qline.cpp

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// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qline.h"
 
#include "qdebug.h"
#include "qdatastream.h"
#include "qmath.h"
#include <private/qnumeric_p.h>
 
QT_BEGIN_NAMESPACE
 
/*!
    \class QLine
    \inmodule QtCore
    \ingroup painting
    \compares equality
    \compareswith equality QLineF
    \endcompareswith
 
    \brief The QLine class provides a two-dimensional vector using
    integer precision.
 
    A QLine describes a finite length line (or a line segment) on a
    two-dimensional surface. The start and end points of the line are
    specified using integer point accuracy for coordinates. Use the
    QLineF constructor to retrieve a floating point copy.
 
    \table
    \row
        \li \inlineimage qline-point.png
        \li \inlineimage qline-coordinates.png
    \endtable
 
    The positions of the line's start and end points can be retrieved
    using the p1(), x1(), y1(), p2(), x2(), and y2() functions. The
    dx() and dy() functions return the horizontal and vertical
    components of the line. Use isNull() to determine whether the
    QLine represents a valid line or a null line.
 
    Finally, the line can be translated a given offset using the
    translate() function.
 
    \sa QLineF, QPolygon, QRect
*/
 
/*!
    \fn QLine::QLine()
 
    Constructs a null line.
*/
 
/*!
    \fn QLine::QLine(const QPoint &p1, const QPoint &p2)
 
    Constructs a line object that represents the line between \a p1 and
    \a p2.
*/
 
/*!
    \fn QLine::QLine(int x1, int y1, int x2, int y2)
 
    Constructs a line object that represents the line between (\a x1, \a y1) and
    (\a x2, \a y2).
*/
 
/*!
    \fn bool QLine::isNull() const
 
    Returns \c true if the line does not have distinct start and end points;
    otherwise returns \c false.
*/
 
/*!
    \fn QPoint QLine::p1() const
 
    Returns the line's start point.
 
    \sa x1(), y1(), p2()
*/
 
/*!
    \fn QPoint QLine::p2() const
 
    Returns the line's end point.
 
    \sa x2(), y2(), p1()
*/
 
/*!
    \fn int QLine::x1() const
 
    Returns the x-coordinate of the line's start point.
 
    \sa p1()
*/
 
/*!
    \fn int QLine::y1() const
 
    Returns the y-coordinate of the line's start point.
 
    \sa p1()
*/
 
/*!
    \fn int QLine::x2() const
 
    Returns the x-coordinate of the line's end point.
 
    \sa p2()
*/
 
/*!
    \fn int QLine::y2() const
 
    Returns the y-coordinate of the line's end point.
 
    \sa p2()
*/
 
/*!
    \fn int QLine::dx() const
 
    Returns the horizontal component of the line's vector.
 
    \sa dy()
*/
 
/*!
    \fn int QLine::dy() const
 
    Returns the vertical component of the line's vector.
 
    \sa dx()
*/
 
/*!
    \fn bool QLine::operator!=(const QLine &lhs, const QLine &rhs)
 
    Returns \c true if the line \a lhs is not the same as line \a rhs.
 
    A line is different from another line if any of their start or
    end points differ, or the internal order of the points is different.
*/
 
/*!
    \fn bool QLine::operator==(const QLine &lhs, const QLine &rhs)
 
    Returns \c true if the line \a lhs is the same as line \a rhs.
 
    A line is identical to another line if the start and end points
    are identical, and the internal order of the points is the same.
*/
 
/*!
    \fn void QLine::translate(const QPoint &offset)
 
    Translates this line by the given \a offset.
*/
 
/*!
    \fn void QLine::translate(int dx, int dy)
    \overload
 
    Translates this line the distance specified by \a dx and \a dy.
*/
 
/*!
    \fn QLine QLine::translated(const QPoint &offset) const
 
    \since 4.4
 
    Returns this line translated by the given \a offset.
*/
 
/*!
    \fn QLine QLine::translated(int dx, int dy) const
    \overload
    \since 4.4
 
    Returns this line translated the distance specified by \a dx and \a dy.
*/
 
/*!
    \fn QPoint QLine::center() const
 
    \since 5.8
 
    Returns the center point of this line. This is equivalent to
    (p1() + p2()) / 2, except it will never overflow.
*/
 
/*!
    \fn void QLine::setP1(const QPoint &p1)
    \since 4.4
 
    Sets the starting point of this line to \a p1.
 
