blob: 487bf5729c2e4880d4950c56d79d543c1bb52686 [file] [log] [blame]
/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "include/core/SkContourMeasure.h"
#include "include/core/SkPath.h"
#include "src/core/SkGeometry.h"
#include "src/core/SkPathMeasurePriv.h"
#include "src/core/SkPathPriv.h"
#include "src/core/SkTSearch.h"
#define kMaxTValue 0x3FFFFFFF
constexpr static inline SkScalar tValue2Scalar(int t) {
SkASSERT((unsigned)t <= kMaxTValue);
// 1/kMaxTValue can't be represented as a float, but it's close and the limits work fine.
const SkScalar kMaxTReciprocal = 1.0f / (SkScalar)kMaxTValue;
return t * kMaxTReciprocal;
}
static_assert(0.0f == tValue2Scalar( 0), "Lower limit should be exact.");
static_assert(1.0f == tValue2Scalar(kMaxTValue), "Upper limit should be exact.");
SkScalar SkContourMeasure::Segment::getScalarT() const {
return tValue2Scalar(fTValue);
}
void SkContourMeasure_segTo(const SkPoint pts[], unsigned segType,
SkScalar startT, SkScalar stopT, SkPath* dst) {
SkASSERT(startT >= 0 && startT <= SK_Scalar1);
SkASSERT(stopT >= 0 && stopT <= SK_Scalar1);
SkASSERT(startT <= stopT);
if (startT == stopT) {
if (!dst->isEmpty()) {
/* if the dash as a zero-length on segment, add a corresponding zero-length line.
The stroke code will add end caps to zero length lines as appropriate */
SkPoint lastPt;
SkAssertResult(dst->getLastPt(&lastPt));
dst->lineTo(lastPt);
}
return;
}
SkPoint tmp0[7], tmp1[7];
switch (segType) {
case kLine_SegType:
if (SK_Scalar1 == stopT) {
dst->lineTo(pts[1]);
} else {
dst->lineTo(SkScalarInterp(pts[0].fX, pts[1].fX, stopT),
SkScalarInterp(pts[0].fY, pts[1].fY, stopT));
}
break;
case kQuad_SegType:
if (0 == startT) {
if (SK_Scalar1 == stopT) {
dst->quadTo(pts[1], pts[2]);
} else {
SkChopQuadAt(pts, tmp0, stopT);
dst->quadTo(tmp0[1], tmp0[2]);
}
} else {
SkChopQuadAt(pts, tmp0, startT);
if (SK_Scalar1 == stopT) {
dst->quadTo(tmp0[3], tmp0[4]);
} else {
SkChopQuadAt(&tmp0[2], tmp1, (stopT - startT) / (1 - startT));
dst->quadTo(tmp1[1], tmp1[2]);
}
}
break;
case kConic_SegType: {
SkConic conic(pts[0], pts[2], pts[3], pts[1].fX);
if (0 == startT) {
if (SK_Scalar1 == stopT) {
dst->conicTo(conic.fPts[1], conic.fPts[2], conic.fW);
} else {
SkConic tmp[2];
if (conic.chopAt(stopT, tmp)) {
dst->conicTo(tmp[0].fPts[1], tmp[0].fPts[2], tmp[0].fW);
}
}
} else {
if (SK_Scalar1 == stopT) {
SkConic tmp1[2];
if (conic.chopAt(startT, tmp1)) {
dst->conicTo(tmp1[1].fPts[1], tmp1[1].fPts[2], tmp1[1].fW);
}
} else {
SkConic tmp;
conic.chopAt(startT, stopT, &tmp);
dst->conicTo(tmp.fPts[1], tmp.fPts[2], tmp.fW);
}
}
} break;
case kCubic_SegType:
if (0 == startT) {
if (SK_Scalar1 == stopT) {
dst->cubicTo(pts[1], pts[2], pts[3]);
} else {
SkChopCubicAt(pts, tmp0, stopT);
dst->cubicTo(tmp0[1], tmp0[2], tmp0[3]);
}
} else {
SkChopCubicAt(pts, tmp0, startT);
if (SK_Scalar1 == stopT) {
dst->cubicTo(tmp0[4], tmp0[5], tmp0[6]);
} else {
SkChopCubicAt(&tmp0[3], tmp1, (stopT - startT) / (1 - startT));
dst->cubicTo(tmp1[1], tmp1[2], tmp1[3]);
}
}
break;
default:
SK_ABORT("unknown segType");
}
}
