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, 249 insertions, 0 deletions

diff --git a/src/corelib/kernel/qpropertyprivate.h b/src/corelib/kernel/qpropertyprivate.h
new file mode 100644
index 0000000000..6d4a729845
--- /dev/null
+++ b/src/corelib/kernel/qpropertyprivate.h
@@ -0,0 +1,249 @@
+/****************************************************************************
+**
+** 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 QPROPERTYPRIVATE_H
+#define QPROPERTYPRIVATE_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 <QtCore/qglobal.h>
+#include <QtCore/QExplicitlySharedDataPointer>
+
+QT_BEGIN_NAMESPACE
+
+class QUntypedPropertyBinding;
+struct QPropertyBindingPrivate;
+using QPropertyBindingPrivatePtr = QExplicitlySharedDataPointer<QPropertyBindingPrivate>;
+struct QPropertyBasePointer;
+
+namespace QtPrivate {
+
+class Q_CORE_EXPORT QPropertyBase
+{
+    // Mutable because the address of the observer of the currently evaluating binding is stored here, for
+    // notification later when the value changes.
+    mutable quintptr d_ptr = 0;
+    friend struct QT_PREPEND_NAMESPACE(QPropertyBasePointer);
+public:
+    QPropertyBase() = default;
+    Q_DISABLE_COPY(QPropertyBase)
+    QPropertyBase(QPropertyBase &&other) = delete;
+    QPropertyBase(QPropertyBase &&other, void *propertyDataPtr);
+    QPropertyBase &operator=(QPropertyBase &&other) = delete;
+    ~QPropertyBase();
+
+    void moveAssign(QPropertyBase &&other, void *propertyDataPtr);
+
+    bool hasBinding() const { return d_ptr & BindingBit; }
+
+    QUntypedPropertyBinding setBinding(const QUntypedPropertyBinding &newBinding, void *propertyDataPtr);
+    QPropertyBindingPrivatePtr binding();
+
+    void evaluateIfDirty();
+    void removeBinding();
+
+    void registerWithCurrentlyEvaluatingBinding() const;
+    void notifyObservers();
+
+    void setExtraBit(bool b)
+    {
+        if (b)
+            d_ptr |= ExtraBit;
+        else
+            d_ptr &= ~ExtraBit;
+    }
+
+    bool extraBit() const { return d_ptr & ExtraBit; }
+
+    static const quintptr ExtraBit = 0x1;   // Used for QProperty<bool> specialization
+    static const quintptr BindingBit = 0x2; // Is d_ptr pointing to a binding (1) or list of notifiers (0)?
+    static const quintptr FlagMask = BindingBit | ExtraBit;
+};
+
+template <typename T>
+struct QPropertyValueStorage
+{
+private:
+    T value;
+public:
+    QPropertyBase priv;
+
+    QPropertyValueStorage() : value() {}
+    Q_DISABLE_COPY(QPropertyValueStorage)
+    explicit QPropertyValueStorage(const T &initialValue) : value(initialValue) {}
+    QPropertyValueStorage &operator=(const T &newValue) { value = newValue; return *this; }
+    explicit QPropertyValueStorage(T &&initialValue) : value(std::move(initialValue)) {}
+    QPropertyValueStorage &operator=(T &&newValue) { value = std::move(newValue); return *this; }
+    QPropertyValueStorage(QPropertyValueStorage &&other) : value(std::move(other.value)), priv(std::move(other.priv), this) {}
+    QPropertyValueStorage &operator=(QPropertyValueStorage &&other) { value = std::move(other.value); priv.moveAssign(std::move(other.priv), &value); return *this; }
+
+    T getValue() const { return value; }
+    bool setValueAndReturnTrueIfChanged(T &&v)
+    {
+        if (v == value)
+            return false;
+        value = std::move(v);
+        return true;
+    }
+    bool setValueAndReturnTrueIfChanged(const T &v)
+    {
+        if (v == value)
+            return false;
+        value = v;
+        return true;
+    }
+};
+
+template<>
+struct QPropertyValueStorage<bool>
+{
+    QPropertyBase priv;
+
+    QPropertyValueStorage() = default;
+    Q_DISABLE_COPY(QPropertyValueStorage)
+    explicit QPropertyValueStorage(bool initialValue) { priv.setExtraBit(initialValue); }
+    QPropertyValueStorage &operator=(bool newValue) { priv.setExtraBit(newValue); return *this; }
+    QPropertyValueStorage(QPropertyValueStorage &&other) : priv(std::move(other.priv), this) {}
+    QPropertyValueStorage &operator=(QPropertyValueStorage &&other) { priv.moveAssign(std::move(other.priv), this); return *this; }
+
+    bool getValue() const { return priv.extraBit(); }
+    bool setValueAndReturnTrueIfChanged(bool v)
+    {
+        if (v == priv.extraBit())
+            return false;
+        priv.setExtraBit(v);
+        return true;
+    }
+};
+
+template <typename T> class QTaggedPointer;
+
+template <typename T, quintptr Mask = 0x3>
+class QPropertyTagPreservingPointerToPointer
+{
+    quintptr *data = nullptr;
+
+public:
+    QPropertyTagPreservingPointerToPointer() = default;
+    QPropertyTagPreservingPointerToPointer(T **ptr)
+        : data(reinterpret_cast<quintptr*>(ptr))
+    {}
+    QPropertyTagPreservingPointerToPointer(quintptr *ptr)
+        : data(ptr)
+    {}
+
+    QPropertyTagPreservingPointerToPointer<T> &operator=(T **ptr)
+    {
+        data = reinterpret_cast<quintptr*>(ptr);
+        return *this;
+    }
+
+    QPropertyTagPreservingPointerToPointer<T> &operator=(QTaggedPointer<T> *ptr)
+    {
+        data = reinterpret_cast<quintptr*>(ptr);
+        return *this;
+    }
+
+    void clear()
+    {
+        data = nullptr;
+    }
+
+    void set(T *ptr)
+    {
+        *data = (*data & Mask) | (reinterpret_cast<quintptr>(ptr) & ~Mask);
+    }
+
+    T *get() const
+    {
+        return reinterpret_cast<T*>(*data & ~Mask);
+    }
+
+    explicit operator bool() const { return data != nullptr; }
+};
+
+template <typename T>
+class QTaggedPointer
+{
+public:
+    QTaggedPointer() = default;
+    QTaggedPointer(T *ptr) : tagAndPointer(reinterpret_cast<quintptr>(ptr)) {}
+
+    void setFlag(bool b)
+    {
+        if (b)
+            tagAndPointer |= Flag1Mask;
+        else
+            tagAndPointer &= ~Flag1Mask;
+    }
+
+    bool flag() const { return tagAndPointer & Flag1Mask; }
+
+    QTaggedPointer &operator=(T *ptr)
+    {
+        quintptr tag = tagAndPointer & TagMask;
+        tagAndPointer = reinterpret_cast<quintptr>(ptr) | tag;
+        return *this;
+    }
+
+    T *data() const { return reinterpret_cast<T*>(tagAndPointer & ~TagMask); }
+
+    explicit operator bool() const { return tagAndPointer & ~TagMask; }
+    T *operator->() const { return data(); }
+
+private:
+    quintptr tagAndPointer = 0;
+    static const quintptr Flag1Mask = 0x1;
+    static const quintptr TagMask = 0x3;
+};
+
+} // namespace QtPrivate
+
+QT_END_NAMESPACE
+
+#endif // QPROPERTYPRIVATE_H