aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/pathops/SkPathOpsWinding.cpp
blob: 48993a69c2732e84f3c2f492e59c3e167259051f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
/*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

// given a prospective edge, compute its initial winding by projecting a ray
// if the ray hits another edge
    // if the edge doesn't have a winding yet, hop up to that edge and start over
        // concern : check for hops forming a loop
    // if the edge is unsortable, or
    // the intersection is nearly at the ends, or
    // the tangent at the intersection is nearly coincident to the ray,
        // choose a different ray and try again
            // concern : if it is unable to succeed after N tries, try another edge? direction?
// if no edge is hit, compute the winding directly

// given the top span, project the most perpendicular ray and look for intersections
    // let's try up and then down. What the hey

// bestXY is initialized by caller with basePt

#include "SkOpContour.h"
#include "SkOpSegment.h"
#include "SkPathOpsCurve.h"

enum class SkOpRayDir {
    kLeft,
    kTop,
    kRight,
    kBottom,
};

#if DEBUG_WINDING
const char* gDebugRayDirName[] = {
    "kLeft",
    "kTop",
    "kRight",
    "kBottom"
};
#endif

static int xy_index(SkOpRayDir dir) {
    return static_cast<int>(dir) & 1;
}

static SkScalar pt_xy(const SkPoint& pt, SkOpRayDir dir) {
    return (&pt.fX)[xy_index(dir)];
}

static SkScalar pt_yx(const SkPoint& pt, SkOpRayDir dir) {
    return (&pt.fX)[!xy_index(dir)];
}

static double pt_dxdy(const SkDVector& v, SkOpRayDir dir) {
    return (&v.fX)[xy_index(dir)];
}

static double pt_dydx(const SkDVector& v, SkOpRayDir dir) {
    return (&v.fX)[!xy_index(dir)];
}

static SkScalar rect_side(const SkRect& r, SkOpRayDir dir) {
    return (&r.fLeft)[static_cast<int>(dir)];
}

static bool sideways_overlap(const SkRect& rect, const SkPoint& pt, SkOpRayDir dir) {
    int i = !xy_index(dir);
    return approximately_between((&rect.fLeft)[i], (&pt.fX)[i], (&rect.fRight)[i]);
}

static bool less_than(SkOpRayDir dir) {
    return static_cast<bool>((static_cast<int>(dir) & 2) == 0);
}

static bool ccw_dxdy(const SkDVector& v, SkOpRayDir dir) {
    bool vPartPos = pt_dydx(v, dir) > 0;
    bool leftBottom = ((static_cast<int>(dir) + 1) & 2) != 0;
    return vPartPos == leftBottom;
}

struct SkOpRayHit {
    SkOpRayDir makeTestBase(SkOpSpan* span, double t) {
        fNext = nullptr;
        fSpan = span;
        fT = span->t() * (1 - t) + span->next()->t() * t;
        SkOpSegment* segment = span->segment();
        fSlope = segment->dSlopeAtT(fT);
        fPt = segment->ptAtT(fT);
        fValid = true;
        return fabs(fSlope.fX) < fabs(fSlope.fY) ? SkOpRayDir::kLeft : SkOpRayDir::kTop;
    }

    SkOpRayHit* fNext;
    SkOpSpan* fSpan;
    SkPoint fPt;
    double fT;
    SkDVector fSlope;
    bool fValid;
};

void SkOpContour::rayCheck(const SkOpRayHit& base, SkOpRayDir dir, SkOpRayHit** hits,
                           SkArenaAlloc* allocator) {
    // if the bounds extreme is outside the best, we're done
    SkScalar baseXY = pt_xy(base.fPt, dir);
    SkScalar boundsXY = rect_side(fBounds, dir);
    bool checkLessThan = less_than(dir);
    if (!approximately_equal(baseXY, boundsXY) && (baseXY < boundsXY) == checkLessThan) {
        return;
    }
    SkOpSegment* testSegment = &fHead;
    do {
        testSegment->rayCheck(base, dir, hits, allocator);
    } while ((testSegment = testSegment->next()));
}

