Fix vertical alignment in data defined labeling

Author: mhugent

src/core/qgspallabeling.cpp

@@ -2029,25 +2029,28 @@ void QgsPalLayerSettings::registerFeature( QgsVectorLayer* layer,  QgsFeature& f
         {
           QString valiString = exprVal.toString();
           QgsDebugMsgLevel( QString( "exprVal Vali:%1" ).arg( valiString ), 4 );
+
           if ( valiString.compare( "Bottom", Qt::CaseInsensitive ) != 0 )
           {
-            if ( valiString.compare( "Top", Qt::CaseInsensitive ) == 0
-                 || valiString.compare( "Cap", Qt::CaseInsensitive ) == 0 )
+            if ( valiString.compare( "Top", Qt::CaseInsensitive ) == 0 )
             {
               ydiff -= labelY;
             }
             else
             {
               double descentRatio = labelFontMetrics->descent() / labelFontMetrics->height();
-
               if ( valiString.compare( "Base", Qt::CaseInsensitive ) == 0 )
               {
                 ydiff -= labelY * descentRatio;
               }
-              else if ( valiString.compare( "Half", Qt::CaseInsensitive ) == 0 )
+              else //'Cap' or 'Half'
               {
-                ydiff -= labelY * descentRatio;
-                ydiff -= labelY * 0.5 * ( 1 - descentRatio );
+                double capHeightRatio = ( labelFontMetrics->boundingRect( 'H' ).height() + 1 + labelFontMetrics->descent() ) / labelFontMetrics->height();
+                ydiff -= labelY * capHeightRatio;
+                if ( valiString.compare( "Half", Qt::CaseInsensitive ) == 0 )
+                {
+                  ydiff += labelY * ( capHeightRatio - descentRatio ) / 2.0;
+                }
               }
             }
           }