Add support for binding directly to QProperty instances

Avoid going through externally managed bindings and instead allocate a
more lightweight property binding. It's basically a
QQmlJavaScriptExpression and one pointer plus the overhead of
QPropertyBindingPrivate.

Change-Id: I1530330926d351b61f2b3bbad39301c628a8bef1
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 83 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlpropertybinding_p.h b/src/qml/qml/qqmlpropertybinding_p.h
new file mode 100644
index 0000000000..3bd6772413
--- /dev/null
+++ b/src/qml/qml/qqmlpropertybinding_p.h
@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml 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 QQMLPROPERTYBINDING_P_H
+#define QQMLPROPERTYBINDING_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qproperty.h>
+#include <private/qpropertybinding_p.h>
+
+#include "qqmlpropertydata_p.h"
+#include "qqmljavascriptexpression_p.h"
+
+#include <memory>
+
+QT_BEGIN_NAMESPACE
+
+class QQmlPropertyBinding final : public QQmlJavaScriptExpression,
+                                  public QPropertyBindingPrivate
+{
+public:
+    static QUntypedPropertyBinding create(const QQmlPropertyData *pd, QV4::Function *function,
+                                          QObject *obj, const QQmlRefPointer<QQmlContextData> &ctxt,
+                                          QV4::ExecutionContext *scope);
+
+    virtual void expressionChanged();
+
+private:
+    QQmlPropertyBinding(const QMetaType &metaType);
+
+    QUntypedPropertyBinding::BindingEvaluationResult evaluateAndReturnTrueIfChanged(const QMetaType &metaType,
+                                                                                    void *dataPtr);
+};
+
+QT_END_NAMESPACE
+
+#endif // QQMLPROPERTYBINDING_P_H