path: root/doc/src/declarative/globalobject.qdoc

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/*!
\page qdeclarativeglobalobject.html
\title QML Global Object

Contains all the properties of the JavaScript global object, plus:

\tableofcontents

\section1 Qt Object

The Qt object provides useful enums and functions from Qt, for use in all QML
files. 

\section2 Enums
The Qt object contains all enums in the Qt namespace. For example, you can
access the AlignLeft member of the Qt::AlignmentFlag enum with \c Qt.AlignLeft.

For a full list of enums, see the \l{Qt Namespace} documentation.

\section2 Types
The Qt object also contains helper functions for creating objects of specific
data types. This is primarily useful when setting the properties of an item
when the property has one of the following types:

\list
\o Color
\o Rect
\o Point
\o Size
\o Vector3D
\endlist

There are also string based constructors for these types, see \l{qdeclarativebasictypes.html}{Qml Types}.

\section3 Qt.rgba(qreal red, qreal green, qreal blue, qreal alpha)
This function returns a Color with the specified \c red, \c green, \c blue and \c alpha components. All components should be in the range 0-1 inclusive.

\section3 Qt.hsla(qreal hue, qreal saturation, qreal lightness, qreal alpha)
This function returns a Color with the specified \c hue, \c saturation, \c lightness and \c alpha components. All components should be in the range 0-1 inclusive.

\section3 Qt.rect(int x, int y, int width, int height) 
This function returns a Rect with the top-left corner at \c x, \c y and the specified \c width and \c height.
\section3 Qt.point(int x, int y)
This function returns a Point with the specified \c x and \c y coordinates.
\section3 Qt.size(int width, int height)
This function returns as Size with the specified \c width and \c height.
\section3 Qt.vector3d(real x, real y, real z)
This function returns a Vector3D with the specified \c x, \c y and \c z.

\section2 Formatters
The Qt object contains several functions for formatting dates and times.

\section3 Qt.formatDate(datetime date, variant format)
This function returns the string representation of \c date, formatted according to \c format.
\section3 Qt.formatTime(datetime time, variant format)
This function returns the string representation of \c time, formatted according to \c format.
\section3 Qt.formatDateTime(datetime dateTime, variant format)
This function returns the string representation of \c dateTime, formatted according to \c format.

\c format for the above formatting functions can be specified as follows.

    These expressions may be used for the date:

    \table
    \header \i Expression \i Output
    \row \i d \i the day as number without a leading zero (1 to 31)
    \row \i dd \i the day as number with a leading zero (01 to 31)
    \row \i ddd
            \i the abbreviated localized day name (e.g. 'Mon' to 'Sun').
            Uses QDate::shortDayName().
    \row \i dddd
            \i the long localized day name (e.g. 'Monday' to 'Qt::Sunday').
            Uses QDate::longDayName().
    \row \i M \i the month as number without a leading zero (1-12)
    \row \i MM \i the month as number with a leading zero (01-12)
    \row \i MMM
            \i the abbreviated localized month name (e.g. 'Jan' to 'Dec').
            Uses QDate::shortMonthName().
    \row \i MMMM
            \i the long localized month name (e.g. 'January' to 'December').
            Uses QDate::longMonthName().
    \row \i yy \i the year as two digit number (00-99)
    \row \i yyyy \i the year as four digit number
    \endtable

    These expressions may be used for the time:

    \table
    \header \i Expression \i Output
    \row \i h
         \i the hour without a leading zero (0 to 23 or 1 to 12 if AM/PM display)
    \row \i hh
         \i the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)
    \row \i m \i the minute without a leading zero (0 to 59)
    \row \i mm \i the minute with a leading zero (00 to 59)
    \row \i s \i the second without a leading zero (0 to 59)
    \row \i ss \i the second with a leading zero (00 to 59)
    \row \i z \i the milliseconds without leading zeroes (0 to 999)
    \row \i zzz \i the milliseconds with leading zeroes (000 to 999)
    \row \i AP
            \i use AM/PM display. \e AP will be replaced by either "AM" or "PM".
    \row \i ap
            \i use am/pm display. \e ap will be replaced by either "am" or "pm".
    \endtable

    All other input characters will be ignored. Any sequence of characters that
    are enclosed in singlequotes will be treated as text and not be used as an
    expression. Two consecutive singlequotes ("''") are replaced by a singlequote
    in the output.

    Example format strings (assumed that the date and time is 21 May 2001
    14:13:09):

    \table
    \header \i Format       \i Result
    \row \i dd.MM.yyyy      \i 21.05.2001
    \row \i ddd MMMM d yy   \i Tue May 21 01
    \row \i hh:mm:ss.zzz    \i 14:13:09.042
    \row \i h:m:s ap        \i 2:13:9 pm
    \endtable

If no format is specified the locale's short format is used. Alternatively, you can specify
\c Qt.DefaultLocaleLongDate to get the locale's long format.

\section2 Functions
The Qt object also contains the following miscellaneous functions which expose Qt functionality for use in QML.

