- Qt 6.9
- Qt Core
- C++ Classes
- QSizeF
- Qt 6.9.3 Reference Documentation

# QSizeF Class

The QSizeF class defines the size of a two-dimensional object using floating point precision. More...

Header: | `#include <QSizeF>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`

- List of all members, including inherited members
- QSizeF is part of Painting Classes.

## Public Functions

| QSizeF()
| QSizeF(const QSize &size)
| QSizeF(qreal width, qreal height)
QSizeF | boundedTo(const QSizeF &otherSize) const
QSizeF | expandedTo(const QSizeF &otherSize) const
QSizeF | grownBy(QMarginsF margins) const
qreal | height() const
bool | isEmpty() const
bool | isNull() const
bool | isValid() const
qreal & | rheight()
qreal & | rwidth()
void | scale(qreal width, qreal height, Qt::AspectRatioMode mode)
void | scale(const QSizeF &size, Qt::AspectRatioMode mode)
QSizeF | scaled(qreal width, qreal height, Qt::AspectRatioMode mode) const
QSizeF | scaled(const QSizeF &s, Qt::AspectRatioMode mode) const
void | setHeight(qreal height)
void | setWidth(qreal width)
QSizeF | shrunkBy(QMarginsF margins) const
CGSize | toCGSize() const
QSize | toSize() const
void | transpose()
QSizeF | transposed() const
qreal | width() const
QSizeF & | operator*=(qreal factor)
QSizeF & | operator+=(const QSizeF &size)
QSizeF & | operator-=(const QSizeF &size)
QSizeF & | operator/=(qreal divisor)

## Static Public Members

QSizeF | fromCGSize(CGSize size)

## Related Non-Members

`(since 6.8)` bool | qFuzzyCompare(const QSizeF &lhs, const QSizeF &rhs)
`(since 6.8)` bool | qFuzzyIsNull(const QSizeF &size)
bool | operator!=(const QSizeF &lhs, const QSizeF &rhs)
QSizeF | operator*(const QSizeF &size, qreal factor)
QSizeF | operator*(qreal factor, const QSizeF &size)
QSizeF | operator+(const QSizeF &s1, const QSizeF &s2)
QSizeF | operator-(const QSizeF &s1, const QSizeF &s2)
QSizeF | operator/(const QSizeF &size, qreal divisor)
QDataStream & | operator<<(QDataStream &stream, const QSizeF &size)
bool | operator==(const QSizeF &lhs, const QSizeF &rhs)
QDataStream & | operator>>(QDataStream &stream, QSizeF &size)

## Detailed Description

A size is specified by a width() and a height(). It can be set in the constructor and changed using the setWidth(), setHeight(), or scale() functions, or using arithmetic operators. A size can also be manipulated directly by retrieving references to the width and height using the rwidth() and rheight() functions. Finally, the width and height can be swapped using the transpose() function.

The isValid() function determines if a size is valid. A valid size has both width and height greater than or equal to zero. The isEmpty() function returns `true` if either of the width and height is less than (or equal to) zero, while the isNull() function returns `true` only if both the width and the height is zero.

Use the expandedTo() function to retrieve a size which holds the maximum height and width of this size and a given size. Similarly, the boundedTo() function returns a size which holds the minimum height and width of this size and a given size.

The QSizeF class also provides the toSize() function returning a QSize copy of this size, constructed by rounding the width and height to the nearest integers.

QSizeF objects can be streamed as well as compared.

See also QSize, QPointF, and QRectF.

## Member Function Documentation

### `[constexpr noexcept]` QSizeF QSizeF::grownBy(QMarginsF margins) const

Returns the size that results from growing this size by margins.

See also shrunkBy().

### `[constexpr noexcept]` QSizeF QSizeF::shrunkBy(QMarginsF margins) const

Returns the size that results from shrinking this size by margins.

See also grownBy().

### `[constexpr noexcept]` QSizeF::QSizeF()

Constructs an invalid size.

See also isValid().

### `[constexpr noexcept]` QSizeF::QSizeF(const QSize &size)

Constructs a size with floating point accuracy from the given size.

