
150 \snippet pointerHandlers/pointHandlerAcceptedButtons.qml 0
151
152 \note On a touchscreen, there are no buttons, so this property does not
153 prevent PointHandler from reacting to touchpoints.
154
155 \note By default, when this property holds \c Qt.LeftButton, if a
156 non-mouse \l {PointerDevice} (such as a touchscreen or graphics tablet
157 stylus) is allowed to generate synthetic mouse events, those usually
158 indicate that the left mouse button is pressed, and those events can
159 temporarily de-activate the PointHandler which was already reacting to an
160 authentic \l eventPoint from the device. It's useful to declare
161 \qml
162 acceptedButtons: \c Qt.NoButton
163 \endqml
164 to avoid this issue. See also
165 \l Qt::AA_SynthesizeMouseForUnhandledTouchEvents and
166 \l Qt::AA_SynthesizeMouseForUnhandledTabletEvents.
167*/
168
169/*!
170 \qmlproperty flags PointHandler::acceptedDevices
171
172 The types of pointing devices that can activate this PointHandler.
173
174 By default, this property is set to
175 \l{QInputDevice::DeviceType}{PointerDevice.AllDevices}.
176 If you set it to an OR combination of device types, it will ignore events
177 from non-matching \l {PointerDevice}{devices}:
178
179 \snippet pointerHandlers/pointHandler.qml 1
180*/
181
182/*!
183 \qmlproperty flags PointHandler::acceptedPointerTypes
184
185 The types of pointing instruments (finger, stylus, eraser, etc.)
186 that can activate this PointHandler.
187
188 By default, this property is set to
189 \l {QPointingDevice::PointerType} {PointerDevice.AllPointerTypes}.
190 If you set it to an OR combination of device types, it will ignore events
191 from non-matching \l {PointerDevice}{devices}:
192
193 \snippet pointerHandlers/pointHandlerCanvasDrawing.qml 0
194
195 The \l {Qt Quick Examples - Pointer Handlers} includes a more complex example for
196 drawing on a Canvas with a graphics tablet.
197*/
198
199/*!
200 \qmlproperty flags PointHandler::acceptedModifiers
201
202 If this property is set, PointHandler requires the given keyboard modifiers
203 to be pressed in order to react to \l {PointerEvent}{PointerEvents}, and
204 otherwise ignores them.
205
206 If this property is set to \c Qt.KeyboardModifierMask (the default value),
207 then PointHandler ignores the modifier keys.
208
209 For example, an \l [QML] Item could have two handlers, one of which is
210 enabled only if the required keyboard modifier is pressed:
211
212 \snippet pointerHandlers/pointHandlerAcceptedModifiers.qml 0
213
214 If you set \c acceptedModifiers to an OR combination of modifier keys,
215 it means \e all of those modifiers must be pressed to activate the handler.
216
217 The available modifiers are as follows:
218
219 \value NoModifier No modifier key is allowed.
220 \value ShiftModifier A Shift key on the keyboard must be pressed.
221 \value ControlModifier A Ctrl key on the keyboard must be pressed.
222 \value AltModifier An Alt key on the keyboard must be pressed.
223 \value MetaModifier A Meta key on the keyboard must be pressed.
224 \value KeypadModifier A keypad button must be pressed.
225 \value GroupSwitchModifier X11 only (unless activated on Windows by a command line argument).
226 A Mode_switch key on the keyboard must be pressed.
227 \value KeyboardModifierMask The handler does not care which modifiers are pressed.
228
229 \sa Qt::KeyboardModifier
230*/
231
232/*!
233 \readonly
234 \qmlproperty bool PointHandler::active
235
236 This holds \c true whenever the constraints are satisfied and this
237 PointHandler is reacting. This means that it is keeping its properties
238 up-to-date according to the movements of the \l {eventPoint}{eventPoints}
239 that satisfy the constraints.
240*/
241
242/*!
243 \internal
244 \qmlproperty flags PointHandler::dragThreshold
245
246 This property is not used in PointHandler.
247*/
248
249/*!
250 \qmlproperty real PointHandler::margin
251
252 The margin beyond the bounds of the \l {PointerHandler::parent}{parent}
253 item within which an \l eventPoint can activate this handler.
254
255 The default value is \c 0.
256
257 \snippet pointerHandlers/pointHandlerMargin.qml 0
258*/
259
260/*!
261 \qmlproperty real PointHandler::target
262
263 A property that can conveniently hold an Item to be manipulated or to show
264 feedback. Unlike other \l {Qt Quick Input Handlers}{Pointer Handlers},
265 PointHandler does not do anything with the \c target on its own: you
266 usually need to create reactive bindings to properties such as
267 \l SinglePointHandler::point and \l PointHandler::active. If you declare
268 an Item instance here, you need to explicitly set its \l {Item::}{parent},
269 because PointHandler is not an Item.
270
271 By default, it is the same as the \l {PointerHandler::}{parent}, the Item
272 within which the handler is declared.
273*/
274
275QT_END_NAMESPACE
276
277#include "moc_qquickpointhandler_p.cpp"
278

source code of qtdeclarative/src/quick/handlers/qquickpointhandler.cpp