///////////////////////////////////////////////////////////////////////////////
static inline int tspan_big_enough(int tspan) {
SkASSERT((unsigned)tspan <= kMaxTValue);
return tspan >> 10;
}
// can't use tangents, since we need [0..1..................2] to be seen
// as definitely not a line (it is when drawn, but not parametrically)
// so we compare midpoints
#define CHEAP_DIST_LIMIT (SK_Scalar1/2) // just made this value up
static bool quad_too_curvy(const SkPoint pts[3], SkScalar tolerance) {
// diff = (a/4 + b/2 + c/4) - (a/2 + c/2)
// diff = -a/4 + b/2 - c/4
SkScalar dx = SkScalarHalf(pts[1].fX) -
SkScalarHalf(SkScalarHalf(pts[0].fX + pts[2].fX));
SkScalar dy = SkScalarHalf(pts[1].fY) -
SkScalarHalf(SkScalarHalf(pts[0].fY + pts[2].fY));
SkScalar dist = std::max(SkScalarAbs(dx), SkScalarAbs(dy));
return dist > tolerance;
}
static bool conic_too_curvy(const SkPoint& firstPt, const SkPoint& midTPt,
const SkPoint& lastPt, SkScalar tolerance) {
SkPoint midEnds = firstPt + lastPt;
midEnds *= 0.5f;
SkVector dxy = midTPt - midEnds;
SkScalar dist = std::max(SkScalarAbs(dxy.fX), SkScalarAbs(dxy.fY));
return dist > tolerance;
}
static bool cheap_dist_exceeds_limit(const SkPoint& pt, SkScalar x, SkScalar y,
SkScalar tolerance) {
SkScalar dist = std::max(SkScalarAbs(x - pt.fX), SkScalarAbs(y - pt.fY));
// just made up the 1/2
return dist > tolerance;
}
static bool cubic_too_curvy(const SkPoint pts[4], SkScalar tolerance) {
return cheap_dist_exceeds_limit(pts[1],
SkScalarInterp(pts[0].fX, pts[3].fX, SK_Scalar1/3),
SkScalarInterp(pts[0].fY, pts[3].fY, SK_Scalar1/3), tolerance)
||
cheap_dist_exceeds_limit(pts[2],
SkScalarInterp(pts[0].fX, pts[3].fX, SK_Scalar1*2/3),
SkScalarInterp(pts[0].fY, pts[3].fY, SK_Scalar1*2/3), tolerance);
}
class SkContourMeasureIter::Impl {
public:
Impl(const SkPath& path, bool forceClosed, SkScalar resScale)
: fIter(SkPathPriv::Iterate(path).begin())
, fPath(path)
, fTolerance(CHEAP_DIST_LIMIT * SkScalarInvert(resScale))
, fForceClosed(forceClosed) {}
bool hasNextSegments() const { return fIter != SkPathPriv::Iterate(fPath).end(); }
SkContourMeasure* buildSegments();
private:
SkPathPriv::RangeIter fIter;
SkPath fPath;
SkScalar fTolerance;
bool fForceClosed;
// temporary
SkTDArray<SkContourMeasure::Segment> fSegments;
SkTDArray<SkPoint> fPts; // Points used to define the segments
SkScalar compute_line_seg(SkPoint p0, SkPoint p1, SkScalar distance, unsigned ptIndex);
SkScalar compute_quad_segs(const SkPoint pts[3], SkScalar distance,
int mint, int maxt, unsigned ptIndex);
SkScalar compute_conic_segs(const SkConic& conic, SkScalar distance,
int mint, const SkPoint& minPt,
int maxt, const SkPoint& maxPt,
unsigned ptIndex);
SkScalar compute_cubic_segs(const SkPoint pts[4], SkScalar distance,
int mint, int maxt, unsigned ptIndex);
};
SkScalar SkContourMeasureIter::Impl::compute_quad_segs(const SkPoint pts[3], SkScalar distance,
int mint, int maxt, unsigned ptIndex) {
if (tspan_big_enough(maxt - mint) && quad_too_curvy(pts, fTolerance)) {
SkPoint tmp[5];
int halft = (mint + maxt) >> 1;
SkChopQuadAtHalf(pts, tmp);
