Qt 4.8: QDeclarativeItem Class Reference

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# QDeclarativeItem Class Reference

The QDeclarativeItem class provides the most basic of all visual items in QML. More...

     #include <QDeclarativeItem>

Inherits: QGraphicsObject and QDeclarativeParserStatus.

This class was introduced in Qt 4.7.

- List of all members, including inherited members

## Public Types

enum | TransformOrigin { TopLeft, Top, TopRight, Left, ..., BottomRight }

## Properties

baselineOffset : qreal childrenRect : const QRectF clip : bool implicitHeight : const qreal | implicitWidth : const qreal parent : QDeclarativeItem * smooth : bool

- 12 properties inherited from QGraphicsObject
- 1 property inherited from QObject

## Public Functions

| QDeclarativeItem ( QDeclarativeItem * parent = 0 )
virtual | ~QDeclarativeItem ()
qreal | baselineOffset () const
QDeclarativeItem * | childAt ( qreal x, qreal y ) const
QRectF | childrenRect ()
bool | clip () const
void | forceActiveFocus ()
qreal | implicitHeight () const
qreal | implicitWidth () const
bool | keepMouseGrab () const
QScriptValue | mapFromItem ( const QScriptValue & item, qreal x, qreal y ) const
QScriptValue | mapToItem ( const QScriptValue & item, qreal x, qreal y ) const
QDeclarativeItem * | parentItem () const
void | setBaselineOffset ( qreal )
void | setClip ( bool )
void | setKeepMouseGrab ( bool keep )
void | setParentItem ( QDeclarativeItem * parent )
void | setSmooth ( bool smooth )
void | setTransformOrigin ( TransformOrigin origin )
bool | smooth () const
TransformOrigin | transformOrigin () const

- 2 public functions inherited from QGraphicsObject
- 2 public functions inherited from QDeclarativeParserStatus
- 29 public functions inherited from QObject
- 177 public functions inherited from QGraphicsItem

## Signals

| Q_REVISION ()
| Q_REVISION ()

- 9 signals inherited from QGraphicsObject
- 1 signal inherited from QObject

## Protected Functions

virtual void | geometryChanged ( const QRectF & newGeometry, const QRectF & oldGeometry )
bool | heightValid () const
bool | isComponentComplete () const
void | setImplicitHeight ( qreal h )
void | setImplicitWidth ( qreal w )
bool | widthValid () const

- 8 protected functions inherited from QObject
- 24 protected functions inherited from QGraphicsItem

### Additional Inherited Members

- 1 public slot inherited from QObject
- 7 static public members inherited from QObject
- 2 static public members inherited from QGraphicsItem
- 1 protected slot inherited from QGraphicsObject

## Detailed Description

The QDeclarativeItem class provides the most basic of all visual items in QML.

All visual items in Qt Declarative inherit from QDeclarativeItem. Although QDeclarativeItem has no visual appearance, it defines all the properties that are common across visual items - such as the x and y position, the width and height, anchoring and key handling.

You can subclass QDeclarativeItem to provide your own custom visual item that inherits these features. Note that, because it does not draw anything, QDeclarativeItem sets the QGraphicsItem::ItemHasNoContents flag. If you subclass QDeclarativeItem to create a visual item, you will need to unset this flag.

## Member Type Documentation

### enum QDeclarativeItem::TransformOrigin

Controls the point about which simple transforms like scale apply.

Constant | Value | Description
--- | --- | ---
`QDeclarativeItem::TopLeft` | `0` | The top-left corner of the item.
`QDeclarativeItem::Top` | `1` | The center point of the top of the item.
`QDeclarativeItem::TopRight` | `2` | The top-right corner of the item.
`QDeclarativeItem::Left` | `3` | The left most point of the vertical middle.
`QDeclarativeItem::Center` | `4` | The center of the item.
`QDeclarativeItem::Right` | `5` | The right most point of the vertical middle.
`QDeclarativeItem::BottomLeft` | `6` | The bottom-left corner of the item.
`QDeclarativeItem::Bottom` | `7` | The center point of the bottom of the item.
`QDeclarativeItem::BottomRight` | `8` | The bottom-right corner of the item.

## Property Documentation

### baselineOffset : qreal

This property holds the position of the item's baseline in local coordinates.

The baseline of a Text item is the imaginary line on which the text sits. Controls containing text usually set their baseline to the baseline of their text.

For non-text items, a default baseline offset of 0 is used.

Access functions:

qreal | baselineOffset () const
void | setBaselineOffset ( qreal )

### childrenRect : const QRectF

This property holds the geometry of an item's children.

This property holds the (collective) position and size of the item's children.

