When the "offset along line" setting for a marker line ori

hash line symbol layer is longer then the size of a closed ring, treat the offset as continuing to loop around the ring E.g. setting the offset to 150% results in the offset being treated as 50% of the length of the closed ring
qgis · Dec 14, 2021 · e8b9aad · e8b9aad
1 parent aac0432
commit e8b9aad
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diff --git a/src/core/symbology/qgslinesymbollayer.cpp b/src/core/symbology/qgslinesymbollayer.cpp
@@ -1701,6 +1701,14 @@ void QgsTemplatedLineSymbolLayerBase::renderPolylineInterval( const QPolygonF &p
         painterUnitOffsetAlongLine = offsetAlongLine / 100 * totalLength;
         break;
     }
+
+    if ( points.isClosed() )
+    {
+      if ( painterUnitOffsetAlongLine > 0 )
+      {
+        painterUnitOffsetAlongLine = std::fmod( painterUnitOffsetAlongLine, totalLength );
+      }
+    }
   }
 
   if ( offsetAlongLineUnit() == QgsUnitTypes::RenderMetersInMapUnits && rc.flags() & Qgis::RenderContextFlag::RenderSymbolPreview )
@@ -1872,6 +1880,13 @@ void QgsTemplatedLineSymbolLayerBase::renderPolylineVertex( const QPolygonF &poi
         offsetAlongLine = offsetAlongLine / 100 * totalLength;
         break;
     }
+    if ( points.isClosed() )
+    {
+      if ( offsetAlongLine > 0 )
+      {
+        offsetAlongLine = std::fmod( offsetAlongLine, totalLength );
+      }
+    }
   }
 
   if ( qgsDoubleNear( offsetAlongLine, 0.0 ) && context.renderContext().geometry()

diff --git a/tests/src/python/test_qgsmarkerlinesymbollayer.py b/tests/src/python/test_qgsmarkerlinesymbollayer.py
@@ -703,6 +703,32 @@ def testFirstVertexOffsetPercentage(self):
         rendered_image = self.renderGeometry(s, g)
         assert self.imageCheck('markerline_first_offset_percent', 'markerline_first_offset_percent', rendered_image)
 
+    def testClosedRingFirstVertexOffsetLarge(self):
+        """
+        Test that an offset larger than the length of a closed line effectively "loops" around the ring
+        """
+        s = QgsLineSymbol()
+        s.deleteSymbolLayer(0)
+
+        marker_line = QgsMarkerLineSymbolLayer(True)
+        marker_line.setPlacements(Qgis.MarkerLinePlacement.FirstVertex)
+        marker_line.setOffsetAlongLine(110)
+        marker_line.setOffsetAlongLineUnit(QgsUnitTypes.RenderPercentage)
+        marker = QgsSimpleMarkerSymbolLayer(QgsSimpleMarkerSymbolLayer.Circle, 4)
+        marker.setColor(QColor(255, 0, 0, 100))
+        marker.setStrokeStyle(Qt.NoPen)
+        marker_symbol = QgsMarkerSymbol()
+        marker_symbol.changeSymbolLayer(0, marker)
+        marker_line.setSubSymbol(marker_symbol)
+        line_symbol = QgsLineSymbol()
+        line_symbol.changeSymbolLayer(0, marker_line)
+
+        s.appendSymbolLayer(marker_line.clone())
+
+        g = QgsGeometry.fromWkt('LineString(0 0, 0 10, 10 10, 0 0)')
+        rendered_image = self.renderGeometry(s, g)
+        assert self.imageCheck('markerline_first_large_offset', 'markerline_first_large_offset', rendered_image)
+
     def testIntervalOffsetPercentage(self):
         s = QgsLineSymbol()
         s.deleteSymbolLayer(0)
@@ -727,6 +753,33 @@ def testIntervalOffsetPercentage(self):
         rendered_image = self.renderGeometry(s, g)
         assert self.imageCheck('markerline_interval_offset_percent', 'markerline_interval_offset_percent', rendered_image)
 
+    def testClosedRingIntervalOffsetLarge(self):
+        """
+        Test that an offset larger than the length of a closed line effectively "loops" around the ring
+        """
+        s = QgsLineSymbol()
+        s.deleteSymbolLayer(0)
+
+        marker_line = QgsMarkerLineSymbolLayer(True)
+        marker_line.setPlacements(Qgis.MarkerLinePlacement.Interval)
+        marker_line.setInterval(6)
+        marker_line.setOffsetAlongLine(150)
+        marker_line.setOffsetAlongLineUnit(QgsUnitTypes.RenderPercentage)
+        marker = QgsSimpleMarkerSymbolLayer(QgsSimpleMarkerSymbolLayer.Circle, 4)
+        marker.setColor(QColor(255, 0, 0, 100))
+        marker.setStrokeStyle(Qt.NoPen)
+        marker_symbol = QgsMarkerSymbol()
+        marker_symbol.changeSymbolLayer(0, marker)
+        marker_line.setSubSymbol(marker_symbol)
+        line_symbol = QgsLineSymbol()
+        line_symbol.changeSymbolLayer(0, marker_line)
+
+        s.appendSymbolLayer(marker_line.clone())
+
+        g = QgsGeometry.fromWkt('LineString(0 0, 0 10, 10 10, 0 0)')
+        rendered_image = self.renderGeometry(s, g)
+        assert self.imageCheck('markerline_interval_large_offset', 'markerline_interval_large_offset', rendered_image)
+
     def testCenterSegment(self):
         s = QgsLineSymbol()
         s.deleteSymbolLayer(0)

diff --git a/...pected_markerline_first_large_offset/expected_markerline_first_large_offset.png b/...pected_markerline_first_large_offset/expected_markerline_first_large_offset.png
diff --git a/..._markerline_interval_large_offset/expected_markerline_interval_large_offset.png b/..._markerline_interval_large_offset/expected_markerline_interval_large_offset.png