ttools: use all available metadata in ConfigParameter

ConfigParameter now acquires enough metadata from the ConfigMeta object
of its ConfigKey to be a fully documented Parameter.
ConfigParameters can now be used as STILTS task parameters
for auto-generation of documentation, as long as the relevant
ConfigMeta objects are properly populated.

ttools/src/main/uk/ac/starlink/ttools/plot2/task/AbstractPlot2Task.java

@@ -1035,10 +1035,9 @@ private ConfigMap createConfigMap( Environment env, String suffix,
     private <T> void putConfigValue( Environment env, String suffix,
                                      final ConfigKey<T> key, ConfigMap map )
             throws TaskException {
-        final String pbase = key.getMeta().getShortName();
         ConfigParameter<T> param = new ParameterFinder<ConfigParameter<T>>() {
             protected ConfigParameter<T> createParameter( String sfix ) {
-                return new ConfigParameter<T>( pbase + sfix, key );
+                return ConfigParameter.createSuffixedParameter( key, sfix );
             }
         }.getParameter( env, suffix );
         T value = param.objectValue( env );

ttools/src/main/uk/ac/starlink/ttools/plot2/task/ConfigParameter.java

@@ -6,6 +6,7 @@
 import uk.ac.starlink.task.TaskException;
 import uk.ac.starlink.ttools.plot2.config.ConfigException;
 import uk.ac.starlink.ttools.plot2.config.ConfigKey;
+import uk.ac.starlink.ttools.plot2.config.ConfigMeta;
 
 /**
  * Typed parameter subclass intended to get the value for a ConfigKey.
@@ -20,11 +21,13 @@ public class ConfigParameter<T> extends Parameter<T> {
     /**
      * Constructor.
      *
-     * @param  name   parameter name
      * @param  key  config key
+     * @param  baseName   parameter name excluding suffix
+     * @param  layerSuffix    layer suffix, may be empty
      */
-    public ConfigParameter( String name, ConfigKey<T> key ) {
-        super( name, key.getValueClass(), true );
+    private ConfigParameter( ConfigKey<T> key,
+                             String baseName, String layerSuffix ) {
+        super( baseName + layerSuffix, key.getValueClass(), true );
         key_ = key;
         setStringDefault( key.valueToString( key.getDefaultValue() ) );
         boolean nullPermitted;
@@ -36,6 +39,40 @@ public ConfigParameter( String name, ConfigKey<T> key ) {
             nullPermitted = false;
         }
         setNullPermitted( nullPermitted );
+
+        ConfigMeta meta = key.getMeta();
+        String usage = meta.getStringUsage();
+        String prompt = meta.getShortDescription();
+        String descrip = meta.getXmlDescription();
+        if ( layerSuffix != null && layerSuffix.length() > 0 ) {
+            if ( prompt != null && prompt.length() > 0 ) {
+                prompt += " for layer " + layerSuffix;
+            }
+            if ( descrip != null && descrip.length() > 0 ) {
+                descrip = new StringBuffer()
+                    .append( descrip )
+                    .append( "<p>This parameter affects layer " )
+                    .append( layerSuffix )
+                    .append( "." )
+                    .append( "</p>" )
+                    .append( "\n" )
+                    .toString();
+            }
+        }
+        if ( usage != null ) {
+            setUsage( usage );
+        }
+        setPrompt( prompt );
+        setDescription( descrip );
+    }
+
+    /**
+     * Constructs an un-suffixed config parameter.
+     *
+     * @param  key  config key
+     */
+    public ConfigParameter( ConfigKey<T> key ) {
+        this( key, key.getMeta().getShortName(), "" );
     }
 
     public T stringToObject( Environment env, String stringval )
@@ -47,4 +84,23 @@ public T stringToObject( Environment env, String stringval )
             throw new ParameterValueException( this, e );
         }
     }
+
+    @Override
+    public String objectToString( Environment env, T objval ) {
+        return key_.valueToString( objval );
+    }
+
+    /**
+     * Returns a config parameter with a given suffix.
+     * The name is construted from the key name followed by the suffix.
+     *
+     * @param  key  config key
+     * @param  layerSuffix   suffix part of name
+     * @return   new parameter
+     */
+    public static <T> ConfigParameter<T>
+            createSuffixedParameter( ConfigKey<T> key, String layerSuffix ) {
+        return new ConfigParameter<T>( key, key.getMeta().getShortName(),
+                                       layerSuffix );
+    }
 }

ttools/src/main/uk/ac/starlink/ttools/plot2/task/PlotterParameter.java

@@ -472,9 +472,9 @@ private static List<String> getConfigUsage( ConfigKey[] configKeys,
                                                 String suffix ) {
         List<String> wordList = new ArrayList<String>();
         for ( int ik = 0; ik < configKeys.length; ik++ ) {
-            ConfigKey key = configKeys[ ik ];
-            String pname = key.getMeta().getShortName() + suffix;
-            ConfigParameter param = new ConfigParameter( pname, key );
+            ConfigParameter param = ConfigParameter
+                                   .createSuffixedParameter( configKeys[ ik ],
+                                                             suffix );
             wordList.add( usageWord( param ) );
         }
         return wordList;

ttools/src/main/uk/ac/starlink/ttools/plot2/task/TypedPlot2Task.java

@@ -98,9 +98,7 @@ public PlotContext getPlotContext() {
     private static List<Parameter> getKeyParams( ConfigKey[] keys ) {
         List<Parameter> plist = new ArrayList<Parameter>();
         for ( int ik = 0; ik < keys.length; ik++ ) {
-            ConfigKey key = keys[ ik ];
-            plist.add( new ConfigParameter( key.getMeta().getShortName(),
-                                            key ) );
+            plist.add( new ConfigParameter( keys[ ik ] ) );
         }
         return plist;
     }