Access functions:

QRectF | childrenRect ()

### clip : bool

This property holds whether clipping is enabled. The default clip value is `false`.

If clipping is enabled, an item will clip its own painting, as well as the painting of its children, to its bounding rectangle. If you set clipping during an item's paint operation, remember to re-set it to prevent clipping the rest of your scene.

Non-rectangular clipping regions are not supported for performance reasons.

Access functions:

bool | clip () const
void | setClip ( bool )

### implicitHeight : const qreal

Access functions:

qreal | implicitHeight () const

### implicitWidth : const qreal

Access functions:

qreal | implicitWidth () const

### parent : QDeclarativeItem *

This property holds the parent of the item.

Access functions:

QDeclarativeItem * | parentItem () const
void | setParentItem ( QDeclarativeItem * parent )

Notifier signal:

void | parentChanged ()

### smooth : bool

This property holds whether the item is smoothly transformed.

This property is provided purely for the purpose of optimization. Turning smooth transforms off is faster, but looks worse; turning smooth transformations on is slower, but looks better.

By default smooth transformations are off.

Access functions:

bool | smooth () const
void | setSmooth ( bool smooth )

## Member Function Documentation

### QDeclarativeItem::QDeclarativeItem ( QDeclarativeItem * parent = 0 )

Constructs a QDeclarativeItem with the given parent.

### QDeclarativeItem::~QDeclarativeItem ()`[virtual]`

Destroys the QDeclarativeItem.

### QDeclarativeItem::Q_REVISION ()`[signal]`

### QDeclarativeItem * QDeclarativeItem::childAt ( qreal x, qreal y ) const

Returns the visible child item at point (x, y), which is in this item's coordinate system, or 0 if there is no such item.

### void QDeclarativeItem::forceActiveFocus ()

Forces active focus on the item.

This method sets focus on the item and makes sure that all the focus scopes higher in the object hierarchy are also given the focus.

### void QDeclarativeItem::geometryChanged ( const QRectF & newGeometry, const QRectF & oldGeometry )`[virtual protected]`

This function is called to handle this item's changes in geometry from oldGeometry to newGeometry. If the two geometries are the same, it doesn't do anything.

### bool QDeclarativeItem::heightValid () const`[protected]`

Returns whether the height property has been set explicitly.

### bool QDeclarativeItem::isComponentComplete () const`[protected]`

Returns true if construction of the QML component is complete; otherwise returns false.

It is often desirable to delay some processing until the component is completed.

See also componentComplete().

### bool QDeclarativeItem::keepMouseGrab () const

Returns a value indicating whether mouse input should remain with this item exclusively.

See also setKeepMouseGrab().

### QScriptValue QDeclarativeItem::mapFromItem ( const QScriptValue & item, qreal x, qreal y ) const

Maps the point (x, y), which is in item's coordinate system, to this item's coordinate system, and returns a script value with `x` and `y` properties matching the mapped cooordinate.

If item is a `null` value, this maps the point from the coordinate system of the root QML view.

See also Item::mapFromItem().

### QScriptValue QDeclarativeItem::mapToItem ( const QScriptValue & item, qreal x, qreal y ) const

Maps the point (x, y), which is in this item's coordinate system, to item's coordinate system, and returns a script value with `x` and `y` properties matching the mapped cooordinate.

If item is a `null` value, this maps x and y to the coordinate system of the root QML view.

See also Item::mapToItem().

### void QDeclarativeItem::setImplicitHeight ( qreal h )`[protected]`

Sets the implied height of the item to h. This is the height implied by other properties that determine the content.

See also implicitHeight().

### void QDeclarativeItem::setImplicitWidth ( qreal w )`[protected]`

Sets the implied width of the item to w. This is the width implied by other properties that determine the content.

See also implicitWidth().

### void QDeclarativeItem::setKeepMouseGrab ( bool keep )

The flag indicating whether the mouse should remain with this item is set to keep.

This is useful for items that wish to grab and keep mouse interaction following a predefined gesture. For example, an item that is interested in horizontal mouse movement may set keepMouseGrab to true once a threshold has been exceeded. Once keepMouseGrab has been set to true, filtering items will not react to mouse events.

If the item does not indicate that it wishes to retain mouse grab, a filtering item may steal the grab. For example, Flickable may attempt to steal a mouse grab if it detects that the user has begun to move the viewport.

See also keepMouseGrab().

### void QDeclarativeItem::setTransformOrigin ( TransformOrigin origin )

Set the transform origin.

See also transformOrigin().

### TransformOrigin QDeclarativeItem::transformOrigin () const

Returns the current transform origin.

See also setTransformOrigin().

### bool QDeclarativeItem::widthValid () const`[protected]`

Returns whether the width property has been set explicitly.