QgsMultiLineString: add method measuredLine

python/core/auto_generated/geometry/qgsmultilinestring.sip.in

@@ -88,6 +88,14 @@ Returns the geometry converted to the more generic curve type :py:class:`QgsMult
     sipRes = PyUnicode_FromString( str.toUtf8().constData() );
 %End
 
+    QgsMultiLineString *measuredLine( double start, double end );
+%Docstring
+Re-write the measure ordinate (or add one, if it isn't already there) interpolating
+the measure between the supplied ``start`` and ``end`` values.
+
+.. versionadded:: 3.36
+%End
+
   protected:
 
     virtual bool wktOmitChildType() const;

src/core/geometry/qgsmultilinestring.cpp

@@ -14,6 +14,7 @@ email                : marco.hugentobler at sourcepole dot com
  ***************************************************************************/
 
 #include "qgsmultilinestring.h"
+#include "qgsabstractgeometry.h"
 #include "qgsapplication.h"
 #include "qgscurve.h"
 #include "qgscircularstring.h"
@@ -178,3 +179,40 @@ bool QgsMultiLineString::wktOmitChildType() const
   return true;
 }
 
+QgsMultiLineString *QgsMultiLineString::measuredLine( double start, double end )
+{
+
+
+  QgsMultiLineString *result{createEmptyWithSameType()};
+
+  if ( isEmpty() )
+  {
+    return result;
+  }
+
+  if ( !result->convertTo( QgsWkbTypes::addM( mWkbType ) ) )
+  {
+    qDebug() << "Impossible to convert type to M type\n";
+    return result;
+  }
+
+  /* Calculate the total length of the line */
+  const double length{this->length()};
+  const double range{end - start};
+  double length_so_far{0.0};
+
+  result->reserve( numGeometries() );
+  for ( int i = 0; i < numGeometries(); i++ )
+  {
+    const double sub_length{geometryN( i )->length()};
+
+    const double sub_start{ ( start + range *length_so_far / length ) };
+    const double sub_end{ ( start + range * ( length_so_far + sub_length ) / length ) };
+
+    result->addGeometry( qgsgeometry_cast<QgsLineString *>( geometryN( i ) )->measuredLine( sub_start, sub_end ) );
+
+    length_so_far += sub_length;
+  }
+
+  return result;
+}

src/core/geometry/qgsmultilinestring.h

@@ -127,6 +127,14 @@ class CORE_EXPORT QgsMultiLineString: public QgsMultiCurve
     % End
 #endif
 
+    /**
+     * Re-write the measure ordinate (or add one, if it isn't already there) interpolating
+     * the measure between the supplied \a start and \a end values.
+     *
+     * \since QGIS 3.36
+     */
+    QgsMultiLineString *measuredLine( double start, double end );
+
   protected:
 
     bool wktOmitChildType() const override;

tests/src/python/CMakeLists.txt

@@ -175,6 +175,7 @@ ADD_PYTHON_TEST(PyQgsMetadataBase test_qgsmetadatabase.py)
 ADD_PYTHON_TEST(PyQgsMetadataUtils test_qgsmetadatautils.py)
 ADD_PYTHON_TEST(PyQgsMemoryProvider test_provider_memory.py)
 ADD_PYTHON_TEST(PyQgsMeshLayerProfileGenerator test_qgsmeshlayerprofilegenerator.py)
+ADD_PYTHON_TEST(PyQgsMultiLineString test_qgsmultilinestring.py)
 ADD_PYTHON_TEST(PyQgsMssqlSqlQueryBuilder test_qgsmssqlsqlquerybuilder.py)
 ADD_PYTHON_TEST(PyQgsNetworkAccessManager test_qgsnetworkaccessmanager.py)
 ADD_PYTHON_TEST(PyQgsNetworkContentFetcher test_qgsnetworkcontentfetcher.py)

tests/src/python/test_qgslinestring.py

@@ -27,18 +27,22 @@ class TestQgsLineString(QgisTestCase):
         self.assertEqual(line.endPoint(), QgsPoint(3, 4))
 
