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# TQLayout Class Reference

The TQLayout class is the base class of geometry managers. More...

`#include <ntqlayout.h>`

Inherits TQObject and TQLayoutItem.

Inherited by TQGridLayout and TQBoxLayout.

List of all member functions.

## Public Members

- enum ResizeMode { FreeResize, Minimum, Fixed, Auto }
- TQLayout ( TQWidget * parent, int margin = 0, int spacing = -1, const char * name = 0 )
- TQLayout ( TQLayout * parentLayout, int spacing = -1, const char * name = 0 )
- TQLayout ( int spacing = -1, const char * name = 0 )
- int margin () const
- int spacing () const
- virtual void setMargin ( int )
- virtual void setSpacing ( int )
- void setResizeMode ( ResizeMode )
- ResizeMode resizeMode () const
- virtual void setMenuBar ( TQMenuBar * w )
- TQMenuBar * menuBar () const
- TQWidget * mainWidget ()
- bool isTopLevel () const
- virtual void setAutoAdd ( bool b )
- bool autoAdd () const
- virtual void invalidate ()
- bool activate ()
- void add ( TQWidget * w )
- virtual void addItem ( TQLayoutItem * item ) = 0
- void remove ( TQWidget * widget )
- void removeItem ( TQLayoutItem * item )
- virtual TQSizePolicy::ExpandData expanding () const
- virtual TQSize minimumSize () const
- virtual TQSize maximumSize () const
- virtual void setGeometry ( const TQRect & r ) = 0
- virtual TQLayoutIterator iterator () = 0
- virtual bool isEmpty () const
- bool supportsMargin () const
- void setEnabled ( bool enable )
- bool isEnabled () const

## Properties

- int margin - the width of the outside border of the layout
- ResizeMode resizeMode - the resize mode of the layout
- int spacing - the spacing between widgets inside the layout

## Protected Members

- void addChildLayout ( TQLayout * l )
- void deleteAllItems ()
- void setSupportsMargin ( bool b )
- TQRect alignmentRect ( const TQRect & r ) const

## Detailed Description

The TQLayout class is the base class of geometry managers.

This is an abstract base class inherited by the concrete classes, TQBoxLayout and TQGridLayout.

For users of TQLayout subclasses or of TQMainWindow there is seldom any need to use the basic functions provided by TQLayout, such as setResizeMode() or setMenuBar(). See the layout overview page for more information.

To make your own layout manager, subclass TQGLayoutIterator and implement the functions addItem(), sizeHint(), setGeometry(), and iterator(). You should also implement minimumSize() to ensure your layout isn't resized to zero size if there is too little space. To support children whose heights depend on their widths, implement hasHeightForWidth() and heightForWidth(). See the custom layout page for an in-depth description.

Geometry management stops when the layout manager is deleted.

See also Widget Appearance and Style and Layout Management.

## Member Type Documentation

### TQLayout::ResizeMode

The possible values are:

- `TQLayout::Auto` - If the main widget is a top-level widget with no height-for-width (hasHeightForWidth()), this is the same as `Minimium`; otherwise, this is the same as FreeResize.
- `TQLayout::Fixed` - The main widget's size is set to sizeHint(); it cannot be resized at all.
- `TQLayout::Minimum` - The main widget's minimum size is set to minimumSize(); it cannot be smaller.
- `TQLayout::FreeResize` - The widget is not constrained.

## Member Function Documentation

### TQLayout::TQLayout ( TQWidget * parent, int margin = 0, int spacing = -1, const char * name = 0 )

Constructs a new top-level TQLayout called name, with main widget parent. parent may not be 0.

The margin is the number of pixels between the edge of the widget and the managed children. The spacing sets the value of spacing(), which gives the spacing between the managed widgets. If spacing is -1 (the default), spacing is set to the value of margin.

There can be only one top-level layout for a widget. It is returned by TQWidget::layout()

### TQLayout::TQLayout ( TQLayout * parentLayout, int spacing = -1, const char * name = 0 )

Constructs a new child TQLayout called name, and places it inside parentLayout by using the default placement defined by addItem().

If spacing is -1, this TQLayout inherits parentLayout's spacing(), otherwise the value of spacing is used.

