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

#include <qsizepolicy.h>

Collaboration diagram for QSizePolicy:

Public Types
enum	PolicyFlag { GrowFlag = 1 , ExpandFlag = 2 , ShrinkFlag = 4 , IgnoreFlag = 8 }
	These flags are combined together to form the various \l{Policy} values: More...

enum	Policy { Fixed = 0 , Minimum = GrowFlag , Maximum = ShrinkFlag , Preferred = GrowFlag \| ShrinkFlag , MinimumExpanding = GrowFlag \| ExpandFlag , Expanding = GrowFlag \| ShrinkFlag \| ExpandFlag , Ignored = ShrinkFlag \| GrowFlag \| IgnoreFlag }
	This enum describes the various per-dimension sizing types used when constructing a QSizePolicy. More...

enum	ControlType { DefaultType = 0x00000001 , ButtonBox = 0x00000002 , CheckBox = 0x00000004 , ComboBox = 0x00000008 , Frame = 0x00000010 , GroupBox = 0x00000020 , Label = 0x00000040 , Line = 0x00000080 , LineEdit = 0x00000100 , PushButton = 0x00000200 , RadioButton = 0x00000400 , Slider = 0x00000800 , SpinBox = 0x00001000 , TabWidget = 0x00002000 , ToolButton = 0x00004000 }

Public Member Functions
constexpr	QSizePolicy () noexcept
	Constructs a QSizePolicy object with \l Fixed as its horizontal and vertical policies.

constexpr	QSizePolicy (Policy horizontal, Policy vertical, ControlType type=DefaultType) noexcept

constexpr Policy	horizontalPolicy () const noexcept
	Returns the horizontal component of the size policy.

constexpr Policy	verticalPolicy () const noexcept
	Returns the vertical component of the size policy.

ControlType	controlType () const noexcept

constexpr void	setHorizontalPolicy (Policy d) noexcept
	Sets the horizontal component to the given policy.

constexpr void	setVerticalPolicy (Policy d) noexcept
	Sets the vertical component to the given policy.

void	setControlType (ControlType type) noexcept

constexpr Qt::Orientations	expandingDirections () const noexcept
	Returns whether a widget can make use of more space than the QWidget::sizeHint() function indicates.

constexpr void	setHeightForWidth (bool b) noexcept
	Sets the flag determining whether the widget's preferred height depends on its width, to dependent.

constexpr bool	hasHeightForWidth () const noexcept
	Returns `true` if the widget's preferred height depends on its width; otherwise returns `false`.

constexpr void	setWidthForHeight (bool b) noexcept
	Sets the flag determining whether the widget's width depends on its height, to dependent.

constexpr bool	hasWidthForHeight () const noexcept
	Returns `true` if the widget's width depends on its height; otherwise returns `false`.

constexpr bool	operator== (const QSizePolicy &s) const noexcept
	Returns `true` if this policy is equal to other; otherwise returns `false`.

constexpr bool	operator!= (const QSizePolicy &s) const noexcept
	Returns `true` if this policy is different from other; otherwise returns `false`.

	operator QVariant () const
	Returns a QVariant storing this QSizePolicy.

constexpr int	horizontalStretch () const noexcept
	Returns the horizontal stretch factor of the size policy.

constexpr int	verticalStretch () const noexcept
	Returns the vertical stretch factor of the size policy.

constexpr void	setHorizontalStretch (int stretchFactor)
	Sets the horizontal stretch factor of the size policy to the given stretchFactor.

constexpr void	setVerticalStretch (int stretchFactor)
	Sets the vertical stretch factor of the size policy to the given stretchFactor.

constexpr bool	retainSizeWhenHidden () const noexcept

constexpr void	setRetainSizeWhenHidden (bool retainSize) noexcept

constexpr void	transpose () noexcept
	Swaps the horizontal and vertical policies and stretches.

constexpr QSizePolicy	transposed () const noexcept

Friends
Q_DECL_CONST_FUNCTION size_t	qHash (QSizePolicy key, size_t seed=0) noexcept

