Fix custom stroke patterns incorrectly scale when data defined

stroke width is set Fixes #39201
qgis · Oct 8, 2020 · 03fdc0c · 03fdc0c
1 parent 1cd5a33
commit 03fdc0c
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Showing 3 changed files with 29 additions and 1 deletion.
diff --git a/src/core/symbology/qgslinesymbollayer.cpp b/src/core/symbology/qgslinesymbollayer.cpp
@@ -594,6 +594,18 @@ void QgsSimpleLineSymbolLayer::applyDataDefinedSymbology( QgsSymbolRenderContext
       pen.setDashPattern( dashVector );
     }
   }
+  else if ( mDataDefinedProperties.isActive( QgsSymbolLayer::PropertyStrokeWidth ) && mUseCustomDashPattern )
+  {
+    //re-scale pattern vector after data defined pen width was applied
+
+    QVector<qreal> scaledVector;
+    for ( double v : mCustomDashVector )
+    {
+      //the dash is specified in terms of pen widths, therefore the division
+      scaledVector << context.renderContext().convertToPainterUnits( v, mCustomDashPatternUnit, mCustomDashPatternMapUnitScale ) / dashWidthDiv;
+    }
+    mPen.setDashPattern( scaledVector );
+  }
 
   // dash pattern offset
   double patternOffset = mDashPatternOffset;

diff --git a/tests/src/python/test_qgssimplelinesymbollayer.py b/tests/src/python/test_qgssimplelinesymbollayer.py
@@ -41,7 +41,9 @@
                        QgsLineSymbolLayer,
                        QgsLineSymbol,
                        QgsUnitTypes,
-                       QgsMapUnitScale
+                       QgsMapUnitScale,
+                       QgsSymbolLayer,
+                       QgsProperty
                        )
 
 from qgis.testing import unittest, start_app
@@ -60,6 +62,20 @@ def tearDown(self):
         with open(report_file_path, 'a') as report_file:
             report_file.write(self.report)
 
+    def testDashPatternWithDataDefinedWidth(self):
+        # rendering test
+        s = QgsLineSymbol.createSimple({'outline_color': '#ff0000', 'outline_width': '2'})
+
+        s[0].setUseCustomDashPattern(True)
+        s[0].setPenCapStyle(Qt.FlatCap)
+        s[0].setCustomDashVector([3, 4, 5, 6])
+
+        s[0].dataDefinedProperties().setProperty(QgsSymbolLayer.PropertyStrokeWidth, QgsProperty.fromExpression('3'))
+
+        g = QgsGeometry.fromWkt('LineString(0 0, 10 0, 10 10, 0 10)')
+        rendered_image = self.renderGeometry(s, g)
+        assert self.imageCheck('simpleline_dashpattern_datadefined_width', 'simpleline_dashpattern_datadefined_width', rendered_image)
+
     def testDashPatternOffset(self):
 
         s = QgsLineSymbol.createSimple({'outline_color': '#ff0000', 'outline_width': '0.6'})

diff --git a/...pattern_datadefined_width/expected_simpleline_dashpattern_datadefined_width.png b/...pattern_datadefined_width/expected_simpleline_dashpattern_datadefined_width.png