distance = this->compute_quad_segs(tmp, distance, mint, halft, ptIndex);
distance = this->compute_quad_segs(&tmp[2], distance, halft, maxt, ptIndex);
} else {
SkScalar d = SkPoint::Distance(pts[0], pts[2]);
SkScalar prevD = distance;
distance += d;
if (distance > prevD) {
SkASSERT(ptIndex < (unsigned)fPts.count());
SkContourMeasure::Segment* seg = fSegments.append();
seg->fDistance = distance;
seg->fPtIndex = ptIndex;
seg->fType = kQuad_SegType;
seg->fTValue = maxt;
}
}
return distance;
}
SkScalar SkContourMeasureIter::Impl::compute_conic_segs(const SkConic& conic, SkScalar distance,
int mint, const SkPoint& minPt,
int maxt, const SkPoint& maxPt,
unsigned ptIndex) {
int halft = (mint + maxt) >> 1;
SkPoint halfPt = conic.evalAt(tValue2Scalar(halft));
if (!halfPt.isFinite()) {
return distance;
}
if (tspan_big_enough(maxt - mint) && conic_too_curvy(minPt, halfPt, maxPt, fTolerance)) {
distance = this->compute_conic_segs(conic, distance, mint, minPt, halft, halfPt, ptIndex);
distance = this->compute_conic_segs(conic, distance, halft, halfPt, maxt, maxPt, ptIndex);
} else {
SkScalar d = SkPoint::Distance(minPt, maxPt);
SkScalar prevD = distance;
distance += d;
if (distance > prevD) {
SkASSERT(ptIndex < (unsigned)fPts.count());
SkContourMeasure::Segment* seg = fSegments.append();
seg->fDistance = distance;
seg->fPtIndex = ptIndex;
seg->fType = kConic_SegType;
seg->fTValue = maxt;
}
}
return distance;
}
SkScalar SkContourMeasureIter::Impl::compute_cubic_segs(const SkPoint pts[4], SkScalar distance,
int mint, int maxt, unsigned ptIndex) {
if (tspan_big_enough(maxt - mint) && cubic_too_curvy(pts, fTolerance)) {
SkPoint tmp[7];
int halft = (mint + maxt) >> 1;
SkChopCubicAtHalf(pts, tmp);
distance = this->compute_cubic_segs(tmp, distance, mint, halft, ptIndex);
distance = this->compute_cubic_segs(&tmp[3], distance, halft, maxt, ptIndex);
} else {
SkScalar d = SkPoint::Distance(pts[0], pts[3]);
SkScalar prevD = distance;
distance += d;
if (distance > prevD) {
SkASSERT(ptIndex < (unsigned)fPts.count());
SkContourMeasure::Segment* seg = fSegments.append();
seg->fDistance = distance;
seg->fPtIndex = ptIndex;
seg->fType = kCubic_SegType;
seg->fTValue = maxt;
}
}
return distance;
}
SkScalar SkContourMeasureIter::Impl::compute_line_seg(SkPoint p0, SkPoint p1, SkScalar distance,
unsigned ptIndex) {
SkScalar d = SkPoint::Distance(p0, p1);
SkASSERT(d >= 0);
SkScalar prevD = distance;
distance += d;
if (distance > prevD) {
SkASSERT((unsigned)ptIndex < (unsigned)fPts.count());
SkContourMeasure::Segment* seg = fSegments.append();
seg->fDistance = distance;
seg->fPtIndex = ptIndex;
seg->fType = kLine_SegType;
seg->fTValue = kMaxTValue;
}
return distance;
}
SkContourMeasure* SkContourMeasureIter::Impl::buildSegments() {
int ptIndex = -1;
SkScalar distance = 0;
bool haveSeenClose = fForceClosed;
bool haveSeenMoveTo = false;
/* Note:
* as we accumulate distance, we have to check that the result of +=
* actually made it larger, since a very small delta might be > 0, but
* still have no effect on distance (if distance >>> delta).
