Default: eliminate internal IDs in DelayButton

An ID in the internal Text element prevented deferred execution for
the whole content item. The ID was used for two reasons. First of all,
it was used to propagate implicit size from the Text element to the
root of the content item. Secondly, it was used to calculate clip areas
to provide the same text in two different colors. This patch provides
two internal C++ helpers, ItemGroup and ClippedText, that provide these
functionalities without the need of using IDs in QML. At the same time
we got rid of two wrapper Items and simplified some QML bindings, which
results to a nice boost (18->22) in qmlbench on TX1.

Task-number: QTBUG-65341
Change-Id: Icf9c09356cf5c0ed641bde537bee7291bd260057
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 83 insertions, 0 deletions

diff --git a/src/quickcontrols2/qquickitemgroup_p.h b/src/quickcontrols2/qquickitemgroup_p.h
new file mode 100644
index 00000000..af062d57
--- /dev/null
+++ b/src/quickcontrols2/qquickitemgroup_p.h
@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Quick Controls 2 module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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.LGPLv3 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.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 later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKITEMGROUP_P_H
+#define QQUICKITEMGROUP_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 <QtQuick/private/qquickimplicitsizeitem_p.h>
+#include <QtQuick/private/qquickitemchangelistener_p.h>
+#include <QtQuickControls2/private/qtquickcontrols2global_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_QUICKCONTROLS2_PRIVATE_EXPORT QQuickItemGroup : public QQuickImplicitSizeItem, protected QQuickItemChangeListener
+{
+    Q_OBJECT
+
+public:
+    explicit QQuickItemGroup(QQuickItem *parent = nullptr);
+    ~QQuickItemGroup();
+
+protected:
+    void watch(QQuickItem *item);
+    void unwatch(QQuickItem *item);
+
+    QSizeF calculateImplicitSize() const;
+    void updateImplicitSize();
+
+    void itemChange(ItemChange change, const ItemChangeData &data) override;
+    void geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry) override;
+
+    void itemImplicitWidthChanged(QQuickItem *item) override;
+    void itemImplicitHeightChanged(QQuickItem *item) override;
+};
+
+QT_END_NAMESPACE
+
+QML_DECLARE_TYPE(QQuickItemGroup)
+
+#endif // QQUICKITEMGROUP_P_H