Initial import of the Qt C++ property binding system

This implements the core value based property binding system with
automatic dependency tracking. More features are to be added later, and
the documentation will need further improvements as well.

Change-Id: I77ec9163ba4dace6c4451f5933962ebe1b3b4b14
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 141 insertions, 0 deletions

diff --git a/src/corelib/kernel/qpropertybinding.cpp b/src/corelib/kernel/qpropertybinding.cpp
new file mode 100644
index 0000000000..23f7075998
--- /dev/null
+++ b/src/corelib/kernel/qpropertybinding.cpp
@@ -0,0 +1,141 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore 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 "qpropertybinding_p.h"
+#include "qproperty_p.h"
+
+#include <QScopedValueRollback>
+
+QT_BEGIN_NAMESPACE
+
+using namespace QtPrivate;
+
+QPropertyBindingPrivate::~QPropertyBindingPrivate()
+{
+    if (firstObserver)
+        firstObserver.unlink();
+}
+
+void QPropertyBindingPrivate::unlinkAndDeref()
+{
+    propertyDataPtr = nullptr;
+    if (!ref.deref())
+        delete this;
+}
+
+void QPropertyBindingPrivate::markDirtyAndNotifyObservers()
+{
+    dirty = true;
+    if (firstObserver)
+        firstObserver.notify(this);
+}
+
+bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged()
+{
+    if (!dirty)
+        return false;
+
+    if (updating) {
+        error = QPropertyBindingError(QPropertyBindingError::BindingLoop);
+        return false;
+    }
+
+    QScopedValueRollback<bool> updateGuard(updating, true);
+
+    BindingEvaluationState evaluationFrame(this);
+    bool changed = false;
+    auto result = evaluationFunction(/*version*/1, propertyDataPtr);
+    if (auto changedPtr = std::get_if<bool>(&result))
+        changed = *changedPtr;
+    else if (auto errorPtr = std::get_if<QPropertyBindingError>(&result))
+        error = std::move(*errorPtr);
+    dirty = false;
+    return changed;
+}
+
+QUntypedPropertyBinding::QUntypedPropertyBinding(QUntypedPropertyBinding::BindingEvaluationFunction function,
+                                                 const QPropertyBindingSourceLocation &location)
+{
+    d = new QPropertyBindingPrivate(std::move(function), std::move(location));
+}
+
+QUntypedPropertyBinding::QUntypedPropertyBinding(QUntypedPropertyBinding &&other)
+    : d(std::move(other.d))
+{
+}
+
+QUntypedPropertyBinding::QUntypedPropertyBinding(const QUntypedPropertyBinding &other)
+    : d(other.d)
+{
+}
+
+QUntypedPropertyBinding &QUntypedPropertyBinding::operator=(const QUntypedPropertyBinding &other)
+{
+    d = other.d;
+    return *this;
+}
+
+QUntypedPropertyBinding &QUntypedPropertyBinding::operator=(QUntypedPropertyBinding &&other)
+{
+    d = std::move(other.d);
+    return *this;
+}
+
+QUntypedPropertyBinding::QUntypedPropertyBinding(const QPropertyBindingPrivatePtr &priv)
+    : d(priv)
+{
+}
+
+QUntypedPropertyBinding::~QUntypedPropertyBinding()
+{
+}
+
+bool QUntypedPropertyBinding::isNull() const
+{
+    return !d;
+}
+
+QPropertyBindingError QUntypedPropertyBinding::error() const
+{
+    if (!d)
+        return QPropertyBindingError();
+    return d->error;
+}
+
+QT_END_NAMESPACE