23d9776024
BUG=skia: GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2221203002 Review-Url: https://codereview.chromium.org/2221203002
706 lines
22 KiB
C++
706 lines
22 KiB
C++
/*
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* Copyright 2008 The Android Open Source Project
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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 "SkPathMeasure.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 SkPathMeasure::Segment::getScalarT() const {
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return tValue2Scalar(fTValue);
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}
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const SkPathMeasure::Segment* SkPathMeasure::NextSegment(const Segment* seg) {
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unsigned ptIndex = seg->fPtIndex;
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do {
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++seg;
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} while (seg->fPtIndex == ptIndex);
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return seg;
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}
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void SkPathMeasure_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 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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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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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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} else {
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if (SK_Scalar1 == stopT) {
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SkConic tmp1[2];
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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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} 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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SkDEBUGFAIL("unknown segType");
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sk_throw();
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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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bool SkPathMeasure::quad_too_curvy(const SkPoint pts[3]) {
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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 > fTolerance;
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}
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bool SkPathMeasure::conic_too_curvy(const SkPoint& firstPt, const SkPoint& midTPt,
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const SkPoint& lastPt) {
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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 > fTolerance;
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}
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bool SkPathMeasure::cheap_dist_exceeds_limit(const SkPoint& pt,
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SkScalar x, SkScalar y) {
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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 > fTolerance;
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}
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bool SkPathMeasure::cubic_too_curvy(const SkPoint pts[4]) {
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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))
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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));
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}
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static SkScalar quad_folded_len(const SkPoint pts[3]) {
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SkScalar t = SkFindQuadMaxCurvature(pts);
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SkPoint pt = SkEvalQuadAt(pts, t);
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SkVector a = pts[2] - pt;
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SkScalar result = a.length();
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if (0 != t) {
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SkVector b = pts[0] - pt;
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result += b.length();
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}
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SkASSERT(SkScalarIsFinite(result));
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return result;
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}
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/* from http://www.malczak.linuxpl.com/blog/quadratic-bezier-curve-length/ */
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/* This works -- more needs to be done to see if it is performant on all platforms.
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To use this to measure parts of quads requires recomputing everything -- perhaps
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a chop-like interface can start from a larger measurement and get two new measurements
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with one call here.
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*/
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static SkScalar compute_quad_len(const SkPoint pts[3]) {
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SkPoint a,b;
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a.fX = pts[0].fX - 2 * pts[1].fX + pts[2].fX;
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a.fY = pts[0].fY - 2 * pts[1].fY + pts[2].fY;
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SkScalar A = 4 * (a.fX * a.fX + a.fY * a.fY);
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if (0 == A) {
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a = pts[2] - pts[0];
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return a.length();
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}
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b.fX = 2 * (pts[1].fX - pts[0].fX);
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b.fY = 2 * (pts[1].fY - pts[0].fY);
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SkScalar B = 4 * (a.fX * b.fX + a.fY * b.fY);
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SkScalar C = b.fX * b.fX + b.fY * b.fY;
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SkScalar Sabc = 2 * SkScalarSqrt(A + B + C);
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SkScalar A_2 = SkScalarSqrt(A);
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SkScalar A_32 = 2 * A * A_2;
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SkScalar C_2 = 2 * SkScalarSqrt(C);
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SkScalar BA = B / A_2;
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if (0 == BA + C_2) {
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return quad_folded_len(pts);
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}
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SkScalar J = A_32 * Sabc + A_2 * B * (Sabc - C_2);
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SkScalar K = 4 * C * A - B * B;
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SkScalar L = (2 * A_2 + BA + Sabc) / (BA + C_2);
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if (L <= 0) {
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return quad_folded_len(pts);
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}
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SkScalar M = SkScalarLog(L);
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SkScalar result = (J + K * M) / (4 * A_32);
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SkASSERT(SkScalarIsFinite(result));
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return result;
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}
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SkScalar SkPathMeasure::compute_quad_segs(const SkPoint pts[3],
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SkScalar distance, int mint, int maxt, int ptIndex) {
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if (tspan_big_enough(maxt - mint) && quad_too_curvy(pts)) {
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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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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 SkPathMeasure::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, int 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 (tspan_big_enough(maxt - mint) && conic_too_curvy(minPt, halfPt, maxPt)) {
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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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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 SkPathMeasure::compute_cubic_segs(const SkPoint pts[4],
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SkScalar distance, int mint, int maxt, int ptIndex) {
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if (tspan_big_enough(maxt - mint) && cubic_too_curvy(pts)) {
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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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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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void SkPathMeasure::buildSegments() {
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SkPoint pts[4];
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int ptIndex = fFirstPtIndex;
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SkScalar distance = 0;
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bool isClosed = fForceClosed;
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bool firstMoveTo = ptIndex < 0;
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Segment* seg;
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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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bool done = false;
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do {
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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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if (!firstMoveTo) {
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done = true;
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break;
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}
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firstMoveTo = false;
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break;
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case SkPath::kLine_Verb: {
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SkScalar d = SkPoint::Distance(pts[0], pts[1]);
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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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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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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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SkScalar prevD = distance;
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if (false) {
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SkScalar length = compute_quad_len(pts);
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if (length) {
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distance += length;
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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 = kMaxTValue;
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}
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} else {
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distance = this->compute_quad_segs(pts, distance, 0, kMaxTValue, ptIndex);
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}
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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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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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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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isClosed = 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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fLength = distance;
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fIsClosed = isClosed;
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fFirstPtIndex = ptIndex;
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#ifdef SK_DEBUG
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{
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const Segment* seg = fSegments.begin();
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const Segment* stop = fSegments.end();
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unsigned ptIndex = 0;
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SkScalar distance = 0;
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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 Segment* s = seg;
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while (s < stop - 1 && s[0].fPtIndex == s[1].fPtIndex) {
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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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}
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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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SkPathMeasure::SkPathMeasure() {
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fPath = nullptr;
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fTolerance = CHEAP_DIST_LIMIT;
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fLength = -1; // signal we need to compute it
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fForceClosed = false;
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fFirstPtIndex = -1;
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}
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SkPathMeasure::SkPathMeasure(const SkPath& path, bool forceClosed, SkScalar resScale) {
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fPath = &path;
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fTolerance = CHEAP_DIST_LIMIT * SkScalarInvert(resScale);
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fLength = -1; // signal we need to compute it
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fForceClosed = forceClosed;
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fFirstPtIndex = -1;
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fIter.setPath(path, forceClosed);
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}
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SkPathMeasure::~SkPathMeasure() {}
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/** Assign a new path, or null to have none.