    \sa setP2(), p1()
*/
 
 
/*!
    \fn void QLine::setP2(const QPoint &p2)
    \since 4.4
 
    Sets the end point of this line to \a p2.
 
    \sa setP1(), p2()
*/
 
 
/*!
    \fn void QLine::setPoints(const QPoint &p1, const QPoint &p2)
    \since 4.4
 
    Sets the start point of this line to \a p1 and the end point of this line to \a p2.
 
    \sa setP1(), setP2(), p1(), p2()
*/
 
 
/*!
    \fn void QLine::setLine(int x1, int y1, int x2, int y2)
    \since 4.4
 
    Sets this line to the start in \a x1, \a y1 and end in \a x2, \a y2.
 
    \sa setP1(), setP2(), p1(), p2()
*/
 
/*!
    \fn QLine::toLineF() const
    \since 6.4
 
    Returns this line as a line with floating point accuracy.
 
    \sa QLineF::toLine()
*/
 
 
 
#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug dbg, const QLine &p)
{
    QDebugStateSaver saver(dbg);
    dbg.nospace() << "QLine(" << p.p1() << ',' << p.p2() << ')';
    return dbg;
}
#endif
 
#ifndef QT_NO_DATASTREAM
/*!
    \relates QLine
 
    Writes the given \a line to the given \a stream and returns a
    reference to the stream.
 
    \sa {Serializing Qt Data Types}
*/
 
QDataStream &operator<<(QDataStream &stream, const QLine &line)
{
    stream << line.p1() << line.p2();
    return stream;
}
 
/*!
    \relates QLine
 
    Reads a line from the given \a stream into the given \a line and
    returns a reference to the stream.
 
    \sa {Serializing Qt Data Types}
*/
 
QDataStream &operator>>(QDataStream &stream, QLine &line)
{
    QPoint p1, p2;
    stream >> p1;
    stream >> p2;
    line = QLine(p1, p2);
 
    return stream;
}
 
#endif // QT_NO_DATASTREAM
 
/*!
    \class QLineF
    \inmodule QtCore
    \ingroup painting
    \compares equality
    \compareswith equality QLine
    \endcompareswith
 
    \brief The QLineF class provides a two-dimensional vector using
    floating point precision.
 
    A QLineF describes a finite length line (or line segment) on a
    two-dimensional surface. QLineF defines the start and end points
    of the line using floating point accuracy for coordinates.  Use
    the toLine() function to retrieve an integer-based copy of this
    line.
 
    \table
    \row
        \li \inlineimage qline-point.png
        \li \inlineimage qline-coordinates.png
    \endtable
 
    The positions of the line's start and end points can be retrieved
    using the p1(), x1(), y1(), p2(), x2(), and y2() functions. The
    dx() and dy() functions return the horizontal and vertical
    components of the line, respectively.
 
    The line's length can be retrieved using the length() function,
    and altered using the setLength() function.  Similarly, angle()
    and setAngle() are respectively used for retrieving and altering
    the angle of the line. Use the isNull()
    function to determine whether the QLineF represents a valid line
    or a null line.
 
    The intersects() function determines the IntersectionType for this
    line and a given line, while the angleTo() function returns the
    angle between the lines. In addition, the unitVector() function
    returns a line that has the same starting point as this line, but
    with a length of only 1, while the normalVector() function returns
    a line that is perpendicular to this line with the same starting
    point and length.
 
    Finally, the line can be translated a given offset using the
    translate() function, and can be traversed using the pointAt()
    function.
 
    \section1 Constraints
 
    QLine is limited to the minimum and maximum values for the
    \c int type. Operations on a QLine that could potentially result
    in values outside this range will result in undefined behavior.
 
    \sa QLine, QPolygonF, QRectF
*/
 
/*!
    \typealias QLineF::IntersectType
    \deprecated Use QLineF::IntersectionType instead.
*/
 
/*!
    \enum QLineF::IntersectionType
 
    Describes the intersection between two lines.
 
    \table
    \row
    \li \inlineimage qlinef-unbounded.png
    \li \inlineimage qlinef-bounded.png
    \row
    \li QLineF::UnboundedIntersection
    \li QLineF::BoundedIntersection
    \endtable
 
    \value NoIntersection Indicates that the lines do not intersect;
    i.e. they are parallel.
 
