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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

Detailed Description

The abstract items which a QLayout manipulates.

For custom layouts.

See also: QLayout.

Member Function Documentation

QLayoutItem::QLayoutItem ( int alignment = 0 )

Constructs a layout item with alignment alignment. 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 QWidgetItem, QBoxLayout, QGridLayout, QSpacerItem and QLayout.

QRect QLayoutItem::geometry () const [virtual]

Returns the rectangle covered by this layout item.

Reimplemented in QWidgetItem, QLayout and QSpacerItem.

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 QWidgetItem, QBoxLayout and QGridLayout.

void QLayoutItem::invalidate () [virtual]

Invalidates any cached information in this layout item.

Reimplemented in 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, QSpacerItem and QLayout.

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 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 QBoxLayout, QLayout, QSpacerItem, QGridLayout and QWidgetItem.

QSize QLayoutItem::minimumSize () const [virtual]

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

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

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

Sets the alignment of this item to a.

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

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

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

QSize QLayoutItem::sizeHint () const [virtual]

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

Reimplemented in QSpacerItem and QWidgetItem.

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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Qt version 2.0.2