CopperSpice API  1.8.1
QGraphicsLinearLayout Class Reference

The QGraphicsLinearLayout class provides a horizontal or vertical layout for managing widgets in Graphics View. More...

Inheritance diagram for QGraphicsLinearLayout:

## Public Methods

QGraphicsLinearLayout (QGraphicsLayoutItem *parent=nullptr)

QGraphicsLinearLayout (Qt::Orientation orientation, QGraphicsLayoutItem *parent=nullptr)

virtual ~QGraphicsLinearLayout ()

Qt::Alignment alignment (QGraphicsLayoutItem *item) const

int count () const override

void insertItem (int index, QGraphicsLayoutItem *item)

void insertStretch (int index, int stretch=1)

void invalidate () override

QGraphicsLayoutItemitemAt (int index) const override

qreal itemSpacing (int index) const

Qt::Orientation orientation () const

void removeAt (int index) override

void removeItem (QGraphicsLayoutItem *item)

void setAlignment (QGraphicsLayoutItem *item, Qt::Alignment alignment)

void setGeometry (const QRectF &rect) override

void setItemSpacing (int index, qreal spacing)

void setOrientation (Qt::Orientation orientation)

void setSpacing (qreal spacing)

void setStretchFactor (QGraphicsLayoutItem *item, int stretch)

QSizeF sizeHint (Qt::SizeHint which, const QSizeF &constraint=QSizeF ()) const override

qreal spacing () const

int stretchFactor (QGraphicsLayoutItem *item) const

Public Methods inherited from QGraphicsLayout
QGraphicsLayout (QGraphicsLayoutItem *parent=nullptr)

~QGraphicsLayout ()

void activate ()

void getContentsMargins (qreal *left, qreal *top, qreal *right, qreal *bottom) const override

bool isActivated () const

void setContentsMargins (qreal left, qreal top, qreal right, qreal bottom)

void updateGeometry () override

virtual void widgetEvent (QEvent *event)

Public Methods inherited from QGraphicsLayoutItem
QGraphicsLayoutItem (QGraphicsLayoutItem *parent=nullptr, bool isLayout=false)

virtual ~QGraphicsLayoutItem ()

QRectF contentsRect () const

QSizeF effectiveSizeHint (Qt::SizeHint which, const QSizeF &constraint=QSizeF ()) const

QRectF geometry () const

QGraphicsItemgraphicsItem () const

bool isLayout () const

qreal maximumHeight () const

QSizeF maximumSize () const

qreal maximumWidth () const

qreal minimumHeight () const

QSizeF minimumSize () const

qreal minimumWidth () const

bool ownedByLayout () const

QGraphicsLayoutItem * parentLayoutItem () const

qreal preferredHeight () const

QSizeF preferredSize () const

qreal preferredWidth () const

void setMaximumHeight (qreal height)

void setMaximumSize (const QSizeF &size)

void setMaximumSize (qreal w, qreal h)

void setMaximumWidth (qreal width)

void setMinimumHeight (qreal height)

void setMinimumSize (const QSizeF &size)

void setMinimumSize (qreal w, qreal h)

void setMinimumWidth (qreal width)

void setParentLayoutItem (QGraphicsLayoutItem *parent)

void setPreferredHeight (qreal height)

void setPreferredSize (const QSizeF &size)

void setPreferredSize (qreal w, qreal h)

void setPreferredWidth (qreal width)

void setSizePolicy (const QSizePolicy &policy)

void setSizePolicy (QSizePolicy::Policy hPolicy, QSizePolicy::Policy vPolicy, QSizePolicy::ControlType controlType=QSizePolicy::DefaultType)

QSizePolicy sizePolicy () const

Static Public Methods inherited from QGraphicsLayout
static bool instantInvalidatePropagation ()

static void setInstantInvalidatePropagation (bool enable)

Protected Methods inherited from QGraphicsLayout

Protected Methods inherited from QGraphicsLayoutItem
void setGraphicsItem (QGraphicsItem *item)

void setOwnedByLayout (bool owner)

## Detailed Description

The QGraphicsLinearLayout class provides a horizontal or vertical layout for managing widgets in Graphics View.

The default orientation for a linear layout is Qt::Horizontal. You can choose a vertical orientation either by calling setOrientation(), or by passing Qt::Vertical to QGraphicsLinearLayout's constructor.

The most common way to use QGraphicsLinearLayout is to construct an object on the heap with no parent, add widgets and layouts by calling addItem(), and finally assign the layout to a widget by calling QGraphicsWidget::setLayout().

form->setLayout(layout);

You can add widgets, layouts, stretches (addStretch(), insertStretch() or setStretchFactor()), and spacings (setItemSpacing()) to a linear layout. The layout takes ownership of the items. In some cases when the layout item also inherits from QGraphicsItem (such as QGraphicsWidget) there will be an ambiguity in ownership because the layout item belongs to two ownership hierarchies. See the documentation of QGraphicsLayoutItem::setOwnedByLayout() how to handle this. You can access each item in the layout by calling count() and itemAt(). Calling removeAt() or removeItem() will remove an item from the layout, without destroying it.

### Size Hints and Size Policies in QGraphicsLinearLayout

QGraphicsLinearLayout respects each item's size hints and size policies, and when the layout contains more space than the items can fill, each item is arranged according to the layout's alignment for that item. You can set an alignment for each item by calling setAlignment(), and check the alignment for any item by calling alignment(). By default, items are aligned to the top left.

### Spacing within QGraphicsLinearLayout

Between the items, the layout distributes some space. The actual amount of space depends on the managed widget's current style, but the common spacing is 4. You can also set your own spacing by calling setSpacing(), and get the current spacing value by calling spacing(). If you want to configure individual spacing for your items, you can call setItemSpacing().

