Add method to "scroll" the vertices of a closed curve geometry,

so that a particular vertex is the first one
qgis · Apr 28, 2021 · e3a73a1 · e3a73a1
1 parent 2a48e2b
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diff --git a/python/core/auto_generated/geometry/qgscircularstring.sip.in b/python/core/auto_generated/geometry/qgscircularstring.sip.in
@@ -222,6 +222,7 @@ Appends the contents of another circular ``string`` to the end of this circular
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     virtual QgsRectangle calculateBoundingBox() const;
 
+    void scroll( int firstVertexIndex ) final;
 
 };
 

diff --git a/python/core/auto_generated/geometry/qgscompoundcurve.sip.in b/python/core/auto_generated/geometry/qgscompoundcurve.sip.in
@@ -206,6 +206,7 @@ Appends first point if not already closed.
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     virtual QgsRectangle calculateBoundingBox() const;
 
+    void scroll( int firstVertexIndex ) final;
 
 };
 

diff --git a/python/core/auto_generated/geometry/qgscurve.sip.in b/python/core/auto_generated/geometry/qgscurve.sip.in
@@ -296,6 +296,24 @@ Returns the curve's orientation, e.g. clockwise or counter-clockwise.
     virtual QgsPoint childPoint( int index ) const;
 
 
+    virtual void scroll( int firstVertexIndex ) = 0;
+%Docstring
+Scrolls the curve vertices so that they start with the vertex at the given index.
+
+.. warning::
+
+   This should only be called on closed curves, or the shape of the curve will be altered and
+   the result is undefined.
+
+.. warning::
+
+   The ``firstVertexIndex`` must correspond to a segment vertex and not a curve point or the result
+   is undefined.
+
+
+.. versionadded:: 3.20
+%End
+
 
 
 };

diff --git a/python/core/auto_generated/geometry/qgslinestring.sip.in b/python/core/auto_generated/geometry/qgslinestring.sip.in
@@ -652,6 +652,7 @@ corresponds to the last point in the line.
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     virtual QgsRectangle calculateBoundingBox() const;
 
+    void scroll( int firstVertexIndex ) final;
 
 };
 

diff --git a/src/core/geometry/qgscircularstring.cpp b/src/core/geometry/qgscircularstring.cpp
@@ -297,6 +297,44 @@ QgsRectangle QgsCircularString::calculateBoundingBox() const
   return bbox;
 }
 
+void QgsCircularString::scroll( int index )
+{
+  const int size = mX.size();
+  if ( index < 1 || index >= size - 1 )
+    return;
+
+  const bool useZ = is3D();
+  const bool useM = isMeasure();
+
+  QVector<double> newX( size );
+  QVector<double> newY( size );
+  QVector<double> newZ( useZ ? size : 0 );
+  QVector<double> newM( useM ? size : 0 );
+  auto it = std::copy( mX.constBegin() + index, mX.constEnd() - 1, newX.begin() );
+  it = std::copy( mX.constBegin(), mX.constBegin() + index, it );
+  *it = *newX.constBegin();
+  mX = std::move( newX );
+
+  it = std::copy( mY.constBegin() + index, mY.constEnd() - 1, newY.begin() );
+  it = std::copy( mY.constBegin(), mY.constBegin() + index, it );
+  *it = *newY.constBegin();
+  mY = std::move( newY );
+  if ( useZ )
+  {
+    it = std::copy( mZ.constBegin() + index, mZ.constEnd() - 1, newZ.begin() );
+    it = std::copy( mZ.constBegin(), mZ.constBegin() + index, it );
+    *it = *newZ.constBegin();
+    mZ = std::move( newZ );
+  }
+  if ( useM )
+  {
+    it = std::copy( mM.constBegin() + index, mM.constEnd() - 1, newM.begin() );
+    it = std::copy( mM.constBegin(), mM.constBegin() + index, it );
+    *it = *newM.constBegin();
+    mM = std::move( newM );
+  }
+}
+
 QgsRectangle QgsCircularString::segmentBoundingBox( const QgsPoint &pt1, const QgsPoint &pt2, const QgsPoint &pt3 )
 {
   double centerX, centerY, radius;

diff --git a/src/core/geometry/qgscircularstring.h b/src/core/geometry/qgscircularstring.h
@@ -201,6 +201,7 @@ class CORE_EXPORT QgsCircularString: public QgsCurve
 