    \value UnboundedIntersection The two lines intersect, but not
    within the range defined by their lengths. This will be the case
    if the lines are not parallel. intersect() will also return this
    value if the intersect point is within the start and end point of
    only one of the lines.
 
    \value BoundedIntersection The two lines intersect with each other
    within the start and end points of each line.
 
    \sa intersects()
*/
 
/*!
    \fn QLineF::QLineF()
 
    Constructs a null line.
*/
 
/*!
    \fn QLineF::QLineF(const QPointF &p1, const QPointF &p2)
 
    Constructs a line object that represents the line between \a p1 and
    \a p2.
*/
 
/*!
    \fn QLineF::QLineF(qreal x1, qreal y1, qreal x2, qreal y2)
 
    Constructs a line object that represents the line between (\a x1, \a y1) and
    (\a x2, \a y2).
*/
 
/*!
    \fn QLineF::QLineF(const QLine &line)
 
    Construct a QLineF object from the given integer-based \a line.
 
    \sa toLine(), QLine::toLineF()
*/
 
/*!
    \fn bool QLineF::isNull() const
 
    Returns \c true if the line does not have distinct start and end points;
    otherwise returns \c false. The start and end points are considered distinct
    if qFuzzyCompare() can distinguish them in at least one coordinate.
 
    \note Due to the use of fuzzy comparison, isNull() may return \c true for
    lines whose length() is not zero.
 
    \sa qFuzzyCompare(), length()
*/
 
/*!
    \fn QPointF QLineF::p1() const
 
    Returns the line's start point.
 
    \sa x1(), y1(), p2()
*/
 
/*!
    \fn QPointF QLineF::p2() const
 
    Returns the line's end point.
 
    \sa x2(), y2(), p1()
*/
 
/*!
    \fn QLine QLineF::toLine() const
 
    Returns an integer-based copy of this line.
 
    Note that the returned line's start and end points are rounded to
    the nearest integer.
 
    \sa QLineF(), QLine::toLineF()
*/
/*!
    \fn qreal QLineF::x1() const
 
    Returns the x-coordinate of the line's start point.
 
    \sa p1()
*/
 
/*!
    \fn qreal QLineF::y1() const
 
    Returns the y-coordinate of the line's start point.
 
    \sa p1()
*/
 
/*!
    \fn qreal QLineF::x2() const
 
    Returns the x-coordinate of the line's end point.
 
    \sa p2()
*/
 
/*!
    \fn qreal QLineF::y2() const
 
    Returns the y-coordinate of the line's end point.
 
    \sa p2()
*/
 
/*!
    \fn qreal QLineF::dx() const
 
    Returns the horizontal component of the line's vector.
 
    \sa dy(), pointAt()
*/
 
/*!
    \fn qreal QLineF::dy() const
 
    Returns the vertical component of the line's vector.
 
    \sa dx(), pointAt()
*/
 
/*!
    \fn void QLineF::setLength(qreal length)
 
    Sets the length of the line to the given finite \a length. QLineF will move
    the end point - p2() - of the line to give the line its new length, unless
    length() was previously zero, in which case no scaling is attempted.
 
    \sa length(), unitVector()
*/
 
/*!
    \fn QLineF QLineF::normalVector() const
 
    Returns a line that is perpendicular to this line with the same starting
    point and length.
 
    \image qlinef-normalvector.png {Diagram showing two vectors with the same
           starting point: (v_x, v_y) and (vy, -vx).}
 
    \sa unitVector()
*/
 
/*!
    \fn bool QLineF::operator!=(const QLineF &lhs, const QLineF &rhs)
 
    Returns \c true if the line \a lhs is not the same as line \a rhs.
 
    A line is different from another line if their start or end points
    differ, or the internal order of the points is different.
*/
 
/*!
    \fn bool QLineF::operator==(const QLineF &lhs, const QLineF &rhs)
 
    Returns \c true if the line \a lhs is the same as line \a rhs.
 
    A line is identical to another line if the start and end points
    are identical, and the internal order of the points is the same.
*/
 
/*!
  \fn qreal QLineF::pointAt(qreal t) const
 
  Returns the point at the position specified by finite parameter \a t. The
  function returns the line's start point if t = 0, and its end point if t = 1.
 
