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49 // This file is not part of the Qt API. It exists for the convenience
50 // of other Qt classes. This header file may change from version to
51 // version without notice, or even be removed.
56 #include "QtCore/qpoint.h"
57 #include "QtCore/qline.h"
58 #include "QtCore/qrect.h"
59 #include "QtCore/qvector.h"
60 #include "QtCore/qlist.h"
61 #include "QtCore/qpair.h"
62 #include "QtGui/qtransform.h"
63 #include <private/qdatabuffer_p.h>
69 class Q_GUI_EXPORT QBezier
72 static QBezier fromPoints(const QPointF &p1, const QPointF &p2,
73 const QPointF &p3, const QPointF &p4);
75 static void coefficients(qreal t, qreal &a, qreal &b, qreal &c, qreal &d);
77 inline QPointF pointAt(qreal t) const;
78 inline QPointF normalVector(qreal t) const;
80 inline QPointF derivedAt(qreal t) const;
81 inline QPointF secondDerivedAt(qreal t) const;
83 QPolygonF toPolygon(qreal bezier_flattening_threshold = 0.5) const;
84 void addToPolygon(QPolygonF *p, qreal bezier_flattening_threshold = 0.5) const;
85 void addToPolygon(QDataBuffer<QPointF> &polygon, qreal bezier_flattening_threshold) const;
87 QRectF bounds() const;
88 qreal length(qreal error = 0.01) const;
89 void addIfClose(qreal *length, qreal error) const;
91 qreal tAtLength(qreal len) const;
93 int stationaryYPoints(qreal &t0, qreal &t1) const;
94 qreal tForY(qreal t0, qreal t1, qreal y) const;
96 QPointF pt1() const { return QPointF(x1, y1); }
97 QPointF pt2() const { return QPointF(x2, y2); }
98 QPointF pt3() const { return QPointF(x3, y3); }
99 QPointF pt4() const { return QPointF(x4, y4); }
101 QBezier mapBy(const QTransform &transform) const;
103 inline QPointF midPoint() const;
104 inline QLineF midTangent() const;
106 inline QLineF startTangent() const;
107 inline QLineF endTangent() const;
109 inline void parameterSplitLeft(qreal t, QBezier *left);
110 inline void split(QBezier *firstHalf, QBezier *secondHalf) const;
112 int shifted(QBezier *curveSegments, int maxSegmets,
113 qreal offset, float threshold) const;
115 QBezier bezierOnInterval(qreal t0, qreal t1) const;
116 QBezier getSubRange(qreal t0, qreal t1) const;
118 qreal x1, y1, x2, y2, x3, y3, x4, y4;
121 inline QPointF QBezier::midPoint() const
123 return QPointF((x1 + x4 + 3*(x2 + x3))/8., (y1 + y4 + 3*(y2 + y3))/8.);
126 inline QLineF QBezier::midTangent() const
128 QPointF mid = midPoint();
129 QLineF dir(QLineF(x1, y1, x2, y2).pointAt(0.5), QLineF(x3, y3, x4, y4).pointAt(0.5));
130 return QLineF(mid.x() - dir.dx(), mid.y() - dir.dy(),
131 mid.x() + dir.dx(), mid.y() + dir.dy());
134 inline QLineF QBezier::startTangent() const
136 QLineF tangent(pt1(), pt2());
137 if (tangent.isNull())
138 tangent = QLineF(pt1(), pt3());
139 if (tangent.isNull())
140 tangent = QLineF(pt1(), pt4());
144 inline QLineF QBezier::endTangent() const
146 QLineF tangent(pt4(), pt3());
147 if (tangent.isNull())
148 tangent = QLineF(pt4(), pt2());
149 if (tangent.isNull())
150 tangent = QLineF(pt4(), pt1());
154 inline void QBezier::coefficients(qreal t, qreal &a, qreal &b, qreal &c, qreal &d)
165 inline QPointF QBezier::pointAt(qreal t) const
167 // numerically more stable:
172 qreal a = x1*m_t + x2*t;
173 qreal b = x2*m_t + x3*t;
174 qreal c = x3*m_t + x4*t;
180 qreal a = y1*m_t + y2*t;
181 qreal b = y2*m_t + y3*t;
182 qreal c = y3*m_t + y4*t;
187 return QPointF(x, y);
190 inline QPointF QBezier::normalVector(qreal t) const
197 return QPointF((y2-y1) * a + (y3-y2) * b + (y4-y3) * c, -(x2-x1) * a - (x3-x2) * b - (x4-x3) * c);
200 inline QPointF QBezier::derivedAt(qreal t) const
202 // p'(t) = 3 * (-(1-2t+t^2) * p0 + (1 - 4 * t + 3 * t^2) * p1 + (2 * t - 3 * t^2) * p2 + t^2 * p3)
207 qreal a = -m_t * m_t;
208 qreal b = 1 - 4 * t + 3 * d;
209 qreal c = 2 * t - 3 * d;
211 return 3 * QPointF(a * x1 + b * x2 + c * x3 + d * x4,
212 a * y1 + b * y2 + c * y3 + d * y4);
215 inline QPointF QBezier::secondDerivedAt(qreal t) const
217 qreal a = 2. - 2. * t;
218 qreal b = -4 + 6 * t;
222 return 3 * QPointF(a * x1 + b * x2 + c * x3 + d * x4,
223 a * y1 + b * y2 + c * y3 + d * y4);
226 inline void QBezier::split(QBezier *firstHalf, QBezier *secondHalf) const
229 Q_ASSERT(secondHalf);
231 qreal c = (x2 + x3)*.5;
232 firstHalf->x2 = (x1 + x2)*.5;
233 secondHalf->x3 = (x3 + x4)*.5;
236 firstHalf->x3 = (firstHalf->x2 + c)*.5;
237 secondHalf->x2 = (secondHalf->x3 + c)*.5;
238 firstHalf->x4 = secondHalf->x1 = (firstHalf->x3 + secondHalf->x2)*.5;
241 firstHalf->y2 = (y1 + y2)*.5;
242 secondHalf->y3 = (y3 + y4)*.5;
245 firstHalf->y3 = (firstHalf->y2 + c)*.5;
246 secondHalf->y2 = (secondHalf->y3 + c)*.5;
247 firstHalf->y4 = secondHalf->y1 = (firstHalf->y3 + secondHalf->y2)*.5;
250 inline void QBezier::parameterSplitLeft(qreal t, QBezier *left)
255 left->x2 = x1 + t * ( x2 - x1 );
256 left->y2 = y1 + t * ( y2 - y1 );
258 left->x3 = x2 + t * ( x3 - x2 ); // temporary holding spot
259 left->y3 = y2 + t * ( y3 - y2 ); // temporary holding spot
261 x3 = x3 + t * ( x4 - x3 );
262 y3 = y3 + t * ( y4 - y3 );
264 x2 = left->x3 + t * ( x3 - left->x3);
265 y2 = left->y3 + t * ( y3 - left->y3);
267 left->x3 = left->x2 + t * ( left->x3 - left->x2 );
268 left->y3 = left->y2 + t * ( left->y3 - left->y2 );
270 left->x4 = x1 = left->x3 + t * (x2 - left->x3);
271 left->y4 = y1 = left->y3 + t * (y2 - left->y3);
276 #endif // QBEZIER_P_H