Q_WIDGETS_EXPORT QDataStream &	operator<< (QDataStream &, const QSizePolicy &)

Q_WIDGETS_EXPORT QDataStream &	operator>> (QDataStream &, QSizePolicy &)

Detailed Description

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

\inmodule QtWidgets

The size policy of a widget is an expression of its willingness to be resized in various ways, and affects how the widget is treated by the \l{Layout Management}{layout engine}. Each widget returns a QSizePolicy that describes the horizontal and vertical resizing policy it prefers when being laid out. You can change this for a specific widget by changing its QWidget::sizePolicy property.

QSizePolicy contains two independent QSizePolicy::Policy values and two stretch factors; 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 policies can be set in the constructor, and altered using the setHorizontalPolicy() and setVerticalPolicy() functions. The stretch factors can be set using the setHorizontalStretch() and setVerticalStretch() functions. The flag indicating whether the widget's \l{QWidget::sizeHint()}{sizeHint()} is width-dependent (such as a menu bar or a word-wrapping label) can be set using the setHeightForWidth() function.

The current size policies and stretch factors be retrieved using the horizontalPolicy(), verticalPolicy(), horizontalStretch() and verticalStretch() functions. Alternatively, use the transpose() function to swap the horizontal and vertical policies and stretches. The hasHeightForWidth() function returns the current status of the flag indicating the size hint dependencies.

Use the expandingDirections() function to determine whether the associated widget can make use of more space than its \l{QWidget::sizeHint()}{sizeHint()} function indicates, as well as find out in which directions it can expand.

Finally, the QSizePolicy class provides operators comparing this size policy to a given policy, as well as a QVariant operator storing this QSizePolicy as a QVariant object.

See also: QSize, QWidget::sizeHint(), QWidget::sizePolicy, QLayoutItem::sizeHint()

Definition at line 17 of file qsizepolicy.h.

Member Enumeration Documentation

◆ ControlType

enum QSizePolicy::ControlType

Since: 4.3

This enum specifies the different types of widgets in terms of layout interaction:

\value DefaultType The default type, when none is specified. \value ButtonBox A QDialogButtonBox instance. \value CheckBox A QCheckBox instance. \value ComboBox A QComboBox instance. \value Frame A QFrame instance. \value GroupBox A QGroupBox instance. \value Label A QLabel instance. \value Line A QFrame instance with QFrame::HLine or QFrame::VLine. \value LineEdit A QLineEdit instance. \value PushButton A QPushButton instance. \value RadioButton A QRadioButton instance. \value Slider A QAbstractSlider instance. \value SpinBox A QAbstractSpinBox instance. \value TabWidget A QTabWidget instance. \value ToolButton A QToolButton instance.

See also: setControlType(), controlType()

Enumerator
DefaultType
ButtonBox
CheckBox
ComboBox
Frame
GroupBox
Label
Line
LineEdit
PushButton
RadioButton
Slider
SpinBox
TabWidget
ToolButton

Definition at line 40 of file qsizepolicy.h.

◆ Policy

enum QSizePolicy::Policy

This enum describes the various per-dimension sizing types used when constructing a QSizePolicy.

\value 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).

\value 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). It cannot be smaller than the size provided by sizeHint().

\value 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). It cannot be larger than the size provided by sizeHint().

\value 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).

\value 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 horizontal slider).

\value 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 horizontal slider).

\value Ignored The sizeHint() is ignored. The widget will get as much space as possible.

See also: PolicyFlag, setHorizontalPolicy(), setVerticalPolicy()

Enumerator
Fixed
Minimum
Maximum
Preferred
MinimumExpanding
Expanding
Ignored

Definition at line 29 of file qsizepolicy.h.

