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 /* * Copyright 2014 Google Inc. * * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ #include "SkDashPathPriv.h" #include "SkPathMeasure.h" #include "SkStrokeRec.h" static inline int is_even(int x) { return !(x & 1); } static SkScalar find_first_interval(const SkScalar intervals[], SkScalar phase, int32_t* index, int count) { for (int i = 0; i < count; ++i) { SkScalar gap = intervals[i]; if (phase > gap || (phase == gap && gap)) { phase -= gap; } else { *index = i; return gap - phase; } } // If we get here, phase "appears" to be larger than our length. This // shouldn't happen with perfect precision, but we can accumulate errors // during the initial length computation (rounding can make our sum be too // big or too small. In that event, we just have to eat the error here. *index = 0; return intervals[0]; } void SkDashPath::CalcDashParameters(SkScalar phase, const SkScalar intervals[], int32_t count, SkScalar* initialDashLength, int32_t* initialDashIndex, SkScalar* intervalLength, SkScalar* adjustedPhase) { SkScalar len = 0; for (int i = 0; i < count; i++) { len += intervals[i]; } *intervalLength = len; // Adjust phase to be between 0 and len, "flipping" phase if negative. // e.g., if len is 100, then phase of -20 (or -120) is equivalent to 80 if (adjustedPhase) { if (phase < 0) { phase = -phase; if (phase > len) { phase = SkScalarMod(phase, len); } phase = len - phase; // Due to finite precision, it's possible that phase == len, // even after the subtract (if len >>> phase), so fix that here. // This fixes http://crbug.com/124652 . SkASSERT(phase <= len); if (phase == len) { phase = 0; } } else if (phase >= len) { phase = SkScalarMod(phase, len); } *adjustedPhase = phase; } SkASSERT(phase >= 0 && phase < len); *initialDashLength = find_first_interval(intervals, phase, initialDashIndex, count); SkASSERT(*initialDashLength >= 0); SkASSERT(*initialDashIndex >= 0 && *initialDashIndex < count); } static void outset_for_stroke(SkRect* rect, const SkStrokeRec& rec) { SkScalar radius = SkScalarHalf(rec.getWidth()); if (0 == radius) { radius = SK_Scalar1; // hairlines } if (SkPaint::kMiter_Join == rec.getJoin()) { radius *= rec.getMiter(); } rect->outset(radius, radius); } // Only handles lines for now. If returns true, dstPath is the new (smaller) // path. If returns false, then dstPath parameter is ignored. static bool cull_path(const SkPath& srcPath, const SkStrokeRec& rec, const SkRect* cullRect, SkScalar intervalLength, SkPath* dstPath) { if (nullptr == cullRect) { return false; } SkPoint pts[2]; if (!srcPath.isLine(pts)) { return false; } SkRect bounds = *cullRect; outset_for_stroke(&bounds, rec); SkScalar dx = pts[1].x() - pts[0].x(); SkScalar dy = pts[1].y() - pts[0].y(); // just do horizontal lines for now (lazy) if (dy) { return false; } SkScalar minX = pts[0].fX; SkScalar maxX = pts[1].fX; if (dx < 0) { SkTSwap(minX, maxX); } SkASSERT(minX <= maxX); if (maxX < bounds.fLeft || minX > bounds.fRight) { return false; } // Now we actually perform the chop, removing the excess to the left and // right of the bounds (keeping our new line "in phase" with the dash, // hence the (mod intervalLength). if (minX < bounds.fLeft) { minX = bounds.fLeft - SkScalarMod(bounds.fLeft - minX, intervalLength); } if (maxX > bounds.fRight) { maxX = bounds.fRight + SkScalarMod(maxX - bounds.fRight, intervalLength); } SkASSERT(maxX >= minX); if (dx < 0) { SkTSwap(minX, maxX); } pts[0].fX = minX; pts[1].fX = maxX; dstPath->moveTo(pts[0]); dstPath->lineTo(pts[1]); return true; } class SpecialLineRec { public: bool init(const SkPath& src, SkPath* dst, SkStrokeRec* rec, int intervalCount, SkScalar intervalLength) { if (rec->isHairlineStyle() || !src.isLine(fPts)) { return false; } // can relax this in the future, if we handle square and round caps if (SkPaint::kButt_Cap != rec->getCap()) { return false; } SkScalar pathLength = SkPoint::Distance(fPts[0], fPts[1]); fTangent = fPts[1] - fPts[0]; if (fTangent.isZero()) { return false; } fPathLength = pathLength; fTangent.scale(SkScalarInvert(pathLength)); fTangent.rotateCCW(&fNormal); fNormal.scale(SkScalarHalf(rec->getWidth())); // now estimate how many quads will be added to the path // resulting segments = pathLen * intervalCount / intervalLen // resulting points = 4 * segments SkScalar ptCount = pathLength * intervalCount / (float)intervalLength; ptCount = SkTMin(ptCount, SkDashPath::kMaxDashCount); int n = SkScalarCeilToInt(ptCount) << 2; dst->incReserve(n); // we will take care of the stroking rec->setFillStyle(); return true; } void addSegment(SkScalar