Fix issue in tool cut spline.

Infinite loop while calculating a t parameter.

ChangeLog.txt

@@ -29,6 +29,7 @@
 - New path validation Invalid segment.
 - [smart-pattern/valentina#43] Background image.
 - Fix alias for tool Cut Arc.
+- Fix infinite loop in tool cut spline.
 
 # Valentina 0.7.49 July 1, 2021
 - Fix crash.

src/libs/vgeometry/vabstractcubicbezier.cpp

@@ -503,28 +503,38 @@ QString VAbstractCubicBezier::NameForHistory(const QString &toolName) const
 }
 
 //---------------------------------------------------------------------------------------------------------------------
-qreal VAbstractCubicBezier::GetParmT(qreal length) const
+auto VAbstractCubicBezier::GetParmT(qreal length) const -> qreal
 {
+    const qreal base = GetRealLength();
     if (length < 0)
     {
         return 0;
     }
-    else if (length > GetLength())
+
+    if (length > base)
     {
-        length = GetLength();
+        length = base;
     }
 
-    const qreal eps = 0.001 * length;
+    constexpr qreal eps = UnitConvertor(0.001, Unit::Mm, Unit::Px);
     qreal parT = 0.5;
     qreal step = parT;
-    qreal splLength = LengthT(parT);
+    qreal splLength = 0;
 
-    while (qAbs(splLength - length) > eps)
+    do
     {
+        splLength = RealLengthByT(parT);
         step /= 2.0;
+
+        if (qFuzzyIsNull(step))
+        {
+            break;
+        }
+
         splLength > length ? parT -= step : parT += step;
-        splLength = LengthT(parT);
     }
+    while (qAbs(splLength - length) > eps);
+
     return parT;
 }
 
@@ -591,7 +601,7 @@ qreal VAbstractCubicBezier::LengthBezier(const QPointF &p1, const QPointF &p2, c
 }
 
 //---------------------------------------------------------------------------------------------------------------------
-qreal VAbstractCubicBezier::LengthT(qreal t) const
+qreal VAbstractCubicBezier::RealLengthByT(qreal t) const
 {
     if (t < 0 || t > 1)
     {
@@ -622,5 +632,5 @@ qreal VAbstractCubicBezier::LengthT(qreal t) const
     seg123_234.setLength(seg123_234.length () * t);
     const QPointF p1234 = seg123_234.p2();
 
-    return LengthBezier ( static_cast<QPointF>(GetP1()), p12, p123, p1234, GetApproximationScale());
+    return LengthBezier ( static_cast<QPointF>(GetP1()), p12, p123, p1234, maxCurveApproximationScale);
 }

src/libs/vgeometry/vabstractcubicbezier.h

@@ -62,7 +62,7 @@ public:
     virtual QString NameForHistory(const QString &toolName) const override;
 
     qreal GetParmT(qreal length) const;
-    qreal LengthT(qreal t) const;
+    qreal RealLengthByT(qreal t) const;
 
 protected:
     virtual void CreateName() override;
@@ -75,6 +75,7 @@ protected:
 
     virtual QPointF GetControlPoint1() const =0;
     virtual QPointF GetControlPoint2() const =0;
+    virtual auto GetRealLength() const -> qreal =0;
 };
 
 QT_WARNING_POP

src/libs/vgeometry/vcubicbezier.cpp

@@ -252,3 +252,10 @@ QPointF VCubicBezier::GetControlPoint2() const
 {
     return static_cast<QPointF>(GetP3());
 }
+
+//---------------------------------------------------------------------------------------------------------------------
+qreal VCubicBezier::GetRealLength() const
+{
+    return LengthBezier (static_cast<QPointF>(GetP1()), static_cast<QPointF>(GetP2()),
+                         static_cast<QPointF>(GetP3()), static_cast<QPointF>(GetP4()), maxCurveApproximationScale);
+}

src/libs/vgeometry/vcubicbezier.h

@@ -84,6 +84,7 @@ public:
 protected:
     virtual QPointF GetControlPoint1() const override;
     virtual QPointF GetControlPoint2() const override;
+    auto GetRealLength() const -> qreal override;
 
 private:
     QSharedDataPointer<VCubicBezierData> d;

src/libs/vgeometry/vspline.cpp

@@ -611,3 +611,10 @@ QPointF VSpline::GetControlPoint2() const
 {
     return static_cast<QPointF>(GetP3 ());
 }
+
+//---------------------------------------------------------------------------------------------------------------------
+auto VSpline::GetRealLength() const -> qreal
+{
+    return LengthBezier(static_cast<QPointF>(GetP1()), static_cast<QPointF>(GetP2()), static_cast<QPointF>(GetP3()),
+                        static_cast<QPointF>(GetP4()), maxCurveApproximationScale);
+}