void SkOpSegment::rayCheck(const SkOpRayHit& base, SkOpRayDir dir, SkOpRayHit** hits,
                           SkArenaAlloc* allocator) {
    if (!sideways_overlap(fBounds, base.fPt, dir)) {
        return;
    }
    SkScalar baseXY = pt_xy(base.fPt, dir);
    SkScalar boundsXY = rect_side(fBounds, dir);
    bool checkLessThan = less_than(dir);
    if (!approximately_equal(baseXY, boundsXY) && (baseXY < boundsXY) == checkLessThan) {
        return;
    }
    double tVals[3];
    SkScalar baseYX = pt_yx(base.fPt, dir);
    int roots = (*CurveIntercept[fVerb * 2 + xy_index(dir)])(fPts, fWeight, baseYX, tVals);
    for (int index = 0; index < roots; ++index) {
        double t = tVals[index];
        if (base.fSpan->segment() == this && approximately_equal(base.fT, t)) {
            continue;
        }
        SkDVector slope;
        SkPoint pt;
        SkDEBUGCODE(sk_bzero(&slope, sizeof(slope)));
        bool valid = false;
        if (approximately_zero(t)) {
            pt = fPts[0];
        } else if (approximately_equal(t, 1)) {
            pt = fPts[SkPathOpsVerbToPoints(fVerb)];
        } else {
            SkASSERT(between(0, t, 1));
            pt = this->ptAtT(t);
            if (SkDPoint::ApproximatelyEqual(pt, base.fPt)) {
                if (base.fSpan->segment() == this) {
                    continue;
                }
            } else {
                SkScalar ptXY = pt_xy(pt, dir);
                if (!approximately_equal(baseXY, ptXY) && (baseXY < ptXY) == checkLessThan) {
                    continue;
                }
                slope = this->dSlopeAtT(t);
                if (fVerb == SkPath::kCubic_Verb && base.fSpan->segment() == this
                        && roughly_equal(base.fT, t)
                        && SkDPoint::RoughlyEqual(pt, base.fPt)) {
    #if DEBUG_WINDING
                    SkDebugf("%s (rarely expect this)\n", __FUNCTION__);
    #endif
                    continue;
                }
                if (fabs(pt_dydx(slope, dir) * 10000) > fabs(pt_dxdy(slope, dir))) {
                    valid = true;
                }
            }
        }
        SkOpSpan* span = this->windingSpanAtT(t);
        if (!span) {
            valid = false;
        } else if (!span->windValue() && !span->oppValue()) {
            continue;
        }
        SkOpRayHit* newHit = allocator->make<SkOpRayHit>();
        newHit->fNext = *hits;
        newHit->fPt = pt;
        newHit->fSlope = slope;
        newHit->fSpan = span;
        newHit->fT = t;
        newHit->fValid = valid;
        *hits = newHit;
    }
}

SkOpSpan* SkOpSegment::windingSpanAtT(double tHit) {
    SkOpSpan* span = &fHead;
    SkOpSpanBase* next;
    do {
        next = span->next();
        if (approximately_equal(tHit, next->t())) {
            return nullptr;
        }
        if (tHit < next->t()) {
            return span;
        }
    } while (!next->final() && (span = next->upCast()));
    return nullptr;
}

static bool hit_compare_x(const SkOpRayHit* a, const SkOpRayHit* b) {
    return a->fPt.fX < b->fPt.fX;
}

static bool reverse_hit_compare_x(const SkOpRayHit* a, const SkOpRayHit* b) {
    return b->fPt.fX  < a->fPt.fX;
}

static bool hit_compare_y(const SkOpRayHit* a, const SkOpRayHit* b) {
    return a->fPt.fY < b->fPt.fY;
}

