QSizePolicy Class Reference

The QSizePolicy class is a layout attribute describing horizontal and vertical resizing policy. More...

#include <qsizepolicy.h>

List of all member functions.

Public Members

enum SizeType { Fixed = 0, Minimum = MayGrow, Maximum = MayShrink, Preferred = MayGrow | MayShrink, MinimumExpanding = MayGrow | ExpMask, Expanding = MayGrow | MayShrink | ExpMask, Ignored = ExpMask }
enum ExpandData { NoDirection = 0, Horizontally = 1, Vertically = 2, Horizontal = Horizontally, Vertical = Vertically, BothDirections = Horizontally | Vertically }
QSizePolicy ()
QSizePolicy ( SizeType hor, SizeType ver, bool hfw = FALSE )
QSizePolicy ( SizeType hor, SizeType ver, uchar horStretch, uchar verStretch, bool hfw = FALSE )
SizeType horData () const
SizeType verData () const
bool mayShrinkHorizontally () const
bool mayShrinkVertically () const
bool mayGrowHorizontally () const
bool mayGrowVertically () const
ExpandData expanding () const
void setHorData ( SizeType d )
void setVerData ( SizeType d )
void setHeightForWidth ( bool b )
bool hasHeightForWidth () const
bool operator== ( const QSizePolicy & s ) const
bool operator!= ( const QSizePolicy & s ) const
uint horStretch () const
uint verStretch () const
void setHorStretch ( uchar sf )
void setVerStretch ( uchar sf )
void transpose ()

Detailed Description

The QSizePolicy class is a layout attribute describing horizontal and vertical resizing policy.

The size policy of a widget is an expression of its willingness to be resized in various ways.

Widgets that reimplement QWidget::sizePolicy() return a QSizePolicy that describes the horizontal and vertical resizing policy they prefer when being laid out. Only one of the constructors is of interest in most applications.

QSizePolicy contains two independent SizeType objects; one describes the widgets's horizontal size policy, and the other describes its vertical size policy. It also contains a flag to indicate whether the height and width of its preferred size are related.

The horizontal and vertical SizeTypes are set in the usual constructor and can be queried using a variety of functions.

The hasHeightForWidth() flag indicates whether the widget's sizeHint() is width-dependent (such as a word-wrapping label) or not.

Member Type Documentation

QSizePolicy::ExpandData

This enum type describes in which directions a widget can make use of extra space. There are four possible values:

QSizePolicy::NoDirection - the widget cannot make use of extra space in any direction.
QSizePolicy::Horizontally - the widget can usefully be wider than the sizeHint().
QSizePolicy::Vertically - the widget can usefully be taller than the sizeHint().
QSizePolicy::BothDirections - the widget can usefully be both wider and taller than the sizeHint().

QSizePolicy::SizeType

The per-dimension sizing types used when constructing a QSizePolicy are:

QSizePolicy::Fixed - the QWidget::sizeHint() is the only acceptable alternative, so the widget can never grow or shrink (e.g. the vertical direction of a push button).
QSizePolicy::Minimum - the sizeHint() is minimal, and sufficient. The widget can be expanded, but there is no advantage to it being larger (e.g. the horizontal direction of a push button).
QSizePolicy::Maximum - the sizeHint() is a maximum. The widget can be shrunk any amount without detriment if other widgets need the space (e.g. a separator line).
QSizePolicy::Preferred - the sizeHint() is best, but the widget can be shrunk and still be useful. The widget can be expanded, but there is no advantage to it being larger than sizeHint() (the default QWidget policy).
QSizePolicy::Expanding - the sizeHint() is a sensible size, but the widget can be shrunk and still be useful. The widget can make use of extra space, so it should get as much space as possible (e.g. the horizontal direction of a slider).
QSizePolicy::MinimumExpanding - the sizeHint() is minimal, and sufficient. The widget can make use of extra space, so it should get as much space as possible (e.g. the horizontal direction of a slider).
QSizePolicy::Ignored - the sizeHint() is ignored. The widget will get as much space as possible.

Member Function Documentation

QSizePolicy::QSizePolicy ()

Constructs a minimally initialized QSizePolicy.

QSizePolicy::QSizePolicy ( SizeType hor, SizeType ver, bool hfw = FALSE )

This is the constructor normally used to return a value in the overridden QWidget::sizePolicy() function of a QWidget subclass.

It constructs a QSizePolicy with independent horizontal and vertical sizing types, hor and ver respectively. These sizing types affect how the widget is treated by the layout engine.

If hfw is TRUE, the preferred height of the widget is dependent on the width of the widget (for example, a QLabel with line wrapping).

See also horData(), verData(), and hasHeightForWidth().

QSizePolicy::QSizePolicy ( SizeType hor, SizeType ver, uchar horStretch, uchar verStretch, bool hfw = FALSE )

Constructs a QSizePolicy with independent horizontal and vertical sizing types hor and ver, and stretch factors horStretch and verStretch.

If hfw is TRUE, the preferred height of the widget is dependent on the width of the widget.

ExpandData QSizePolicy::expanding () const

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.