See also toSize() and QSize::toSizeF().

### `[constexpr noexcept]` QSizeF::QSizeF(qreal width, qreal height)

Constructs a size with the given finite width and height.

### `[constexpr noexcept]` QSizeF QSizeF::boundedTo(const QSizeF &otherSize) const

Returns a size holding the minimum width and height of this size and the given otherSize.

See also expandedTo() and scale().

### `[constexpr noexcept]` QSizeF QSizeF::expandedTo(const QSizeF &otherSize) const

Returns a size holding the maximum width and height of this size and the given otherSize.

See also boundedTo() and scale().

### `[static noexcept]` QSizeF QSizeF::fromCGSize(CGSize size)

Creates a QSizeF from size.

See also toCGSize().

### `[constexpr noexcept]` qreal QSizeF::height() const

Returns the height.

See also width() and setHeight().

### `[constexpr noexcept]` bool QSizeF::isEmpty() const

Returns `true` if either of the width and height is less than or equal to 0; otherwise returns `false`.

See also isNull() and isValid().

### `[noexcept]` bool QSizeF::isNull() const

Returns `true` if both the width and height are 0.0 (ignoring the sign); otherwise returns `false`.

See also isValid() and isEmpty().

### `[constexpr noexcept]` bool QSizeF::isValid() const

Returns `true` if both the width and height are equal to or greater than 0; otherwise returns `false`.

See also isNull() and isEmpty().

### `[constexpr noexcept]` qreal &QSizeF::rheight()

Returns a reference to the height.

Using a reference makes it possible to manipulate the height directly. For example:

     QSizeF size(100, 10.2);
     size.rheight() += 5.5;

     // size becomes (100,15.7)

See also rwidth() and setHeight().

### `[constexpr noexcept]` qreal &QSizeF::rwidth()

Returns a reference to the width.

Using a reference makes it possible to manipulate the width directly. For example:

     QSizeF size(100.3, 10);
     size.rwidth() += 20.5;

      // size becomes (120.8,10)

See also rheight() and setWidth().

### `[noexcept]` void QSizeF::scale(qreal width, qreal height, Qt::AspectRatioMode mode)

Scales the size to a rectangle with the given width and height, according to the specified mode.

- If mode is Qt::IgnoreAspectRatio, the size is set to (width, height).
- If mode is Qt::KeepAspectRatio, the current size is scaled to a rectangle as large as possible inside (width, height), preserving the aspect ratio.
- If mode is Qt::KeepAspectRatioByExpanding, the current size is scaled to a rectangle as small as possible outside (width, height), preserving the aspect ratio.

Example:

     QSizeF t1(10, 12);
     t1.scale(60, 60, Qt::IgnoreAspectRatio);
     // t1 is (60, 60)

     QSizeF t2(10, 12);
     t2.scale(60, 60, Qt::KeepAspectRatio);
     // t2 is (50, 60)

     QSizeF t3(10, 12);
     t3.scale(60, 60, Qt::KeepAspectRatioByExpanding);
     // t3 is (60, 72)

See also setWidth(), setHeight(), and scaled().

### `[noexcept]` void QSizeF::scale(const QSizeF &size, Qt::AspectRatioMode mode)

Scales the size to a rectangle with the given size, according to the specified mode.

This is an overloaded function.

### `[noexcept]` QSizeF QSizeF::scaled(qreal width, qreal height, Qt::AspectRatioMode mode) const

Returns a size scaled to a rectangle with the given width and height, according to the specified mode.

See also scale().

### `[noexcept]` QSizeF QSizeF::scaled(const QSizeF &s, Qt::AspectRatioMode mode) const

Returns a size scaled to a rectangle with the given size s, according to the specified mode.

This is an overloaded function.

### `[constexpr noexcept]` void QSizeF::setHeight(qreal height)

Sets the height to the given finite height.

See also height(), rheight(), and setWidth().

### `[constexpr noexcept]` void QSizeF::setWidth(qreal width)

Sets the width to the given finite width.

See also width(), rwidth(), and setHeight().

