1/*
2 * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 *
8 * 1. Redistributions of source code must retain the above
9 *    copyright notice, this list of conditions and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above
12 *    copyright notice, this list of conditions and the following
13 *    disclaimer in the documentation and/or other materials
14 *    provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
19 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
20 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
21 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
23 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
25 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
27 * OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#include "config.h"
31#include "core/rendering/shapes/PolygonShape.h"
32
33#include "platform/geometry/LayoutPoint.h"
34#include "wtf/MathExtras.h"
35
36namespace blink {
37
38static inline FloatSize inwardEdgeNormal(const FloatPolygonEdge& edge)
39{
40    FloatSize edgeDelta = edge.vertex2() - edge.vertex1();
41    if (!edgeDelta.width())
42        return FloatSize((edgeDelta.height() > 0 ? -1 : 1), 0);
43    if (!edgeDelta.height())
44        return FloatSize(0, (edgeDelta.width() > 0 ? 1 : -1));
45    float edgeLength = edgeDelta.diagonalLength();
46    return FloatSize(-edgeDelta.height() / edgeLength, edgeDelta.width() / edgeLength);
47}
48
49static inline FloatSize outwardEdgeNormal(const FloatPolygonEdge& edge)
50{
51    return -inwardEdgeNormal(edge);
52}
53
54static inline bool overlapsYRange(const FloatRect& rect, float y1, float y2) { return !rect.isEmpty() && y2 >= y1 && y2 >= rect.y() && y1 <= rect.maxY(); }
55
56float OffsetPolygonEdge::xIntercept(float y) const
57{
58    ASSERT(y >= minY() && y <= maxY());
59
60    if (vertex1().y() == vertex2().y() || vertex1().x() == vertex2().x())
61        return minX();
62    if (y == minY())
63        return vertex1().y() < vertex2().y() ? vertex1().x() : vertex2().x();
64    if (y == maxY())
65        return vertex1().y() > vertex2().y() ? vertex1().x() : vertex2().x();
66
67    return vertex1().x() + ((y - vertex1().y()) * (vertex2().x() - vertex1().x()) / (vertex2().y() - vertex1().y()));
68}
69
70FloatShapeInterval OffsetPolygonEdge::clippedEdgeXRange(float y1, float y2) const
71{
72    if (!overlapsYRange(y1, y2) || (y1 == maxY() && minY() <= y1) || (y2 == minY() && maxY() >= y2))
73        return FloatShapeInterval();
74
75    if (isWithinYRange(y1, y2))
76        return FloatShapeInterval(minX(), maxX());
77
78    // Clip the edge line segment to the vertical range y1,y2 and then return
79    // the clipped line segment's horizontal range.
80
81    FloatPoint minYVertex;
82    FloatPoint maxYVertex;
83    if (vertex1().y() < vertex2().y()) {
84        minYVertex = vertex1();
85        maxYVertex = vertex2();
86    } else {
87        minYVertex = vertex2();
88        maxYVertex = vertex1();
89    }
90    float xForY1 = (minYVertex.y() < y1) ? xIntercept(y1) : minYVertex.x();
91    float xForY2 = (maxYVertex.y() > y2) ? xIntercept(y2) : maxYVertex.x();
92    return FloatShapeInterval(std::min(xForY1, xForY2), std::max(xForY1, xForY2));
93}
94
95static float circleXIntercept(float y, float radius)
96{
97    ASSERT(radius > 0);
98    return radius * sqrt(1 - (y * y) / (radius * radius));
99}
100
101static FloatShapeInterval clippedCircleXRange(const FloatPoint& center, float radius, float y1, float y2)
102{
103    if (y1 >= center.y() + radius || y2 <= center.y() - radius)
104        return FloatShapeInterval();
105
106    if (center.y() >= y1 && center.y() <= y2)
107        return FloatShapeInterval(center.x() - radius, center.x() + radius);
108
109    // Clip the circle to the vertical range y1,y2 and return the extent of the clipped circle's
110    // projection on the X axis
111
112    float xi =  circleXIntercept((y2 < center.y() ? y2 : y1) - center.y(), radius);
113    return FloatShapeInterval(center.x() - xi, center.x() + xi);
114}
115
116LayoutRect PolygonShape::shapeMarginLogicalBoundingBox() const
117{
118    FloatRect box = m_polygon.boundingBox();
119    box.inflate(shapeMargin());
120    return LayoutRect(box);
121}
122
123LineSegment PolygonShape::getExcludedInterval(LayoutUnit logicalTop, LayoutUnit logicalHeight) const
124{
125    float y1 = logicalTop.toFloat();
126    float y2 = logicalTop.toFloat() + logicalHeight.toFloat();
127
128    if (m_polygon.isEmpty() || !overlapsYRange(m_polygon.boundingBox(), y1 - shapeMargin(), y2 + shapeMargin()))
129        return LineSegment();
130
131    Vector<const FloatPolygonEdge*> overlappingEdges;
132    if (!m_polygon.overlappingEdges(y1 - shapeMargin(), y2 + shapeMargin(), overlappingEdges))
133        return LineSegment();
134
135    FloatShapeInterval excludedInterval;
136    for (unsigned i = 0; i < overlappingEdges.size(); i++) {
137        const FloatPolygonEdge& edge = *(overlappingEdges[i]);
138        if (edge.maxY() == edge.minY())
139            continue;
140        if (!shapeMargin()) {
141            excludedInterval.unite(OffsetPolygonEdge(edge, FloatSize()).clippedEdgeXRange(y1, y2));
142        } else {
143            excludedInterval.unite(OffsetPolygonEdge(edge, outwardEdgeNormal(edge) * shapeMargin()).clippedEdgeXRange(y1, y2));
144            excludedInterval.unite(OffsetPolygonEdge(edge, inwardEdgeNormal(edge) * shapeMargin()).clippedEdgeXRange(y1, y2));
145            excludedInterval.unite(clippedCircleXRange(edge.vertex1(), shapeMargin(), y1, y2));
146            excludedInterval.unite(clippedCircleXRange(edge.vertex2(), shapeMargin(), y1, y2));
147        }
148    }
149
150    if (excludedInterval.isEmpty())
151        return LineSegment();
152
153    return LineSegment(excludedInterval.x1(), excludedInterval.x2());
154}
155
156void PolygonShape::buildDisplayPaths(DisplayPaths& paths) const
157{
158    if (!m_polygon.numberOfVertices())
159        return;
160    paths.shape.moveTo(m_polygon.vertexAt(0));
161    for (size_t i = 1; i < m_polygon.numberOfVertices(); ++i)
162        paths.shape.addLineTo(m_polygon.vertexAt(i));
163    paths.shape.closeSubpath();
164}
165
166} // namespace blink
167