\section3 Qt.lighter(color baseColor)
This function returns a color 50% lighter than \c baseColor. See QColor::lighter() for further details.
\section3 Qt.darker(color baseColor)
This function returns a color 50% darker than \c baseColor. See QColor::darker() for further details.
\section3 Qt.tint(color baseColor, color tintColor)
    This function allows tinting one color with another.

    The tint color should usually be mostly transparent, or you will not be able to see the underlying color. The below example provides a slight red tint by having the tint color be pure red which is only 1/16th opaque.

    \qml
    Rectangle { x: 0; width: 80; height: 80; color: "lightsteelblue" }
    Rectangle { x: 100; width: 80; height: 80; color: Qt.tint("lightsteelblue", "#10FF0000") }
    \endqml
    \image declarative-rect_tint.png

    Tint is most useful when a subtle change is intended to be conveyed due to some event; you can then use tinting to more effectively tune the visible color.
\section3 Qt.closestAngle(number fromAngle, number toAngle)
This function returns an equivalent angle to toAngle, such that the difference between fromAngle and toAngle is never more than 180 degrees. This is useful when animating angles using a NumberAnimation, which does not know about equivalent angles, when you always want to take the shortest path. 

For example, the following would rotate myItem counterclockwise from 350 degrees to 10 degrees, for a total of 340 degrees of rotation.
\qml
NumberAnimation { target: myItem; property: "rotation"; from: 350; to: 10 }
\endqml

while the following would rotate myItem clockwise from 350 degrees to 370 degrees (which is visually equivilant to 10 degrees), for a total of 20 degrees of rotation.
\qml
NumberAnimation { target: myItem; property: "rotation"; from: 350; to: Qt.closetAngle(350, 10) }
\endqml

\section3 Qt.openUrlExternally(url target)
This function attempts to open the specified \c target url in an external application, based on the user's desktop preferences. It will return true if it succeeds, and false otherwise.

\section3 Qt.md5(data)
This function returns a hex string of the md5 hash of \c data.

\section1 Dynamic Object Creation
The following functions on the global object allow you to dynamically create QML
items from files or strings. See \l{Dynamic Object Management} for an overview
of their use.

\section2 createComponent(url file)
    This function takes the URL of a QML file as its only argument. It returns
    a component object which can be used to create and load that QML file.

    Example QML script is below. Remember that QML files that might be loaded
    over the network cannot be expected to be ready immediately.
    \code
        var component;
        var sprite;
        function finishCreation(){
            if(component.isReady()){
                sprite = component.createObject();
                if(sprite == 0){
                    // Error Handling
                }else{
                    sprite.parent = page;
                    sprite.x = 200;
                    //...
                }
            }else if(component.isError()){
                // Error Handling
            }
        }

        component = createComponent("Sprite.qml");
        if(component.isReady()){
            finishCreation();
        }else{
            component.statusChanged.connect(finishCreation);
        }
    \endcode

    If you are certain the files will be local, you could simplify to

    \code
        component = createComponent("Sprite.qml");
        sprite = component.createObject();
        if(sprite == 0){
            // Error Handling
            console.log(component.errorsString());
        }else{
            sprite.parent = page;
            sprite.x = 200;
            //...
        }
    \endcode

    If you want to just create an arbitrary string of QML, instead of
    loading a QML file, consider the createQmlObject() function.

\section2 createQmlObject(string qml, object parent, string filepath)
    Creates a new object from the specified string of QML. It requires a
    second argument, which is the id of an existing QML object to use as
    the new object's parent. If a third argument is provided, this is used
    for error reporting as the filepath that the QML came from.

    Example (where targetItem is the id of an existing QML item):
    \code
    newObject = createQmlObject('import Qt 4.6; Rectangle {color: "red"; width: 20; height: 20}',
        targetItem, "dynamicSnippet1");
    \endcode

    This function is intended for use inside QML only. It is intended to behave
    similarly to eval, but for creating QML elements.

    Returns the created object, or null if there is an error. In the case of an
    error, details of the error are output using qWarning().

    Note that this function returns immediately, and therefore may not work if
    the QML loads new components. If you are trying to load a new component,
    for example from a QML file, consider the createComponent() function
    instead. 'New components' refers to external QML files that have not yet
    been loaded, and so it is safe to use createQmlObject to load built-in
    components.

\section1 Asynchronous JavaScript and XML 
QML script supports the XMLHttpRequest object, which can be used to asynchronously obtain data from over a network.
\section2 XMLHttpRequest()
In QML you can construct an XMLHttpRequest object just like in a web browser! TODO: Real documentation for this object.
\section1 Offline Storage API

The \c openDatabase() and related functions
provide the ability to access local offline storage in an SQL database.

These databases are user-specific and QML-specific. They are stored in the \c Databases subdirectory
of QDeclarativeEngine::offlineStoragePath(), currently as SQLite databases.

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 API can be used from JavaScript functions in your QML:

\quotefile declarative/sql/hello.qml

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 of the database passed to \c openDatabase()
\row \o Driver \o Currently "QSQLITE"
\endtable

This data can be used by application tools.

*/