### `[noexcept]` CGSize QSizeF::toCGSize() const

Creates a CGSize from a QSizeF.

See also fromCGSize().

### `[constexpr noexcept]` QSize QSizeF::toSize() const

Returns an integer based copy of this size.

Note that the coordinates in the returned size will be rounded to the nearest integer.

See also QSizeF() and QSize::toSizeF().

### `[noexcept]` void QSizeF::transpose()

Swaps the width and height values.

See also setWidth(), setHeight(), and transposed().

### `[constexpr noexcept]` QSizeF QSizeF::transposed() const

Returns the size with width and height values swapped.

See also transpose().

### `[constexpr noexcept]` qreal QSizeF::width() const

Returns the width.

See also height() and setWidth().

### `[constexpr noexcept]` QSizeF &QSizeF::operator*=(qreal factor)

Multiplies both the width and height by the given finite factor and returns a reference to the size.

See also scale().

### `[constexpr noexcept]` QSizeF &QSizeF::operator+=(const QSizeF &size)

Adds the given size to this size and returns a reference to this size. For example:

     QSizeF s( 3, 7);
     QSizeF r(-1, 4);
     s += r;

     // s becomes (2,11)

### `[constexpr noexcept]` QSizeF &QSizeF::operator-=(const QSizeF &size)

Subtracts the given size from this size and returns a reference to this size. For example:

     QSizeF s( 3, 7);
     QSizeF r(-1, 4);
     s -= r;

     // s becomes (4,3)

### QSizeF &QSizeF::operator/=(qreal divisor)

Divides both the width and height by the given divisor and returns a reference to the size. The divisor must not be either zero or NaN.

See also scale().

## Related Non-Members

### `[constexpr noexcept, since 6.8]` bool qFuzzyCompare(const QSizeF &lhs, const QSizeF &rhs)

Returns `true` if the size lhs is approximately equal to the size rhs; otherwise returns `false`.

The sizes are considered approximately equal if their width and height are approximately equal.

This function was introduced in Qt 6.8.

### `[constexpr noexcept, since 6.8]` bool qFuzzyIsNull(const QSizeF &size)

Returns `true` if both width and height of the size size are approximately equal to zero.

This function was introduced in Qt 6.8.

### `[constexpr noexcept]` bool operator!=(const QSizeF &lhs, const QSizeF &rhs)

Returns `true` if lhs and rhs are sufficiently different; otherwise returns `false`.

Warning: This function does not check for strict inequality; instead, it uses a fuzzy comparison to compare the sizes' extents.

### `[constexpr noexcept]` QSizeF operator*(const QSizeF &size, qreal factor)

Multiplies the given size by the given finite factor and returns the result.

This is an overloaded function.

See also QSizeF::scale().

### `[constexpr noexcept]` QSizeF operator*(qreal factor, const QSizeF &size)

Multiplies the given size by the given finite factor and returns the result.

This is an overloaded function.

### `[constexpr noexcept]` QSizeF operator+(const QSizeF &s1, const QSizeF &s2)

Returns the sum of s1 and s2; each component is added separately.

### `[constexpr noexcept]` QSizeF operator-(const QSizeF &s1, const QSizeF &s2)

Returns s2 subtracted from s1; each component is subtracted separately.

### QSizeF operator/(const QSizeF &size, qreal divisor)

Divides the given size by the given divisor and returns the result. The divisor must not be either zero or NaN.

See also QSizeF::scale().

### QDataStream &operator<<(QDataStream &stream, const QSizeF &size)

Writes the given size to the given stream and returns a reference to the stream.

See also Serializing Qt Data Types.

### `[constexpr noexcept]` bool operator==(const QSizeF &lhs, const QSizeF &rhs)

Returns `true` if lhs and rhs are approximately equal; otherwise returns false.

Warning: This function does not check for strict equality; instead, it uses a fuzzy comparison to compare the sizes' extents.

See also qFuzzyCompare.

### QDataStream &operator>>(QDataStream &stream, QSizeF &size)

Reads a size from the given stream into the given size and returns a reference to the stream.

See also Serializing Qt Data Types.