Detailed 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 Documentation
QLayout::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: layout/layout.cpp, popup/popup.cpp, scrollview/scrollview.cpp, and sql/overview/form1/main.cpp.
void QLayout::add ( QWidget * 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 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: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.
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.
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 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: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.
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.
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: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.
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.
See also autoAdd().
Examples: hierarchy/objects.cpp and i18n/main.cpp.
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: customlayout/border.cpp, customlayout/card.cpp, and customlayout/flow.cpp.
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
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: layout/layout.cpp and scrollview/scrollview.cpp.
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().
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().
This file is part of the Qt toolkit.
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Trolltech. All Rights Reserved.
