SkIntersectionHelper.h revision dac1d17027dcaa5596885a9f333979418b35001c
1/*
2 * Copyright 2012 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7#include "SkOpContour.h"
8#include "SkPath.h"
9
10#ifdef SK_DEBUG
11#include "SkPathOpsPoint.h"
12#endif
13
14class SkIntersectionHelper {
15public:
16    enum SegmentType {
17        kHorizontalLine_Segment = -1,
18        kVerticalLine_Segment = 0,
19        kLine_Segment = SkPath::kLine_Verb,
20        kQuad_Segment = SkPath::kQuad_Verb,
21        kCubic_Segment = SkPath::kCubic_Verb,
22    };
23
24    bool addCoincident(SkIntersectionHelper& other, const SkIntersections& ts, bool swap) {
25        return fContour->addCoincident(fIndex, other.fContour, other.fIndex, ts, swap);
26    }
27
28    // FIXME: does it make sense to write otherIndex now if we're going to
29    // fix it up later?
30    void addOtherT(int index, double otherT, int otherIndex) {
31        fContour->addOtherT(fIndex, index, otherT, otherIndex);
32    }
33
34    bool addPartialCoincident(SkIntersectionHelper& other, const SkIntersections& ts, int index,
35            bool swap) {
36        return fContour->addPartialCoincident(fIndex, other.fContour, other.fIndex, ts, index,
37                swap);
38    }
39
40    // Avoid collapsing t values that are close to the same since
41    // we walk ts to describe consecutive intersections. Since a pair of ts can
42    // be nearly equal, any problems caused by this should be taken care
43    // of later.
44    // On the edge or out of range values are negative; add 2 to get end
45    int addT(const SkIntersectionHelper& other, const SkPoint& pt, double newT) {
46        return fContour->addT(fIndex, other.fContour, other.fIndex, pt, newT);
47    }
48
49    int addSelfT(const SkPoint& pt, double newT) {
50        return fContour->addSelfT(fIndex, pt, newT);
51    }
52
53    bool advance() {
54        return ++fIndex < fLast;
55    }
56
57    void alignTPt(SkIntersectionHelper& other, bool swap, int index,
58            SkIntersections* ts, SkPoint* point) {
59        fContour->alignTPt(fIndex, other.fContour, other.fIndex, swap, index, ts, point);
60    }
61
62    SkScalar bottom() const {
63        return bounds().fBottom;
64    }
65
66    const SkPathOpsBounds& bounds() const {
67        return fContour->segments()[fIndex].bounds();
68    }
69
70    void init(SkOpContour* contour) {
71        fContour = contour;
72        fIndex = 0;
73        fLast = contour->segments().count();
74    }
75
76    bool isAdjacent(const SkIntersectionHelper& next) {
77        return fContour == next.fContour && fIndex + 1 == next.fIndex;
78    }
79
80    bool isFirstLast(const SkIntersectionHelper& next) {
81        return fContour == next.fContour && fIndex == 0
82                && next.fIndex == fLast - 1;
83    }
84
85    bool isPartial(double t1, double t2, const SkDPoint& pt1, const SkDPoint& pt2) const {
86        const SkOpSegment& segment = fContour->segments()[fIndex];
87        double mid = (t1 + t2) / 2;
88        SkDPoint midPtByT = segment.dPtAtT(mid);
89        SkDPoint midPtByAvg = SkDPoint::Mid(pt1, pt2);
90        return midPtByT.approximatelyPEqual(midPtByAvg);
91    }
92
93    SkScalar left() const {
94        return bounds().fLeft;
95    }
96
97    const SkPoint* pts() const {
98        return fContour->segments()[fIndex].pts();
99    }
100
101    SkScalar right() const {
102        return bounds().fRight;
103    }
104
105    SegmentType segmentType() const {
106        const SkOpSegment& segment = fContour->segments()[fIndex];
107        SegmentType type = (SegmentType) segment.verb();
108        if (type != kLine_Segment) {
109            return type;
110        }
111        if (segment.isHorizontal()) {
112            return kHorizontalLine_Segment;
113        }
114        if (segment.isVertical()) {
115            return kVerticalLine_Segment;
116        }
117        return kLine_Segment;
118    }
119
120    bool startAfter(const SkIntersectionHelper& after) {
121        fIndex = after.fIndex;
122        return advance();
123    }
124
125    SkScalar top() const {
126        return bounds().fTop;
127    }
128
129    SkPath::Verb verb() const {
130        return fContour->segments()[fIndex].verb();
131    }
132
133    SkScalar x() const {
134        return bounds().fLeft;
135    }
136
137    bool xFlipped() const {
138        return x() != pts()[0].fX;
139    }
140
141    SkScalar y() const {
142        return bounds().fTop;
143    }
144
145    bool yFlipped() const {
146        return y() != pts()[0].fY;
147    }
148
149private:
150    // utility callable by the user from the debugger when the implementation code is linked in
151    void dump() const;
152
153    SkOpContour* fContour;
154    int fIndex;
155    int fLast;
156};
157