*
* We do this check below, and in compute_quad_segs and compute_cubic_segs
*/
fSegments.reset();
fPts.reset();
auto end = SkPathPriv::Iterate(fPath).end();
for (; fIter != end; ++fIter) {
auto [verb, pts, w] = *fIter;
if (haveSeenMoveTo && verb == SkPathVerb::kMove) {
break;
}
switch (verb) {
case SkPathVerb::kMove:
ptIndex += 1;
fPts.append(1, pts);
SkASSERT(!haveSeenMoveTo);
haveSeenMoveTo = true;
break;
case SkPathVerb::kLine: {
SkASSERT(haveSeenMoveTo);
SkScalar prevD = distance;
distance = this->compute_line_seg(pts[0], pts[1], distance, ptIndex);
if (distance > prevD) {
fPts.append(1, pts + 1);
ptIndex++;
}
} break;
case SkPathVerb::kQuad: {
SkASSERT(haveSeenMoveTo);
SkScalar prevD = distance;
distance = this->compute_quad_segs(pts, distance, 0, kMaxTValue, ptIndex);
if (distance > prevD) {
fPts.append(2, pts + 1);
ptIndex += 2;
}
} break;
case SkPathVerb::kConic: {
SkASSERT(haveSeenMoveTo);
const SkConic conic(pts, *w);
SkScalar prevD = distance;
distance = this->compute_conic_segs(conic, distance, 0, conic.fPts[0],
kMaxTValue, conic.fPts[2], ptIndex);
if (distance > prevD) {
// we store the conic weight in our next point, followed by the last 2 pts
// thus to reconstitue a conic, you'd need to say
// SkConic(pts[0], pts[2], pts[3], weight = pts[1].fX)
fPts.append()->set(conic.fW, 0);
fPts.append(2, pts + 1);
ptIndex += 3;
}
} break;
case SkPathVerb::kCubic: {
SkASSERT(haveSeenMoveTo);
SkScalar prevD = distance;
distance = this->compute_cubic_segs(pts, distance, 0, kMaxTValue, ptIndex);
if (distance > prevD) {
fPts.append(3, pts + 1);
ptIndex += 3;
}
} break;
case SkPathVerb::kClose:
haveSeenClose = true;
break;
}
}
if (!SkScalarIsFinite(distance)) {
return nullptr;
}
if (fSegments.count() == 0) {
return nullptr;
}
if (haveSeenClose) {
SkScalar prevD = distance;
SkPoint firstPt = fPts[0];
distance = this->compute_line_seg(fPts[ptIndex], firstPt, distance, ptIndex);
if (distance > prevD) {
*fPts.append() = firstPt;
}
}
#ifdef SK_DEBUG
{
const SkContourMeasure::Segment* seg = fSegments.begin();
const SkContourMeasure::Segment* stop = fSegments.end();
unsigned ptIndex = 0;
SkScalar distance = 0;
// limit the loop to a reasonable number; pathological cases can run for minutes
int maxChecks = 10000000; // set to INT_MAX to defeat the check
while (seg < stop) {
SkASSERT(seg->fDistance > distance);
SkASSERT(seg->fPtIndex >= ptIndex);
SkASSERT(seg->fTValue > 0);
const SkContourMeasure::Segment* s = seg;
while (s < stop - 1 && s[0].fPtIndex == s[1].fPtIndex && --maxChecks > 0) {
SkASSERT(s[0].fType == s[1].fType);
SkASSERT(s[0].fTValue < s[1].fTValue);
s += 1;
}
distance = seg->fDistance;
ptIndex = seg->fPtIndex;
seg += 1;
}
// SkDebugf("\n");
}
#endif
return new SkContourMeasure(std::move(fSegments), std::move(fPts), distance, haveSeenClose);