### TQLayout::TQLayout ( int spacing = -1, const char * name = 0 )

Constructs a new child TQLayout called name. If spacing is -1, this TQLayout inherits its parent's spacing(); otherwise the value of spacing is used.

This layout has to be inserted into another layout before geometry management will work.

### bool TQLayout::activate ()

Redoes the layout for mainWidget(). You should generally not need to call this because it is automatically called at the most appropriate times.

However, if you set up a TQLayout for a visible widget without resizing that widget, you will need to call this function in order to lay it out.

See also TQWidget::updateGeometry().

Examples: layout/layout.cpp, popup/popup.cpp, scrollview/scrollview.cpp, and sql/overview/form1/main.cpp.

### void TQLayout::add ( TQWidget * w )

Adds widget w to this layout in a manner specific to the layout. This function uses addItem().

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

### void TQLayout::addChildLayout ( TQLayout * l )`[protected]`

This function is called from addLayout() functions in subclasses to add layout l as a sub-layout.

### void TQLayout::addItem ( TQLayoutItem * item )`[pure virtual]`

Implemented in subclasses to add an item. How it is added is specific to each subclass.

The ownership of item is transferred to the layout, and it's the layout's responsibility to delete it.

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

Reimplemented in TQGridLayout and TQBoxLayout.

### TQRect TQLayout::alignmentRect ( const TQRect & r ) const`[protected]`

Returns the rectangle that should be covered when the geometry of this layout is set to r, provided that this layout supports setAlignment().

The result is derived from sizeHint() and expanding(). It is never larger than r.

### bool TQLayout::autoAdd () const

Returns TRUE if this layout automatically grabs all new mainWidget()'s new children and adds them as defined by addItem(); otherwise returns FALSE. This has effect only for top-level layouts, i.e. layouts that are direct children of their mainWidget().

autoAdd() is disabled by default.

Note that a top-level layout is not necessarily associated with the top-level widget.

See also setAutoAdd().

### void TQLayout::deleteAllItems ()`[protected]`

Removes and deletes all items in this layout.

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

Returns whether this layout can make use of more space than sizeHint(). A value of Vertical or Horizontal means that it wants to grow in only one dimension, whereas `BothDirections` means that it wants to grow in both dimensions.

The default implementation returns `BothDirections`.

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

Reimplemented from TQLayoutItem.

Reimplemented in TQGridLayout and TQBoxLayout.

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

Invalidates cached information. Reimplementations must call this.

Reimplemented from TQLayoutItem.

Reimplemented in TQGridLayout and TQBoxLayout.

### bool TQLayout::isEmpty () const`[virtual]`

Returns TRUE if this layout is empty. The default implementation returns FALSE.

Reimplemented from TQLayoutItem.

### bool TQLayout::isEnabled () const

Returns TRUE if the layout is enabled; otherwise returns FALSE.

See also setEnabled().

### bool TQLayout::isTopLevel () const

Returns TRUE if this layout is a top-level layout, i.e. not a child of another layout; otherwise returns FALSE.

### TQLayoutIterator TQLayout::iterator ()`[pure virtual]`

Implemented in subclasses to return an iterator that iterates over this layout's children.

A typical implementation will be:

            TQLayoutIterator MyLayout::iterator()
            {
                TQGLayoutIterator *i = new MyLayoutIterator( internal_data );
                return TQLayoutIterator( i );
            }

where MyLayoutIterator is a subclass of TQGLayoutIterator.

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

Reimplemented from TQLayoutItem.

### TQWidget * TQLayout::mainWidget ()

Returns the main widget (parent widget) of this layout, or 0 if this layout is a sub-layout that is not yet inserted.

### int TQLayout::margin () const

Returns the width of the outside border of the layout. See the "margin" property for details.

### TQSize TQLayout::maximumSize () const`[virtual]`

Returns the maximum size of this layout. This is the largest size that the layout can have while still respecting the specifications. Does not include what's needed by margin() or menuBar().

The default implementation allows unlimited resizing.

Reimplemented from TQLayoutItem.

Reimplemented in TQGridLayout and TQBoxLayout.

