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

#include <qlayoutitem.h>

Inheritance diagram for QLayoutItem:

Collaboration diagram for QLayoutItem:

Public Member Functions
	QLayoutItem (Qt::Alignment alignment=Qt::Alignment())

virtual	~QLayoutItem ()

virtual QSize	sizeHint () const =0

virtual QSize	minimumSize () const =0

virtual QSize	maximumSize () const =0

virtual Qt::Orientations	expandingDirections () const =0

virtual void	setGeometry (const QRect &)=0

virtual QRect	geometry () const =0

virtual bool	isEmpty () const =0

virtual bool	hasHeightForWidth () const

virtual int	heightForWidth (int) const

virtual int	minimumHeightForWidth (int) const

virtual void	invalidate ()

virtual QWidget *	widget () const

virtual QLayout *	layout ()

virtual QSpacerItem *	spacerItem ()

Qt::Alignment	alignment () const

void	setAlignment (Qt::Alignment a)

virtual QSizePolicy::ControlTypes	controlTypes () const

Protected Attributes
Qt::Alignment	align

Detailed Description

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

\inmodule QtWidgets

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().

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(). For more explanation see the {Qt Quarterly} article \l{http://doc.qt.io/archives/qq/qq04-height-for-width.html}{Trading Height for Width}.

See also: QLayout

Definition at line 60 of file qlayoutitem.h.

Constructor & Destructor Documentation

◆ QLayoutItem()

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

inlineexplicit

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

Definition at line 89 of file qlayoutitem.h.

◆ ~QLayoutItem()

QLayoutItem::~QLayoutItem ( )

virtualdefault

Destroys the QLayoutItem.

Member Function Documentation

◆ alignment()

Qt::Alignment QLayoutItem::alignment ( ) const

inline

Returns the alignment of this item.

Definition at line 81 of file qlayoutitem.h.

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◆ controlTypes()

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, and QLayout.

Definition at line 433 of file qlayoutitem.cpp.

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◆ expandingDirections()

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 LayoutItem, QToolBarLayout, QWidgetItem, QSpacerItem, QLayout, QGridLayout, QFormLayout, QBoxLayout, FlowLayout, and BorderLayout.

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◆ geometry()

QRect QLayoutItem::geometry ( ) const

pure virtual

Returns the rectangle covered by this layout item.

See also: setGeometry()

Implemented in LayoutItem, QWidgetItem, QSpacerItem, and QLayout.

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◆ hasHeightForWidth()

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 QStackedLayout, QWidgetItem, QGridLayout, QFormLayout, QBoxLayout, FlowLayout, and BorderLayout.

Definition at line 386 of file qlayoutitem.cpp.

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◆ heightForWidth()

int QLayoutItem::heightForWidth ( int ) const

virtual

Returns the preferred height for this layout item, given the width, which is not used in this default implementation.

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:

Caching is strongly recommended; without it layout will take exponential time.

See also: hasHeightForWidth()

Reimplemented in QWidgetItem, QGridLayout, QBoxLayout, FlowLayout, QStackedLayout, QWidgetItemV2, and QFormLayout.

Definition at line 420 of file qlayoutitem.cpp.

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◆ invalidate()

void QLayoutItem::invalidate ( )

virtual

Invalidates any cached information in this layout item.

Reimplemented in MyLayout, QToolBarLayout, QMainWindowLayout, QLayout, QGridLayout, QFormLayout, and QBoxLayout.

Definition at line 304 of file qlayoutitem.cpp.

◆ isEmpty()

bool QLayoutItem::isEmpty ( ) const

pure virtual

Implemented in subclasses to return whether this item is empty, i.e. whether it contains any widgets.

Implemented in LayoutItem, QToolBarLayout, QToolBarItem, QWidgetItem, QSpacerItem, and QLayout.

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◆ layout()

QLayout * QLayoutItem::layout ( )

virtual

If this item is a QLayout, it is returned as a QLayout; otherwise \nullptr is returned. This function provides type-safe casting.

See also: spacerItem(), widget()

Reimplemented in QLayout.

Definition at line 314 of file qlayoutitem.cpp.

