QLayout(3qt)QLayout(3qt)NAME
QLayout - The base class of geometry managers
SYNOPSIS
#include <qlayout.h>
Inherits QObject and QLayoutItem.
Inherited by QGridLayout and QBoxLayout.
Public Members
enum ResizeMode { FreeResize, Minimum, Fixed, Auto }
QLayout ( QWidget * parent, int margin = 0, int spacing = -1, const
char * name = 0 )
QLayout ( QLayout * parentLayout, int spacing = -1, const char * name =
0 )
QLayout ( 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 ( QMenuBar * w )
QMenuBar * menuBar () const
QWidget * mainWidget ()
bool isTopLevel () const
virtual void setAutoAdd ( bool b )
bool autoAdd () const
virtual void invalidate ()
bool activate ()
void add ( QWidget * w )
virtual void addItem ( QLayoutItem * item ) = 0
void remove ( QWidget * widget )
void removeItem ( QLayoutItem * item )
virtual QSizePolicy::ExpandData expanding () const
virtual QSize minimumSize () const
virtual QSize maximumSize () const
virtual void setGeometry ( const QRect & r ) = 0
virtual QLayoutIterator 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 ( QLayout * l )
void deleteAllItems ()
void setSupportsMargin ( bool b )
QRect alignmentRect ( const QRect & r ) const
DESCRIPTION
The QLayout class is the base class of geometry managers.
This is an abstract base class inherited by the concrete classes,
QBoxLayout and QGridLayout.
For users of QLayout subclasses or of QMainWindow there is seldom any
need to use the basic functions provided by QLayout, such as
setResizeMode() or setMenuBar(). See the layout overview page for more
information.
To make your own layout manager, subclass QGLayoutIterator 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
QLayout::ResizeMode
The possible values are:
QLayout::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.
QLayout::Fixed - The main widget's size is set to sizeHint(); it cannot
be resized at all.
QLayout::Minimum - The main widget's minimum size is set to
minimumSize(); it cannot be smaller.
QLayout::FreeResize - The widget is not constrained.
MEMBER FUNCTION DOCUMENTATIONQLayout::QLayout ( QWidget * parent, int margin = 0, int spacing = -1, const
char * name = 0 )
Constructs a new top-level QLayout 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
QWidget::layout()QLayout::QLayout ( QLayout * parentLayout, int spacing = -1, const char * name
= 0 )
Constructs a new child QLayout called name, and places it inside
parentLayout by using the default placement defined by addItem().
If spacing is -1, this QLayout inherits parentLayout's spacing(),
otherwise the value of spacing is used.
QLayout::QLayout ( int spacing = -1, const char * name = 0 )
Constructs a new child QLayout called name. If spacing is -1, this
QLayout 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 QLayout::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 QLayout for a visible widget without resizing
that widget, you will need to call this function in order to lay it
out.
See also QWidget::updateGeometry().
Examples:
void QLayout::add ( QWidget * w )
Adds widget w to this layout in a manner specific to the layout. This
function uses addItem().
Examples:
void QLayout::addChildLayout ( QLayout * l ) [protected]
This function is called from addLayout() functions in subclasses to add
layout l as a sub-layout.
void QLayout::addItem ( QLayoutItem * 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:
Reimplemented in QGridLayout and QBoxLayout.
QRect QLayout::alignmentRect ( const QRect & 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 QLayout::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 QLayout::deleteAllItems () [protected]
Removes and deletes all items in this layout.
QSizePolicy::ExpandData QLayout::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:
Reimplemented from QLayoutItem.
Reimplemented in QGridLayout and QBoxLayout.
void QLayout::invalidate () [virtual]
Invalidates cached information. Reimplementations must call this.
Reimplemented from QLayoutItem.
Reimplemented in QGridLayout and QBoxLayout.
bool QLayout::isEmpty () const [virtual]
Returns TRUE if this layout is empty. The default implementation
returns FALSE.
Reimplemented from QLayoutItem.
bool QLayout::isEnabled () const
Returns TRUE if the layout is enabled; otherwise returns FALSE.
See also setEnabled().
bool QLayout::isTopLevel () const
Returns TRUE if this layout is a top-level layout, i.e. not a child of
another layout; otherwise returns FALSE.
QLayoutIterator QLayout::iterator () [pure virtual]
Implemented in subclasses to return an iterator that iterates over this
layout's children.
A typical implementation will be:
QLayoutIterator MyLayout::iterator()
{
QGLayoutIterator *i = new MyLayoutIterator( internal_data );
return QLayoutIterator( i );
}
where MyLayoutIterator is a subclass of QGLayoutIterator.
Examples:
Reimplemented from QLayoutItem.
QWidget * QLayout::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 QLayout::margin () const
Returns the width of the outside border of the layout. See the "margin"
property for details.
QSize QLayout::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 QLayoutItem.
Reimplemented in QGridLayout and QBoxLayout.
QMenuBar * QLayout::menuBar () const
Returns the menu bar set for this layout, or 0 if no menu bar is set.
QSize QLayout::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:
Reimplemented from QLayoutItem.
Reimplemented in QGridLayout and QBoxLayout.
void QLayout::remove ( QWidget * 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(), QWidget::geometry, and add().
void QLayout::removeItem ( QLayoutItem * 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 QLayout inherits QLayoutItem).
See also remove() and addItem().
ResizeMode QLayout::resizeMode () const
Returns the resize mode of the layout. See the "resizeMode" property
for details.
void QLayout::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:
void QLayout::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 QLayout::setGeometry ( const QRect & 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:
Reimplemented from QLayoutItem.
Reimplemented in QGridLayout and QBoxLayout.
void QLayout::setMargin ( int ) [virtual]
Sets the width of the outside border of the layout. See the "margin"
property for details.
void QLayout::setMenuBar ( QMenuBar * 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
QMenuBar.
Examples:
void QLayout::setResizeMode ( ResizeMode )
Sets the resize mode of the layout. See the "resizeMode" property for
details.
void QLayout::setSpacing ( int ) [virtual]
Sets the spacing between widgets inside the layout. See the "spacing"
property for details.
void QLayout::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),
QLayout 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 QLayout::spacing () const
Returns the spacing between widgets inside the layout. See the
"spacing" property for details.
bool QLayout::supportsMargin () const
Returns TRUE if this layout supports QLayout::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; QBoxLayout and QGridLayout 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 QLayout::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().
SEE ALSO
http://doc.trolltech.com/qlayout.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qlayout.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QLayout(3qt)