}
static void compute_pos_tan(const SkPoint pts[], unsigned segType,
SkScalar t, SkPoint* pos, SkVector* tangent) {
switch (segType) {
case kLine_SegType:
if (pos) {
pos->set(SkScalarInterp(pts[0].fX, pts[1].fX, t),
SkScalarInterp(pts[0].fY, pts[1].fY, t));
}
if (tangent) {
tangent->setNormalize(pts[1].fX - pts[0].fX, pts[1].fY - pts[0].fY);
}
break;
case kQuad_SegType:
SkEvalQuadAt(pts, t, pos, tangent);
if (tangent) {
tangent->normalize();
}
break;
case kConic_SegType: {
SkConic(pts[0], pts[2], pts[3], pts[1].fX).evalAt(t, pos, tangent);
if (tangent) {
tangent->normalize();
}
} break;
case kCubic_SegType:
SkEvalCubicAt(pts, t, pos, tangent, nullptr);
if (tangent) {
tangent->normalize();
}
break;
default:
SkDEBUGFAIL("unknown segType");
}
}
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
SkContourMeasureIter::SkContourMeasureIter() {
}
SkContourMeasureIter::SkContourMeasureIter(const SkPath& path, bool forceClosed,
SkScalar resScale) {
this->reset(path, forceClosed, resScale);
}
SkContourMeasureIter::~SkContourMeasureIter() {}
/** Assign a new path, or null to have none.
*/
void SkContourMeasureIter::reset(const SkPath& path, bool forceClosed, SkScalar resScale) {
if (path.isFinite()) {
fImpl = std::make_unique<Impl>(path, forceClosed, resScale);
} else {
fImpl.reset();
}
}
sk_sp<SkContourMeasure> SkContourMeasureIter::next() {
if (!fImpl) {
return nullptr;
}
while (fImpl->hasNextSegments()) {
auto cm = fImpl->buildSegments();
if (cm) {
return sk_sp<SkContourMeasure>(cm);
}
}
return nullptr;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
SkContourMeasure::SkContourMeasure(SkTDArray<Segment>&& segs, SkTDArray<SkPoint>&& pts, SkScalar length, bool isClosed)
: fSegments(std::move(segs))
, fPts(std::move(pts))
, fLength(length)
, fIsClosed(isClosed)
{}
template <typename T, typename K>
int SkTKSearch(const T base[], int count, const K& key) {
SkASSERT(count >= 0);
if (count <= 0) {
return ~0;
}
SkASSERT(base != nullptr); // base may be nullptr if count is zero
unsigned lo = 0;
unsigned hi = count - 1;
while (lo < hi) {
unsigned mid = (hi + lo) >> 1;
if (base[mid].fDistance < key) {
lo = mid + 1;
} else {
hi = mid;
}
}
if (base[hi].fDistance < key) {
hi += 1;
hi = ~hi;
} else if (key < base[hi].fDistance) {
hi = ~hi;
}
return hi;
}
const SkContourMeasure::Segment* SkContourMeasure::distanceToSegment( SkScalar distance,
SkScalar* t) const {
SkDEBUGCODE(SkScalar length = ) this->length();
SkASSERT(distance >= 0 && distance <= length);
const Segment* seg = fSegments.begin();
int count = fSegments.count();
int index = SkTKSearch<Segment, SkScalar>(seg, count, distance);
// don't care if we hit an exact match or not, so we xor index if it is negative
index ^= (index >> 31);
seg = &seg[index];
