Introduce QInputDevice hierarchy; replace QTouchDevice

We have seen during the Qt 5 series that QMouseEvent::source() does
not provide enough information: if it is synthesized, it could have
come from any device for which mouse events are synthesized, not only
from a touchscreen. By providing in every QInputEvent as complete
information about the actual source device as possible, we will enable
very fine-tuned behavior in the object that handles each event.

Further, we would like to support multiple keyboards, pointing devices,
and named groups of devices that are known as "seats" in Wayland.

In Qt 5, QPA plugins registered each touchscreen as it was discovered.
Now we extend this pattern to all input devices.  This new requirement
can be implemented gradually; for now, if a QTWSI input event is
received wtihout a device pointer, a default "core" device will be
created on-the-fly, and a warning emitted.

In Qt 5, QTouchEvent::TouchPoint::id() was forced to be unique even when
multiple devices were in use simultaneously. Now that each event
identifies the device it came from, this hack is no longer needed.

A stub of the new QPointerEvent is added; it will be developed further
in subsequent patches.

[ChangeLog][QtGui][QInputEvent] Every QInputEvent now carries a pointer
to an instance of QInputDevice, or the subclass QPointingDevice in case
of mouse, touch and tablet events. Each platform plugin is expected to
create the device instances, register them, and provide valid pointers
with all input events. If this is not done, warnings are emitted and
default devices are created as necessary. When the device has accurate
information, it provides the opportunity to fine-tune behavior depending
on device type and capabilities: for example if a QMouseEvent is
synthesized from a touchscreen, the recipient can see which touchscreen
it came from. Each device also has a seatName to distinguish users on
multi-user windowing systems. Touchpoint IDs are no longer unique on
their own, but the combination of ID and device is.

Fixes: QTBUG-46412
Fixes: QTBUG-72167
Task-number: QTBUG-69433
Task-number: QTBUG-52430
Change-Id: I933fb2b86182efa722037b7a33e404c5daf5292a
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 293 insertions, 0 deletions

