| /* |
| * 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) { |
| if (phase > intervals[i]) { |
| phase -= intervals[i]; |
| } else { |
| *index = i; |
| return intervals[i] - 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; |
| |
| // watch out for values that might make us go out of bounds |
| if ((len > 0) && SkScalarIsFinite(phase) && SkScalarIsFinite(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); |
| } else { |
| *initialDashLength = -1; // signal bad dash intervals |
| } |
| } |
| |
| 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 = SkScalarMul(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 = SkScalarMulDiv(pathLength, |
| SkIntToScalar(intervalCount), |
| intervalLength); |
| 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 + SkScalarMul(fTangent.fX, d0); |
| SkScalar x1 = fPts[0].fX + SkScalarMul(fTangent.fX, d1); |
| SkScalar y0 = fPts[0].fY + SkScalarMul(fTangent.fY, d0); |
| SkScalar y1 = fPts[0].fY + SkScalarMul(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::FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec* rec, |
| const SkRect* cullRect, const SkScalar aIntervals[], |
| int32_t count, SkScalar initialDashLength, int32_t initialDashIndex, |
| SkScalar intervalLength) { |
| |
| // we do nothing if the src wants to be filled, or if our dashlength is 0 |
| if (rec->isFillStyle() || initialDashLength < 0) { |
| 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 = 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. |
| static const SkScalar kMaxDashCount = 1000000; |
| 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) { |
| SkScalar initialDashLength = 0; |
| int32_t initialDashIndex = 0; |
| SkScalar intervalLength = 0; |
| CalcDashParameters(info.fPhase, info.fIntervals, info.fCount, |
| &initialDashLength, &initialDashIndex, &intervalLength); |
| return FilterDashPath(dst, src, rec, cullRect, info.fIntervals, info.fCount, initialDashLength, |
| initialDashIndex, intervalLength); |
| } |
