[mvt] halo width must not be greater than 1/4 of text size

qgis · Sep 10, 2024 · b6adff3 · b6adff3
1 parent 8db3ed6
commit b6adff3
Show file tree

Hide file tree

Showing 2 changed files with 77 additions and 3 deletions.
diff --git a/src/core/vectortile/qgsmapboxglstyleconverter.cpp b/src/core/vectortile/qgsmapboxglstyleconverter.cpp
@@ -1447,6 +1447,7 @@ void QgsMapBoxGlStyleConverter::parseSymbolLayer( const QVariantMap &jsonLayer,
   if ( jsonPaint.contains( QStringLiteral( "text-halo-width" ) ) )
   {
     const QVariant jsonHaloWidth = jsonPaint.value( QStringLiteral( "text-halo-width" ) );
+    QString bufferSizeDataDefined;
     switch ( jsonHaloWidth.userType() )
     {
       case QMetaType::Type::Int:
@@ -1457,19 +1458,42 @@ void QgsMapBoxGlStyleConverter::parseSymbolLayer( const QVariantMap &jsonLayer,
 
       case QMetaType::Type::QVariantMap:
         bufferSize = 1;
-        ddLabelProperties.setProperty( QgsPalLayerSettings::Property::BufferSize, parseInterpolateByZoom( jsonHaloWidth.toMap(), context, context.pixelSizeConversionFactor() * BUFFER_SIZE_SCALE, &bufferSize ) );
+        bufferSizeDataDefined = parseInterpolateByZoom( jsonHaloWidth.toMap(), context, context.pixelSizeConversionFactor() * BUFFER_SIZE_SCALE, &bufferSize ).asExpression();
         break;
 
       case QMetaType::Type::QVariantList:
       case QMetaType::Type::QStringList:
         bufferSize = 1;
-        ddLabelProperties.setProperty( QgsPalLayerSettings::Property::BufferSize, parseValueList( jsonHaloWidth.toList(), PropertyType::Numeric, context, context.pixelSizeConversionFactor() * BUFFER_SIZE_SCALE, 255, nullptr, &bufferSize ) );
+        bufferSizeDataDefined = QgsPalLayerSettings::Property::BufferSize, parseValueList( jsonHaloWidth.toList(), PropertyType::Numeric, context, context.pixelSizeConversionFactor() * BUFFER_SIZE_SCALE, 255, nullptr, &bufferSize ).asExpression();
         break;
 
       default:
         context.pushWarning( QObject::tr( "%1: Skipping unsupported text-halo-width type (%2)" ).arg( context.layerId(), QMetaType::typeName( static_cast<QMetaType::Type>( jsonHaloWidth.userType() ) ) ) );
         break;
     }
+
+    // from the specs halo should not be bigget than 1/4 of the text-size
+    // https://docs.mapbox.com/style-spec/reference/layers/#paint-symbol-text-halo-width
+    if ( bufferSize > 0 )
+    {
+      if ( textSize > 0 && bufferSizeDataDefined.isEmpty() )
+      {
+        bufferSize = std::min( bufferSize, textSize * BUFFER_SIZE_SCALE / 4 );
+      }
+      else if ( textSize > 0 )
+      {
+        bufferSizeDataDefined = QStringLiteral( "min( %1/4, %2)" ).arg( textSize * BUFFER_SIZE_SCALE ).arg( bufferSizeDataDefined );
+        ddLabelProperties.setProperty( QgsPalLayerSettings::Property::BufferSize, QgsProperty::fromExpression( bufferSizeDataDefined ) );
+      }
+      else
+      {
+        bufferSizeDataDefined = QStringLiteral( "min( %1*%2/4, %2)" )
+                                .arg( textSizeProperty.asExpression() )
+                                .arg( BUFFER_SIZE_SCALE )
+                                .arg( textSizeProperty.asExpression() );
+        ddLabelProperties.setProperty( QgsPalLayerSettings::Property::BufferSize, QgsProperty::fromExpression( bufferSizeDataDefined ) );
+      }
+    }
   }
 
   double haloBlurSize = 0;

diff --git a/tests/src/python/test_qgsmapboxglconverter.py b/tests/src/python/test_qgsmapboxglconverter.py
@@ -23,6 +23,7 @@
     QgsMapBoxGlStyleConversionContext,
     QgsMapBoxGlStyleConverter,
     QgsMapBoxGlStyleRasterSource,
+    QgsPalLayerSettings,
     QgsRasterLayer,
     QgsRasterPipe,
     QgsSettings,
@@ -664,7 +665,6 @@ def testConvertLabels(self):
         self.assertTrue(labeling.labelSettings().isExpression)
 
         # text-transform
-
         style = {
             "layout": {
                 "text-field": "name_en",
@@ -727,6 +727,56 @@ def testConvertLabels(self):
                          '''lower(concat(concat("name_en",' - ',"name_fr"),"bar"))''')
         self.assertTrue(labeling.labelSettings().isExpression)
 
+    def testHaloMaxSize(self):
+        # text-halo-width is max 1/4 of font-size
+        # https://docs.mapbox.com/style-spec/reference/layers/#paint-symbol-text-halo-width
+        context = QgsMapBoxGlStyleConversionContext()
+
+        # the pixel based text buffers appear larger when rendered on the web - so automatically scale
+        # them up when converting to a QGIS style
+        BUFFER_SIZE_SCALE = 2.0
+
+        # (text_size, halo_size, expected_size, expected_data_defined)
+        data = (
+            (12, 3, 3, None),
+            (12, 5, 4, None),
+            (12, ["get", "some_field_1"], None, 'min(24/4, "some_field_1")'),
+            (["get", "some_field_2"], 4, None, 'min("some_field_2"*2/4, 4)'),
+            (["get", "some_field_3"], ["get", "some_field_4"], None, 'min("some_field_3"*2/4, "some_field_4")'),
+        )
+
+        for (text_size, halo_size, expected_size, expected_data_defined) in data:
+            style = {
+                "layout": {
+                    "text-field": "name_en",
+                    "text-font": [
+                        "Open Sans Semibold",
+                        "Arial Unicode MS Bold"
+                    ],
+                    "text-transform": "uppercase",
+                    "text-max-width": 8,
+                    "text-anchor": "top",
+                    "text-size": text_size,
+                    "icon-size": 1
+                },
+                "type": "symbol",
+                "id": "poi_label",
+                "paint": {
+                    "text-color": "#666",
+                    "text-halo-width": halo_size,
+                    "text-halo-color": "rgba(255,255,255,0.95)",
+                    "text-halo-blur": 1
+                },
+                "source-layer": "poi_label"
+            }
+            renderer, has_renderer, labeling, has_labeling = QgsMapBoxGlStyleConverter.parseSymbolLayer(style, context)
+            self.assertFalse(has_renderer)
+            self.assertTrue(has_labeling)
+            if expected_size:
+                self.assertEqual(labeling.labelSettings().format().buffer().size(), expected_size)
+            if expected_data_defined:
+                self.assertEqual(labeling.labelSettings().dataDefinedProperties().property(QgsPalLayerSettings.Property.BufferSize), expected_data_defined)
+
     def testFontFamilyReplacement(self):
         context = QgsMapBoxGlStyleConversionContext()
         style = {