fix(profileGenerator): refix qgis#54422 and simplify algorithm

src/core/elevation/qgsabstractprofilesurfacegenerator.cpp

@@ -325,34 +325,26 @@ void QgsAbstractProfileSurfaceResults::renderResults( QgsProfileRenderContext &c
 
   QPolygonF currentLine;
   double prevDistance = std::numeric_limits< double >::quiet_NaN();
-  double prevHeight = std::numeric_limits< double >::quiet_NaN();
   double currentPartStartDistance = 0;
   for ( auto pointIt = mDistanceToHeightMap.constBegin(); pointIt != mDistanceToHeightMap.constEnd(); ++pointIt )
   {
-    if ( std::isnan( prevDistance ) )
+    if ( currentLine.empty() ) // new part
     {
+      if ( std::isnan( pointIt.value() ) ) // skip emptiness
+        continue;
       currentPartStartDistance = pointIt.key();
     }
-    else if ( currentLine.empty() )
-    {
-      currentPartStartDistance = prevDistance;
-      currentLine.append( context.worldTransform().map( QPointF( prevDistance, prevHeight ) ) );
-    }
 
     if ( std::isnan( pointIt.value() ) )
     {
       checkLine( currentLine, context, minZ, maxZ, prevDistance, currentPartStartDistance );
       currentLine.clear();
-      continue;
     }
-
-    if ( currentLine.length() < 1 )
+    else
     {
-      currentPartStartDistance = pointIt.key();
+      currentLine.append( context.worldTransform().map( QPointF( pointIt.key(), pointIt.value() ) ) );
+      prevDistance = pointIt.key();
     }
-    currentLine.append( context.worldTransform().map( QPointF( pointIt.key(), pointIt.value() ) ) );
-    prevDistance = pointIt.key();
-    prevHeight = pointIt.value();
   }
 
   checkLine( currentLine, context, minZ, maxZ, prevDistance, currentPartStartDistance );

tests/src/python/test_qgsvectorlayerprofilegenerator.py

@@ -1741,8 +1741,31 @@ def testRenderProfileAsSurfaceLinesWithMarkers(self):
         res = plot_renderer.renderToImage(400, 400, 0, curve.length(), 0, 14)
         self.assertTrue(self.image_check('vector_lines_as_surface_with_markers', 'vector_lines_as_surface_with_markers', res))
 
+    def testRenderProfileAsLineWithHoledDtm(self):
+        rl = QgsRasterLayer(os.path.join(unitTestDataPath(), '3d', 'dtm_with_holes.tif'), 'DTM')
+        self.assertTrue(rl.isValid())
+
+        rl.elevationProperties().setEnabled(True)
+        rl.elevationProperties().setProfileSymbology(Qgis.ProfileSurfaceSymbology.Line)
+        line_symbol = QgsLineSymbol.createSimple({'color': '#ff00ff', 'width': '0.8'})
+        rl.elevationProperties().setProfileLineSymbol(line_symbol)
+
+        curve = QgsLineString()
+        curve.fromWkt('LineString (320900 129000, 322900 129000)')
+        req = QgsProfileRequest(curve)
+        req.setTransformContext(self.create_transform_context())
+
+        req.setCrs(QgsCoordinateReferenceSystem())
+
+        plot_renderer = QgsProfilePlotRenderer([rl], req)
+        plot_renderer.startGeneration()
+        plot_renderer.waitForFinished()
+
+        res = plot_renderer.renderToImage(1600, 800, 0, curve.length(), 0, 90)
+        self.assertTrue(self.image_check('vector_lines_as_line_with_holed_dtm', 'vector_lines_as_line_with_holed_dtm', res))
+
     def testRenderProfileAsSurfaceFillBelowWithHoledDtm(self):
-        rl = QgsRasterLayer(os.path.join(unitTestDataPath(), '3d', 'dtm.tif'), 'DTM')
+        rl = QgsRasterLayer(os.path.join(unitTestDataPath(), '3d', 'dtm_with_holes.tif'), 'DTM')
         self.assertTrue(rl.isValid())
 
         rl.elevationProperties().setEnabled(True)
@@ -1753,8 +1776,7 @@ def testRenderProfileAsSurfaceFillBelowWithHoledDtm(self):
         rl.elevationProperties().setProfileLineSymbol(line_symbol)
 
         curve = QgsLineString()
-        curve.fromWkt(
-            'LineString (322900 129000, 320900 129000)')
+        curve.fromWkt('LineString (320900 129000, 322900 129000)')
         req = QgsProfileRequest(curve)
         req.setTransformContext(self.create_transform_context())