Aggregate display of simple outputs into a table

This change is an attempt to address two related problems:

1. There are no Display plugins (and hence no DisplayViewers)
   for numbers or booleans.

2. The DisplayPostprocessor tries to handle each output using its own
   Display, which is pretty clunky when there are several simple
   (text/number/boolean) outputs and several windows pop up.

This postprocessor acts just before the display postprocessor,
aggregating all simple outputs into a single GenericTable, which is
then shown to the user via the UIService.

The heuristic on whether and how to use a table is as follows:

- Only simple outputs are included: text, numbers and booleans.

- If there is only a single simple output, and it is text, no
  table is created. This minimizes negative impact on certain
  existing plugins which produce a large amount of text output
  and expect it to be displayed in a TextDisplay.

Author: ctrueden

src/main/java/net/imagej/table/process/ResultsPostprocessor.java

@@ -0,0 +1,112 @@
+/*
+ * #%L
+ * ImageJ software for multidimensional image processing and analysis.
+ * %%
+ * Copyright (C) 2009 - 2016 Board of Regents of the University of
+ * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
+ * Institute of Molecular Cell Biology and Genetics.
+ * %%
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ * #L%
+ */
+
+package net.imagej.table.process;
+
+import java.util.ArrayList;
+
+import net.imagej.table.DefaultColumn;
+import net.imagej.table.DefaultGenericTable;
+import net.imagej.table.GenericTable;
+
+import org.scijava.Priority;
+import org.scijava.module.Module;
+import org.scijava.module.ModuleItem;
+import org.scijava.module.process.AbstractPostprocessorPlugin;
+import org.scijava.module.process.PostprocessorPlugin;
+import org.scijava.plugin.Parameter;
+import org.scijava.plugin.Plugin;
+import org.scijava.ui.UIService;
+import org.scijava.util.ClassUtils;
+
+/**
+ * A postprocessor which aggregates simple output values into a single table,
+ * for a nicer UI experience.
+ * 
+ * @author Curtis Rueden
+ */
+@Plugin(type = PostprocessorPlugin.class,
+	priority = Priority.VERY_LOW_PRIORITY + 1)
+public class ResultsPostprocessor extends AbstractPostprocessorPlugin {
+
+	@Parameter
+	private UIService ui;
+
+	// -- ModuleProcessor methods --
+
+	@Override
+	public void process(final Module module) {
+		// filter the compatible outputs (simple types: number, boolean, text)
+		final ArrayList<ModuleItem<?>> outputs = new ArrayList<>();
+		module.getInfo().outputs().forEach(output -> {
+			final String name = output.getName();
+			if (module.isOutputResolved(name)) return;
+			if (module.getOutput(name) == null) return;
+			if (!isSimpleType(output.getType())) return;
+			outputs.add(output);
+		});
+
+		if (outputs.isEmpty()) return; // no compatible outputs
+		if (outputs.size() == 1 && ClassUtils.isText(outputs.get(0).getType())) {
+			// sole compatible output is a string; let the TextDisplay handle it
+			return;
+		}
+
+		// create a table to house the output values
+		final GenericTable outputTable = new DefaultGenericTable();
+		final DefaultColumn<String> names = //
+			new DefaultColumn<>(String.class, "Name");
+		final DefaultColumn<Object> values = //
+			new DefaultColumn<>(Object.class, "Value");
+
+		// populate the columns
+		for (final ModuleItem<?> output : outputs) {
+			final String name = output.getName();
+			names.addValue(name);
+			values.addValue(module.getOutput(name));
+			module.resolveOutput(name);
+		}
+
+		// show the table
+		outputTable.add(names);
+		outputTable.add(values);
+		final String title = module.getInfo().getTitle();
+		ui.show(title, outputTable);
+	}
+
+	// -- Helper methods --
+
+	private boolean isSimpleType(final Class<?> type) {
+		return ClassUtils.isText(type) || //
+			ClassUtils.isNumber(type) || //
+			ClassUtils.isBoolean(type);
+	}
+}