1 /*
2 * Copyright (C) 2006, 2007 Eric Seidel <eric@webkit.org>
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public License
15 * along with this library; see the file COPYING.LIB. If not, write to
16 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
17 * Boston, MA 02110-1301, USA.
18 */
19
20 #include "config.h"
21 #include "platform/graphics/PathTraversalState.h"
22
23 #include "wtf/MathExtras.h"
24 #include "wtf/Vector.h"
25
26 namespace blink {
27
midPoint(const FloatPoint & first,const FloatPoint & second)28 static inline FloatPoint midPoint(const FloatPoint& first, const FloatPoint& second)
29 {
30 return FloatPoint((first.x() + second.x()) / 2.0f, (first.y() + second.y()) / 2.0f);
31 }
32
distanceLine(const FloatPoint & start,const FloatPoint & end)33 static inline float distanceLine(const FloatPoint& start, const FloatPoint& end)
34 {
35 return sqrtf((end.x() - start.x()) * (end.x() - start.x()) + (end.y() - start.y()) * (end.y() - start.y()));
36 }
37
38 struct QuadraticBezier {
QuadraticBezierblink::QuadraticBezier39 QuadraticBezier() { }
QuadraticBezierblink::QuadraticBezier40 QuadraticBezier(const FloatPoint& s, const FloatPoint& c, const FloatPoint& e)
41 : start(s)
42 , control(c)
43 , end(e)
44 , splitDepth(0)
45 {
46 }
47
magnitudeSquaredblink::QuadraticBezier48 double magnitudeSquared() const
49 {
50 return ((double)(start.dot(start)) + (double)(control.dot(control)) + (double)(end.dot(end))) / 9.0;
51 }
52
approximateDistanceblink::QuadraticBezier53 float approximateDistance() const
54 {
55 return distanceLine(start, control) + distanceLine(control, end);
56 }
57
splitblink::QuadraticBezier58 void split(QuadraticBezier& left, QuadraticBezier& right) const
59 {
60 left.control = midPoint(start, control);
61 right.control = midPoint(control, end);
62
63 FloatPoint leftControlToRightControl = midPoint(left.control, right.control);
64 left.end = leftControlToRightControl;
65 right.start = leftControlToRightControl;
66
67 left.start = start;
68 right.end = end;
69
70 left.splitDepth = right.splitDepth = splitDepth + 1;
71 }
72
73 FloatPoint start;
74 FloatPoint control;
75 FloatPoint end;
76 unsigned short splitDepth;
77 };
78
79 struct CubicBezier {
CubicBezierblink::CubicBezier80 CubicBezier() { }
CubicBezierblink::CubicBezier81 CubicBezier(const FloatPoint& s, const FloatPoint& c1, const FloatPoint& c2, const FloatPoint& e)
82 : start(s)
83 , control1(c1)
84 , control2(c2)
85 , end(e)
86 , splitDepth(0)
87 {
88 }
89
magnitudeSquaredblink::CubicBezier90 double magnitudeSquared() const
91 {
92 return ((double)(start.dot(start)) + (double)(control1.dot(control1)) + (double)(control2.dot(control2)) + (double)(end.dot(end))) / 16.0;
93 }
94
approximateDistanceblink::CubicBezier95 float approximateDistance() const
96 {
97 return distanceLine(start, control1) + distanceLine(control1, control2) + distanceLine(control2, end);
98 }
99
splitblink::CubicBezier100 void split(CubicBezier& left, CubicBezier& right) const
101 {
102 FloatPoint startToControl1 = midPoint(control1, control2);
103
104 left.start = start;
105 left.control1 = midPoint(start, control1);
106 left.control2 = midPoint(left.control1, startToControl1);
107
108 right.control2 = midPoint(control2, end);
109 right.control1 = midPoint(right.control2, startToControl1);
110 right.end = end;
111
112 FloatPoint leftControl2ToRightControl1 = midPoint(left.control2, right.control1);
113 left.end = leftControl2ToRightControl1;
114 right.start = leftControl2ToRightControl1;
115
116 left.splitDepth = right.splitDepth = splitDepth + 1;
117 }
118
119 FloatPoint start;
120 FloatPoint control1;
121 FloatPoint control2;
122 FloatPoint end;
123 unsigned short splitDepth;
124 };
125
126 template<class CurveType>
curveLength(PathTraversalState & traversalState,CurveType curve)127 static float curveLength(PathTraversalState& traversalState, CurveType curve)