  \sa dx(), dy()
*/
 
/*!
    Returns the length of the line.
 
    \sa setLength(), isNull()
*/
qreal QLineF::length() const
{
    return qHypot(dx(), dy());
}
 
/*!
    \since 4.4
 
    Returns the angle of the line in degrees.
 
    The return value will be in the range of values from 0.0 up to but not
    including 360.0. The angles are measured counter-clockwise from a point
    on the x-axis to the right of the origin (x > 0).
 
    \sa setAngle()
*/
qreal QLineF::angle() const
{
    const qreal dx = pt2.x() - pt1.x();
    const qreal dy = pt2.y() - pt1.y();
 
    const qreal theta = qRadiansToDegrees(qAtan2(-dy, dx));
 
    const qreal theta_normalized = theta < 0 ? theta + 360 : theta;
 
    if (qFuzzyCompare(theta_normalized, qreal(360)))
        return qreal(0);
    else
        return theta_normalized;
}
 
/*!
    \since 4.4
 
    Sets the angle of the line to the given \a angle (in degrees).
    This will change the position of the second point of the line such that
    the line has the given angle.
 
    Positive values for the angles mean counter-clockwise while negative values
    mean the clockwise direction. Zero degrees is at the 3 o'clock position.
 
    \sa angle()
*/
void QLineF::setAngle(qreal angle)
{
    const qreal angleR = qDegreesToRadians(angle);
    const qreal l = length();
 
    const qreal dx = qCos(angleR) * l;
    const qreal dy = -qSin(angleR) * l;
 
    pt2.rx() = pt1.x() + dx;
    pt2.ry() = pt1.y() + dy;
}
 
/*!
    \since 4.4
 
    Returns a QLineF with the given \a length and \a angle.
 
    The first point of the line will be on the origin.
 
    Positive values for the angles mean counter-clockwise while negative values
    mean the clockwise direction. Zero degrees is at the 3 o'clock position.
*/
QLineF QLineF::fromPolar(qreal length, qreal angle)
{
    const qreal angleR = qDegreesToRadians(angle);
    return QLineF(0, 0, qCos(angleR) * length, -qSin(angleR) * length);
}
 
/*!
    Returns the unit vector for this line, i.e a line starting at the
    same point as \e this line with a length of 1.0, provided the line
    is non-null.
 
    \sa normalVector(), setLength()
*/
QLineF QLineF::unitVector() const
{
    const qreal x = dx();
    const qreal y = dy();
 
    const qreal len = qHypot(x, y);
    QLineF f(p1(), QPointF(pt1.x() + x / len, pt1.y() + y / len));
 
#ifndef QT_NO_DEBUG
    if (qAbs(f.length() - 1) >= 0.001)
        qWarning("QLine::unitVector: New line does not have unit length");
#endif
 
    return f;
}
 
/*!
    \fn QLineF::IntersectionType QLineF::intersects(const QLineF &line, QPointF *intersectionPoint) const
    \since 5.14
 
    Returns a value indicating whether or not \e this line intersects
    with the given \a line.
 
    The actual intersection point is extracted to \a intersectionPoint
    (if the pointer is valid). If the lines are parallel, the
    intersection point is undefined.
*/
QLineF::IntersectionType QLineF::intersects(const QLineF &l, QPointF *intersectionPoint) const
{
    // ipmlementation is based on Graphics Gems III's "Faster Line Segment Intersection"
    const QPointF a = pt2 - pt1;
    const QPointF b = l.pt1 - l.pt2;
    const QPointF c = pt1 - l.pt1;
 
    const qreal denominator = a.y() * b.x() - a.x() * b.y();
    if (denominator == 0 || !qt_is_finite(denominator))
        return NoIntersection;
 
    const qreal reciprocal = 1 / denominator;
    const qreal na = (b.y() * c.x() - b.x() * c.y()) * reciprocal;
    if (intersectionPoint)
        *intersectionPoint = pt1 + a * na;
 
    if (na < 0 || na > 1)
        return UnboundedIntersection;
 
    const qreal nb = (a.x() * c.y() - a.y() * c.x()) * reciprocal;
    if (nb < 0 || nb > 1)
        return UnboundedIntersection;
 
    return BoundedIntersection;
}
 
/*!
    \fn void QLineF::translate(const QPointF &offset)
 