d0, SkScalar d1, SkPath* path) const { SkASSERT(d0 <= fPathLength); // clamp the segment to our length if (d1 > fPathLength) { d1 = fPathLength; } SkScalar x0 = fPts[0].fX + fTangent.fX * d0; SkScalar x1 = fPts[0].fX + fTangent.fX * d1; SkScalar y0 = fPts[0].fY + fTangent.fY * d0; SkScalar y1 = fPts[0].fY + fTangent.fY * d1; SkPoint pts[4]; pts[0].set(x0 + fNormal.fX, y0 + fNormal.fY); // moveTo pts[1].set(x1 + fNormal.fX, y1 + fNormal.fY); // lineTo pts[2].set(x1 - fNormal.fX, y1 - fNormal.fY); // lineTo pts[3].set(x0 - fNormal.fX, y0 - fNormal.fY); // lineTo path->addPoly(pts, SK_ARRAY_COUNT(pts), false); } private: SkPoint fPts[2]; SkVector fTangent; SkVector fNormal; SkScalar fPathLength; }; bool SkDashPath::InternalFilter(SkPath* dst, const SkPath& src, SkStrokeRec* rec, const SkRect* cullRect, const SkScalar aIntervals[], int32_t count, SkScalar initialDashLength, int32_t initialDashIndex, SkScalar intervalLength, StrokeRecApplication strokeRecApplication) { // we do nothing if the src wants to be filled SkStrokeRec::Style style = rec->getStyle(); if (SkStrokeRec::kFill_Style == style || SkStrokeRec::kStrokeAndFill_Style == style) { return false; } const SkScalar* intervals = aIntervals; SkScalar dashCount = 0; int segCount = 0; SkPath cullPathStorage; const SkPath* srcPtr = &src; if (cull_path(src, *rec, cullRect, intervalLength, &cullPathStorage)) { srcPtr = &cullPathStorage; } SpecialLineRec lineRec; bool specialLine = (StrokeRecApplication::kAllow == strokeRecApplication) && lineRec.init(*srcPtr, dst, rec, count >> 1, intervalLength); SkPathMeasure meas(*srcPtr, false, rec->getResScale()); do { bool skipFirstSegment = meas.isClosed(); bool addedSegment = false; SkScalar length = meas.getLength(); int index = initialDashIndex; // Since the path length / dash length ratio may be arbitrarily large, we can exert // significant memory pressure while attempting to build the filtered path. To avoid this, // we simply give up dashing beyond a certain threshold. // // The original bug report (http://crbug.com/165432) is based on a path yielding more than // 90 million dash segments and crashing the memory allocator. A limit of 1 million // segments seems reasonable: at 2 verbs per segment * 9 bytes per verb, this caps the // maximum dash memory overhead at roughly 17MB per path. dashCount += length * (count >> 1) / intervalLength; if (dashCount > kMaxDashCount) { dst->reset(); return false; } // Using double precision to avoid looping indefinitely due to single precision rounding // (for extreme path_length/dash_length ratios). See test_infinite_dash() unittest. double distance = 0; double dlen = initialDashLength; while (distance < length) { SkASSERT(dlen >= 0); addedSegment = false; if (is_even(index) && !skipFirstSegment) { addedSegment = true; ++segCount; if (specialLine) { lineRec.addSegment(SkDoubleToScalar(distance), SkDoubleToScalar(distance + dlen), dst); } else { meas.getSegment(SkDoubleToScalar(distance), SkDoubleToScalar(distance + dlen), dst, true); } } distance += dlen; // clear this so we only respect it the first time around skipFirstSegment = false; // wrap around our intervals array if necessary index += 1; SkASSERT(index <= count); if (index == count) { index = 0; } // fetch our next dlen dlen = intervals[index]; } // extend if we ended on a segment and we need to join up with the (skipped) initial segment if (meas.isClosed() && is_even(initialDashIndex) && initialDashLength >= 0) { meas.getSegment(0, initialDashLength, dst, !addedSegment); ++segCount; } } while (meas.nextContour()); if (segCount > 1) { dst->setConvexity(SkPath::kConcave_Convexity); } return true; } bool SkDashPath::FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec* rec, const SkRect* cullRect, const SkPathEffect::DashInfo& info) { if (!ValidDashPath(info.fPhase, info.fIntervals, info.fCount)) { return false; } SkScalar initialDashLength = 0; int32_t initialDashIndex = 0; SkScalar intervalLength = 0; CalcDashParameters(info.fPhase, info.fIntervals, info.fCount, &initialDashLength, &initialDashIndex, &intervalLength); return InternalFilter(dst, src, rec, cullRect, info.fIntervals, info.fCount, initialDashLength, initialDashIndex, intervalLength); } bool SkDashPath::ValidDashPath(SkScalar phase, const SkScalar intervals[], int32_t count) { if (count < 2 || !SkIsAlign2(count)) { return false; } SkScalar length = 0; for (int i = 0; i < count; i++) { if (intervals[i] < 0) { return false; } length += intervals[i]; } // watch out for values that might make us go out of bounds return length > 0 && SkScalarIsFinite(phase) && SkScalarIsFinite(length); }