/* * Copyright 2018 Google Inc. * * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ #include "include/core/SkContourMeasure.h" #include "include/core/SkPath.h" #include "src/core/SkGeometry.h" #include "src/core/SkPathMeasurePriv.h" #include "src/core/SkTSearch.h" #define kMaxTValue 0x3FFFFFFF static inline SkScalar tValue2Scalar(int t) { SkASSERT((unsigned)t <= kMaxTValue); const SkScalar kMaxTReciprocal = 1.0f / kMaxTValue; return t * kMaxTReciprocal; } SkScalar SkContourMeasure::Segment::getScalarT() const { return tValue2Scalar(fTValue); } void SkContourMeasure_segTo(const SkPoint pts[], unsigned segType, SkScalar startT, SkScalar stopT, SkPath* dst) { SkASSERT(startT >= 0 && startT <= SK_Scalar1); SkASSERT(stopT >= 0 && stopT <= SK_Scalar1); SkASSERT(startT <= stopT); if (startT == stopT) { if (!dst->isEmpty()) { /* if the dash as a zero-length on segment, add a corresponding zero-length line. The stroke code will add end caps to zero length lines as appropriate */ SkPoint lastPt; SkAssertResult(dst->getLastPt(&lastPt)); dst->lineTo(lastPt); } return; } SkPoint tmp0[7], tmp1[7]; switch (segType) { case kLine_SegType: if (SK_Scalar1 == stopT) { dst->lineTo(pts[1]); } else { dst->lineTo(SkScalarInterp(pts[0].fX, pts[1].fX, stopT), SkScalarInterp(pts[0].fY, pts[1].fY, stopT)); } break; case kQuad_SegType: if (0 == startT) { if (SK_Scalar1 == stopT) { dst->quadTo(pts[1], pts[2]); } else { SkChopQuadAt(pts, tmp0, stopT); dst->quadTo(tmp0[1], tmp0[2]); } } else { SkChopQuadAt(pts, tmp0, startT); if (SK_Scalar1 == stopT) { dst->quadTo(tmp0[3], tmp0[4]); } else { SkChopQuadAt(&tmp0[2], tmp1, (stopT - startT) / (1 - startT)); dst->quadTo(tmp1[1], tmp1[2]); } } break; case kConic_SegType: { SkConic conic(pts[0], pts[2], pts[3], pts[1].fX); if (0 == startT) { if (SK_Scalar1 == stopT) { dst->conicTo(conic.fPts[1], conic.fPts[2], conic.fW); } else { SkConic tmp[2]; if (conic.chopAt(stopT, tmp)) { dst->conicTo(tmp[0].fPts[1], tmp[0].fPts[2], tmp[0].fW); } } } else { if (SK_Scalar1 == stopT) { SkConic tmp1[2]; if (conic.chopAt(startT, tmp1)) { dst->conicTo(tmp1[1].fPts[1], tmp1[1].fPts[2], tmp1[1].fW); } } else { SkConic tmp; conic.chopAt(startT, stopT, &tmp); dst->conicTo(tmp.fPts[1], tmp.fPts[2], tmp.fW); } } } break; case kCubic_SegType: if (0 == startT) { if (SK_Scalar1 == stopT) { dst->cubicTo(pts[1], pts[2], pts[3]); } else { SkChopCubicAt(pts, tmp0, stopT); dst->cubicTo(tmp0[1], tmp0[2], tmp0[3]); } } else { SkChopCubicAt(pts, tmp0, startT); if (SK_Scalar1 == stopT) { dst->cubicTo(tmp0[4], tmp0[5], tmp0[6]); } else { SkChopCubicAt(&tmp0[3], tmp1, (stopT - startT) / (1 - startT)); dst->cubicTo(tmp1[1], tmp1[2], tmp1[3]); } } break; default: SK_ABORT("unknown segType"); } } /////////////////////////////////////////////////////////////////////////////// static inline int tspan_big_enough(int tspan) { SkASSERT((unsigned)tspan <= kMaxTValue); return tspan >> 10; } // can't use tangents, since we need [0..1..................2] to be seen // as definitely not a line (it is when drawn, but not parametrically) // so we compare midpoints #define CHEAP_DIST_LIMIT (SK_Scalar1/2) // just made this value up static bool quad_too_curvy(const SkPoint pts[3], SkScalar tolerance) { // diff = (a/4 + b/2 + c/4) - (a/2 + c/2) // diff = -a/4 + b/2 - c/4 SkScalar dx = SkScalarHalf(pts[1].fX) - SkScalarHalf(SkScalarHalf(pts[0].fX + pts[2].fX)); SkScalar dy = SkScalarHalf(pts[1].fY) - SkScalarHalf(SkScalarHalf(pts[0].fY + pts[2].fY)); SkScalar dist = SkMaxScalar(SkScalarAbs(dx), SkScalarAbs(dy)); return dist > tolerance; } static bool conic_too_curvy(const SkPoint& firstPt, const SkPoint& midTPt, const SkPoint& lastPt, SkScalar tolerance) { SkPoint midEnds = firstPt + lastPt; midEnds *= 0.5f; SkVector dxy = midTPt - midEnds; SkScalar dist = SkMaxScalar(SkScalarAbs(dxy.fX), SkScalarAbs(dxy.fY)); return dist > tolerance; } static bool cheap_dist_exceeds_limit(const SkPoint& pt, SkScalar x, SkScalar y, SkScalar tolerance) { SkScalar dist = SkMaxScalar(SkScalarAbs(x - pt.fX), SkScalarAbs(y - pt.fY)); // just made up the 1/2 return dist > tolerance; } static bool cubic_too_curvy(const SkPoint pts[4], SkScalar tolerance) { return cheap_dist_exceeds_limit(pts[1], SkScalarInterp(pts[0].fX, pts[3].fX, SK_Scalar1/3), SkScalarInterp(pts[0].fY, pts[3].fY, SK_Scalar1/3), tolerance) || cheap_dist_exceeds_limit(pts[2], SkScalarInterp(pts[0].fX, pts[3].fX, SK_Scalar1*2/3), SkScalarInterp(pts[0].fY, pts[3].fY, SK_Scalar1*2/3), tolerance); } SkScalar SkContourMeasureIter::compute_quad_segs(const SkPoint pts[3], SkScalar distance, int mint, int maxt, unsigned ptIndex) { if (tspan_big_enough(maxt - mint) && quad_too_curvy(pts, fTolerance)) { SkPoint tmp[5]; int halft = (mint + maxt) >> 1; SkChopQuadAtHalf(pts, tmp); distance = this->compute_quad_segs(tmp, distance, mint, halft, ptIndex); distance = this->compute_quad_segs(&tmp[2], distance, halft, maxt, ptIndex); } else { SkScalar d = SkPoint::Distance(pts[0], pts[2]); SkScalar prevD = distance; distance += d; if (distance > prevD) { SkASSERT(ptIndex < (unsigned)fPts.count()); SkContourMeasure::Segment* seg = fSegments.append(); seg->fDistance = distance; seg->fPtIndex = ptIndex; seg->fType = kQuad_SegType; seg->fTValue = maxt; } } return distance; } SkScalar SkContourMeasureIter::compute_conic_segs(const SkConic& conic, SkScalar distance, int mint, const SkPoint& minPt, int maxt, const SkPoint& maxPt, unsigned ptIndex) { int halft = (mint + maxt) >> 1; SkPoint halfPt = conic.evalAt(tValue2Scalar(halft)); if (!halfPt.isFinite()) { return distance; } if (tspan_big_enough(maxt - mint) && conic_too_curvy(minPt, halfPt, maxPt, fTolerance)) { distance = this->compute_conic_segs(conic, distance, mint, minPt, halft, halfPt, ptIndex); distance = this->compute_conic_segs(conic, distance, halft, halfPt, maxt, maxPt, ptIndex); } else { SkScalar d = SkPoint::Distance(minPt, maxPt); SkScalar prevD = distance; distance += d; if (distance > prevD) { SkASSERT(ptIndex < (unsigned)fPts.count()); SkContourMeasure::Segment* seg = fSegments.append(); seg->fDistance = distance; seg->fPtIndex = ptIndex; seg->fType = kConic_SegType; seg->fTValue = maxt; } } return distance; } SkScalar SkContourMeasureIter::compute_cubic_segs(const SkPoint pts[4], SkScalar distance, int mint, int maxt, unsigned ptIndex) { if (tspan_big_enough(maxt - mint) && cubic_too_curvy(pts, fTolerance)) { SkPoint tmp[7]; int halft = (mint + maxt) >> 1; SkChopCubicAtHalf(pts, tmp); distance = this->compute_cubic_segs(tmp, distance, mint, halft, ptIndex); distance = this->compute_cubic_segs(&tmp[3], distance, halft, maxt, ptIndex); } else { SkScalar d = SkPoint::Distance(pts[0], pts[3]); SkScalar prevD = distance; distance += d; if (distance > prevD) { SkASSERT(ptIndex < (unsigned)fPts.count()); SkContourMeasure::Segment* seg = fSegments.append(); seg->fDistance = distance; seg->fPtIndex = ptIndex; seg->fType = kCubic_SegType; seg->fTValue = maxt; } } return distance; } SkScalar SkContourMeasureIter::compute_line_seg(SkPoint p0, SkPoint p1, SkScalar distance, unsigned ptIndex) { SkScalar d = SkPoint::Distance(p0, p1); SkASSERT(d >= 0); SkScalar prevD = distance; distance += d; if (distance > prevD) { SkASSERT((unsigned)ptIndex < (unsigned)fPts.count()); SkContourMeasure::Segment* seg = fSegments.append(); seg->fDistance = distance; seg->fPtIndex = ptIndex; seg->fType = kLine_SegType; seg->fTValue = kMaxTValue; } return distance; } SkContourMeasure* SkContourMeasureIter::buildSegments() { SkPoint pts[4]; int ptIndex = -1; SkScalar distance = 0; bool haveSeenClose = fForceClosed; bool haveSeenMoveTo = false; /* Note: * as we accumulate distance, we have to check that the result of += * actually made it larger, since a very small delta might be > 0, but * still have no effect on distance (if distance >>> delta). * * We do this check below, and in compute_quad_segs and compute_cubic_segs */ fSegments.reset(); fPts.reset(); bool done = false; do { if (haveSeenMoveTo && fIter.peek() == SkPath::kMove_Verb) { break; } switch (fIter.next(pts)) { case SkPath::kMove_Verb: ptIndex += 1; fPts.append(1, pts); SkASSERT(!haveSeenMoveTo); haveSeenMoveTo = true; break; case SkPath::kLine_Verb: { SkASSERT(haveSeenMoveTo); SkScalar prevD = distance; distance = this->compute_line_seg(pts[0], pts[1], distance, ptIndex); if (distance > prevD) { fPts.append(1, pts + 1); ptIndex++; } } break; case SkPath::kQuad_Verb: { SkASSERT(haveSeenMoveTo); SkScalar prevD = distance; distance = this->compute_quad_segs(pts, distance, 0, kMaxTValue, ptIndex); if (distance > prevD) { fPts.append(2, pts + 1); ptIndex += 2; } } break; case SkPath::kConic_Verb: { SkASSERT(haveSeenMoveTo); const SkConic conic(pts, fIter.conicWeight()); SkScalar prevD = distance; distance = this->compute_conic_segs(conic, distance, 0, conic.fPts[0], kMaxTValue, conic.fPts[2], ptIndex); if (distance > prevD) { // we store the conic weight in our next point, followed by the last 2 pts // thus to reconstitue a conic, you'd need to say // SkConic(pts[0], pts[2], pts[3], weight = pts[1].fX) fPts.append()->set(conic.fW, 0); fPts.append(2, pts + 1); ptIndex += 3; } } break; case SkPath::kCubic_Verb: { SkASSERT(haveSeenMoveTo); SkScalar prevD = distance; distance = this->compute_cubic_segs(pts, distance, 0, kMaxTValue, ptIndex); if (distance > prevD) { fPts.append(3, pts + 1); ptIndex += 3; } } break; case SkPath::kClose_Verb: haveSeenClose = true; break; case SkPath::kDone_Verb: done = true; break; } } while (!done); if (!SkScalarIsFinite(distance)) { return nullptr; } if (fSegments.count() == 0) { return nullptr; } // Handle the close segment ourselves, since we're using RawIter if (haveSeenClose) { SkScalar prevD = distance; SkPoint firstPt = fPts[0]; distance = this->compute_line_seg(fPts[ptIndex], firstPt, distance, ptIndex); if (distance > prevD) { *fPts.append() = firstPt; } } #ifdef SK_DEBUG { const SkContourMeasure::Segment* seg = fSegments.begin(); const SkContourMeasure::Segment* stop = fSegments.end(); unsigned ptIndex = 0; SkScalar distance = 0; // limit the loop to a reasonable number; pathological cases can run for minutes int maxChecks = 10000000; // set to INT_MAX to defeat the check while (seg < stop) { SkASSERT(seg->fDistance > distance); SkASSERT(seg->fPtIndex >= ptIndex); SkASSERT(seg->fTValue > 0); const SkContourMeasure::Segment* s = seg; while (s < stop - 1 && s[0].fPtIndex == s[1].fPtIndex && --maxChecks > 0) { SkASSERT(s[0].fType == s[1].fType); SkASSERT(s[0].fTValue < s[1].fTValue); s += 1; } distance = seg->fDistance; ptIndex = seg->fPtIndex; seg += 1; } // SkDebugf("\n"); } #endif return new SkContourMeasure(std::move(fSegments), std::move(fPts), distance, haveSeenClose); } static void compute_pos_tan(const SkPoint pts[], unsigned segType, SkScalar t, SkPoint* pos, SkVector* tangent) { switch (segType) { case kLine_SegType: if (pos) { pos->set(SkScalarInterp(pts[0].fX, pts[1].fX, t), SkScalarInterp(pts[0].fY, pts[1].fY, t)); } if (tangent) { tangent->setNormalize(pts[1].fX - pts[0].fX, pts[1].fY - pts[0].fY); } break; case kQuad_SegType: SkEvalQuadAt(pts, t, pos, tangent); if (tangent) { tangent->normalize(); } break; case kConic_SegType: { SkConic(pts[0], pts[2], pts[3], pts[1].fX).evalAt(t, pos, tangent); if (tangent) { tangent->normalize(); } } break; case kCubic_SegType: SkEvalCubicAt(pts, t, pos, tangent, nullptr); if (tangent) { tangent->normalize(); } break; default: SkDEBUGFAIL("unknown segType"); } } //////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////// SkContourMeasureIter::SkContourMeasureIter() { fTolerance = CHEAP_DIST_LIMIT; fForceClosed = false; } SkContourMeasureIter::SkContourMeasureIter(const SkPath& path, bool forceClosed, SkScalar resScale) { fPath = path.isFinite() ? path : SkPath(); fTolerance = CHEAP_DIST_LIMIT * SkScalarInvert(resScale); fForceClosed = forceClosed; fIter.setPath(fPath); } SkContourMeasureIter::~SkContourMeasureIter() {} /** Assign a new path, or null to have none. */ void SkContourMeasureIter::reset(const SkPath& path, bool forceClosed, SkScalar resScale) { if (path.isFinite()) { fPath = path; } else { fPath.reset(); } fForceClosed = forceClosed; fIter.setPath(fPath); fSegments.reset(); fPts.reset(); } sk_sp SkContourMeasureIter::next() { while (fIter.peek() != SkPath::kDone_Verb) { auto cm = this->buildSegments(); if (cm) { return sk_sp(cm); } } return nullptr; } /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// SkContourMeasure::SkContourMeasure(SkTDArray&& segs, SkTDArray&& pts, SkScalar length, bool isClosed) : fSegments(std::move(segs)) , fPts(std::move(pts)) , fLength(length) , fIsClosed(isClosed) {} template int SkTKSearch(const T base[], int count, const K& key) { SkASSERT(count >= 0); if (count <= 0) { return ~0; } SkASSERT(base != nullptr); // base may be nullptr if count is zero unsigned lo = 0; unsigned hi = count - 1; while (lo < hi) { unsigned mid = (hi + lo) >> 1; if (base[mid].fDistance < key) { lo = mid + 1; } else { hi = mid; } } if (base[hi].fDistance < key) { hi += 1; hi = ~hi; } else if (key < base[hi].fDistance) { hi = ~hi; } return hi; } const SkContourMeasure::Segment* SkContourMeasure::distanceToSegment( SkScalar distance, SkScalar* t) const { SkDEBUGCODE(SkScalar length = ) this->length(); SkASSERT(distance >= 0 && distance <= length); const Segment* seg = fSegments.begin(); int count = fSegments.count(); int index = SkTKSearch(seg, count, distance); // don't care if we hit an exact match or not, so we xor index if it is negative index ^= (index >> 31); seg = &seg[index]; // now interpolate t-values with the prev segment (if possible) SkScalar startT = 0, startD = 0; // check if the prev segment is legal, and references the same set of points if (index > 0) { startD = seg[-1].fDistance; if (seg[-1].fPtIndex == seg->fPtIndex) { SkASSERT(seg[-1].fType == seg->fType); startT = seg[-1].getScalarT(); } } SkASSERT(seg->getScalarT() > startT); SkASSERT(distance >= startD); SkASSERT(seg->fDistance > startD); *t = startT + (seg->getScalarT() - startT) * (distance - startD) / (seg->fDistance - startD); return seg; } bool SkContourMeasure::getPosTan(SkScalar distance, SkPoint* pos, SkVector* tangent) const { if (SkScalarIsNaN(distance)) { return false; } const SkScalar length = this->length(); SkASSERT(length > 0 && fSegments.count() > 0); // pin the distance to a legal range if (distance < 0) { distance = 0; } else if (distance > length) { distance = length; } SkScalar t; const Segment* seg = this->distanceToSegment(distance, &t); if (SkScalarIsNaN(t)) { return false; } SkASSERT((unsigned)seg->fPtIndex < (unsigned)fPts.count()); compute_pos_tan(&fPts[seg->fPtIndex], seg->fType, t, pos, tangent); return true; } bool SkContourMeasure::getMatrix(SkScalar distance, SkMatrix* matrix, MatrixFlags flags) const { SkPoint position; SkVector tangent; if (this->getPosTan(distance, &position, &tangent)) { if (matrix) { if (flags & kGetTangent_MatrixFlag) { matrix->setSinCos(tangent.fY, tangent.fX, 0, 0); } else { matrix->reset(); } if (flags & kGetPosition_MatrixFlag) { matrix->postTranslate(position.fX, position.fY); } } return true; } return false; } bool SkContourMeasure::getSegment(SkScalar startD, SkScalar stopD, SkPath* dst, bool startWithMoveTo) const { SkASSERT(dst); SkScalar length = this->length(); // ensure we have built our segments if (startD < 0) { startD = 0; } if (stopD > length) { stopD = length; } if (!(startD <= stopD)) { // catch NaN values as well return false; } if (!fSegments.count()) { return false; } SkPoint p; SkScalar startT, stopT; const Segment* seg = this->distanceToSegment(startD, &startT); if (!SkScalarIsFinite(startT)) { return false; } const Segment* stopSeg = this->distanceToSegment(stopD, &stopT); if (!SkScalarIsFinite(stopT)) { return false; } SkASSERT(seg <= stopSeg); if (startWithMoveTo) { compute_pos_tan(&fPts[seg->fPtIndex], seg->fType, startT, &p, nullptr); dst->moveTo(p); } if (seg->fPtIndex == stopSeg->fPtIndex) { SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, stopT, dst); } else { do { SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, SK_Scalar1, dst); seg = SkContourMeasure::Segment::Next(seg); startT = 0; } while (seg->fPtIndex < stopSeg->fPtIndex); SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, 0, stopT, dst); } return true; }