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Diffstat (limited to 'doc/src')
-rw-r--r-- | doc/src/declarative/declarativeui.qdoc | 1 | ||||
-rw-r--r-- | doc/src/declarative/qdeclarativeperformance.qdoc | 120 |
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 + +*/ |