◆ PolicyFlag

enum QSizePolicy::PolicyFlag

These flags are combined together to form the various \l{Policy} values:

\value GrowFlag The widget can grow beyond its size hint if necessary. \value ExpandFlag The widget should get as much space as possible. \value ShrinkFlag The widget can shrink below its size hint if necessary. \value IgnoreFlag The widget's size hint is ignored. The widget will get as much space as possible.

See also: Policy

Enumerator
GrowFlag
ExpandFlag
ShrinkFlag
IgnoreFlag

Definition at line 22 of file qsizepolicy.h.

Constructor & Destructor Documentation

◆ QSizePolicy() [1/2]

QSizePolicy::QSizePolicy ( )

inlineconstexprnoexcept

Constructs a QSizePolicy object with \l Fixed as its horizontal and vertical policies.

The policies can be altered using the setHorizontalPolicy() and setVerticalPolicy() functions. Use the setHeightForWidth() function if the preferred height of the widget is dependent on the width of the widget (for example, a QLabel with line wrapping).

See also: setHorizontalStretch(), setVerticalStretch()

Definition at line 60 of file qsizepolicy.h.

◆ QSizePolicy() [2/2]

QSizePolicy::QSizePolicy	(	Policy	horizontal,
		Policy	vertical,
		ControlType	type = DefaultType )

inlineconstexprnoexcept

Since: 4.3

Constructs a QSizePolicy object with the given horizontal and vertical policies, and the specified control type.

Use setHeightForWidth() if the preferred height of the widget is dependent on the width of the widget (for example, a QLabel with line wrapping).

See also: setHorizontalStretch(), setVerticalStretch(), controlType()

Definition at line 62 of file qsizepolicy.h.

Member Function Documentation

◆ controlType()

QSizePolicy::ControlType QSizePolicy::controlType ( ) const

noexcept

Since: 4.3

Returns the control type associated with the widget for which this size policy applies.

Definition at line 199 of file qsizepolicy.cpp.

◆ expandingDirections()

Qt::Orientations QSizePolicy::expandingDirections ( ) const

inlineconstexprnoexcept

Returns whether a widget can make use of more space than the QWidget::sizeHint() function indicates.

A value of Qt::Horizontal or Qt::Vertical means that the widget can grow horizontally or vertically (i.e., the horizontal or vertical policy is \l Expanding or \l MinimumExpanding), whereas Qt::Horizontal | Qt::Vertical means that it can grow in both dimensions.

See also: horizontalPolicy(), verticalPolicy()

Definition at line 75 of file qsizepolicy.h.

◆ hasHeightForWidth()

bool QSizePolicy::hasHeightForWidth ( ) const

inlineconstexprnoexcept

Returns true if the widget's preferred height depends on its width; otherwise returns false.

See also: setHeightForWidth()

Definition at line 81 of file qsizepolicy.h.

◆ hasWidthForHeight()

bool QSizePolicy::hasWidthForHeight ( ) const

inlineconstexprnoexcept

Returns true if the widget's width depends on its height; otherwise returns false.

See also: setWidthForHeight()

Definition at line 83 of file qsizepolicy.h.

◆ horizontalPolicy()

Policy QSizePolicy::horizontalPolicy ( ) const

inlineconstexprnoexcept

Returns the horizontal component of the size policy.

See also: setHorizontalPolicy(), verticalPolicy(), horizontalStretch()

Definition at line 66 of file qsizepolicy.h.

◆ horizontalStretch()

int QSizePolicy::horizontalStretch ( ) const

inlineconstexprnoexcept

Returns the horizontal stretch factor of the size policy.

See also: setHorizontalStretch(), verticalStretch(), horizontalPolicy()

Definition at line 92 of file qsizepolicy.h.

◆ operator QVariant()

QSizePolicy::operator QVariant ( ) const

Returns a QVariant storing this QSizePolicy.

Definition at line 403 of file qsizepolicy.cpp.

◆ operator!=()

bool QSizePolicy::operator!= ( const QSizePolicy & other ) const

inlineconstexprnoexcept

Returns true if this policy is different from other; otherwise returns false.

