QRect Class

The QRect class defines a rectangle in the plane using integer precision. More...

Header: #include <QRect>
qmake: QT += core

Note: All functions in this class are reentrant.

Public Functions

QRect()
QRect(const QPoint &topleft, const QPoint &bottomright)
QRect(const QPoint &topleft, const QSize &size)
QRect(int left, int top, int width, int height)
void adjust(int x1, int y1, int x2, int y2)
QRect adjusted(int x1, int y1, int x2, int y2) const
int bottom() const
QPoint bottomLeft() const
QPoint bottomRight() const
QPoint center() const
bool contains(const QRect &r, bool proper = false) const
bool contains(const QPoint &p, bool proper = false) const
bool contains(int x, int y) const
bool contains(int x, int y, bool proper) const
void getCoords(int *x1, int *y1, int *x2, int *y2) const
void getRect(int *x, int *y, int *w, int *h) const
int height() const
QRect intersect(const QRect &r) const
QRect intersected(const QRect &other) const
bool intersects(const QRect &r) const
bool isEmpty() const
bool isNull() const
bool isValid() const
int left() const
QRect marginsAdded(const QMargins &margins) const
QRect marginsRemoved(const QMargins &margins) const
void moveBottom(int pos)
void moveBottomLeft(const QPoint &p)
void moveBottomRight(const QPoint &p)
void moveCenter(const QPoint &p)
void moveLeft(int pos)
void moveRight(int pos)
void moveTo(int x, int t)
void moveTo(const QPoint &p)
void moveTop(int pos)
void moveTopLeft(const QPoint &p)
void moveTopRight(const QPoint &p)
QRect normalized() const
int right() const
void setBottom(int pos)
void setBottomLeft(const QPoint &p)
void setBottomRight(const QPoint &p)
void setCoords(int x1, int y1, int x2, int y2)
void setHeight(int h)
void setLeft(int pos)
void setRect(int x, int y, int w, int h)
void setRight(int pos)
void setSize(const QSize &s)
void setTop(int pos)
void setTopLeft(const QPoint &p)
void setTopRight(const QPoint &p)
void setWidth(int w)
void setX(int x)
void setY(int y)
QSize size() const
CGRect toCGRect() const
int top() const
QPoint topLeft() const
QPoint topRight() const
void translate(int dx, int dy)
void translate(const QPoint &p)
QRect translated(int dx, int dy) const
QRect translated(const QPoint &p) const
QRect transposed() const
QRect unite(const QRect &r) const
QRect united(const QRect &other) const
int width() const
int x() const
int y() const
QRect operator&(const QRect &r) const
QRect &operator&=(const QRect &r)
QRect &operator+=(const QMargins &margins)
QRect &operator-=(const QMargins &margins)
QRect operator|(const QRect &r) const
QRect &operator|=(const QRect &r)
bool operator!=(const QRect &r1, const QRect &r2)
QRect operator+(const QRect &rectangle, const QMargins &margins)
QRect operator+(const QMargins &margins, const QRect &rectangle)
QRect operator-(const QRect &lhs, const QMargins &rhs)
QDataStream &operator<<(QDataStream &stream, const QRect &rectangle)
bool operator==(const QRect &r1, const QRect &r2)
QDataStream &operator>>(QDataStream &stream, QRect &rectangle)

Detailed Description

The QRect class defines a rectangle in the plane using integer precision.

A rectangle is normally expressed as a top-left corner and a size. The size (width and height) of a QRect is always equivalent to the mathematical rectangle that forms the basis for its rendering.

A QRect can be constructed with a set of left, top, width and height integers, or from a QPoint and a QSize. The following code creates two identical rectangles.


  QRect r1(100, 200, 11, 16);
  QRect r2(QPoint(100, 200), QSize(11, 16));

There is a third constructor that creates a QRect using the top-left and bottom-right coordinates, but we recommend that you avoid using it. The rationale is that for historical reasons the values returned by the bottom() and right() functions deviate from the true bottom-right corner of the rectangle.

The QRect class provides a collection of functions that return the various rectangle coordinates, and enable manipulation of these. QRect also provides functions to move the rectangle relative to the various coordinates. In addition there is a moveTo() function that moves the rectangle, leaving its top left corner at the given coordinates. Alternatively, the translate() function moves the rectangle the given offset relative to the current position, and the translated() function returns a translated copy of this rectangle.