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◆ maximumSize()

QSize QLayoutItem::maximumSize ( ) const

pure virtual

Implemented in subclasses to return the maximum size of this item.

Implemented in LayoutItem, QDockWidgetItem, QDockWidgetLayout, QWidgetItemV2, QWidgetItem, QSpacerItem, QLayout, QGridLayout, and QBoxLayout.

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◆ minimumHeightForWidth()

int QLayoutItem::minimumHeightForWidth ( int w ) const

virtual

Returns the minimum height this widget needs for the given width, w. The default implementation simply returns heightForWidth(w).

Reimplemented in QWidgetItem, QGridLayout, and QBoxLayout.

Definition at line 396 of file qlayoutitem.cpp.

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◆ minimumSize()

QSize QLayoutItem::minimumSize ( ) const

pure virtual

Implemented in subclasses to return the minimum size of this item.

Implemented in LayoutItem, QToolBarLayout, QMainWindowLayout, QDockWidgetItem, QDockWidgetLayout, QStackedLayout, QWidgetItemV2, QWidgetItem, QSpacerItem, QLayout, QGridLayout, QFormLayout, QBoxLayout, CardLayout, FlowLayout, and BorderLayout.

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◆ setAlignment()

void QLayoutItem::setAlignment ( Qt::Alignment alignment )

Sets the alignment of this item to alignment.

{Note:} Item alignment is only supported by QLayoutItem subclasses where it would have a visual effect. Except for QSpacerItem, which provides blank space for layouts, all public Qt classes that inherit QLayoutItem support item alignment.

Definition at line 192 of file qlayoutitem.cpp.

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◆ setGeometry()

void QLayoutItem::setGeometry ( const QRect & r )

pure virtual

Implemented in subclasses to set this item's geometry to r.

See also: geometry()

Implemented in QStackedLayout, QFormLayout, CardLayout, FlowLayout, BorderLayout, LayoutItem, QToolBarLayout, QMainWindowLayout, QDockWidgetLayout, QWidgetItem, QSpacerItem, QLayout, QGridLayout, and QBoxLayout.

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◆ sizeHint()

QSize QLayoutItem::sizeHint ( ) const

pure virtual

Implemented in subclasses to return the preferred size of this item.

Implemented in MyLayout, LayoutItem, QToolBarLayout, QMainWindowLayout, QDockWidgetItem, QDockWidgetLayout, QStackedLayout, QWidgetItemV2, QWidgetItem, QSpacerItem, QGridLayout, QFormLayout, QBoxLayout, CardLayout, FlowLayout, and BorderLayout.

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◆ spacerItem()

QSpacerItem * QLayoutItem::spacerItem ( )

virtual

If this item is a QSpacerItem, it is returned as a QSpacerItem; otherwise \nullptr is returned. This function provides type-safe casting.

See also: layout(), widget()

Reimplemented in QSpacerItem.

Definition at line 325 of file qlayoutitem.cpp.

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◆ widget()

QWidget * QLayoutItem::widget ( ) const

virtual

If this item manages a QWidget, returns that widget. Otherwise, \nullptr is returned.

Note: While the functions layout() and spacerItem() perform casts, this function returns another object: QLayout and QSpacerItem inherit QLayoutItem, while QWidget does not.

See also: layout(), spacerItem()

Reimplemented in QWidgetItem.

Definition at line 363 of file qlayoutitem.cpp.

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Member Data Documentation

◆ align

Qt::Alignment QLayoutItem::align

protected

Definition at line 86 of file qlayoutitem.h.

The documentation for this class was generated from the following files:

src/widgets/kernel/qlayoutitem.h
src/widgets/kernel/qlayoutitem.cpp

Public Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ QLayoutItem()

◆ ~QLayoutItem()

Member Function Documentation

◆ alignment()

◆ controlTypes()

◆ expandingDirections()

◆ geometry()

◆ hasHeightForWidth()

◆ heightForWidth()

◆ invalidate()

◆ isEmpty()

◆ layout()

◆ maximumSize()

◆ minimumHeightForWidth()

◆ minimumSize()

◆ setAlignment()

◆ setGeometry()

◆ sizeHint()

◆ spacerItem()

◆ widget()

Member Data Documentation

◆ align