TQLayoutItem Class

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# TQLayoutItem Class Reference

The TQLayoutItem class provides an abstract item that a TQLayout manipulates. More...

`#include <ntqlayout.h>`

Inherited by TQLayout, TQSpacerItem, and TQWidgetItem.

List of all member functions.

## Public Members

- TQLayoutItem ( int alignment = 0 )
- virtual ~TQLayoutItem ()
- virtual TQSize sizeHint () const = 0
- virtual TQSize minimumSize () const = 0
- virtual TQSize maximumSize () const = 0
- virtual TQSizePolicy::ExpandData expanding () const = 0
- virtual void setGeometry ( const TQRect & r ) = 0
- virtual TQRect geometry () const = 0
- virtual bool isEmpty () const = 0
- virtual bool hasHeightForWidth () const
- virtual int heightForWidth ( int w ) const
- virtual void invalidate ()
- virtual TQWidget * widget ()
- virtual TQLayoutIterator iterator ()
- virtual TQLayout * layout ()
- virtual TQSpacerItem * spacerItem ()
- int alignment () const
- virtual void setAlignment ( int a )

## Detailed Description

The TQLayoutItem class provides an abstract item that a TQLayout 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().

isEmpty() returns whether the layout is empty. iterator() returns an iterator for the layout's children. If the concrete item is a TQWidget, it can be retrieved using widget(). Similarly for layout() and spacerItem().

See also TQLayout, Widget Appearance and Style, and Layout Management.

## Member Function Documentation

### TQLayoutItem::TQLayoutItem ( int alignment = 0 )

Constructs a layout item with an alignment that is a bitwise OR of the TQt::AlignmentFlags. Not all subclasses support alignment.

### TQLayoutItem::~TQLayoutItem ()`[virtual]`

Destroys the TQLayoutItem.

### int TQLayoutItem::alignment () const

Returns the alignment of this item.

### TQSizePolicy::ExpandData TQLayoutItem::expanding () const`[pure virtual]`

Implemented in subclasses to return the direction(s) this item "wants" to expand in (if any).

Reimplemented in TQLayout, TQSpacerItem, and TQWidgetItem.

### TQRect TQLayoutItem::geometry () const`[pure virtual]`

Returns the rectangle covered by this layout item.

Example: customlayout/border.cpp.

### bool TQLayoutItem::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() and TQWidget::heightForWidth().

Examples: customlayout/border.cpp and customlayout/flow.cpp.

Reimplemented in TQGridLayout and TQBoxLayout.

### int TQLayoutItem::heightForWidth ( int w ) 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"
                    MyLayout *that = (MyLayout*)this;
                    int h = calculateHeightForWidth( w );
                    that->cached_hfw = h;
                    return h;
                }
                return cached_hfw;
            }

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

See also hasHeightForWidth().

Example: customlayout/flow.cpp.

Reimplemented in TQGridLayout and TQBoxLayout.

### void TQLayoutItem::invalidate ()`[virtual]`

Invalidates any cached information in this layout item.

Reimplemented in TQLayout.

### bool TQLayoutItem::isEmpty () const`[pure virtual]`

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

Reimplemented in TQLayout, TQSpacerItem, and TQWidgetItem.

### TQLayoutIterator TQLayoutItem::iterator ()`[virtual]`

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

Reimplement this function in subclasses that can have children.

Reimplemented in TQLayout.

### TQLayout * TQLayoutItem::layout ()`[virtual]`

If this item is a TQLayout, it is returned as a TQLayout; otherwise 0 is returned. This function provides type-safe casting.

### TQSize TQLayoutItem::maximumSize () const`[pure virtual]`

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

Reimplemented in TQLayout, TQSpacerItem, and TQWidgetItem.

### TQSize TQLayoutItem::minimumSize () const`[pure virtual]`

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

Examples: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.

Reimplemented in TQLayout, TQSpacerItem, and TQWidgetItem.

### void TQLayoutItem::setAlignment ( int a )`[virtual]`

Sets the alignment of this item to a, which is a bitwise OR of the TQt::AlignmentFlags. Not all subclasses support alignment.

Example: chart/optionsform.cpp.

### void TQLayoutItem::setGeometry ( const TQRect & r )`[pure virtual]`

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

Examples: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.

Reimplemented in TQLayout, TQSpacerItem, and TQWidgetItem.

### TQSize TQLayoutItem::sizeHint () const`[pure virtual]`

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

Examples: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.

Reimplemented in TQSpacerItem, TQWidgetItem, TQGridLayout, and TQBoxLayout.

### TQSpacerItem * TQLayoutItem::spacerItem ()`[virtual]`

If this item is a TQSpacerItem, it is returned as a TQSpacerItem; otherwise 0 is returned. This function provides type-safe casting.

### TQWidget * TQLayoutItem::widget ()`[virtual]`

If this item is a TQWidget, it is returned as a TQWidget; otherwise 0 is returned. This function provides type-safe casting.

Reimplemented in TQWidgetItem.

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