static bool reverse_hit_compare_y(const SkOpRayHit* a, const SkOpRayHit* b) {
    return b->fPt.fY  < a->fPt.fY;
}

static double get_t_guess(int tTry, int* dirOffset) {
    double t = 0.5;
    *dirOffset = tTry & 1;
    int tBase = tTry >> 1;
    int tBits = 0;
    while (tTry >>= 1) {
        t /= 2;
        ++tBits;
    }
    if (tBits) {
        int tIndex = (tBase - 1) & ((1 << tBits) - 1);
        t += t * 2 * tIndex;
    }
    return t;
}

bool SkOpSpan::sortableTop(SkOpContour* contourHead) {
    SkSTArenaAlloc<1024> allocator;
    int dirOffset;
    double t = get_t_guess(fTopTTry++, &dirOffset);
    SkOpRayHit hitBase;
    SkOpRayDir dir = hitBase.makeTestBase(this, t);
    if (hitBase.fSlope.fX == 0 && hitBase.fSlope.fY == 0) {
        return false;
    }
    SkOpRayHit* hitHead = &hitBase;
    dir = static_cast<SkOpRayDir>(static_cast<int>(dir) + dirOffset);
    if (hitBase.fSpan && hitBase.fSpan->segment()->verb() > SkPath::kLine_Verb
            && !pt_dydx(hitBase.fSlope, dir)) {
        return false;
    }
    SkOpContour* contour = contourHead;
    do {
        if (!contour->count()) {
            continue;
        }
        contour->rayCheck(hitBase, dir, &hitHead, &allocator);
    } while ((contour = contour->next()));
    // sort hits
    SkSTArray<1, SkOpRayHit*> sorted;
    SkOpRayHit* hit = hitHead;
    while (hit) {
        sorted.push_back(hit);
        hit = hit->fNext;
    }
    int count = sorted.count();
    SkTQSort(sorted.begin(), sorted.end() - 1, xy_index(dir)
            ? less_than(dir) ? hit_compare_y : reverse_hit_compare_y
            : less_than(dir) ? hit_compare_x : reverse_hit_compare_x);
    // verify windings
#if DEBUG_WINDING
    SkDebugf("%s dir=%s seg=%d t=%1.9g pt=(%1.9g,%1.9g)\n", __FUNCTION__,
            gDebugRayDirName[static_cast<int>(dir)], hitBase.fSpan->segment()->debugID(),
            hitBase.fT, hitBase.fPt.fX, hitBase.fPt.fY);
    for (int index = 0; index < count; ++index) {
        hit = sorted[index];
        SkOpSpan* span = hit->fSpan;
        SkOpSegment* hitSegment = span ? span->segment() : nullptr;
        bool operand = span ? hitSegment->operand() : false;
        bool ccw = ccw_dxdy(hit->fSlope, dir);
        SkDebugf("%s [%d] valid=%d operand=%d span=%d ccw=%d ", __FUNCTION__, index,
                hit->fValid, operand, span ? span->debugID() : -1, ccw);
        if (span) {
            hitSegment->dumpPtsInner();
        }
        SkDebugf(" t=%1.9g pt=(%1.9g,%1.9g) slope=(%1.9g,%1.9g)\n", hit->fT,
                hit->fPt.fX, hit->fPt.fY, hit->fSlope.fX, hit->fSlope.fY);
    }
#endif
    const SkPoint* last = nullptr;
    int wind = 0;
    int oppWind = 0;
    for (int index = 0; index < count; ++index) {
        hit = sorted[index];
        if (!hit->fValid) {
            return false;
        }
        bool ccw = ccw_dxdy(hit->fSlope, dir);
//        SkASSERT(!approximately_zero(hit->fT) || !hit->fValid);
        SkOpSpan* span = hit->fSpan;
        if (!span) {
            return false;
        }
        SkOpSegment* hitSegment = span->segment();
        if (span->windValue() == 0 && span->oppValue() == 0) {
            continue;
        }
        if (last && SkDPoint::ApproximatelyEqual(*last, hit->fPt)) {
            return false;
        }
        if (index < count - 1) {
            const SkPoint& next = sorted[index + 1]->fPt;
            if (SkDPoint::ApproximatelyEqual(next, hit->fPt)) {
                return false;
            }
        }
        bool operand = hitSegment->operand();
        if (operand) {
            SkTSwap(wind, oppWind);
        }
        int lastWind = wind;
        int lastOpp = oppWind;
        int windValue = ccw ? -span->windValue() : span->windValue();
        int oppValue = ccw ? -span->oppValue() : span->oppValue();
        wind += windValue;
        oppWind += oppValue;
        bool sumSet = false;
        int spanSum = span->windSum();
        int windSum = SkOpSegment::UseInnerWinding(lastWind, wind) ? wind : lastWind;
        if (spanSum == SK_MinS32) {
            span->setWindSum(windSum);
            sumSet = true;
        } else {
            // the need for this condition suggests that UseInnerWinding is flawed
            // happened when last = 1 wind = -1
#if 0
            SkASSERT((hitSegment->isXor() ? (windSum & 1) == (spanSum & 1) : windSum == spanSum)
                    || (abs(wind) == abs(lastWind)
                    && (windSum ^ wind ^ lastWind) == spanSum));
#endif
        }
        int oSpanSum = span->oppSum();
        int oppSum = SkOpSegment::UseInnerWinding(lastOpp, oppWind) ? oppWind : lastOpp;
        if (oSpanSum == SK_MinS32) {
            span->setOppSum(oppSum);
        } else {
#if 0
            SkASSERT(hitSegment->oppXor() ? (oppSum & 1) == (oSpanSum & 1) : oppSum == oSpanSum
                    || (abs(oppWind) == abs(lastOpp)
                    && (oppSum ^ oppWind ^ lastOpp) == oSpanSum));
#endif
        }
        if (sumSet) {
            if (this->globalState()->phase() == SkOpPhase::kFixWinding) {
                hitSegment->contour()->setCcw(ccw);
            } else {
                (void) hitSegment->markAndChaseWinding(span, span->next(), windSum, oppSum, nullptr);
                (void) hitSegment->markAndChaseWinding(span->next(), span, windSum, oppSum, nullptr);
            }
        }
        if (operand) {
            SkTSwap(wind, oppWind);
        }
        last = &hit->fPt;
        this->globalState()->bumpNested();
    }
    return true;
}

