QSizePolicy Class Reference
The QSizePolicy class is a layout attribute describing horizontal and vertical resizing.
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#include <qsizepolicy.h>
List of all member functions.
Public Members
enum
SizeType { Fixed = 0, Minimum = MayGrow, Maximum = MayShrink, Preferred = MayGrow | MayShrink, Expanding = MayGrow | MayShrink | ExpMask }
enum
ExpandData { NoDirection = 0, Horizontally = 1, Vertically = 2, BothDirections = Horizontally | Vertically, Horizontal = Horizontally, Vertical = Vertically }
QSizePolicy ( SizeType hor, SizeType ver, bool hfw = FALSE )
Detailed Description
The QSizePolicy class is a layout attribute describing horizontal and vertical resizing.
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
describing the horizontal and vertical resizing policy best used
when laying out the widget. 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 per-dimension SizeType objects are set in the usual constructor
and can be queried using a variety of functions, none of which are
really interesting to application programmers.
The hasHeightForWidth() flag indicates whether the widget's sizeHint()
is width-dependent (such as a word-wrapping label).
See also QSizePolicy::SizeType.
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 sizeHint()
says.
- QSizePolicy::Vertically - the widget can usefully be taller than sizeHint()
says.
- QSizePolicy::BothDirections - the widget can usefully be both wider and
taller than sizeHint() says.
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 below that 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 below that 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).
In any case, QLayout never shrinks a widget below the
QWidget::minimumSizeHint().
Member Function Documentation
QSizePolicy::QSizePolicy ()
Default constructor; produces 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 automatic word-breaking).
ExpandData QSizePolicy::expanding () const
Returns a value indicating whether the widget can make use of extra space
(i.e., if it "wants" to grow) horizontally and/or vertically.
bool QSizePolicy::hasHeightForWidth () const
Returns TRUE if the widget's preferred height depends on its width.
SizeType QSizePolicy::horData () const
Returns the horizontal component of the size policy.
bool QSizePolicy::mayGrowHorizontally () const
Returns TRUE if the widget can sensibly be wider than its sizeHint().
bool QSizePolicy::mayGrowVertically () const
Returns TRUE if the widget can sensibly be taller than its sizeHint().
bool QSizePolicy::mayShrinkHorizontally () const
Returns TRUE if the widget can sensibly be narrower than its sizeHint().
bool QSizePolicy::mayShrinkVertically () const
Returns TRUE if the widget can sensibly be lower than its sizeHint().
bool QSizePolicy::operator!= ( const QSizePolicy & s ) const
Returns TRUE if this policy is different from s, or FALSE if
they are equal.
bool QSizePolicy::operator== ( const QSizePolicy & s ) const
Returns TRUE if this policy is equal to s, or FALSE if
they are different.
void QSizePolicy::setHeightForWidth ( bool b )
Sets the hasHeightForWidth() flag to b.
void QSizePolicy::setHorData ( SizeType d )
Sets the horizontal component of the size policy to d.
void QSizePolicy::setVerData ( SizeType d )
Sets the vertical component of the size policy to d.
SizeType QSizePolicy::verData () const
Returns the vertical component of the size policy.
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