C++ SkDQuad::dxdyAtT方法代码示例

// returns false if there's more than one intercept or the intercept doesn't match the point
// returns true if the intercept was successfully added or if the
// original quads need to be subdivided
static bool add_intercept(const SkDQuad& q1, const SkDQuad& q2, double tMin, double tMax,
                          SkIntersections* i, bool* subDivide) {
    double tMid = (tMin + tMax) / 2;
    SkDPoint mid = q2.ptAtT(tMid);
    SkDLine line;
    line[0] = line[1] = mid;
    SkDVector dxdy = q2.dxdyAtT(tMid);
    line[0] -= dxdy;
    line[1] += dxdy;
    SkIntersections rootTs;
    rootTs.allowNear(false);
    int roots = rootTs.intersect(q1, line);
    if (roots == 0) {
        if (subDivide) {
            *subDivide = true;
        }
        return true;
    }
    if (roots == 2) {
        return false;
    }
    SkDPoint pt2 = q1.ptAtT(rootTs[0][0]);
    if (!pt2.approximatelyEqualHalf(mid)) {
        return false;
    }
    i->insertSwap(rootTs[0][0], tMid, pt2);
    return true;
}

// determine that slop required after quad/quad finds a candidate intersection
// use the cross of the tangents plus the distance from 1 or 0 as knobs
DEF_TEST(PathOpsCubicQuadSlop, reporter) {
    // create a random non-selfintersecting cubic
    // break it into quadratics
    // offset the quadratic, measuring the slop required to find the intersection
    if (!gPathOpCubicQuadSlopVerbose) {  // takes a while to run -- so exclude it by default
        return;
    }
    int results[101];
    sk_bzero(results, sizeof(results));
    double minCross[101];
    sk_bzero(minCross, sizeof(minCross));
    double maxCross[101];
    sk_bzero(maxCross, sizeof(maxCross));
    double sumCross[101];
    sk_bzero(sumCross, sizeof(sumCross));
    int foundOne = 0;
    int slopCount = 1;
    SkRandom ran;
    for (int index = 0; index < 10000000; ++index) {
        if (index % 1000 == 999) SkDebugf(".");
        SkDCubic cubic = {{
                {ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)},
                {ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)},
                {ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)},
                {ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)}
        }};
        SkIntersections i;
        if (i.intersect(cubic)) {
            continue;
        }
        SkSTArray<kCubicToQuadSubdivisionDepth, double, true> ts;
        cubic.toQuadraticTs(cubic.calcPrecision(), &ts);
        double tStart = 0;
        int tsCount = ts.count();
        for (int i1 = 0; i1 <= tsCount; ++i1) {
            const double tEnd = i1 < tsCount ? ts[i1] : 1;
            SkDCubic part = cubic.subDivide(tStart, tEnd);
            SkDQuad quad = part.toQuad();
            SkReduceOrder reducer;
            int order = reducer.reduce(quad);
            if (order != 3) {
                continue;
            }
            for (int i2 = 0; i2 < 100; ++i2) {
                SkDPoint endDisplacement = {ran.nextRangeF(-100, 100), ran.nextRangeF(-100, 100)};
                SkDQuad nearby = {{
                        {quad[0].fX + endDisplacement.fX, quad[0].fY + endDisplacement.fY},
                        {quad[1].fX + ran.nextRangeF(-100, 100), quad[1].fY + ran.nextRangeF(-100, 100)},
                        {quad[2].fX - endDisplacement.fX, quad[2].fY - endDisplacement.fY}
                }};
                order = reducer.reduce(nearby);
                if (order != 3) {
                    continue;
                }
                SkIntersections locals;
                locals.allowNear(false);
                locals.intersect(quad, nearby);
                if (locals.used() != 1) {
                    continue;
                }
                // brute force find actual intersection
                SkDLine cubicLine = {{ {0, 0}, {cubic[0].fX, cubic[0].fY } }};
                SkIntersections liner;
                int i3;
                int found = -1;
                int foundErr = true;
                for (i3 = 1; i3 <= 1000; ++i3) {
                    cubicLine[0] = cubicLine[1];
                    cubicLine[1] = cubic.ptAtT(i3 / 1000.);
                    liner.reset();
                    liner.allowNear(false);
                    liner.intersect(nearby, cubicLine);
                    if (liner.used() == 0) {
                        continue;
                    }
                    if (liner.used() > 1) {
                        foundErr = true;
                        break;
                    }
                    if (found > 0) {
                        foundErr = true;
                        break;
                    }
                    foundErr = false;
                    found = i3;
                }
                if (foundErr) {
                    continue;
                }
                SkDVector dist = liner.pt(0) - locals.pt(0);
                SkDVector qV = nearby.dxdyAtT(locals[0][0]);
                double cubicT = (found - 1 + liner[1][0]) / 1000.;
                SkDVector cV = cubic.dxdyAtT(cubicT);
                double qxc = qV.crossCheck(cV);
                double qvLen = qV.length();
                double cvLen = cV.length();
                double maxLen = SkTMax(qvLen, cvLen);
                qxc /= maxLen;
//.........这里部分代码省略.........