See also: operator==()

Definition at line 86 of file qsizepolicy.h.

◆ operator==()

bool QSizePolicy::operator== ( const QSizePolicy & other ) const

inlineconstexprnoexcept

Returns true if this policy is equal to other; otherwise returns false.

See also: operator!=()

Definition at line 85 of file qsizepolicy.h.

◆ retainSizeWhenHidden()

bool QSizePolicy::retainSizeWhenHidden ( ) const

inlineconstexprnoexcept

Since: 5.2

Returns whether the layout should retain the widget's size when it is hidden. This is false by default.

See also: setRetainSizeWhenHidden()

Definition at line 97 of file qsizepolicy.h.

◆ setControlType()

void QSizePolicy::setControlType ( ControlType type )

noexcept

Since: 4.3

Sets the control type associated with the widget for which this size policy applies to type.

The control type specifies the type of the widget for which this size policy applies. It is used by some styles, notably QMacStyle, to insert proper spacing between widgets. For example, the \macos Aqua guidelines specify that push buttons should be separated by 12 pixels, whereas vertically stacked radio buttons only require 6 pixels.

See also: QStyle::layoutSpacing()

Definition at line 220 of file qsizepolicy.cpp.

◆ setHeightForWidth()

void QSizePolicy::setHeightForWidth ( bool dependent )

inlineconstexprnoexcept

Sets the flag determining whether the widget's preferred height depends on its width, to dependent.

See also: hasHeightForWidth(), setWidthForHeight()

Definition at line 80 of file qsizepolicy.h.

◆ setHorizontalPolicy()

void QSizePolicy::setHorizontalPolicy ( Policy policy )

inlineconstexprnoexcept

Sets the horizontal component to the given policy.

See also: horizontalPolicy(), setVerticalPolicy(), setHorizontalStretch()

Definition at line 70 of file qsizepolicy.h.

◆ setHorizontalStretch()

void QSizePolicy::setHorizontalStretch ( int stretchFactor )

inlineconstexpr

Sets the horizontal stretch factor of the size policy to the given stretchFactor.

stretchFactor must be in the range [0,255].

When two widgets are adjacent to each other in a horizontal layout, setting the horizontal stretch factor of the widget on the left to 2 and the factor of widget on the right to 1 will ensure that the widget on the left will always be twice the size of the one on the right.

See also: horizontalStretch(), setVerticalStretch(), setHorizontalPolicy()

Definition at line 94 of file qsizepolicy.h.

◆ setRetainSizeWhenHidden()

void QSizePolicy::setRetainSizeWhenHidden ( bool retainSize )

inlineconstexprnoexcept

Since: 5.2

Sets whether a layout should retain the widget's size when it is hidden. If retainSize is true, the layout will not be changed by hiding the widget.

See also: retainSizeWhenHidden()

Definition at line 98 of file qsizepolicy.h.

◆ setVerticalPolicy()

void QSizePolicy::setVerticalPolicy ( Policy policy )

inlineconstexprnoexcept

Sets the vertical component to the given policy.

See also: verticalPolicy(), setHorizontalPolicy(), setVerticalStretch()

Definition at line 71 of file qsizepolicy.h.

◆ setVerticalStretch()

void QSizePolicy::setVerticalStretch ( int stretchFactor )

inlineconstexpr

Sets the vertical stretch factor of the size policy to the given stretchFactor.

stretchFactor must be in the range [0,255].

When two widgets are adjacent to each other in a vertical layout, setting the vertical stretch factor of the widget on the top to 2 and the factor of widget on the bottom to 1 will ensure that the widget on the top will always be twice the size of the one on the bottom.

See also: verticalStretch(), setHorizontalStretch(), setVerticalPolicy()

Definition at line 95 of file qsizepolicy.h.

◆ setWidthForHeight()

void QSizePolicy::setWidthForHeight ( bool dependent )

inlineconstexprnoexcept

Sets the flag determining whether the widget's width depends on its height, to dependent.

