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 /* * Copyright 2011 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/SkScalar.h" #include "src/core/SkMathPriv.h" #include "src/core/SkPointPriv.h" #include "tests/Test.h" /* Duplicates lots of code from gpu/src/GrPathUtils.cpp It'd be nice not to do so, but that code's set up currently to only have a single implementation. */ // Sk uses 6, Gr (implicitly) used 10, both apparently arbitrarily. #define MAX_COEFF_SHIFT 6 static const uint32_t MAX_POINTS_PER_CURVE = 1 << MAX_COEFF_SHIFT; // max + 0.5 min has error [0.0, 0.12] // max + 0.375 min has error [-.03, 0.07] // 0.96043387 max + 0.397824735 min has error [-.06, +.05] // For determining the maximum possible number of points to use in // drawing a quadratic, we want to err on the high side. static inline int cheap_distance(SkScalar dx, SkScalar dy) { int idx = SkAbs32(SkScalarRoundToInt(dx)); int idy = SkAbs32(SkScalarRoundToInt(dy)); if (idx > idy) { idx += idy >> 1; } else { idx = idy + (idx >> 1); } return idx; } static inline int estimate_distance(const SkPoint points[]) { return cheap_distance(points[1].fX * 2 - points[2].fX - points[0].fX, points[1].fY * 2 - points[2].fY - points[0].fY); } static inline SkScalar compute_distance(const SkPoint points[]) { return SkPointPriv::DistanceToLineSegmentBetween(points[1], points[0], points[2]); } static inline uint32_t estimate_pointCount(int distance) { // Includes -2 bias because this estimator runs 4x high? int shift = 30 - SkCLZ(distance); // Clamp to zero if above subtraction went negative. shift &= ~(shift>>31); if (shift > MAX_COEFF_SHIFT) { shift = MAX_COEFF_SHIFT; } return 1 << shift; } static inline uint32_t compute_pointCount(SkScalar d, SkScalar tol) { if (d < tol) { return 1; } else { int temp = SkScalarCeilToInt(SkScalarSqrt(d / tol)); uint32_t count = std::min(SkNextPow2(temp), MAX_POINTS_PER_CURVE); return count; } } static uint32_t quadraticPointCount_EE(const SkPoint points[]) { int distance = estimate_distance(points); return estimate_pointCount(distance); } static uint32_t quadraticPointCount_EC(const SkPoint points[], SkScalar tol) { int distance = estimate_distance(points); return compute_pointCount(SkIntToScalar(distance), tol); } static uint32_t quadraticPointCount_CE(const SkPoint points[]) { SkScalar distance = compute_distance(points); return estimate_pointCount(SkScalarRoundToInt(distance)); } static uint32_t quadraticPointCount_CC(const SkPoint points[], SkScalar tol) { SkScalar distance = compute_distance(points); return compute_pointCount(distance, tol); } // Curve from samplecode/SampleSlides.cpp static const int gXY[] = { 4, 0, 0, -4, 8, -4, 12, 0, 8, 4, 0, 4 }; static const int gSawtooth[] = { 0, 0, 10, 10, 20, 20, 30, 10, 40, 0, 50, -10, 60, -20, 70, -10, 80, 0 }; static const int gOvalish[] = { 0, 0, 5, 15, 20, 20, 35, 15, 40, 0 }; static const int gSharpSawtooth[] = { 0, 0, 1, 10, 2, 0, 3, -10, 4, 0 }; // Curve crosses back over itself around 0,10 static const int gRibbon[] = { -4, 0, 4, 20, 0, 25, -4, 20, 4, 0 }; static bool one_d_pe(const int* array, const unsigned int count, skiatest::Reporter* reporter) { SkPoint path [3]; path[1] = SkPoint::Make(SkIntToScalar(array[0]), SkIntToScalar(array[1])); path[2] = SkPoint::Make(SkIntToScalar(array[2]), SkIntToScalar(array[3])); int numErrors = 0; for (unsigned i = 4; i < count; i += 2) { path[0] = path[1]; path[1] = path[2]; path[2] = SkPoint::Make(SkIntToScalar(array[i]), SkIntToScalar(array[i+1])); uint32_t computedCount = quadraticPointCount_CC(path, SkIntToScalar(1)); uint32_t estimatedCount = quadraticPointCount_EE(path); if ((false)) { // avoid bit rot, suppress warning computedCount = quadraticPointCount_EC(path, SkIntToScalar(1)); estimatedCount = quadraticPointCount_CE(path); } // Allow estimated to be high by a factor of two, but no less than // the computed value. bool isAccurate = (estimatedCount >= computedCount) && (estimatedCount <= 2 * computedCount); if (!isAccurate) { ERRORF(reporter, "Curve from %.2f %.2f through %.2f %.2f to " "%.2f %.2f computes %d, estimates %d\n", path[0].fX, path[0].fY, path[1].fX, path[1].fY, path[2].fX, path[2].fY, computedCount, estimatedCount); numErrors++; } } return (numErrors == 0); } static void TestQuadPointCount(skiatest::Reporter* reporter) { one_d_pe(gXY, std::size(gXY), reporter); one_d_pe(gSawtooth, std::size(gSawtooth), reporter); one_d_pe(gOvalish, std::size(gOvalish), reporter); one_d_pe(gSharpSawtooth, std::size(gSharpSawtooth), reporter); one_d_pe(gRibbon, std::size(gRibbon), reporter); } DEF_TEST(PathCoverage, reporter) { TestQuadPointCount(reporter); }