### Stretch Factor in QGraphicsLinearLayout

You can assign a stretch factor to each item to control how much space it will get compared to the other items. By default, two identical widgets arranged in a linear layout will have the same size, but if the first widget has a stretch factor of 1 and the second widget has a stretch factor of 2, the first widget will get 1/3 of the available space, and the second will get 2/3.

QGraphicsLinearLayout calculates the distribution of sizes by adding up the stretch factors of all items, and then dividing the available space accordingly. The default stretch factor is 0 for all items; a factor of 0 means the item does not have any defined stretch factor; effectively this is the same as setting the stretch factor to 1. The stretch factor only applies to the available space in the lengthwise direction of the layout (following its orientation). If you want to control both the item's horizontal and vertical stretch, you can use QGraphicsGridLayout instead.

### QGraphicsLinearLayout Compared to Other Layouts

QGraphicsLinearLayout is very similar to QVBoxLayout and QHBoxLayout, but in contrast to these classes, it is used to manage QGraphicsWidget and QGraphicsLayout instead of QWidget and QLayout.

QGraphicsGridLayout, QGraphicsWidget

## Constructor & Destructor Documentation

 QGraphicsLinearLayout::QGraphicsLinearLayout ( QGraphicsLayoutItem * parent = nullptr )

Constructs a QGraphicsLinearLayout instance using Qt::Horizontal orientation. The parent object is passed to the QGraphicsLayout constructor.

 QGraphicsLinearLayout::QGraphicsLinearLayout ( Qt::Orientation orientation, QGraphicsLayoutItem * parent = nullptr )

Constructs a QGraphicsLinearLayout object. The orientation for the layout can either be horizontal or vertical. The parent object is passed to the QGraphicsLayout constructor.

 QGraphicsLinearLayout::~QGraphicsLinearLayout ( )
virtual

Destroys the QGraphicsLinearLayout object.

## Method Documentation

 void QGraphicsLinearLayout::addItem ( QGraphicsLayoutItem * item )
inline

This convenience function is equivalent to calling insertItem(-1, item).

 void QGraphicsLinearLayout::addStretch ( int stretch = 1 )
inline

This convenience function is equivalent to calling insertStretch(-1, stretch).

 Qt::Alignment QGraphicsLinearLayout::alignment ( QGraphicsLayoutItem * item ) const

Returns the alignment for item. The default alignment is Qt::AlignTop | Qt::AlignLeft.

The alignment decides how the item is positioned within its assigned space in the case where there's more space available in the layout than the widgets can occupy.

setAlignment()
 int QGraphicsLinearLayout::count ( ) const
overridevirtual
 void QGraphicsLinearLayout::insertItem ( int index, QGraphicsLayoutItem * item )

Inserts item into the layout at index, or before any item that is currently at index.

 void QGraphicsLinearLayout::insertStretch ( int index, int stretch = 1 )

Inserts a stretch of stretch at index, or before any item that is currently at index.

 void QGraphicsLinearLayout::invalidate ( )
overridevirtual

Reimplemented from QGraphicsLayout::invalidate()

 QGraphicsLayoutItem * QGraphicsLinearLayout::itemAt ( int index ) const
overridevirtual

When iterating from 0 and up, it will return the items in the visual arranged order.

Implements QGraphicsLayout::itemAt()

 qreal QGraphicsLinearLayout::itemSpacing ( int index ) const

Returns the spacing after item at index.

setItemSpacing()
 Qt::Orientation QGraphicsLinearLayout::orientation ( ) const

Returns the layout orientation.

setOrientation()
 void QGraphicsLinearLayout::removeAt ( int index )
overridevirtual

Removes the item at index without destroying it. Ownership of the item is transferred to the caller.

removeItem(), insertItem()

Implements QGraphicsLayout::removeAt()

 void QGraphicsLinearLayout::removeItem ( QGraphicsLayoutItem * item )

Removes item from the layout without destroying it. Ownership of item is transferred to the caller.

removeAt(), insertItem()
 void QGraphicsLinearLayout::setAlignment ( QGraphicsLayoutItem * item, Qt::Alignment alignment )

Sets the alignment of item to alignment. If item's alignment changes, the layout is automatically invalidated.

alignment(), invalidate()
 void QGraphicsLinearLayout::setGeometry ( const QRectF & rect )
overridevirtual
 void QGraphicsLinearLayout::setItemSpacing ( int index, qreal spacing )

Sets the spacing after item at index to spacing.

itemSpacing()
 void QGraphicsLinearLayout::setOrientation ( Qt::Orientation orientation )

Change the layout orientation to orientation. Changing the layout orientation will automatically invalidate the layout.

orientation()
 void QGraphicsLinearLayout::setSpacing ( qreal spacing )

Sets the layout's spacing to spacing. Spacing refers to the vertical and horizontal distances between items.

spacing(), setItemSpacing(), setStretchFactor(), QGraphicsGridLayout::setSpacing()
 void QGraphicsLinearLayout::setStretchFactor ( QGraphicsLayoutItem * item, int stretch )

Sets the stretch factor for item to stretch. If an item's stretch factor changes, this function will invalidate the layout.

Setting stretch to 0 removes the stretch factor from the item, and is effectively equivalent to setting stretch to 1.

stretchFactor()
 QSizeF QGraphicsLinearLayout::sizeHint ( Qt::SizeHint which, const QSizeF & constraint = QSizeF() ) const
overridevirtual
 qreal QGraphicsLinearLayout::spacing ( ) const

Returns the layout's spacing. Spacing refers to the vertical and horizontal distances between items.