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*/
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void SkPathMeasure::setPath(const SkPath* path, bool forceClosed) {
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fPath = path;
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fLength = -1; // signal we need to compute it
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fForceClosed = forceClosed;
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fFirstPtIndex = -1;
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if (path) {
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fIter.setPath(*path, forceClosed);
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}
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fSegments.reset();
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fPts.reset();
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}
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SkScalar SkPathMeasure::getLength() {
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if (fPath == nullptr) {
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return 0;
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}
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if (fLength < 0) {
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this->buildSegments();
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}
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SkASSERT(fLength >= 0);
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return fLength;
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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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int lo = 0;
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int hi = count - 1;
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while (lo < hi) {
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int 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 SkPathMeasure::Segment* SkPathMeasure::distanceToSegment(
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SkScalar distance, SkScalar* t) {
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SkDEBUGCODE(SkScalar length = ) this->getLength();
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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 + SkScalarMulDiv(seg->getScalarT() - startT,
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distance - startD,
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seg->fDistance - startD);
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return seg;
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}
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bool SkPathMeasure::getPosTan(SkScalar distance, SkPoint* pos,
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SkVector* tangent) {
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if (nullptr == fPath) {
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return false;
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}
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SkScalar length = this->getLength(); // call this to force computing it
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int count = fSegments.count();
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if (count == 0 || length == 0) {
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return false;
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}
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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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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 SkPathMeasure::getMatrix(SkScalar distance, SkMatrix* matrix,
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MatrixFlags flags) {
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if (nullptr == fPath) {
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return false;
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}
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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 SkPathMeasure::getSegment(SkScalar startD, SkScalar stopD, SkPath* dst,
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bool startWithMoveTo) {
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SkASSERT(dst);
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SkScalar length = this->getLength(); // ensure we have built our segments
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if (startD < 0) {
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startD = 0;
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}
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if (stopD > length) {
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stopD = length;
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}
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if (startD > stopD) {
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return false;
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}
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if (!fSegments.count()) {
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return false;
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}
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SkPoint p;
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SkScalar startT, stopT;
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const Segment* seg = this->distanceToSegment(startD, &startT);
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const Segment* stopSeg = this->distanceToSegment(stopD, &stopT);
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SkASSERT(seg <= stopSeg);
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if (startWithMoveTo) {
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compute_pos_tan(&fPts[seg->fPtIndex], seg->fType, startT, &p, nullptr);
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dst->moveTo(p);
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}
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if (seg->fPtIndex == stopSeg->fPtIndex) {
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SkPathMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, stopT, dst);
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} else {
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do {
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SkPathMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, SK_Scalar1, dst);
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seg = SkPathMeasure::NextSegment(seg);
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startT = 0;
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} while (seg->fPtIndex < stopSeg->fPtIndex);
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SkPathMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, 0, stopT, dst);
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}
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return true;
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}
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bool SkPathMeasure::isClosed() {
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(void)this->getLength();
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return fIsClosed;
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}
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/** Move to the next contour in the path. Return true if one exists, or false if
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we're done with the path.
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*/
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bool SkPathMeasure::nextContour() {
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fLength = -1;
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return this->getLength() > 0;
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}
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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#ifdef SK_DEBUG
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void SkPathMeasure::dump() {
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SkDebugf("pathmeas: length=%g, segs=%d\n", fLength, fSegments.count());
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for (int i = 0; i < fSegments.count(); i++) {
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const Segment* seg = &fSegments[i];
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SkDebugf("pathmeas: seg[%d] distance=%g, point=%d, t=%g, type=%d\n",
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i, seg->fDistance, seg->fPtIndex, seg->getScalarT(),
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seg->fType);
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}
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}
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#endif
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