Add some performance tips to QML docs.

2 files changed, 121 insertions, 0 deletions

diff --git a/doc/src/declarative/declarativeui.qdoc b/doc/src/declarative/declarativeui.qdoc
index 1199b26..7a49d0a 100644
--- a/doc/src/declarative/declarativeui.qdoc
+++ b/doc/src/declarative/declarativeui.qdoc
@@ -118,6 +118,7 @@ application or to build completely new applications.  QML is fully \l
 \o \l {QML Security}
 \o \l {QtDeclarative Module}
 \o \l {Debugging QML}
+\o \l {QML Performance}
 \o \l {QML Coding Conventions}
 \endlist
 */
diff --git a/doc/src/declarative/qdeclarativeperformance.qdoc b/doc/src/declarative/qdeclarativeperformance.qdoc
new file mode 100644
index 0000000..b535e4b
--- /dev/null
+++ b/doc/src/declarative/qdeclarativeperformance.qdoc
@@ -0,0 +1,120 @@
+/****************************************************************************
+**
+** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (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 Technology Preview License Agreement accompanying
+** this package.
+**
+** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+\page qdeclarativeperformance.html
+\title QML Performance
+
+\section1 Opaque Items
+
+Items hidden behind an opaque item incur a cost.  If an item will be enitrely
+obscured by an opaque item, set its opacity to 0.  One common example of
+this is when a "details" page is shown over the main application view.
+
+\section1 Clipping
+
+\e clip is set to false by default.  Enable clipping only when necessary.
+
+\section1 Anchors vs. Binding
+
+It is more efficient to use anchors rather than bindings to position items
+relative to each other.  Consider this use of bindings to position rect2
+relative to rect1:
+
+\code
+Rectangle {
+    id: rect1
+    x: 20
+    width: 200; height: 200
+}
+Rectange {
+    id: rect2
+    x: rect1.x
+    y: rect1.y + rect1.height
+    width: rect1.width - 20
+    height: 200
+}
+\endcode
+
+This is achieved more efficiently using anchors:
+
+\code
+Rectangle {
+    id: rect1
+    x: 20
+    width: 200; height: 200
+}
+Rectange {
+    id: rect2
+    height: 200
+    anchors.left: rect1.left
+    anchors.top: rect1.bottom
+    anchors.right: rect1.right
+    anchors.rightMargin: 20
+}
+\endcode
+
+\section1 Images
+
+Images consume a great deal of memory and may also be costly to load.  In order
+to deal with large images efficiently it is recommended that the Image::sourceSize
+property be set to a size no greater than that necessary to render it.  Beware that
+changing the sourceSize will cause the image to be reloaded.
+
+Images on the local filesystem are usually loaded synchronously.  This is usually
+the desired behavior for user interface elements, however for large images that
+do not necessarily need to be visible immediately, set the Image::asynchronous
+property to true.  This will load the image in a low priority thread.
+
+\section1 View Delegates
+
+Delegates must be created quickly as the view is flicked.  There are two important
+aspects to maintaining a smooth view:
+
+\list
+\o Small delegates - keep the amount of QML to a minimum.  Have just enough
+QML in the delegate to display the necessary information.  Any additional functionality
+that is only needed when the delegate is clicked, for example, should be created by
+a Loader as needed.
+\o Fast data access - ensure the data model is as fast as possible.
+\endlist
+
+*/