         # With list
-        line = QgsLineString([ [1, 2], [3, 4] ])
+        line = QgsLineString([[1, 2], [3, 4]])
         self.assertEqual(line.startPoint(), QgsPoint(1, 2))
         self.assertEqual(line.endPoint(), QgsPoint(3, 4))
 
     def testMeasureLine(self):
-        line = QgsLineString([ [0, 0], [2, 0], [4, 0]])
+        line = QgsLineString()
         m_line = line.measuredLine(10, 20)
-        self.assertEqual(m_line, QgsLineString([QgsPoint(0, 0, m=10),QgsPoint(2, 0, m=15) ,QgsPoint(4, 0, m=20) ]))
+        self.assertEqual(m_line, QgsLineString())
 
-        line = QgsLineString([ [0, 0], [9, 0], [10, 0]])
+        line = QgsLineString([[0, 0], [2, 0], [4, 0]])
         m_line = line.measuredLine(10, 20)
-        self.assertEqual(m_line, QgsLineString([QgsPoint(0, 0, m=10),QgsPoint(9, 0, m=19) ,QgsPoint(10, 0, m=20) ]))
+        self.assertEqual(m_line, QgsLineString([QgsPoint(0, 0, m=10), QgsPoint(2, 0, m=15), QgsPoint(4, 0, m=20)]))
+
+        line = QgsLineString([[0, 0], [9, 0], [10, 0]])
+        m_line = line.measuredLine(10, 20)
+        self.assertEqual(m_line, QgsLineString([QgsPoint(0, 0, m=10), QgsPoint(9, 0, m=19), QgsPoint(10, 0, m=20)]))
 
 
 if __name__ == '__main__':

tests/src/python/test_qgsmultilinestring.py

@@ -0,0 +1,56 @@
+"""QGIS Unit tests for QgsMultiLineString.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = 'Loïc Bartoletti'
+__date__ = '12/12/2023'
+__copyright__ = 'Copyright 2023, The QGIS Project'
+
+import qgis  # NOQA
+
+from qgis.core import QgsMultiLineString, QgsLineString, QgsPoint
+import unittest
+from qgis.testing import start_app, QgisTestCase
+
+start_app()
+
+
+class TestQgsLineString(QgisTestCase):
+
+    def testConstruct(self):
+        # With list
+        line = QgsLineString([QgsPoint(1, 2), QgsPoint(3, 4)])
+        multiline = QgsMultiLineString()
+        multiline.addGeometry(line)
+        self.assertEqual(multiline.numGeometries(), 1)
+        line = multiline.geometryN(0)
+        self.assertEqual(line.startPoint(), QgsPoint(1, 2))
+        self.assertEqual(line.endPoint(), QgsPoint(3, 4))
+
+    def testMeasureLine(self):
+        multiline = QgsMultiLineString()
+        m_line = multiline.measuredLine(10, 20)
+        self.assertEqual(m_line, QgsMultiLineString())
+
+        multiline.addGeometry(QgsLineString([[0, 0], [2, 0], [4, 0]]))
+        m_line = multiline.measuredLine(10, 20)
+        self.assertEqual(m_line.geometryN(0), QgsLineString([QgsPoint(0, 0, m=10), QgsPoint(2, 0, m=15), QgsPoint(4, 0, m=20)]))
+
+        multiline = QgsMultiLineString()
+        multiline.addGeometry(QgsLineString([[0, 0], [9, 0], [10, 0]]))
+        m_line = multiline.measuredLine(10, 20)
+        self.assertEqual(m_line.geometryN(0), QgsLineString([QgsPoint(0, 0, m=10), QgsPoint(9, 0, m=19), QgsPoint(10, 0, m=20)]))
+
+        multiline = QgsMultiLineString()
+        multiline.addGeometry(QgsLineString([[1, 0], [3, 0], [4, 0]]))
+        multiline.addGeometry(QgsLineString([[0, 0], [9, 0], [10, 0]]))
+        m_line = multiline.measuredLine(10, 20)
+        self.assertEqual(m_line.numGeometries(), 2)
+        self.assertEqual(m_line.asWkt(0), "MultiLineStringM ((1 0 10, 3 0 12, 4 0 12),(0 0 12, 9 0 19, 10 0 20))")
+
+
+if __name__ == '__main__':
+    unittest.main()