The QLayoutItem class provides an abstract item that a QLayout manipulates. More...

Inheritance diagram for QLayoutItem:

Public Methods
	QLayoutItem (Qt::Alignment alignment=Qt::Alignment ())

virtual	~QLayoutItem ()

Qt::Alignment	alignment () const

virtual QSizePolicy::ControlTypes	controlTypes () const

virtual Qt::Orientations	expandingDirections () const = 0

virtual QRect	geometry () const = 0

virtual bool	hasHeightForWidth () const

virtual int	heightForWidth (int width) const

virtual void	invalidate ()

virtual bool	isEmpty () const = 0

virtual QLayout *	layout ()

virtual QSize	maximumSize () const = 0

virtual int	minimumHeightForWidth (int width) const

virtual QSize	minimumSize () const = 0

void	setAlignment (Qt::Alignment alignment)

virtual void	setGeometry (const QRect &rect) = 0

virtual QSize	sizeHint () const = 0

virtual QSpacerItem *	spacerItem ()

virtual QWidget *	widget ()

Detailed Description

The QLayoutItem class provides an abstract item that a QLayout manipulates. This is used by custom layouts.

Pure virtual functions are provided to return information about the layout, including, sizeHint(), minimumSize(), maximumSize() and expanding().

The layout's geometry can be set and retrieved with setGeometry() and geometry(), and its alignment with setAlignment() and alignment(). The function isEmpty() returns whether the layout item is empty. If the concrete item is a QWidget, it can be retrieved using widget(). Similarly for layout() and spacerItem().

Some layouts have width and height interdependencies. These can be expressed using hasHeightForWidth(), heightForWidth(), and minimumHeightForWidth().

See also: QLayout

Constructor & Destructor Documentation

QLayoutItem::QLayoutItem ( Qt::Alignment alignment = Qt::Alignment() )

inlineexplicit

Constructs a layout item with an alignment. Not all subclasses support alignment.

QLayoutItem::~QLayoutItem ( )

virtual

Destroys the QLayoutItem.

Method Documentation

Qt::Alignment QLayoutItem::alignment ( ) const

inline

Returns the alignment of this item.

See also: setAlignment()

QSizePolicy::ControlTypes QLayoutItem::controlTypes ( ) const

virtual

Returns the control type(s) for the layout item. For a QWidgetItem, the control type comes from the widget's size policy; for a QLayoutItem, the control types is derived from the layout's contents.

See also: QSizePolicy::controlType()

Reimplemented in QWidgetItem::controlTypes(), QLayout::controlTypes()

Qt::Orientations QLayoutItem::expandingDirections ( ) const

pure virtual

Returns whether this layout item can make use of more space than sizeHint(). A value of Qt::Vertical or Qt::Horizontal means that it wants to grow in only one dimension, whereas Qt::Vertical | Qt::Horizontal means that it wants to grow in both dimensions.

Implemented in QFormLayout::expandingDirections(), QWidgetItem::expandingDirections(), QLayout::expandingDirections(), QSpacerItem::expandingDirections(), QBoxLayout::expandingDirections(), QGridLayout::expandingDirections()

QRect QLayoutItem::geometry ( ) const

pure virtual

Returns the rectangle covered by this layout item.

See also: setGeometry()

Implemented in QWidgetItem::geometry(), QLayout::geometry(), QSpacerItem::geometry()

bool QLayoutItem::hasHeightForWidth ( ) const

virtual

Returns true if this layout's preferred height depends on its width, otherwise returns false. The default implementation returns false.

Reimplement this function in layout managers that support height for width.

See also: heightForWidth(), QWidget::heightForWidth()

Reimplemented in QFormLayout::hasHeightForWidth(), QWidgetItem::hasHeightForWidth(), QStackedLayout::hasHeightForWidth(), QBoxLayout::hasHeightForWidth(), QGridLayout::hasHeightForWidth()

int QLayoutItem::heightForWidth ( int width ) const

virtual

Returns the preferred height for this layout item, given the width.

The default implementation returns -1, indicating that the preferred height is independent of the width of the item. Using the function hasHeightForWidth() will typically be much faster than calling this function and testing for -1.

Reimplement this function in layout managers that support height for width. A typical implementation will look like this:

int MyLayout::heightForWidth(int width) const
{
    if (cache_dirty || cached_width != w) {
        // not all C++ compilers support "mutable"
        MyLayout *that = (MyLayout*)this;
        int h = calculateHeightForWidth(w);
        that->cached_hfw = h;
        return h;
    }
    return cached_hfw;
}