QLayoutItem Class Reference

The abstract items which a QLayout manipulates. More...

#include <qabstractlayout.h>

Inherited by QLayout, QSpacerItem and QWidgetItem.

List of all member functions.

Public Members

• QLayoutItem ( int alignment = 0 ) 
• virtual ~QLayoutItem () 
• virtual QSize sizeHint () const
• virtual QSize minimumSize () const
• virtual QSize maximumSize () const
• virtual QSizePolicy::ExpandData expanding () const
• virtual void setGeometry ( const QRect & ) 
• virtual QRect geometry () const
• virtual bool isEmpty () const
• virtual bool hasHeightForWidth () const
• virtual int heightForWidth ( int ) const
• virtual void invalidate () 
• virtual QWidget* widget () 
• virtual QLayoutIterator iterator () 
• virtual QLayout* layout () 
• virtual QSpacerItem* spacerItem () 
• int alignment () const
• virtual void setAlignment ( int a ) 

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Detailed Description

The abstract items which a QLayout manipulates.

For custom layouts.

See also QLayout.

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Member Function Documentation

QLayoutItem::QLayoutItem ( int alignment = 0 )

Constructs a layout item with an alignment that is a bitwise OR of Qt::AlignmentFlags. Alignment may not be supported by all subclasses.

QLayoutItem::~QLayoutItem () [virtual]

Destructs the QLayoutItem.

int QLayoutItem::alignment () const

Returns the alignment of this item.

QSizePolicy::ExpandData QLayoutItem::expanding() const [virtual]

Implemented in subclasses to return whether this item "wants" to expand.

Reimplemented in QLayout, QBoxLayout, QGridLayout, QWidgetItem and QSpacerItem.

QRect QLayoutItem::geometry () const [virtual]

Returns the rectangle covered by this layout item.

Reimplemented in QSpacerItem, QWidgetItem and QLayout.

bool QLayoutItem::hasHeightForWidth () const [virtual]

Returns TRUE if this layout's preferred height depends on its width. The default implementation returns FALSE;

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

See also heightForWidth() and QWidget::heightForWidth().

Reimplemented in QBoxLayout, QGridLayout and QWidgetItem.

int QLayoutItem::heightForWidth ( int ) const [virtual]

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

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

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

See also hasHeightForWidth().

Reimplemented in QGridLayout, QBoxLayout and QWidgetItem.

void QLayoutItem::invalidate () [virtual]

Invalidates any cached information in this layout item.

Reimplemented in QLayout, QBoxLayout and QGridLayout.

virtual bool QLayoutItem::isEmpty () const [virtual]

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

Reimplemented in QWidgetItem, QLayout and QSpacerItem.

QLayoutIterator QLayoutItem::iterator () [virtual]

Returns an iterator over this item's QLayoutItem children. The default implementation returns an empty iterator.

Reimplement this function in subclasses that can have children.

Reimplemented in QGridLayout, QLayout and QBoxLayout.

QLayout * QLayoutItem::layout () [virtual]

If this item is a QLayout, return it as a QLayout, otherwise return 0. This function provides type-safe casting.

Reimplemented in QLayout.

QSize QLayoutItem::maximumSize () const [virtual]

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

Reimplemented in QWidgetItem, QGridLayout, QLayout, QBoxLayout and QSpacerItem.

QSize QLayoutItem::minimumSize () const [virtual]

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

Reimplemented in QBoxLayout, QLayout, QWidgetItem, QSpacerItem and QGridLayout.

void QLayoutItem::setAlignment ( int a ) [virtual]

Sets the alignment of this item to a, which is a bitwise OR of Qt::AlignmentFlags.

void QLayoutItem::setGeometry ( const QRect & r ) [virtual]

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

Reimplemented in QBoxLayout, QGridLayout, QLayout, QWidgetItem and QSpacerItem.

QSize QLayoutItem::sizeHint () const [virtual]

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

Reimplemented in QSpacerItem, QBoxLayout, QWidgetItem and QGridLayout.

QSpacerItem * QLayoutItem::spacerItem () [virtual]

If this item is a QSpacerItem, return it as a QSpacerItem, otherwise return 0. This function provides type-safe casting.

Reimplemented in QSpacerItem.

QWidget * QLayoutItem::widget () [virtual]

If this item is a QWidgetItem, the managed widget is returned. The default implementation returns 0;.

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