diff --git a/src/gui/kernel/qinputdevice.cpp b/src/gui/kernel/qinputdevice.cpp
new file mode 100644
index 0000000000..1344edb09c
--- /dev/null
+++ b/src/gui/kernel/qinputdevice.cpp
@@ -0,0 +1,293 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui 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
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+** 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 "qinputdevice.h"
+#include "qinputdevice_p.h"
+#include <QCoreApplication>
+#include <QDebug>
+#include <QMutex>
+#include <QScreen>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QInputDevice
+    \brief The QInputDevice class describes a device from which a QInputEvent originates.
+    \since 6.0
+    \inmodule QtGui
+
+    Each QInputEvent contains a QInputDevice pointer to allow accessing
+    device-specific properties like type, capabilities and seat. It is the
+    responsibility of the platform or generic plug-ins to discover, create and
+    register an instance of this class corresponding to each available input
+    device, via QWindowSystemInterface::registerInputDevice(), before
+    generating any input event referring to that device.
+
+    Applications do not need to instantiate this class, but can read the
+    instances pointed to by QInputEvent::device() and QInputDevice::devices().
+*/
+
+/*!
+    Creates a new invalid input device instance.
+*/
+QInputDevice::QInputDevice()
+    : QObject(*(new QInputDevicePrivate(QString(), -1, QInputDevice::DeviceType::Unknown)), nullptr)
+{
+}
+
+QInputDevice::~QInputDevice()
+{
+    QInputDevicePrivate::unregisterDevice(this);
+}
+
+/*!
+    Creates a new input device instance. The given \a name is normally a
+    manufacturer-assigned model name if available, or something else
+    identifiable; \a id is a platform-specific number that will be unique per
+    device (for example the xinput ID on X11); \a type identifies what kind of
+    device. On window systems that are capable of handling input from multiple
+    users or sets of input devices at the same time (such as Wayland or X11),
+    \a seatName identifies the name of the set of devices that will be used
+    together. If the device is a child or slave device (for example one of
+    several mice that can take turns moving the "core pointer"), the master
+    device should be given as the \a parent.
+
+    The platform plugin creates, registers and continues to own each device
+    instance; usually \a parent should be given for memory management purposes
+    even if there is no master for a particular device.
+
+    By default, capabilities() are \c None.
+*/
+QInputDevice::QInputDevice(const QString &name, qint64 id, QInputDevice::DeviceType type,
+                           const QString &seatName, QObject *parent)
+    : QObject(*new QInputDevicePrivate(name, id, type, QInputDevice::Capability::None, seatName), parent)
+{
+}
+
+/*!
+    \internal
+*/
+QInputDevice::QInputDevice(QInputDevicePrivate &d, QObject *parent)
+    : QObject(d, parent)
+{
+}
+
+/*!
+    Returns the device name.
+
+    This string may be empty. It is however useful on systems that have
+    multiple input devices: it can be used to differentiate from which device a
+    QPointerEvent originates.
+*/
+QString QInputDevice::name() const
+{
+    Q_D(const QInputDevice);
+    return d->name;
+}
+
+/*!
+    Returns the device type.
+*/
+QInputDevice::DeviceType QInputDevice::type() const
+{
+    Q_D(const QInputDevice);
+    return d->deviceType;
+}
+
+/*!
+    Returns the device capabilities.
+*/
+QInputDevice::Capabilities QInputDevice::capabilities() const
+{
+    Q_D(const QInputDevice);
+    return QInputDevice::Capabilities(d->capabilities);
+}
+
+/*!
+    Returns whether the device capabilities include the given \a capability.
+*/
+bool QInputDevice::hasCapability(QInputDevice::Capability capability) const
+{
+    return capabilities().testFlag(capability);
+}
+
+/*!
+    Returns the platform ID (for example xinput ID on the X11 platform).
+
+    All platforms are expected to provide a unique ID for each device.
+*/
+qint64 QInputDevice::id() const
+{
+    Q_D(const QInputDevice);
+    return d->id;
+}
+
+/*!
+    Returns the seat with which the device is associated, if known; otherwise empty.
+
+    Devices that are intended to be used together by one user may be configured
+    to have the same seat name. That is only possible on Wayland and X11
+    platforms so far.
+*/
+QString QInputDevice::seatName() const
+{
+    Q_D(const QInputDevice);
+    return d->seatName;
+}
+
+typedef QVector<const QInputDevice *> InputDevicesVector;
+Q_GLOBAL_STATIC(InputDevicesVector, deviceList)
+static QBasicMutex devicesMutex;
+
+/*!
+    Returns a list of all registered input devices (keyboards and pointing devices).
+
+    \note The returned list cannot be used to add new devices. To add a simulated
+    touch screen for an autotest, QTest::createTouchDevice() can be used.
+    Platform plugins should call \l QWindowSystemInterface::registerInputDevice()
+    to add devices as they are discovered.
+*/
+QVector<const QInputDevice *> QInputDevice::devices()
+{
+    QMutexLocker lock(&devicesMutex);
+    return *deviceList();
+}
+
+/*!
+    Returns the core or master keyboard on the given seat \a seatName.
+*/
+const QInputDevice *QInputDevice::primaryKeyboard(const QString& seatName)
+{
+    QMutexLocker locker(&devicesMutex);
+    InputDevicesVector v = *deviceList();
+    locker.unlock();
+    const QInputDevice *ret = nullptr;
+    for (const QInputDevice *d : v) {
+        if (d->type() == DeviceType::Keyboard && d->seatName() == seatName) {
+            // the master keyboard's parent is not another input device
+            if (!d->parent() || !qobject_cast<const QInputDevice *>(d->parent()))
+                return d;
+            if (!ret)
+                ret = d;
+        }
+    }
+    if (!ret) {
+        qWarning() << "no keyboards registered for seat" << seatName
+                   << "The platform plugin should have provided one via "
+                      "QWindowSystemInterface::registerInputDevice(). Creating a default one for now.";
+        ret = new QInputDevice(QLatin1String("core keyboard"), 0, DeviceType::Keyboard, seatName);
+        QInputDevicePrivate::registerDevice(ret);
+        return ret;
+    }
+    qWarning() << "core keyboard ambiguous for seat" << seatName;
+    return ret;
+}
+
+/*!
+    \internal
+    Checks whether a matching device is already registered
+    (via operator==, not pointer equality).
+*/
+bool QInputDevicePrivate::isRegistered(const QInputDevice *dev)
+{
+    if (!dev)
+        return false;
+    QMutexLocker locker(&devicesMutex);
+    InputDevicesVector v = *deviceList();
+    for (const QInputDevice *d : v)
+        if (d && *d == *dev)
+            return true;
+    return false;
+}
+
+/*!
+    \internal
+    Find the device with the given \a id, which must be unique.
+
+    \note Use QPointingDevice::tabletDevice() if the device is a tablet
+    or a tablet stylus; in that case, \a id is not unique.
+*/
+const QInputDevice *QInputDevicePrivate::fromId(qint64 id)
+{
+    QMutexLocker locker(&devicesMutex);
+    for (const QInputDevice *dev : *deviceList())
+        if (const_cast<QInputDevicePrivate *>(QInputDevicePrivate::get(dev))->id == id)
+            return dev;
+    return nullptr;
+}
+
+void QInputDevicePrivate::registerDevice(const QInputDevice *dev)
+{
+    QMutexLocker lock(&devicesMutex);
+    deviceList()->append(dev);
+}
+
+/*!
+    \internal
+*/
+void QInputDevicePrivate::unregisterDevice(const QInputDevice *dev)
+{
+    QMutexLocker lock(&devicesMutex);
+    deviceList()->removeOne(dev);
+}
+
+bool QInputDevice::operator==(const QInputDevice &other) const
+{
+    return id() == other.id();
+}
+
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug debug, const QInputDevice *device)
+{
+    QDebugStateSaver saver(debug);
+    debug.nospace();
+    debug.noquote();
+    debug << "QInputDevice(";
+    if (device) {
+        debug << '"' << device->name() << "\", type=" << device->type()
+              << Qt::hex << ", ID=" << device->id() << ", seat='" << device->seatName() << "'";
+    } else {
+        debug << '0';
+    }
+    debug << ')';
+    return debug;
+}
+#endif // !QT_NO_DEBUG_STREAM
+
+QT_END_NAMESPACE