static bool is_linear_inner(const SkDQuad& q1, double t1s, double t1e, const SkDQuad& q2,
                            double t2s, double t2e, SkIntersections* i, bool* subDivide) {
    SkDQuad hull = q1.subDivide(t1s, t1e);
    SkDLine line = {{hull[2], hull[0]}};
    const SkDLine* testLines[] = { &line, (const SkDLine*) &hull[0], (const SkDLine*) &hull[1] };
    const size_t kTestCount = SK_ARRAY_COUNT(testLines);
    SkSTArray<kTestCount * 2, double, true> tsFound;
    for (size_t index = 0; index < kTestCount; ++index) {
        SkIntersections rootTs;
        rootTs.allowNear(false);
        int roots = rootTs.intersect(q2, *testLines[index]);
        for (int idx2 = 0; idx2 < roots; ++idx2) {
            double t = rootTs[0][idx2];
#ifdef SK_DEBUG
            SkDPoint qPt = q2.ptAtT(t);
            SkDPoint lPt = testLines[index]->ptAtT(rootTs[1][idx2]);
            SkASSERT(qPt.approximatelyEqual(lPt));
#endif
            if (approximately_negative(t - t2s) || approximately_positive(t - t2e)) {
                continue;
            }
            tsFound.push_back(rootTs[0][idx2]);
        }
    }
    int tCount = tsFound.count();
    if (tCount <= 0) {
        return true;
    }
    double tMin, tMax;
    if (tCount == 1) {
        tMin = tMax = tsFound[0];
    } else {
        SkASSERT(tCount > 1);
        SkTQSort<double>(tsFound.begin(), tsFound.end() - 1);
        tMin = tsFound[0];
        tMax = tsFound[tsFound.count() - 1];
    }
    SkDPoint end = q2.ptAtT(t2s);
    bool startInTriangle = hull.pointInHull(end);
    if (startInTriangle) {
        tMin = t2s;
    }
    end = q2.ptAtT(t2e);
    bool endInTriangle = hull.pointInHull(end);
    if (endInTriangle) {
        tMax = t2e;
    }
    int split = 0;
    SkDVector dxy1, dxy2;
    if (tMin != tMax || tCount > 2) {
        dxy2 = q2.dxdyAtT(tMin);
        for (int index = 1; index < tCount; ++index) {
            dxy1 = dxy2;
            dxy2 = q2.dxdyAtT(tsFound[index]);
            double dot = dxy1.dot(dxy2);
            if (dot < 0) {
                split = index - 1;
                break;
            }
        }
    }
    if (split == 0) {  // there's one point
        if (add_intercept(q1, q2, tMin, tMax, i, subDivide)) {
            return true;
        }
        i->swap();
        return is_linear_inner(q2, tMin, tMax, q1, t1s, t1e, i, subDivide);
    }
    // At this point, we have two ranges of t values -- treat each separately at the split
    bool result;
    if (add_intercept(q1, q2, tMin, tsFound[split - 1], i, subDivide)) {
        result = true;
    } else {
        i->swap();
        result = is_linear_inner(q2, tMin, tsFound[split - 1], q1, t1s, t1e, i, subDivide);
    }
    if (add_intercept(q1, q2, tsFound[split], tMax, i, subDivide)) {
        result = true;
    } else {
        i->swap();
        result |= is_linear_inner(q2, tsFound[split], tMax, q1, t1s, t1e, i, subDivide);
    }
    return result;
}