    Translates this line by the given \a offset.
*/
 
/*!
    \fn void QLineF::translate(qreal dx, qreal dy)
    \overload
 
    Translates this line the distance specified by \a dx and \a dy.
*/
 
/*!
    \fn QLineF QLineF::translated(const QPointF &offset) const
 
    \since 4.4
 
    Returns this line translated by the given \a offset.
*/
 
/*!
    \fn QLineF QLineF::translated(qreal dx, qreal dy) const
    \overload
    \since 4.4
 
    Returns this line translated the distance specified by \a dx and \a dy.
*/
 
/*!
    \fn QPointF QLineF::center() const
 
    \since 5.8
 
    Returns the center point of this line. This is equivalent to
    0.5 * p1() + 0.5 * p2().
*/
 
/*!
    \fn void QLineF::setP1(const QPointF &p1)
    \since 4.4
 
    Sets the starting point of this line to \a p1.
 
    \sa setP2(), p1()
*/
 
 
/*!
    \fn void QLineF::setP2(const QPointF &p2)
    \since 4.4
 
    Sets the end point of this line to \a p2.
 
    \sa setP1(), p2()
*/
 
 
/*!
    \fn void QLineF::setPoints(const QPointF &p1, const QPointF &p2)
    \since 4.4
 
    Sets the start point of this line to \a p1 and the end point of this line to \a p2.
 
    \sa setP1(), setP2(), p1(), p2()
*/
 
 
/*!
    \fn void QLineF::setLine(qreal x1, qreal y1, qreal x2, qreal y2)
    \since 4.4
 
    Sets this line to the start in \a x1, \a y1 and end in \a x2, \a y2.
 
    \sa setP1(), setP2(), p1(), p2()
*/
 
/*!
  \fn qreal QLineF::angleTo(const QLineF &line) const
 
  \since 4.4
 
  Returns the angle (in degrees) from this line to the given \a
  line, taking the direction of the lines into account. If the lines
  do not \l{intersects()}{intersect} within their range, it is the
  intersection point of the extended lines that serves as origin (see
  QLineF::UnboundedIntersection).
 
  The returned value represents the number of degrees you need to add
  to this line to make it have the same angle as the given \a line,
  going counter-clockwise.
 
  \sa intersects()
*/
qreal QLineF::angleTo(const QLineF &l) const
{
    if (isNull() || l.isNull())
        return 0;
 
    const qreal a1 = angle();
    const qreal a2 = l.angle();
 
    const qreal delta = a2 - a1;
    const qreal delta_normalized = delta < 0 ? delta + 360 : delta;
 
    if (qFuzzyCompare(delta, qreal(360)))
        return 0;
    else
        return delta_normalized;
}
 
/*!
    \fn bool QLineF::qFuzzyCompare(const QLineF &lhs, const QLineF &rhs)
    \since 6.8
 
    Returns \c true if line \a lhs is approximately equal to line \a rhs;
    otherwise returns \c false.
 
    The lines are considered approximately equal if their start and end
    points are approximately equal.
*/
 
/*!
    \fn bool QLineF::qFuzzyIsNull(const QLineF &line)
    \since 6.8
 
    Returns \c true if the start point of line \a line is approximately
    equal to its end point; otherwise returns \c false.
*/
 
#ifndef QT_NO_DEBUG_STREAM
QDebug operator<<(QDebug dbg, const QLineF &p)
{
    QDebugStateSaver saver(dbg);
    dbg.nospace() << "QLineF(" << p.p1() << ',' << p.p2() << ')';
    return dbg;
}
#endif
 
#ifndef QT_NO_DATASTREAM
/*!
    \relates QLineF
 
    Writes the given \a line to the given \a stream and returns a
    reference to the stream.
 
    \sa {Serializing Qt Data Types}
*/
 
QDataStream &operator<<(QDataStream &stream, const QLineF &line)
{
    stream << line.p1() << line.p2();
    return stream;
}
 
/*!
    \relates QLineF
 
    Reads a line from the given \a stream into the given \a line and
    returns a reference to the stream.
 
    \sa {Serializing Qt Data Types}
*/
 
QDataStream &operator>>(QDataStream &stream, QLineF &line)
{
    QPointF start, end;
    stream >> start;
    stream >> end;
    line = QLineF(start, end);
 
    return stream;
}
 
#endif // QT_NO_DATASTREAM
 
QT_END_NAMESPACE