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     QgsRectangle calculateBoundingBox() const override;
+    void scroll( int firstVertexIndex ) final;
 
   private:
     QVector<double> mX;

diff --git a/src/core/geometry/qgscompoundcurve.cpp b/src/core/geometry/qgscompoundcurve.cpp
@@ -161,6 +161,28 @@ QgsRectangle QgsCompoundCurve::calculateBoundingBox() const
   return bbox;
 }
 
+void QgsCompoundCurve::scroll( int index )
+{
+  const int size = numPoints();
+  if ( index < 1 || index >= size - 1 )
+    return;
+
+  auto [p1, p2 ] = splitCurveAtVertex( index );
+
+  mCurves.clear();
+  if ( QgsCompoundCurve *curve2 = qgsgeometry_cast< QgsCompoundCurve *>( p2.get() ) )
+  {
+    // take the curves from the second part and make them our first lot of curves
+    mCurves = std::move( curve2->mCurves );
+  }
+  if ( QgsCompoundCurve *curve1 = qgsgeometry_cast< QgsCompoundCurve *>( p1.get() ) )
+  {
+    // take the curves from the first part and append them to our curves
+    mCurves.append( curve1->mCurves );
+    curve1->mCurves.clear();
+  }
+}
+
 bool QgsCompoundCurve::fromWkb( QgsConstWkbPtr &wkbPtr )
 {
   clear();

diff --git a/src/core/geometry/qgscompoundcurve.h b/src/core/geometry/qgscompoundcurve.h
@@ -186,6 +186,7 @@ class CORE_EXPORT QgsCompoundCurve: public QgsCurve
 
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     QgsRectangle calculateBoundingBox() const override;
+    void scroll( int firstVertexIndex ) final;
 
   private:
     QVector< QgsCurve * > mCurves;

diff --git a/src/core/geometry/qgscurve.h b/src/core/geometry/qgscurve.h
@@ -306,6 +306,19 @@ class CORE_EXPORT QgsCurve: public QgsAbstractGeometry SIP_ABSTRACT
     int childCount() const override;
     QgsPoint childPoint( int index ) const override;
 
+    /**
+     * Scrolls the curve vertices so that they start with the vertex at the given index.
+     *
+     * \warning This should only be called on closed curves, or the shape of the curve will be altered and
+     * the result is undefined.
+     *
+     * \warning The \a firstVertexIndex must correspond to a segment vertex and not a curve point or the result
+     * is undefined.
+     *
+     * \since QGIS 3.20
+     */
+    virtual void scroll( int firstVertexIndex ) = 0;
+
 #ifndef SIP_RUN
 
     /**
@@ -326,6 +339,8 @@ class CORE_EXPORT QgsCurve: public QgsAbstractGeometry SIP_ABSTRACT
 
     mutable bool mHasCachedValidity = false;
     mutable QString mValidityFailureReason;
+
+    friend class TestQgsGeometry;
 };
 
 #endif // QGSCURVE_H
diff --git a/src/core/geometry/qgslinestring.cpp b/src/core/geometry/qgslinestring.cpp
@@ -581,6 +581,44 @@ QgsRectangle QgsLineString::calculateBoundingBox() const
   return QgsRectangle( xmin, ymin, xmax, ymax, false );
 }
 