### TQMenuBar * TQLayout::menuBar () const

Returns the menu bar set for this layout, or 0 if no menu bar is set.

### TQSize TQLayout::minimumSize () const`[virtual]`

Returns the minimum size of this layout. This is the smallest size that the layout can have while still respecting the specifications. Does not include what's needed by margin() or menuBar().

The default implementation allows unlimited resizing.

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

Reimplemented from TQLayoutItem.

Reimplemented in TQGridLayout and TQBoxLayout.

### void TQLayout::remove ( TQWidget * widget )

Removes the widget widget from the layout. After this call, it is the caller's responsibility to give the widget a reasonable geometry or to put the widget back into a layout.

See also removeItem(), TQWidget::geometry, and add().

### void TQLayout::removeItem ( TQLayoutItem * item )

Removes the layout item item from the layout. It is the caller's responsibility to delete the item.

Notice that item can be a layout (since TQLayout inherits TQLayoutItem).

See also remove() and addItem().

### ResizeMode TQLayout::resizeMode () const

Returns the resize mode of the layout. See the "resizeMode" property for details.

### void TQLayout::setAutoAdd ( bool b )`[virtual]`

If b is TRUE, auto-add is enabled; otherwise auto-add is disabled.

Warning: If auto-add is enabled, you cannot set stretch factors on the child widgets until the widgets are actually inserted in the layout (after control returned to the event loop). We therefore recommend that you avoid the auto-add feature in new programs.

See also autoAdd().

Examples: hierarchy/objects.cpp and i18n/main.cpp.

### void TQLayout::setEnabled ( bool enable )

Enables this layout if enable is TRUE, otherwise disables it.

An enabled layout adjusts dynamically to changes; a disabled layout acts as if it did not exist.

By default all layouts are enabled.

See also isEnabled().

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

This function is reimplemented in subclasses to perform layout.

The default implementation maintains the geometry() information given by rect r. Reimplementors must call this function.

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

Reimplemented from TQLayoutItem.

Reimplemented in TQGridLayout and TQBoxLayout.

### void TQLayout::setMargin ( int )`[virtual]`

Sets the width of the outside border of the layout. See the "margin" property for details.

### void TQLayout::setMenuBar ( TQMenuBar * w )`[virtual]`

Makes the geometry manager take account of the menu bar w. All child widgets are placed below the bottom edge of the menu bar.

A menu bar does its own geometry management: never do addWidget() on a TQMenuBar.

Examples: layout/layout.cpp and scrollview/scrollview.cpp.

### void TQLayout::setResizeMode ( ResizeMode )

Sets the resize mode of the layout. See the "resizeMode" property for details.

### void TQLayout::setSpacing ( int )`[virtual]`

Sets the spacing between widgets inside the layout. See the "spacing" property for details.

### void TQLayout::setSupportsMargin ( bool b )`[protected]`

Sets the value returned by supportsMargin(). If b is TRUE, margin() handling is implemented by the subclass. If b is FALSE (the default), TQLayout will add margin() around top-level layouts.

If b is TRUE, margin handling needs to be implemented in setGeometry(), maximumSize(), minimumSize(), sizeHint() and heightForWidth().

See also supportsMargin().

### int TQLayout::spacing () const

Returns the spacing between widgets inside the layout. See the "spacing" property for details.

### bool TQLayout::supportsMargin () const

Returns TRUE if this layout supports TQLayout::margin on non-top-level layouts; otherwise returns FALSE.

See also margin.

## Property Documentation

### int margin

This property holds the width of the outside border of the layout.

For some layout classes this property has an effect only on top-level layouts; TQBoxLayout and TQGridLayout support margins for child layouts. The default value is 0.

See also spacing.

Set this property's value with setMargin() and get this property's value with margin().

### ResizeMode resizeMode

This property holds the resize mode of the layout.

The default mode is Auto.

See also TQLayout::ResizeMode.

Set this property's value with setResizeMode() and get this property's value with resizeMode().

### int spacing

This property holds the spacing between widgets inside the layout.

The default value is -1, which signifies that the layout's spacing should not override the widget's spacing.

See also margin.

Set this property's value with setSpacing() and get this property's value with spacing().

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