app: make it possible to lock the mouse when using the remote input

It makes it possible to use normal touchpads and mice

declarativeplugin/pointerlocker.cpp

@@ -0,0 +1,72 @@
+/*
+    SPDX-FileCopyrightText: 2018 Roman Gilg <subdiff@gmail.com>
+    SPDX-FileCopyrightText: 2021 Aleix Pol Gonzalez <aleixpol@kde.org>
+
+    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
+*/
+
+#include "pointerlocker.h"
+
+#include <QGuiApplication>
+#include <QQmlContext>
+#include <QQmlEngine>
+#include <QCursor>
+
+#include <QDebug>
+#include <QScopedPointer>
+
+void AbstractPointerLocker::setWindow(QWindow* window)
+{
+    if (m_window == window) {
+        return;
+    }
+    m_window = window;
+    Q_EMIT windowChanged();
+}
+
+PointerLockerQt::PointerLockerQt(QObject *parent)
+    : AbstractPointerLocker(parent)
+{
+}
+
+PointerLockerQt::~PointerLockerQt() = default;
+
+void PointerLockerQt::setLocked(bool lock)
+{
+    if (isLocked() == lock) {
+        return;
+    }
+
+    if (lock) {
+        /* Cursor needs to be hidden such that Xwayland emulates warps. */
+        QGuiApplication::setOverrideCursor(QCursor(Qt::BlankCursor));
+        m_originalPosition = QCursor::pos();
+        m_window->installEventFilter(this);
+        Q_EMIT lockedChanged(true);
+        Q_EMIT lockEffectiveChanged(true);
+    } else {
+        m_window->removeEventFilter(this);
+        QGuiApplication::restoreOverrideCursor();
+        Q_EMIT lockedChanged(false);
+        Q_EMIT lockEffectiveChanged(false);
+    }
+}
+
+bool PointerLockerQt::isLocked() const
+{
+    return !m_originalPosition.isNull();
+}
+
+bool PointerLockerQt::eventFilter(QObject *watched, QEvent *event)
+{
+    if (watched != m_window || event->type() != QEvent::MouseMove || !isLocked()) {
+        return false;
+    }
+
+    const auto newPos = QCursor::pos();
+    const QPointF dist = newPos - m_originalPosition;
+    Q_EMIT pointerMoved({ dist.x(), dist.y() });
+    QCursor::setPos(m_originalPosition);
+
+    return true;
+}