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/****************************************************************************
**
** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** 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 Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qdeclarativeglobalobject.html
\title QML Global Object
Contains all the properties of the JavaScript global object, plus:
\tableofcontents
\section1 Qt Object
The \l{QmlGlobalQtObject}{Qt object} provides useful enums and functions from Qt, for use in all QML
files.
\section1 XMLHttpRequest
\target XMLHttpRequest
QML script supports the XMLHttpRequest object, which can be used to asynchronously obtain
data from over a network.
The XMLHttpRequest API implements the same \l {http://www.w3.org/TR/XMLHttpRequest/}{W3C standard}
as many popular web browsers with following exceptions:
\list
\i QML's XMLHttpRequest does not enforce the same origin policy.
\i QML's XMLHttpRequest does not support \e synchronous requests.
\endlist
Additionally, the \c responseXML XML DOM tree currently supported by QML is a reduced subset
of the \l {http://www.w3.org/TR/DOM-Level-3-Core/}{DOM Level 3 Core} API supported in a web
browser. The following objects and properties are supported by the QML implementation:
\table
\header
\o \bold {Node}
\o \bold {Document}
\o \bold {Element}
\o \bold {Attr}
\o \bold {CharacterData}
\o \bold {Text}
\row
\o
\list
\o nodeName
\o nodeValue
\o nodeType
\o parentNode
\o childNodes
\o firstChild
\o lastChild
\o previousSibling
\o nextSibling
\o attributes
\endlist
\o
\list
\o xmlVersion
\o xmlEncoding
\o xmlStandalone
\o documentElement
\endlist
\o
\list
\o tagName
\endlist
\o
\list
\o name
\o value
\o ownerElement
\endlist
\o
\list
\o data
\o length
\endlist
\o
\list
\o isElementContentWhitespace
\o wholeText
\endlist
\endtable
The \l{declarative/xml/xmlhttprequest}{XMLHttpRequest example} demonstrates how to
use the XMLHttpRequest object to make a request and read the response headers.
\section1 Offline Storage API
\section2 Database API
The \c openDatabaseSync() and related functions
provide the ability to access local offline storage in an SQL database.
These databases are user-specific and QML-specific, but accessible to all QML applications.
They are stored in the \c Databases subdirectory
of QDeclarativeEngine::offlineStoragePath(), currently as SQLite databases.
The API can be used from JavaScript functions in your QML:
\snippet declarative/sqllocalstorage/hello.qml 0
The API conforms to the Synchronous API of the HTML5 Web Database API,
\link http://www.w3.org/TR/2009/WD-webdatabase-20091029/ W3C Working Draft 29 October 2009\endlink.
The \l{declarative/sqllocalstorage}{SQL Local Storage example} demonstrates the basics of
using the Offline Storage API.
\section3 db = openDatabaseSync(identifier, version, description, estimated_size, callback(db))
Returns the database identified by \e identifier. If the database does not already exist, it
is created, and the function \e callback is called with the database as a parameter. \e description
and \e estimated_size are written to the INI file (described below), but are otherwise currently
unused.
May throw exception with code property SQLException.DATABASE_ERR, or SQLException.VERSION_ERR.
When a database is first created, an INI file is also created specifying its characteristics:
\table
\header \o \bold {Key} \o \bold {Value}
\row \o Name \o The name of the database passed to \c openDatabase()
\row \o Version \o The version of the database passed to \c openDatabase()
\row \o Description \o The description of the database passed to \c openDatabase()
\row \o EstimatedSize \o The estimated size (in bytes) of the database passed to \c openDatabase()
\row \o Driver \o Currently "QSQLITE"
\endtable
This data can be used by application tools.
\section3 db.changeVersion(from, to, callback(tx))
This method allows you to perform a \e{Scheme Upgrade}.
If the current version of \e db is not \e from, then an exception is thrown.
Otherwise, a database transaction is created and passed to \e callback. In this function,
you can call \e executeSql on \e tx to upgrade the database.
May throw exception with code property SQLException.DATABASE_ERR or SQLException.UNKNOWN_ERR.
\section3 db.transaction(callback(tx))
This method creates a read/write transaction and passed to \e callback. In this function,
you can call \e executeSql on \e tx to read and modify the database.
If the callback throws exceptions, the transaction is rolled back.
\section3 db.readTransaction(callback(tx))
This method creates a read-only transaction and passed to \e callback. In this function,
you can call \e executeSql on \e tx to read the database (with SELECT statements).
\section3 results = tx.executeSql(statement, values)
This method executes a SQL \e statement, binding the list of \e values to SQL positional parameters ("?").
It returns a results object, with the following properties:
\table
\header \o \bold {Type} \o \bold {Property} \o \bold {Value} \o \bold {Applicability}
\row \o int \o rows.length \o The number of rows in the result \o SELECT
\row \o var \o rows.item(i) \o Function that returns row \e i of the result \o SELECT
\row \o int \o rowsAffected \o The number of rows affected by a modification \o UPDATE, DELETE
\row \o string \o insertId \o The id of the row inserted \o INSERT
\endtable
May throw exception with code property SQLException.DATABASE_ERR, SQLException.SYNTAX_ERR, or SQLException.UNKNOWN_ERR.
\section1 Logging
\c console.log() and \c console.debug() can be used to print information
to the console. See \l{Debugging QML} for more information.
*/
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