Add method to calculate total length of a QPolygonF line

qgis · Mar 18, 2021 · 99c5ac3 · 99c5ac3
1 parent cfde40d
commit 99c5ac3
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diff --git a/python/core/auto_generated/symbology/qgssymbollayerutils.sip.in b/python/core/auto_generated/symbology/qgssymbollayerutils.sip.in
@@ -732,6 +732,13 @@ Calculate a point on the surface of a QPolygonF
     static bool pointInPolygon( const QPolygonF &points, QPointF point );
 %Docstring
 Calculate whether a point is within of a QPolygonF
+%End
+
+    static double polylineLength( const QPolygonF &polyline );
+%Docstring
+Returns the total length of a ``polyline``.
+
+.. versionadded:: 3.20
 %End
 
     static QPolygonF polylineSubstring( const QPolygonF &polyline, double startOffset, double endOffset );

diff --git a/src/core/symbology/qgssymbollayerutils.cpp b/src/core/symbology/qgssymbollayerutils.cpp
@@ -4189,6 +4189,24 @@ bool QgsSymbolLayerUtils::pointInPolygon( const QPolygonF &points, QPointF point
   return inside;
 }
 
+double QgsSymbolLayerUtils::polylineLength( const QPolygonF &polyline )
+{
+  if ( polyline.size() < 2 )
+    return 0;
+
+  double totalLength = 0;
+  auto it = polyline.begin();
+  QPointF p1 = *it++;
+  for ( ; it != polyline.end(); ++it )
+  {
+    QPointF p2 = *it;
+    const double segmentLength = std::sqrt( std::pow( p1.x() - p2.x(), 2.0 ) + std::pow( p1.y() - p2.y(), 2.0 ) );
+    totalLength += segmentLength;
+    p1 = p2;
+  }
+  return totalLength;
+}
+
 QPolygonF QgsSymbolLayerUtils::polylineSubstring( const QPolygonF &polyline, double startOffset, double endOffset )
 {
   if ( polyline.size() < 2 )

diff --git a/src/core/symbology/qgssymbollayerutils.h b/src/core/symbology/qgssymbollayerutils.h
@@ -657,6 +657,13 @@ class CORE_EXPORT QgsSymbolLayerUtils
     //! Calculate whether a point is within of a QPolygonF
     static bool pointInPolygon( const QPolygonF &points, QPointF point );
 
+    /**
+     * Returns the total length of a \a polyline.
+     *
+     * \since QGIS 3.20
+     */
+    static double polylineLength( const QPolygonF &polyline );
+
     /**
      * Returns the substring of a \a polyline which starts at \a startOffset from the beginning of the line
      * and ends at \a endOffset from the start of the line.

diff --git a/tests/src/python/test_qgssymbollayerutils.py b/tests/src/python/test_qgssymbollayerutils.py
@@ -270,6 +270,17 @@ def testDecodeSldUom(self):
         decode = QgsSymbolLayerUtils.decodeSldUom("http://www.opengeospatial.org/se/units/pixel")
         self.assertEqual(decode, (QgsUnitTypes.RenderPixels, 1.0))
 
+    def testPolylineLength(self):
+        """
+        Test QgsSymbolLayerUtils.polylineLength
+        """
+        self.assertEqual(QgsSymbolLayerUtils.polylineLength(QPolygonF()), 0.0)
+        self.assertEqual(
+            QgsSymbolLayerUtils.polylineLength(QPolygonF([QPointF(11, 12), QPointF(11, 12)])), 0.0)
+        self.assertEqual(
+            QgsSymbolLayerUtils.polylineLength(QPolygonF([QPointF(11, 2), QPointF(11, 12), QPointF(11, 12)])), 10.0)
+        self.assertEqual(QgsSymbolLayerUtils.polylineLength(QPolygonF([QPointF(11, 2), QPointF(11, 12), QPointF(111, 12)])), 110.0)
+
     def testPolylineSubstring(self):
         res = QgsSymbolLayerUtils.polylineSubstring(QPolygonF(), 1, 2)  # no crash
         self.assertFalse(res)