The size() function returns the rectange's dimensions as a QSize. The dimensions can also be retrieved separately using the width() and height() functions. To manipulate the dimensions use the setSize(), setWidth() or setHeight() functions. Alternatively, the size can be changed by applying either of the functions setting the rectangle coordinates, for example, setBottom() or setRight().

The contains() function tells whether a given point is inside the rectangle or not, and the intersects() function returns true if this rectangle intersects with a given rectangle. The QRect class also provides the intersected() function which returns the intersection rectangle, and the united() function which returns the rectangle that encloses the given rectangle and this:

The isEmpty() function returns true if left() > right() or top() > bottom(). Note that an empty rectangle is not valid: The isValid() function returns true if left() <= right() and top() <= bottom(). A null rectangle (isNull() == true) on the other hand, has both width and height set to 0.

Note that due to the way QRect and QRectF are defined, an empty QRect is defined in essentially the same way as QRectF.

Finally, QRect objects can be streamed as well as compared.

Rendering

When using an anti-aliased painter, the boundary line of a QRect will be rendered symmetrically on both sides of the mathematical rectangle's boundary line. But when using an aliased painter (the default) other rules apply.

Then, when rendering with a one pixel wide pen the QRect's boundary line will be rendered to the right and below the mathematical rectangle's boundary line.

When rendering with a two pixels wide pen the boundary line will be split in the middle by the mathematical rectangle. This will be the case whenever the pen is set to an even number of pixels, while rendering with a pen with an odd number of pixels, the spare pixel will be rendered to the right and below the mathematical rectangle as in the one pixel case.

Logical representationOne pixel wide pen
Two pixel wide penThree pixel wide pen

Coordinates

The QRect class provides a collection of functions that return the various rectangle coordinates, and enable manipulation of these. QRect also provides functions to move the rectangle relative to the various coordinates.

For example the left(), setLeft() and moveLeft() functions as an example: left() returns the x-coordinate of the rectangle's left edge, setLeft() sets the left edge of the rectangle to the given x coordinate (it may change the width, but will never change the rectangle's right edge) and moveLeft() moves the entire rectangle horizontally, leaving the rectangle's left edge at the given x coordinate and its size unchanged.

Note that for historical reasons the values returned by the bottom() and right() functions deviate from the true bottom-right corner of the rectangle: The right() function returns left() + width() - 1 and the bottom() function returns top() + height() - 1. The same is the case for the point returned by the bottomRight() convenience function. In addition, the x and y coordinate of the topRight() and bottomLeft() functions, respectively, contain the same deviation from the true right and bottom edges.

We recommend that you use x() + width() and y() + height() to find the true bottom-right corner, and avoid right() and bottom(). Another solution is to use QRectF: The QRectF class defines a rectangle in the plane using floating point accuracy for coordinates, and the QRectF::right() and QRectF::bottom() functions do return the right and bottom coordinates.

It is also possible to add offsets to this rectangle's coordinates using the adjust() function, as well as retrieve a new rectangle based on adjustments of the original one using the adjusted() function. If either of the width and height is negative, use the normalized() function to retrieve a rectangle where the corners are swapped.

In addition, QRect provides the getCoords() function which extracts the position of the rectangle's top-left and bottom-right corner, and the getRect() function which extracts the rectangle's top-left corner, width and height. Use the setCoords() and setRect() function to manipulate the rectangle's coordinates and dimensions in one go.

Constraints

QRect is limited to the minimum and maximum values for the int type. Operations on a QRect that could potentially result in values outside this range will result in undefined behavior.

See also QRectF and QRegion.

Member Function Documentation

QRect::QRect()

Default constructs an instance of QRect.

QRect::QRect(const QPoint &topleft, const QPoint &bottomright)

Default constructs an instance of QRect.

QRect::QRect(const QPoint &topleft, const QSize &size)

Default constructs an instance of QRect.

QRect::QRect(int left, int top, int width, int height)

Default constructs an instance of QRect.

void QRect::adjust(int x1, int y1, int x2, int y2)

QRect QRect::adjusted(int x1, int y1, int x2, int y2) const

int QRect::bottom() const

See also setBottom().

QPoint QRect::bottomLeft() const

See also setBottomLeft().

QPoint QRect::bottomRight() const

See also setBottomRight().

QPoint QRect::center() const

bool QRect::contains(const QRect &r, bool proper = false) const

bool QRect::contains(const QPoint &p, bool proper = false) const

bool QRect::contains(int x, int y) const

bool QRect::contains(int x, int y, bool proper) const

void QRect::getCoords(int *x1, int *y1, int *x2, int *y2) const

void QRect::getRect(int *x, int *y, int *w, int *h) const

int QRect::height() const

See also setHeight().

QRect QRect::intersect(const QRect &r) const

QRect QRect::intersected(const QRect &other) const

bool QRect::intersects(const QRect &r) const

bool QRect::isEmpty() const

bool QRect::isNull() const

bool QRect::isValid() const

int QRect::left() const

See also setLeft().

QRect QRect::marginsAdded(const QMargins &margins) const

QRect QRect::marginsRemoved(const QMargins &margins) const

void QRect::moveBottom(int pos)

void QRect::moveBottomLeft(const QPoint &p)

void QRect::moveBottomRight(const QPoint &p)

void QRect::moveCenter(const QPoint &p)

void QRect::moveLeft(int pos)

void QRect::moveRight(int pos)

void QRect::moveTo(int x, int t)

void QRect::moveTo(const QPoint &p)

void QRect::moveTop(int pos)

void QRect::moveTopLeft(const QPoint &p)

void QRect::moveTopRight(const QPoint &p)

QRect QRect::normalized() const

Returns a normalized rectangle; i.e., a rectangle that has a non-negative width and height.

If width() < 0 the function swaps the left and right corners, and it swaps the top and bottom corners if height() < 0.

See also isValid() and isEmpty().

See also setRight().

void QRect::setBottom(int pos)

See also bottom().

void QRect::setBottomLeft(const QPoint &p)

See also bottomLeft().

void QRect::setBottomRight(const QPoint &p)

See also bottomRight().

void QRect::setCoords(int x1, int y1, int x2, int y2)

void QRect::setHeight(int h)

See also height().

void QRect::setLeft(int pos)

See also left().

void QRect::setRect(int x, int y, int w, int h)

void QRect::setRight(int pos)

See also right().

void QRect::setSize(const QSize &s)

See also size().

void QRect::setTop(int pos)

See also top().

void QRect::setTopLeft(const QPoint &p)

See also topLeft().

void QRect::setTopRight(const QPoint &p)

See also topRight().

void QRect::setWidth(int w)

See also width().

void QRect::setX(int x)

See also x().

void QRect::setY(int y)

See also y().

QSize QRect::size() const

See also setSize().

CGRect QRect::toCGRect() const

Creates a CGRect from a QRect.

This function was introduced in Qt 5.8.

See also QRectF::fromCGRect().

int QRect::top() const

See also setTop().

QPoint QRect::topLeft() const

See also setTopLeft().

QPoint QRect::topRight() const

See also setTopRight().

void QRect::translate(int dx, int dy)

void QRect::translate(const QPoint &p)

QRect QRect::translated(int dx, int dy) const

QRect QRect::translated(const QPoint &p) const

QRect QRect::transposed() const

QRect QRect::unite(const QRect &r) const

QRect QRect::united(const QRect &other) const

int QRect::width() const

See also setWidth().

int QRect::x() const

See also setX().

int QRect::y() const

See also setY().

QRect QRect::operator&(const QRect &r) const

QRect &QRect::operator&=(const QRect &r)

QRect &QRect::operator+=(const QMargins &margins)

QRect &QRect::operator-=(const QMargins &margins)

QRect QRect::operator|(const QRect &r) const

QRect &QRect::operator|=(const QRect &r)

Related Non-Members

bool operator!=(const QRect &r1, const QRect &r2)

Returns true if the rectangles r1 and r2 are different, otherwise returns false.

QRect operator+(const QRect &rectangle, const QMargins &margins)

Returns the rectangle grown by the margins.

This function was introduced in Qt 5.1.

QRect operator+(const QMargins &margins, const QRect &rectangle)

This is an overloaded function.

Returns the rectangle grown by the margins.

This function was introduced in Qt 5.1.

QRect operator-(const QRect &lhs, const QMargins &rhs)

Returns the lhs rectangle shrunken by the rhs margins.

This function was introduced in Qt 5.3.

QDataStream &operator<<(QDataStream &stream, const QRect &rectangle)

Writes the given rectangle to the given stream, and returns a reference to the stream.

See also Serializing Qt Data Types.

bool operator==(const QRect &r1, const QRect &r2)

Returns true if the rectangles r1 and r2 are equal, otherwise returns false.

QDataStream &operator>>(QDataStream &stream, QRect &rectangle)

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

See also Serializing Qt Data Types.