Add documentation for integrating with existing Qt UI code

2 files changed, 92 insertions, 1 deletions

diff --git a/doc/src/declarative/integrating.qdoc b/doc/src/declarative/integrating.qdoc
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+++ b/doc/src/declarative/integrating.qdoc
@@ -0,0 +1,90 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** 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, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, 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.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+\page qml-integration.html
+\title Integrating QML with existing Qt UI code
+
+If you have existing Qt UI code which does not use QML, you can still
+use QML in some ways without having to rewrite your UI.
+
+\section1 Adding QML to a QWidget based UI
+If you have an existing QWidget based UI you can simply write new custom
+widgets in QML. To integrate them into your application you can create a
+QmlView widget, and load the QML file into that. You'll then have a new widget
+containing your declarative UI, and you can interact with it through the
+QmlView interface. The one drawback of this approach is that QmlView is a lot
+heavier than a QWidget in terms of memory consumption and initialization speed,
+and so having large numbers of them may lead to performance degredation.
+
+For a smooth transition from a QWidget based UI to a QML based UI, simply
+rewrite your widgets in QML one at a time, using the above method. When
+all of your widgets are written in QML you can rewrite your main widget in
+QML, so as to load the other widgets in QML instead of using QmlViews. Then
+you just load the main QML file on startup.
+
+Keep in mind that QWidgets were designed for different sorts of UIs than QML
+was, and so it is not always a good idea to switch. QWidgets are a better
+choice if your UI is comprised of a small number of complex and static
+elements, and QML is a better choice if your UI is comprised of a large number
+of simple and dynamic elements.
+
+\section1 Adding QML to a QGraphicsView based UI
+If you have an existing QGraphicsView based UI you can create new items in QML,
+and use QmlComponent to create QGraphicsObjects from the QML primitives. These
+QGraphicsObjects can then be manually placed into your QGraphicsScene just like
+any other.
+
+\section1 Using existing QGraphicsWidgets in QML
+Another way of integrating with a QGraphicsView based UI is to expose your
+existing QGraphicsWidgets to QML, and constructing your scene in QML. Note that
+this approach will not work with QGraphicsItems which are not QGraphicsWidgets,
+and that this approach allows you to integrate new items written in QML
+without using the above method.
+
+As per the instructions in \l{Extending QML}, you can make custom C++ types 
+available in QML using a pair of macros. While this is normally only useful for
+types that were designed for QML use, in conjunction with the
+\l{GraphicsObjectContainer} element it works for QGraphicsWidgets which can be
+controlled through properties. See the \l{GraphicsObjectContainer}
+documentation for details about its use. This way you can write your UI using
+QML, without having to rewrite any of your complex existing items.
+*/
diff --git a/doc/src/declarative/qtprogrammers.qdoc b/doc/src/declarative/qtprogrammers.qdoc
index 7b1ab44..26f73cb 100644
--- a/doc/src/declarative/qtprogrammers.qdoc
+++ b/doc/src/declarative/qtprogrammers.qdoc
@@ -65,7 +65,7 @@ QML provides direct access to the following concepts from Qt:
  \o Qt models - used directly in data binding (QAbstractItemModel and next generation QListModelInterface)
 \endlist
 
-Qt knowledge is \e required for \l {Extending QML}.
+Qt knowledge is \e required for \l {Extending QML}, and also for \l{Integrating QML with existing Qt UI code}.
 
 \section1 QML Items compared with QWidgets
 
@@ -159,4 +159,5 @@ users of the compound item might wish to employ. For example, a spinbox might ne
 transition from an arbitrary Text item, or characters within a Text item, so your spinbox
 item would need to be sufficiently flexible to allow such animation.
 
+\section1 QML Items Compared With QGraphicsWidgets
 */