Add Window attached property on Item

An Item sometimes needs to know a few things about the window
in which it is being displayed; this attached property can expose
them without needing to go up the heirarchy to find the window.
Instead of adding the QQuickWindow pointer as a property on Item
as in 8f49f50a169db85401eb37daf4fe3a0fc3280603, having an attached
property means that it will not be found by introspection; and
it solves the problem that Window is in the QtQuick.Window module:
you must import the module to use the attached property, instead
of having access to a pointer whose type might not be defined
if you didn't import it.  The Window attached property is created
on-demand (so the memory cost adds up if you use it in too many
places); the tradeoff is that it can exist even when the item
is not yet being shown in a window, so bindings at startup work.
The API is purposely incomplete compared to that in QQuickWindow
so that we can introduce what is needed in a controlled fasion
over time.  For now we know of use cases for visibility, active
and activeFocusItem.

[ChangeLog][QtQuick][Window] Added Item.Window attached property

Change-Id: I649404cbd1383326678aa2144f790b2f2542dbbc
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/src/quick/items/qquickwindowattached_p.h b/src/quick/items/qquickwindowattached_p.h
new file mode 100644
index 0000000000..007ff007f7
--- /dev/null
+++ b/src/quick/items/qquickwindowattached_p.h
@@ -0,0 +1,84 @@
+/****************************************************************************
+**
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtQuick 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 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 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QQUICKWINDOW_ATTACHED_P_H
+#define QQUICKWINDOW_ATTACHED_P_H
+
+#include <qqml.h>
+#include <QWindow>
+
+QT_BEGIN_NAMESPACE
+
+class QQuickItem;
+class QQuickWindow;
+
+class Q_AUTOTEST_EXPORT QQuickWindowAttached : public QObject
+{
+    Q_OBJECT
+
+    Q_PROPERTY(QWindow::Visibility visibility READ visibility NOTIFY visibilityChanged)
+    Q_PROPERTY(bool active READ isActive NOTIFY activeChanged)
+    Q_PROPERTY(QQuickItem* activeFocusItem READ activeFocusItem NOTIFY activeFocusItemChanged)
+
+public:
+    QQuickWindowAttached(QObject* attachee);
+
+    QWindow::Visibility visibility() const;
+    bool isActive() const;
+    QQuickItem* activeFocusItem() const;
+
+Q_SIGNALS:
+
+    void visibilityChanged();
+    void activeChanged();
+    void activeFocusItemChanged();
+
+protected Q_SLOTS:
+    void windowChanged(QQuickWindow*);
+
+private:
+    QQuickWindow* m_window;
+    QQuickItem* m_attachee;
+};
+
+QT_END_NAMESPACE
+
+#endif