128 {
129 static const unsigned short curveSplitDepthLimit = 20;
130 static const double pathSegmentLengthToleranceSquared = 1.e-16;
131
132 double curveScaleForToleranceSquared = curve.magnitudeSquared();
133 if (curveScaleForToleranceSquared < pathSegmentLengthToleranceSquared)
134 return 0;
135
136 Vector<CurveType> curveStack;
137 curveStack.append(curve);
138
139 float totalLength = 0;
140 do {
141 float length = curve.approximateDistance();
142 double lengthDiscrepancy = length - distanceLine(curve.start, curve.end);
143 if ((lengthDiscrepancy * lengthDiscrepancy) / curveScaleForToleranceSquared > pathSegmentLengthToleranceSquared && curve.splitDepth < curveSplitDepthLimit) {
144 CurveType leftCurve;
145 CurveType rightCurve;
146 curve.split(leftCurve, rightCurve);
147 curve = leftCurve;
148 curveStack.append(rightCurve);
149 } else {
150 totalLength += length;
151 if (traversalState.m_action == PathTraversalState::TraversalPointAtLength || traversalState.m_action == PathTraversalState::TraversalNormalAngleAtLength) {
152 traversalState.m_previous = curve.start;
153 traversalState.m_current = curve.end;
154 if (traversalState.m_totalLength + totalLength > traversalState.m_desiredLength)
155 return totalLength;
156 }
157 curve = curveStack.last();
158 curveStack.removeLast();
159 }
160 } while (!curveStack.isEmpty());
161
162 return totalLength;
163 }
164
PathTraversalState(PathTraversalAction action)165 PathTraversalState::PathTraversalState(PathTraversalAction action)
166 : m_action(action)
167 , m_success(false)
168 , m_totalLength(0)
169 , m_segmentIndex(0)
170 , m_desiredLength(0)
171 , m_normalAngle(0)
172 {
173 }
174
closeSubpath()175 float PathTraversalState::closeSubpath()
176 {
177 float distance = distanceLine(m_current, m_start);
178 m_current = m_start;
179 return distance;
180 }
181
moveTo(const FloatPoint & point)182 float PathTraversalState::moveTo(const FloatPoint& point)
183 {
184 m_current = m_start = point;
185 return 0;
186 }
187
lineTo(const FloatPoint & point)188 float PathTraversalState::lineTo(const FloatPoint& point)
189 {
190 float distance = distanceLine(m_current, point);
191 m_current = point;
192 return distance;
193 }
194
quadraticBezierTo(const FloatPoint & newControl,const FloatPoint & newEnd)195 float PathTraversalState::quadraticBezierTo(const FloatPoint& newControl, const FloatPoint& newEnd)
196 {
197 float distance = curveLength<QuadraticBezier>(*this, QuadraticBezier(m_current, newControl, newEnd));
198
199 if (m_action != TraversalPointAtLength && m_action != TraversalNormalAngleAtLength)
200 m_current = newEnd;
201
202 return distance;
203 }
204
cubicBezierTo(const FloatPoint & newControl1,const FloatPoint & newControl2,const FloatPoint & newEnd)205 float PathTraversalState::cubicBezierTo(const FloatPoint& newControl1, const FloatPoint& newControl2, const FloatPoint& newEnd)
206 {
207 float distance = curveLength<CubicBezier>(*this, CubicBezier(m_current, newControl1, newControl2, newEnd));
208
209 if (m_action != TraversalPointAtLength && m_action != TraversalNormalAngleAtLength)
210 m_current = newEnd;
211
212 return distance;
213 }
214
processSegment()215 void PathTraversalState::processSegment()
216 {
217 if (m_action == TraversalSegmentAtLength && m_totalLength >= m_desiredLength)
218 m_success = true;
219
220 if ((m_action == TraversalPointAtLength || m_action == TraversalNormalAngleAtLength) && m_totalLength >= m_desiredLength) {
221 float slope = FloatPoint(m_current - m_previous).slopeAngleRadians();
222 if (m_action == TraversalPointAtLength) {
223 float offset = m_desiredLength - m_totalLength;
224 m_current.move(offset * cosf(slope), offset * sinf(slope));
225 } else {
226 m_normalAngle = rad2deg(slope);
227 }
228 m_success = true;
229 }
230 m_previous = m_current;
231 }
232
233 } // namespace blink
234
235