Enable default parameter values in scripts

You can now write:

  @int(value = 5) sigma

And the sigma variable will have a default value of 5 the first time
the script is run.

Nicer would be:

  @int sigma = 5

But implementing that would be more involved, and so should probably
wait till script parameter parsing is truly fixed as described in #156.

Author: ctrueden

src/main/java/org/scijava/module/process/DefaultValuePreprocessor.java

@@ -34,41 +34,39 @@
 import org.scijava.Priority;
 import org.scijava.module.Module;
 import org.scijava.module.ModuleItem;
-import org.scijava.module.ModuleService;
-import org.scijava.plugin.Parameter;
 import org.scijava.plugin.Plugin;
 
 /**
  * A preprocessor plugin that populates default parameter values.
  * <p>
- * Default values are determined using {@link ModuleService#getDefaultValue}.
+ * Default values are determined using {@link ModuleItem#getDefaultValue}.
  * </p>
  *
  * @author Curtis Rueden
  */
 @Plugin(type = PreprocessorPlugin.class, priority = Priority.VERY_HIGH_PRIORITY)
 public class DefaultValuePreprocessor extends AbstractPreprocessorPlugin {
 
-	@Parameter
-	private ModuleService moduleService;
-
 	// -- ModuleProcessor methods --
 
 	@Override
 	public void process(final Module module) {
 		for (final ModuleItem<?> input : module.getInfo().inputs()) {
 			assignDefaultValue(module, input);
 		}
+		for (final ModuleItem<?> output : module.getInfo().outputs()) {
+			assignDefaultValue(module, output);
+		}
 	}
 
 	// -- Helper methods --
 
 	private <T> void assignDefaultValue(final Module module,
-		final ModuleItem<T> input)
+		final ModuleItem<T> item)
 	{
-		final T defaultValue = moduleService.getDefaultValue(input);
+		final T defaultValue = item.getDefaultValue();
 		if (defaultValue == null) return;
-		input.setValue(module, defaultValue);
+		item.setValue(module, defaultValue);
 	}
 
 }

src/main/java/org/scijava/script/ScriptInfo.java

@@ -461,7 +461,7 @@ else if ("visibility".equalsIgnoreCase(key)) {
 			item.setVisibility(convertService.convert(value, ItemVisibility.class));
 		}
 		else if ("value".equalsIgnoreCase(key)) {
-			item.setWidgetStyle(value);
+			item.setDefaultValue(convertService.convert(value, item.getType()));
 		}
 		else {
 			throw new ScriptException("Invalid attribute name: " + key);