+void QgsLineString::scroll( int index )
+{
+  const int size = mX.size();
+  if ( index < 1 || index >= size - 1 )
+    return;
+
+  const bool useZ = is3D();
+  const bool useM = isMeasure();
+
+  QVector<double> newX( size );
+  QVector<double> newY( size );
+  QVector<double> newZ( useZ ? size : 0 );
+  QVector<double> newM( useM ? size : 0 );
+  auto it = std::copy( mX.constBegin() + index, mX.constEnd() - 1, newX.begin() );
+  it = std::copy( mX.constBegin(), mX.constBegin() + index, it );
+  *it = *newX.constBegin();
+  mX = std::move( newX );
+
+  it = std::copy( mY.constBegin() + index, mY.constEnd() - 1, newY.begin() );
+  it = std::copy( mY.constBegin(), mY.constBegin() + index, it );
+  *it = *newY.constBegin();
+  mY = std::move( newY );
+  if ( useZ )
+  {
+    it = std::copy( mZ.constBegin() + index, mZ.constEnd() - 1, newZ.begin() );
+    it = std::copy( mZ.constBegin(), mZ.constBegin() + index, it );
+    *it = *newZ.constBegin();
+    mZ = std::move( newZ );
+  }
+  if ( useM )
+  {
+    it = std::copy( mM.constBegin() + index, mM.constEnd() - 1, newM.begin() );
+    it = std::copy( mM.constBegin(), mM.constBegin() + index, it );
+    *it = *newM.constBegin();
+    mM = std::move( newM );
+  }
+}
+
 /***************************************************************************
  * This class is considered CRITICAL and any change MUST be accompanied with
  * full unit tests.

diff --git a/src/core/geometry/qgslinestring.h b/src/core/geometry/qgslinestring.h
@@ -798,6 +798,7 @@ class CORE_EXPORT QgsLineString: public QgsCurve
 
     int compareToSameClass( const QgsAbstractGeometry *other ) const final;
     QgsRectangle calculateBoundingBox() const override;
+    void scroll( int firstVertexIndex ) final;
 
   private:
     QVector<double> mX;
@@ -820,6 +821,7 @@ class CORE_EXPORT QgsLineString: public QgsCurve
 
     friend class QgsPolygon;
     friend class QgsTriangle;
+    friend class TestQgsGeometry;
 
 };
 

diff --git a/tests/src/core/testqgsgeometry.cpp b/tests/src/core/testqgsgeometry.cpp
@@ -166,6 +166,9 @@ class TestQgsGeometry : public QObject
     void compareTo_data();
     void compareTo();
 
+    void scroll_data();
+    void scroll();
+
     // MK, Disabled 14.11.2014
     // Too unclear what exactly should be tested and which variations are allowed for the line
 #if 0
@@ -17783,6 +17786,61 @@ void TestQgsGeometry::compareTo()
   QCOMPARE( QgsGeometry::fromWkt( geom1 ).get()->compareTo( QgsGeometry::fromWkt( geom2 ).get() ), expected );
 }
 
