[legend] insure multi-line labels are vertically centered with tall symbols

(cherry-picked from 4558742)

Author: nirvn

src/core/layertree/qgslayertreemodellegendnode.cpp

@@ -109,9 +109,9 @@ QSizeF QgsLayerTreeModelLegendNode::drawSymbolText( const QgsLegendSettings& set
 
     // Vertical alignment of label with symbol
     if ( labelSize.height() < symbolSize.height() )
-      labelY += symbolSize.height() / 2 + textHeight / 2;  // label centered with symbol
-    else
-      labelY += textHeight; // label starts at top and runs under symbol
+      labelY += symbolSize.height() / 2 - labelSize.height() / 2;  // label centered with symbol
+
+    labelY += textHeight;
   }
 
   for ( QStringList::Iterator itemPart = lines.begin(); itemPart != lines.end(); ++itemPart )

tests/src/core/testqgslegendrenderer.cpp

@@ -115,6 +115,7 @@ class TestQgsLegendRenderer : public QObject
     void testBasic();
     void testBigMarker();
     void testMapUnits();
+    void testTallSymbol();
     void testLongSymbolText();
     void testThreeColumns();
     void testFilterByMap();
@@ -336,6 +337,28 @@ void TestQgsLegendRenderer::testMapUnits()
   QVERIFY( _verifyImage( testName, mReport ) );
 }
 
+void TestQgsLegendRenderer::testTallSymbol()
+{
+  QString testName = "legend_tall_symbol";
+
+  QgsCategorizedSymbolRenderer* catRenderer = dynamic_cast<QgsCategorizedSymbolRenderer*>( mVL3->renderer() );
+  QVERIFY( catRenderer );
+  catRenderer->updateCategoryLabel( 1, "This is\nthree lines\nlong label" );
+
+  mVL2->setName( "This is a two lines\nlong label" );
+
+  QgsLayerTreeModel legendModel( mRoot );
+
+  QgsLegendSettings settings;
+  settings.setWrapChar( "\n" );
+  settings.setSymbolSize( QSizeF( 10.0, 10.0 ) );
+  _setStandardTestFont( settings );
+  _renderLegend( testName, &legendModel, settings );
+  QVERIFY( _verifyImage( testName, mReport ) );
+
+  mVL2->setName( "Polygon Layer" );
+}
+
 void TestQgsLegendRenderer::testLongSymbolText()
 {
   QString testName = "legend_long_symbol_text";