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/*
* 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 "src/pathops/SkOpContour.h"
#include "src/pathops/SkOpSegment.h"
#include "src/pathops/SkPathOpsCurve.h"
#include <utility>
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) {
using std::swap;
swap(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) {
using std::swap;
swap(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;
}