+void TestQgsGeometry::scroll_data()
+{
+  QTest::addColumn<QString>( "curve" );
+  QTest::addColumn<int>( "vertex" );
+  QTest::addColumn<QString>( "expected" );
+
+  QTest::newRow( "linestring empty" ) << QStringLiteral( "LINESTRING()" ) << 2 << QStringLiteral( "LineString EMPTY" );
+  QTest::newRow( "linestring no matching point" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3)" ) << 4 << QStringLiteral( "LineString (1 1, 1 2, 1 3)" );
+  QTest::newRow( "linestring one vertex" ) << QStringLiteral( "LINESTRING( 1 1)" ) << 0 << QStringLiteral( "LineString (1 1)" );
+  QTest::newRow( "linestring match first" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3, 1 4, 1 1)" ) << 0 << QStringLiteral( "LineString (1 1, 1 2, 1 3, 1 4, 1 1)" );
+  QTest::newRow( "linestring match second" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3, 1 4, 1 1)" ) << 1 << QStringLiteral( "LineString (1 2, 1 3, 1 4, 1 1, 1 2)" );
+  QTest::newRow( "linestring match third" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3, 1 4, 1 1)" ) << 2 << QStringLiteral( "LineString (1 3, 1 4, 1 1, 1 2, 1 3)" );
+  QTest::newRow( "linestring match forth" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3, 1 4, 1 1)" ) << 3 << QStringLiteral( "LineString (1 4, 1 1, 1 2, 1 3, 1 4)" );
+  QTest::newRow( "linestring match last" ) << QStringLiteral( "LINESTRING( 1 1, 1 2, 1 3, 1 4, 1 1)" ) << 4 << QStringLiteral( "LineString (1 1, 1 2, 1 3, 1 4, 1 1)" );
+  QTest::newRow( "linestringz" ) << QStringLiteral( "LINESTRINGZ( 1 1 3 , 1 2 4, 1 3 5 , 1 4 6, 1 1 3)" ) << 2 << QStringLiteral( "LineStringZ (1 3 5, 1 4 6, 1 1 3, 1 2 4, 1 3 5)" );
+  QTest::newRow( "linestringm" ) << QStringLiteral( "LINESTRINGM( 1 1 3 , 1 2 4, 1 3 5 , 1 4 6, 1 1 3)" ) << 2 << QStringLiteral( "LineStringM (1 3 5, 1 4 6, 1 1 3, 1 2 4, 1 3 5)" );
+  QTest::newRow( "linestringzm" ) << QStringLiteral( "LINESTRINGZM( 1 1 3 5, 1 2 4 6, 1 3 5 7, 1 4 6 8, 1 1 3 5)" ) << 2 << QStringLiteral( "LineStringZM (1 3 5 7, 1 4 6 8, 1 1 3 5, 1 2 4 6, 1 3 5 7)" );
+
+  QTest::newRow( "circularstring empty" ) << QStringLiteral( "CIRCULARSTRING()" ) << 2 << QStringLiteral( "CircularString EMPTY" );
+  QTest::newRow( "circularstring no matching point" ) << QStringLiteral( "CIRCULARSTRING( 1 1, 1 2, 1 3)" ) << 4 << QStringLiteral( "CircularString (1 1, 1 2, 1 3)" );
+  // technically not valid, but we don't want a crash
+  QTest::newRow( "circularstring one vertex" ) << QStringLiteral( "CIRCULARSTRING( 1 1)" ) << 0 << QStringLiteral( "CircularString (1 1)" );
+  QTest::newRow( "circularstring match first" ) << QStringLiteral( "CIRCULARSTRING( 1 1, 2 1, 2 2, 1 4, 1 1)" ) << 0 << QStringLiteral( "CircularString (1 1, 2 1, 2 2, 1 4, 1 1)" );
+  QTest::newRow( "circularstring match third" ) << QStringLiteral( "CIRCULARSTRING( 1 1, 2 1, 2 2, 1 4, 1 1)" ) << 2 << QStringLiteral( "CircularString (2 2, 1 4, 1 1, 2 1, 2 2)" );
+  QTest::newRow( "circularstring match 5th" ) << QStringLiteral( "CIRCULARSTRING( 1 1, 2 1, 2 2, 3 4, 2 4, 1 4, 1 1)" ) << 4 << QStringLiteral( "CircularString (2 4, 1 4, 1 1, 2 1, 2 2, 3 4, 2 4)" );
+  QTest::newRow( "circularstring match last" ) << QStringLiteral( "CIRCULARSTRING( 1 1, 2 1, 2 2, 3 4, 2 4, 1 4, 1 1)" ) << 6 << QStringLiteral( "CircularString (1 1, 2 1, 2 2, 3 4, 2 4, 1 4, 1 1)" );
