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, 118 insertions, 0 deletions

diff --git a/src/corelib/kernel/qproperty_p.h b/src/corelib/kernel/qproperty_p.h
new file mode 100644
index 0000000000..1b96e09d58
--- /dev/null
+++ b/src/corelib/kernel/qproperty_p.h
@@ -0,0 +1,118 @@
+/****************************************************************************
+**
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QPROPERTY_P_H
+#define QPROPERTY_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of qapplication_*.cpp, qwidget*.cpp and qfiledialog.cpp.  This header
+// file may change from version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <qglobal.h>
+#include <qvarlengtharray.h>
+
+#include "qproperty.h"
+
+QT_BEGIN_NAMESPACE
+
+// This is a helper "namespace"
+struct Q_AUTOTEST_EXPORT QPropertyBasePointer
+{
+    const QtPrivate::QPropertyBase *ptr = nullptr;
+
+    QPropertyBindingPrivate *bindingPtr() const;
+
+    QtPrivate::QPropertyTagPreservingPointerToPointer<QPropertyObserver> firstObserverPtr() const;
+    QPropertyObserverPointer firstObserver() const;
+
+    int observerCount() const;
+
+    template <typename T>
+    static QPropertyBasePointer get(QProperty<T> &property)
+    {
+        return QPropertyBasePointer{&property.d.priv};
+    }
+};
+
+// This is a helper "namespace"
+struct QPropertyObserverPointer
+{
+    QPropertyObserver *ptr = nullptr;
+
+    void unlink();
+
+    void setBindingToMarkDirty(QPropertyBindingPrivate *binding);
+    void setChangeHandler(void (*changeHandler)(QPropertyObserver*));
+
+    void notify(QPropertyBindingPrivate *triggeringBinding);
+    void observeProperty(QPropertyBasePointer property);
+    void prependToBinding(QPropertyBindingPrivate *binding);
+
+    explicit operator bool() const { return ptr != nullptr; }
+
+    QPropertyObserverPointer nextObserver() const { return {ptr->next.data()}; }
+};
+
+class QPropertyBindingErrorPrivate : public QSharedData
+{
+public:
+    QPropertyBindingError::Type type = QPropertyBindingError::NoError;
+    QString description;
+    QPropertyBindingSourceLocation location;
+};
+
+struct BindingEvaluationState
+{
+    BindingEvaluationState(QPropertyBindingPrivate *binding);
+    ~BindingEvaluationState();
+    QPropertyBindingPrivate *binding;
+    QVarLengthArray<QPropertyObserver, 4> *dependencyObservers = nullptr;
+    BindingEvaluationState *previousState = nullptr;
+};
+
+QT_END_NAMESPACE
+
+#endif // QPROPERTY_P_H