// now interpolate t-values with the prev segment (if possible)
SkScalar startT = 0, startD = 0;
// check if the prev segment is legal, and references the same set of points
if (index > 0) {
startD = seg[-1].fDistance;
if (seg[-1].fPtIndex == seg->fPtIndex) {
SkASSERT(seg[-1].fType == seg->fType);
startT = seg[-1].getScalarT();
}
}
SkASSERT(seg->getScalarT() > startT);
SkASSERT(distance >= startD);
SkASSERT(seg->fDistance > startD);
*t = startT + (seg->getScalarT() - startT) * (distance - startD) / (seg->fDistance - startD);
return seg;
}
bool SkContourMeasure::getPosTan(SkScalar distance, SkPoint* pos, SkVector* tangent) const {
if (SkScalarIsNaN(distance)) {
return false;
}
const SkScalar length = this->length();
SkASSERT(length > 0 && fSegments.count() > 0);
// pin the distance to a legal range
if (distance < 0) {
distance = 0;
} else if (distance > length) {
distance = length;
}
SkScalar t;
const Segment* seg = this->distanceToSegment(distance, &t);
if (SkScalarIsNaN(t)) {
return false;
}
SkASSERT((unsigned)seg->fPtIndex < (unsigned)fPts.count());
compute_pos_tan(&fPts[seg->fPtIndex], seg->fType, t, pos, tangent);
return true;
}
bool SkContourMeasure::getMatrix(SkScalar distance, SkMatrix* matrix, MatrixFlags flags) const {
SkPoint position;
SkVector tangent;
if (this->getPosTan(distance, &position, &tangent)) {
if (matrix) {
if (flags & kGetTangent_MatrixFlag) {
matrix->setSinCos(tangent.fY, tangent.fX, 0, 0);
} else {
matrix->reset();
}
if (flags & kGetPosition_MatrixFlag) {
matrix->postTranslate(position.fX, position.fY);
}
}
return true;
}
return false;
}
bool SkContourMeasure::getSegment(SkScalar startD, SkScalar stopD, SkPath* dst,
bool startWithMoveTo) const {
SkASSERT(dst);
SkScalar length = this->length(); // ensure we have built our segments
if (startD < 0) {
startD = 0;
}
if (stopD > length) {
stopD = length;
}
if (!(startD <= stopD)) { // catch NaN values as well
return false;
}
if (!fSegments.count()) {
return false;
}
SkPoint p;
SkScalar startT, stopT;
const Segment* seg = this->distanceToSegment(startD, &startT);
if (!SkScalarIsFinite(startT)) {
return false;
}
const Segment* stopSeg = this->distanceToSegment(stopD, &stopT);
if (!SkScalarIsFinite(stopT)) {
return false;
}
SkASSERT(seg <= stopSeg);
if (startWithMoveTo) {
compute_pos_tan(&fPts[seg->fPtIndex], seg->fType, startT, &p, nullptr);
dst->moveTo(p);
}
if (seg->fPtIndex == stopSeg->fPtIndex) {
SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, stopT, dst);
} else {
do {
SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, startT, SK_Scalar1, dst);
seg = SkContourMeasure::Segment::Next(seg);
startT = 0;
} while (seg->fPtIndex < stopSeg->fPtIndex);
SkContourMeasure_segTo(&fPts[seg->fPtIndex], seg->fType, 0, stopT, dst);
}
return true;
}