Contents

• Public Types
• Public Functions
• Related Non-Members
• Detailed Description

Detailed Description

TheQSizePolicy 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, and affects how the widget is treated by thelayout engine. Each widget returns aQSizePolicy that describes the horizontal and vertical resizing policy it prefers when being laid out. You can change this for a specific widget by changing itsQWidget::sizePolicy property.

QSizePolicy contains two independentQSizePolicy::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 thesetHorizontalPolicy() andsetVerticalPolicy() functions. The stretch factors can be set using thesetHorizontalStretch() andsetVerticalStretch() functions. The flag indicating whether the widget'ssizeHint() is width-dependent (such as a menu bar or a word-wrapping label) can be set using thesetHeightForWidth() function.

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

Use theexpandingDirections() function to determine whether the associated widget can make use of more space than itssizeHint() function indicates, as well as find out in which directions it can expand.

Finally, theQSizePolicy class provides operators comparing this size policy to a given policy, as well as aQVariant operator storing thisQSizePolicy as aQVariant object.

Member Type Documentation

enum QSizePolicy::ControlType
flags QSizePolicy::ControlTypes

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

This enum was introduced or modified in Qt 4.3.

The ControlTypes type is a typedef forQFlags<ControlType>. It stores an OR combination of ControlType values.

See alsosetControlType() andcontrolType().

enum QSizePolicy::Policy

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

See alsoPolicyFlag,setHorizontalPolicy(), andsetVerticalPolicy().

enum QSizePolicy::PolicyFlag

These flags are combined together to form the variousPolicy values:

See alsoPolicy.

Member Function Documentation

QSizePolicy::QSizePolicy()

Constructs aQSizePolicy object withFixed as its horizontal and vertical policies.

The policies can be altered using thesetHorizontalPolicy() andsetVerticalPolicy() functions. Use thesetHeightForWidth() function if the preferred height of the widget is dependent on the width of the widget (for example, aQLabel with line wrapping).

See alsosetHorizontalStretch() andsetVerticalStretch().

QSizePolicy::QSizePolicy(Policy horizontal,Policy vertical)

Constructs aQSizePolicy object with the givenhorizontal andvertical policies, andDefaultType as the control type.

UsesetHeightForWidth() if the preferred height of the widget is dependent on the width of the widget (for example, aQLabel with line wrapping).

See alsosetHorizontalStretch() andsetVerticalStretch().

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

Constructs aQSizePolicy object with the givenhorizontal andvertical policies, and the specified controltype.

UsesetHeightForWidth() if the preferred height of the widget is dependent on the width of the widget (for example, aQLabel with line wrapping).

This function was introduced in Qt 4.3.

See alsosetHorizontalStretch(),setVerticalStretch(), andcontrolType().

ControlType QSizePolicy::controlType() const

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

This function was introduced in Qt 4.3.

See alsosetControlType().

Qt::Orientations QSizePolicy::expandingDirections() const

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

A value ofQt::Horizontal orQt::Vertical means that the widget can grow horizontally or vertically (i.e., the horizontal or vertical policy isExpanding orMinimumExpanding), whereasQt::Horizontal |Qt::Vertical means that it can grow in both dimensions.

See alsohorizontalPolicy() andverticalPolicy().

bool QSizePolicy::hasHeightForWidth() const

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

See alsosetHeightForWidth().

bool QSizePolicy::hasWidthForHeight() const

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

This function was introduced in Qt 4.8.

See alsosetWidthForHeight().

Policy QSizePolicy::horizontalPolicy() const

Returns the horizontal component of the size policy.

See alsosetHorizontalPolicy(),verticalPolicy(), andhorizontalStretch().

int QSizePolicy::horizontalStretch() const

Returns the horizontal stretch factor of the size policy.

See alsosetHorizontalStretch(),verticalStretch(), andhorizontalPolicy().

void QSizePolicy::setControlType(ControlType type)

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

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

This function was introduced in Qt 4.3.

See alsocontrolType() andQStyle::layoutSpacing().

void QSizePolicy::setHeightForWidth(bool dependent)

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

See alsohasHeightForWidth() andsetWidthForHeight().

void QSizePolicy::setHorizontalPolicy(Policy policy)

Sets the horizontal component to the givenpolicy.

See alsohorizontalPolicy(),setVerticalPolicy(), andsetHorizontalStretch().

void QSizePolicy::setHorizontalStretch(uchar stretchFactor)

Sets the horizontal stretch factor of the size policy to the givenstretchFactor.

See alsohorizontalStretch(),setVerticalStretch(), andsetHorizontalPolicy().

void QSizePolicy::setVerticalPolicy(Policy policy)

Sets the vertical component to the givenpolicy.

See alsoverticalPolicy(),setHorizontalPolicy(), andsetVerticalStretch().

void QSizePolicy::setVerticalStretch(uchar stretchFactor)

Sets the vertical stretch factor of the size policy to the givenstretchFactor.

See alsoverticalStretch(),setHorizontalStretch(), andsetVerticalPolicy().

void QSizePolicy::setWidthForHeight(bool dependent)

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

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

This function was introduced in Qt 4.8.

See alsohasWidthForHeight() andsetHeightForWidth().

void QSizePolicy::transpose()

Swaps the horizontal and vertical policies and stretches.

Policy QSizePolicy::verticalPolicy() const

Returns the vertical component of the size policy.

See alsosetVerticalPolicy(),horizontalPolicy(), andverticalStretch().

int QSizePolicy::verticalStretch() const

Returns the vertical stretch factor of the size policy.

See alsosetVerticalStretch(),horizontalStretch(), andverticalPolicy().

QSizePolicy::operator QVariant() const

Returns aQVariant storing thisQSizePolicy.

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

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

See alsooperator==().

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

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

See alsooperator!=().

Related Non-Members

QDataStream &operator<<(QDataStream & stream, constQSizePolicy & policy)

Writes the sizepolicy to the data streamstream.

This function was introduced in Qt 4.2.

See alsoFormat of the QDataStream operators.

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

Reads the sizepolicy from the data streamstream.

This function was introduced in Qt 4.2.

See alsoFormat of the QDataStream operators.