[labeling] Fix incorrect handling of word spacing for curved labels

src/core/qgspalgeometry.h

@@ -117,11 +117,15 @@ class QgsPalGeometry : public PalGeometry
             int nxt = i + 1;
             wordSpaceFix = ( nxt < mClusters.count() && mClusters[nxt] != QString( " " ) ) ? mWordSpacing : qreal( 0.0 );
           }
-          if ( fm->width( QString( mClusters[i] ) ) - fm->width( mClusters[i] ) - mLetterSpacing != qreal( 0.0 ) )
+          // this workaround only works for clusters with a single character. Not sure how it should be handled
+          // with multi-character clusters.
+          if ( mClusters[i].length() == 1 &&
+               !qgsDoubleNear( fm->width( QString( mClusters[i].at( 0 ) ) ), fm->width( mClusters[i].at( 0 ) ) + mLetterSpacing ) )
           {
             // word spacing applied when it shouldn't be
             wordSpaceFix -= mWordSpacing;
           }
+
           charWidth = fm->width( QString( mClusters[i] ) ) + wordSpaceFix;
         }
 
@@ -172,10 +176,10 @@ class QgsPalGeometry : public PalGeometry
     qreal mLetterSpacing; // for use with curved labels
     qreal mWordSpacing; // for use with curved labels
     bool mCurvedLabeling; // whether the geometry is to be used for curved labeling placement
-    /**Stores attribute values for data defined properties*/
+    /** Stores attribute values for data defined properties*/
     QMap< QgsPalLayerSettings::DataDefinedProperties, QVariant > mDataDefinedValues;
 
-    /**Stores attribute values for diagram rendering*/
+    /** Stores attribute values for diagram rendering*/
     QgsAttributes mDiagramAttributes;
 
     QString mDxfLayer;