ttools: fix plan bug in LabelPlotter

A plan was being construed as matching even when the value type of the
associated cache map did not match (String instead of DepthString).
Actually, I'm not sure how this could happen, because I thought that
2D plots would always use String and 3D plots would always use DepthString,
but the fix, which involves storing Class<T> in the relevant places and
testing for equality, is harmless in any case.

ttools/src/main/uk/ac/starlink/ttools/plot2/layer/LabelPlotter.java

@@ -113,6 +113,7 @@ private static abstract class LabelDrawing<T> implements Drawing {
         final DataSpec dataSpec_;
         final LabelStyle style_;
         final Surface surface_;
+        final Class<T> clazz_;
         final DataGeom geom_;
         final int icLabel_;
 
@@ -123,13 +124,15 @@ private static abstract class LabelDrawing<T> implements Drawing {
          * @param  dataSpec  full data specification
          * @param  style  style
          * @param  surface  plot surface
+         * @param  clazz  parameterising class
          */
         LabelDrawing( DataGeom geom, DataSpec dataSpec, LabelStyle style,
-                      Surface surface ) {
+                      Surface surface, Class<T> clazz ) {
             geom_ = geom;
             dataSpec_ = dataSpec;
             style_ = style;
             surface_ = surface;
+            clazz_ = clazz;
             icLabel_ = geom.getPosCoords().length;
         }
 
@@ -155,12 +158,12 @@ public Object calculatePlan( Object[] knownPlans,
                 Object plan = knownPlans[ i ];
                 if ( plan instanceof LabelPlan &&
                      ((LabelPlan) plan).matches( geom_, dataSpec_,
-                                                 surface_ ) ) {
+                                                 surface_, clazz_ ) ) {
                     return plan;
                 }
             }
             Map<Point,T> map = createMap( dataStore );
-            return new LabelPlan<T>( geom_, dataSpec_, surface_, map );
+            return new LabelPlan<T>( geom_, dataSpec_, surface_, map, clazz_ );
         }
 
         public void paintData( Object plan, Paper paper, DataStore dataStore ) {
@@ -188,7 +191,7 @@ private static class LabelDrawing2D extends LabelDrawing<String> {
          */
         LabelDrawing2D( DataGeom geom, DataSpec dataSpec, LabelStyle style,
                         Surface surface, PaperType2D paperType ) {
-            super( geom, dataSpec, style, surface );
+            super( geom, dataSpec, style, surface, String.class );
             paperType_ = paperType;
         }
 
@@ -245,7 +248,7 @@ private static class LabelDrawing3D extends LabelDrawing<DepthString> {
          */
         LabelDrawing3D( DataGeom geom, DataSpec dataSpec, LabelStyle style,
                         Surface surface, PaperType3D paperType ) {
-            super( geom, dataSpec, style, surface );
+            super( geom, dataSpec, style, surface, DepthString.class );
             paperType_ = paperType;
         }
 
@@ -316,6 +319,7 @@ private static class LabelPlan<T> {
         final DataSpec dataSpec_;
         final Surface surface_;
         final Map<Point,T> map_;
+        final Class<T> clazz_;
 
         /**
          * Constructor.
@@ -325,13 +329,15 @@ private static class LabelPlan<T> {
          * @param  surface  plot surface
          * @param  map  plan payload - a map from screen position to
          *              placeable label
+         * @param  clazz  class parameterising map values
          */
         LabelPlan( DataGeom geom, DataSpec dataSpec, Surface surface,
-                   Map<Point,T> map ) {
+                   Map<Point,T> map, Class<T> clazz ) {
             geom_ = geom;
             dataSpec_ = dataSpec;
             surface_ = surface;
             map_ = map;
+            clazz_ = clazz;
         }
 
         /**
@@ -341,11 +347,14 @@ private static class LabelPlan<T> {
          * @param  geom  data geom
          * @param  dataSpec  data specfication
          * @param  surface  plot surface
+         * @param  parameterising class
          */
-        boolean matches( DataGeom geom, DataSpec dataSpec, Surface surface ) {
+        boolean matches( DataGeom geom, DataSpec dataSpec, Surface surface,
+                         Class clazz ) {
             return geom.equals( geom_ )
                 && dataSpec.equals( dataSpec_ )
-                && surface.equals( surface_ );
+                && surface.equals( surface_ ) 
+                && clazz.equals( clazz_ );
         }
     }