- Qt 5.15
- Qt Core
- C++ Classes
- QSizeF
- Qt 5.15.19 Reference Documentation

# QSizeF Class

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

Header: | #include <QSizeF>
qmake: | QT += core

- List of all members, including inherited members

## Public Functions

| QSizeF(qreal width, qreal height)
| QSizeF(const QSize &size)
| QSizeF()
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

bool | operator!=(const QSizeF &s1, const QSizeF &s2)
const QSizeF | operator*(const QSizeF &size, qreal factor)
const QSizeF | operator*(qreal factor, const QSizeF &size)
const QSizeF | operator+(const QSizeF &s1, const QSizeF &s2)
const QSizeF | operator-(const QSizeF &s1, const QSizeF &s2)
const QSizeF | operator/(const QSizeF &size, qreal divisor)
QDataStream & | operator<<(QDataStream &stream, const QSizeF &size)
bool | operator==(const QSizeF &s1, const QSizeF &s2)
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

### QSizeF QSizeF::shrunkBy(QMarginsF margins) const

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

This function was introduced in Qt 5.14.

See also grownBy().

### QSizeF QSizeF::grownBy(QMarginsF margins) const

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

This function was introduced in Qt 5.14.

See also shrunkBy().

### QSizeF::QSizeF(qreal width, qreal height)

Constructs a size with the given width and height.

### QSizeF::QSizeF(const QSize &size)

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

See also toSize().

### QSizeF::QSizeF()

Constructs an invalid size.

See also isValid().

### 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().

### 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]` QSizeF QSizeF::fromCGSize(CGSize size)

Creates a QSizeF from size.

This function was introduced in Qt 5.8.

See also toCGSize().

### qreal QSizeF::height() const

Returns the height.

See also width() and setHeight().

### 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().

### 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().

### bool QSizeF::isValid() const

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

See also isNull() and isEmpty().

### 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().

### 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().

### 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().

### void QSizeF::scale(const QSizeF &size, Qt::AspectRatioMode mode)

This is an overloaded function.

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

### 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.

This function was introduced in Qt 5.0.

See also scale().

### QSizeF QSizeF::scaled(const QSizeF &s, Qt::AspectRatioMode mode) const

This is an overloaded function.

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

This function was introduced in Qt 5.0.

### void QSizeF::setHeight(qreal height)

Sets the height to the given height.

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

### void QSizeF::setWidth(qreal width)

Sets the width to the given width.

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

### CGSize QSizeF::toCGSize() const

Creates a CGSize from a QSizeF.

This function was introduced in Qt 5.8.

See also fromCGSize().

### 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().

### void QSizeF::transpose()

Swaps the width and height values.

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

### QSizeF QSizeF::transposed() const

Returns the size with width and height values swapped.

This function was introduced in Qt 5.0.

See also transpose().

### qreal QSizeF::width() const

Returns the width.

See also height() and setWidth().

### QSizeF &QSizeF::operator*=(qreal factor)

This is an overloaded function.

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

See also scale().

### 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)

### 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)

This is an overloaded function.

Divides both the width and height by the given divisor and returns a reference to the size.

See also scale().

## Related Non-Members

### bool operator!=(const QSizeF &s1, const QSizeF &s2)

Returns `true` if s1 and s2 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.

### const QSizeF operator*(const QSizeF &size, qreal factor)

This is an overloaded function.

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

See also QSizeF::scale().

### const QSizeF operator*(qreal factor, const QSizeF &size)

This is an overloaded function.

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

### const QSizeF operator+(const QSizeF &s1, const QSizeF &s2)

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

### const QSizeF operator-(const QSizeF &s1, const QSizeF &s2)

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

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

This is an overloaded function.

Divides the given size by the given divisor and returns the result.

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.

### bool operator==(const QSizeF &s1, const QSizeF &s2)

Returns `true` if s1 and s2 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.