This is only supported for QGraphicsLayout's subclasses. It is not possible to have a layout with both height-for-width and width-for-height constraints at the same time.

See also: hasWidthForHeight(), setHeightForWidth()

Definition at line 82 of file qsizepolicy.h.

◆ transpose()

void QSizePolicy::transpose ( )

inlineconstexprnoexcept

Swaps the horizontal and vertical policies and stretches.

See also: transposed()

Definition at line 100 of file qsizepolicy.h.

◆ transposed()

QSizePolicy QSizePolicy::transposed ( ) const

inlinenodiscardconstexprnoexcept

Since: 5.9

Returns a size policy object with the horizontal and vertical policies and stretches swapped.

See also: transpose()

Definition at line 101 of file qsizepolicy.h.

◆ verticalPolicy()

Policy QSizePolicy::verticalPolicy ( ) const

inlineconstexprnoexcept

Returns the vertical component of the size policy.

See also: setVerticalPolicy(), horizontalPolicy(), verticalStretch()

Definition at line 67 of file qsizepolicy.h.

◆ verticalStretch()

int QSizePolicy::verticalStretch ( ) const

inlineconstexprnoexcept

Returns the vertical stretch factor of the size policy.

See also: setVerticalStretch(), horizontalStretch(), verticalPolicy()

Definition at line 93 of file qsizepolicy.h.

Friends And Related Symbol Documentation

◆ operator<<

QDataStream & operator<<	(	QDataStream &	stream,
		const QSizePolicy &	policy )

friend

Since: 4.2

Writes the size policy to the data stream stream.

See also: {Serializing Qt Data Types}{Format of the QDataStream operators}

Definition at line 418 of file qsizepolicy.cpp.

◆ operator>>

QDataStream & operator>>	(	QDataStream &	stream,
		QSizePolicy &	policy )

friend

Since: 4.2

Reads the size policy from the data stream stream.

See also: {Serializing Qt Data Types}{Format of the QDataStream operators}

Definition at line 442 of file qsizepolicy.cpp.

◆ qHash

Q_DECL_CONST_FUNCTION size_t qHash	(	QSizePolicy	key,
		size_t	seed = 0 )

friend

Since: 5.6

Returns the hash value for key, using seed to seed the calculation.

Definition at line 88 of file qsizepolicy.h.

Member Data Documentation

◆ bits

Bits QSizePolicy::bits

Definition at line 157 of file qsizepolicy.h.

◆ data

quint32 QSizePolicy::data

Definition at line 158 of file qsizepolicy.h.

The documentation for this class was generated from the following files:

qtbase/src/widgets/kernel/qsizepolicy.h (05fc3aef53348fb58be6308076e000825b704e58)
qtbase/src/widgets/kernel/qsizepolicy.cpp (05fc3aef53348fb58be6308076e000825b704e58)

Public Types

Public Member Functions

Friends

Detailed Description

Member Enumeration Documentation

◆ ControlType

◆ Policy

◆ PolicyFlag

Constructor & Destructor Documentation

◆ QSizePolicy() [1/2]

◆ QSizePolicy() [2/2]

Member Function Documentation

◆ controlType()

◆ expandingDirections()

◆ hasHeightForWidth()

◆ hasWidthForHeight()

◆ horizontalPolicy()

◆ horizontalStretch()

◆ operator QVariant()

◆ operator!=()

◆ operator==()

◆ retainSizeWhenHidden()

◆ setControlType()

◆ setHeightForWidth()

◆ setHorizontalPolicy()

◆ setHorizontalStretch()

◆ setRetainSizeWhenHidden()

◆ setVerticalPolicy()

◆ setVerticalStretch()

◆ setWidthForHeight()

◆ transpose()

◆ transposed()

◆ verticalPolicy()

◆ verticalStretch()

Friends And Related Symbol Documentation

◆ operator<<

◆ operator>>

◆ qHash

Member Data Documentation

◆ bits

◆ data