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