SkOpSpan* SkOpSegment::findSortableTop(SkOpContour* contourHead) {
    SkOpSpan* span = &fHead;
    SkOpSpanBase* next;
    do {
        next = span->next();
        if (span->done()) {
            continue;
        }
        if (span->windSum() != SK_MinS32) {
            return span;
        }
        if (span->sortableTop(contourHead)) {
            return span;
        }
    } while (!next->final() && (span = next->upCast()));
    return nullptr;
}

SkOpSpan* SkOpContour::findSortableTop(SkOpContour* contourHead) {
    bool allDone = true;
    if (fCount) {
        SkOpSegment* testSegment = &fHead;
        do {
            if (testSegment->done()) {
                continue;
            }
            allDone = false;
            SkOpSpan* result = testSegment->findSortableTop(contourHead);
            if (result) {
                return result;
            }
        } while ((testSegment = testSegment->next()));
    }
    if (allDone) {
      fDone = true;
    }
    return nullptr;
}

SkOpSpan* FindSortableTop(SkOpContourHead* contourHead) {
    for (int index = 0; index < SkOpGlobalState::kMaxWindingTries; ++index) {
        SkOpContour* contour = contourHead;
        do {
            if (contour->done()) {
                continue;
            }
            SkOpSpan* result = contour->findSortableTop(contourHead);
            if (result) {
                return result;
            }
        } while ((contour = contour->next()));
    }
    return nullptr;
}