+  QTest::newRow( "circularstringz" ) << QStringLiteral( "CIRCULARSTRINGZ( 1 1 3 , 2 1 4, 2 2 5 , 1 4 6, 1 1 3)" ) << 2 << QStringLiteral( "CircularStringZ (2 2 5, 1 4 6, 1 1 3, 2 1 4, 2 2 5)" );
+  QTest::newRow( "circularstringm" ) << QStringLiteral( "CIRCULARSTRINGM( 1 1 3 , 2 1 4, 2 2 5 , 1 4 6, 1 1 3)" ) << 2 << QStringLiteral( "CircularStringM (2 2 5, 1 4 6, 1 1 3, 2 1 4, 2 2 5)" );
+  QTest::newRow( "circularstringzm" ) << QStringLiteral( "CIRCULARSTRINGZM( 1 1 3 5, 2 1 4 6, 2 2 5 7, 1 4 6 8, 1 1 3 5)" ) << 2 << QStringLiteral( "CircularStringZM (2 2 5 7, 1 4 6 8, 1 1 3 5, 2 1 4 6, 2 2 5 7)" );
+
+  QTest::newRow( "compoundcurve empty" ) << QStringLiteral( "COMPOUNDCURVE()" ) << 2 << QStringLiteral( "CompoundCurve EMPTY" );
+  QTest::newRow( "compoundcurve no matching point" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2, 1 3))" ) << 4 << QStringLiteral( "CompoundCurve ((1 1, 1 2, 1 3))" );
+  QTest::newRow( "compoundcurve one vertex" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1))" ) << 0 << QStringLiteral( "CompoundCurve ((1 1))" );
+  QTest::newRow( "compoundcurve match first" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2),( 1 2, 1 3, 1 4, 1 1))" ) << 0 << QStringLiteral( "CompoundCurve ((1 1, 1 2),(1 2, 1 3, 1 4, 1 1))" );
+  QTest::newRow( "compoundcurve match second" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2),( 1 2, 1 3, 1 4, 1 1))" ) << 1 << QStringLiteral( "CompoundCurve ((1 2, 1 3, 1 4, 1 1),(1 1, 1 2))" );
+  QTest::newRow( "compoundcurve match third" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2),( 1 2, 1 3, 1 4, 1 1))" ) << 2 << QStringLiteral( "CompoundCurve ((1 3, 1 4, 1 1),(1 1, 1 2),(1 2, 1 3))" );
+  QTest::newRow( "compoundcurve match forth" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2),( 1 2, 1 3, 1 4, 1 1))" ) << 3 << QStringLiteral( "CompoundCurve ((1 4, 1 1),(1 1, 1 2),(1 2, 1 3, 1 4))" );
+  QTest::newRow( "compoundcurve match last" ) << QStringLiteral( "COMPOUNDCURVE(( 1 1, 1 2),( 1 2, 1 3, 1 4, 1 1))" ) << 4 << QStringLiteral( "CompoundCurve ((1 1, 1 2),(1 2, 1 3, 1 4, 1 1))" );
+  QTest::newRow( "compoundcurvez" ) << QStringLiteral( "COMPOUNDCURVEZ(( 1 1 3 , 1 2 4, 1 3 5 , 1 4 6, 1 1 3))" ) << 2 << QStringLiteral( "CompoundCurveZ ((1 3 5, 1 4 6, 1 1 3),(1 1 3, 1 2 4, 1 3 5))" );
+  QTest::newRow( "compoundcurvem" ) << QStringLiteral( "COMPOUNDCURVEM(( 1 1 3 , 1 2 4, 1 3 5 , 1 4 6, 1 1 3))" ) << 2 << QStringLiteral( "CompoundCurveM ((1 3 5, 1 4 6, 1 1 3),(1 1 3, 1 2 4, 1 3 5))" );
+  QTest::newRow( "compoundcurvezm" ) << QStringLiteral( "COMPOUNDCURVEZM(( 1 1 3 5, 1 2 4 6, 1 3 5 7, 1 4 6 8, 1 1 3 5))" ) << 2 << QStringLiteral( "CompoundCurveZM ((1 3 5 7, 1 4 6 8, 1 1 3 5),(1 1 3 5, 1 2 4 6, 1 3 5 7))" );
+}
+
+void TestQgsGeometry::scroll()
+{
+  QFETCH( QString, curve );
+  QFETCH( int, vertex );
+  QFETCH( QString, expected );
+
+  QgsGeometry geom = QgsGeometry::fromWkt( curve );
+  qgsgeometry_cast< QgsCurve * >( geom.get() )->scroll( vertex );
+
+  QCOMPARE( geom.get()->asWkt(), expected );
+}
+
 // MK, Disabled 14.11.2014
 // Too unclear what exactly should be tested and which variations are allowed for the line
 #if 0