src/libs/vgeometry/vspline.h

@@ -117,6 +117,7 @@ public:
 protected:
     virtual QPointF GetControlPoint1() const override;
     virtual QPointF GetControlPoint2() const override;
+    auto GetRealLength () const -> qreal override;
 private:
     QSharedDataPointer<VSplineData> d;
     QVector<qreal> CalcT(qreal curveCoord1, qreal curveCoord2, qreal curveCoord3, qreal curveCoord4,

src/test/ValentinaTest/tst_vspline.cpp

@@ -28,6 +28,7 @@
 
 #include "tst_vspline.h"
 #include "../vgeometry/vspline.h"
+#include "def.h"
 
 #include <QtTest>
 
@@ -717,18 +718,56 @@ void TST_VSpline::CompareThreeWays()
     CompareSplines(spl3, spl1);
 }
 
+//---------------------------------------------------------------------------------------------------------------------
+void TST_VSpline::TestParametrT_data()
+{
+    QTest::addColumn<VSpline>("spl");
+    QTest::addColumn<qreal>("length");
+
+    VPointF p1(30, 39.999874015748034, QStringLiteral("p1"), 15, 30);
+    VPointF p4(2883.86674323853821, 805.33182541168674, QStringLiteral("p4"), 9.9999874015748045, 15);
+
+    VSpline spl(p1, p4, 240.60499999999999, QStringLiteral("240.605"), 260.36399999999998, QStringLiteral("260.364"),
+                6614.8535433070883, QStringLiteral("175.018"), 10695.382677165355, QStringLiteral("282.982"));
+
+    qreal base = spl.GetLength();
+
+    qreal step = 0;
+    do
+    {
+        QTest::newRow(qUtf8Printable(QStringLiteral("Curve 1. Step = %1").arg(step))) << spl << base * step;
+        step += 0.001;
+    }
+    while(step <= 1);
+
+    p1 = VPointF(3476.6410658375944, 334.08136371135333, QStringLiteral("p1"), -141.34148031496062, 109.00951181102363);
+    p4 = VPointF(3483.5141183177025, 333.72231804361377, QStringLiteral("p4"), 48, 102.99930708661418);
+
+    spl = VSpline(p1, p4, 3.1976200000000001, QStringLiteral("3.19762"), 175.24700000000001, QStringLiteral("175.247"),
+                  7.5076913385826796, QStringLiteral("0.198641"), 9.7351181102362219, QStringLiteral("0.257575"));
+
+    base = spl.GetLength();
+
+    step = 0;
+    do
+    {
+        QTest::newRow(qUtf8Printable(QStringLiteral("Curve 2. Step = %1").arg(step))) << spl << base * step;
+        step += 0.001;
+    }
+    while(step <= 1);
+
+    QTest::newRow(qUtf8Printable(QStringLiteral("Curve 2. Bug.").arg(step))) << spl << 4.7813492845686536;
+}
+
 //---------------------------------------------------------------------------------------------------------------------
 void TST_VSpline::TestParametrT()
 {
-    VPointF p1(1168.8582803149607, 39.999874015748034, "p1", 5.0000125984251973, 9.9999874015748045);
+    QFETCH(VSpline, spl);
-    VPointF p4(681.33729132409951, 1815.7969526662778, "p4", 5.0000125984251973, 9.9999874015748045);
+    QFETCH(qreal, length);
 
-    VSpline spl(p1, p4, 229.381, 41.6325, 0.96294100000000005, 1.00054, 1);
+    const qreal resLength = spl.RealLengthByT(spl.GetParmT(length));
 
-    const qreal halfLength = spl.GetLength()/2.0;
+    QVERIFY(qAbs(length - resLength) < UnitConvertor(1, Unit::Mm, Unit::Px));
-    const qreal resLength = spl.LengthT(spl.GetParmT(halfLength));
-
-    QVERIFY(qAbs(halfLength - resLength) < UnitConvertor(0.5, Unit::Mm, Unit::Px));
 }
 
 //---------------------------------------------------------------------------------------------------------------------

src/test/ValentinaTest/tst_vspline.h

@@ -49,6 +49,7 @@ private slots:
     void GetSegmentPoints_RotateTool();
     void GetSegmentPoints_issue767();
     void CompareThreeWays();
+    void TestParametrT_data();
     void TestParametrT();
     void TestLengthByPoint_data();
     void TestLengthByPoint();