Improve multiple file input API

* