Detailed Description
The QPoint class defines a point in the plane.
A point is specified by an x coordinate and a y coordinate.
The coordinate type is QCOORD (a 32-bit integer). The minimum
value of QCOORD is QCOORD_MIN (-2147483648) and the maximum
value is QCOORD_MAX (2147483647).
The coordinates are accessed by the functions x() and y(); they
can be set by setX() and setY() or by the reference functions rx()
and ry().
Given a point p, the following statements are all equivalent:
p.setX( p.x() + 1 );
p += QPoint( 1, 0 );
p.rx()++;
A QPoint can also be used as a vector. Addition and subtraction
of QPoints are defined as for vectors (each component is added
separately). You can divide or multiply a QPoint by an int or a
double. The function manhattanLength() gives an inexpensive
approximation of the length of the QPoint interpreted as a vector.
Example:
//QPoint oldPos is defined somewhere else
MyWidget::mouseMoveEvent( QMouseEvent *e )
{
QPoint vector = e->pos() - oldPos;
if ( vector.manhattanLength() > 3 )
... //mouse has moved more than 3 pixels since oldPos
}
QPoints can be compared for equality or inequality, and they can
be written to and read from a QStream.
See also QPointArray, QSize, QRect, Graphics Classes, and Image Processing Classes.
Member Function Documentation
QPoint::QPoint ()
Constructs a point with coordinates (0, 0) (isNull() returns TRUE).
QPoint::QPoint ( int xpos, int ypos )
Constructs a point with x value xpos and y value ypos.
bool QPoint::isNull () const
Returns TRUE if both the x value and the y value are 0; otherwise
returns FALSE.
int QPoint::manhattanLength () const
Returns the sum of the absolute values of x() and y(),
traditionally known as the "Manhattan length" of the vector from
the origin to the point. The tradition arises because such
distances apply to travelers who can only travel on a rectangular
grid, like the streets of Manhattan.
This is a useful, and quick to calculate, approximation to the
true length: sqrt(pow(x(),2)+pow(y(),2)).
QPoint & QPoint::operator*= ( int c )
Multiplies this point's x and y by c, and returns a reference
to this point.
Example:
QPoint p( -1, 4 );
p *= 2; // p becomes (-2,8)
QPoint & QPoint::operator*= ( double c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Multiplies this point's x and y by c, and returns a reference
to this point.
Example:
QPoint p( -1, 4 );
p *= 2.5; // p becomes (-3,10)
Note that the result is truncated because points are held as
integers.
QPoint & QPoint::operator+= ( const QPoint & p )
Adds point p to this point and returns a reference to this
point.
Example:
QPoint p( 3, 7 );
QPoint q( -1, 4 );
p += q; // p becomes (2,11)
QPoint & QPoint::operator-= ( const QPoint & p )
Subtracts point p from this point and returns a reference to
this point.
Example:
QPoint p( 3, 7 );
QPoint q( -1, 4 );
p -= q; // p becomes (4,3)
QPoint & QPoint::operator/= ( int c )
Divides both x and y by c, and returns a reference to this
point.
Example:
QPoint p( -2, 8 );
p /= 2; // p becomes (-1,4)
QPoint & QPoint::operator/= ( double c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Divides both x and y by c, and returns a reference to this
point.
Example:
QPoint p( -3, 10 );
p /= 2.5; // p becomes (-1,4)
Note that the result is truncated because points are held as
integers.
QCOORD & QPoint::rx ()
Returns a reference to the x coordinate of the point.
Using a reference makes it possible to directly manipulate x.
Example:
QPoint p( 1, 2 );
p.rx()--; // p becomes (0, 2)
See also ry().
QCOORD & QPoint::ry ()
Returns a reference to the y coordinate of the point.
Using a reference makes it possible to directly manipulate y.
Example:
QPoint p( 1, 2 );
p.ry()++; // p becomes (1, 3)
See also rx().
void QPoint::setX ( int x )
Sets the x coordinate of the point to x.
See also x() and setY().
Example: t14/cannon.cpp.
void QPoint::setY ( int y )
Sets the y coordinate of the point to y.
See also y() and setX().
Example: t14/cannon.cpp.
int QPoint::x () const
Returns the x coordinate of the point.
See also setX() and y().
Examples: canvas/canvas.cpp, chart/canvasview.cpp, dirview/dirview.cpp, fileiconview/qfileiconview.cpp, helpsystem/tooltip.cpp, life/life.cpp, and t14/cannon.cpp.
int QPoint::y () const
Returns the y coordinate of the point.
See also setY() and x().
Examples: canvas/canvas.cpp, chart/canvasview.cpp, fileiconview/qfileiconview.cpp, helpsystem/tooltip.cpp, life/life.cpp, t14/cannon.cpp, and themes/wood.cpp.
Related Functions
bool operator!= ( const QPoint & p1, const QPoint & p2 )
Returns TRUE if p1 and p2 are not equal; otherwise returns FALSE.
const QPoint operator* ( const QPoint & p, int c )
Returns the QPoint formed by multiplying both components of p
by c.
const QPoint operator* ( int c, const QPoint & p )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the QPoint formed by multiplying both components of p
by c.
const QPoint operator* ( const QPoint & p, double c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the QPoint formed by multiplying both components of p
by c.
Note that the result is truncated because points are held as
integers.
const QPoint operator* ( double c, const QPoint & p )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the QPoint formed by multiplying both components of p
by c.
Note that the result is truncated because points are held as
integers.
const QPoint operator+ ( const QPoint & p1, const QPoint & p2 )
Returns the sum of p1 and p2; each component is added separately.
const QPoint operator- ( const QPoint & p1, const QPoint & p2 )
Returns p2 subtracted from p1; each component is subtracted
separately.
const QPoint operator- ( const QPoint & p )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the QPoint formed by changing the sign of both components
of p, equivalent to QPoint(0,0) - p.
const QPoint operator/ ( const QPoint & p, int c )
Returns the QPoint formed by dividing both components of p by
c.
const QPoint operator/ ( const QPoint & p, double c )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Returns the QPoint formed by dividing both components of p
by c.
Note that the result is truncated because points are held as
integers.
Writes point p to the stream s and returns a reference to
the stream.
See also Format of the QDataStream operators.
bool operator== ( const QPoint & p1, const QPoint & p2 )
Returns TRUE if p1 and p2 are equal; otherwise returns FALSE.
Reads a QPoint from the stream s into point p and returns a
reference to the stream.
See also Format of the QDataStream operators.
This file is part of the Qt toolkit.
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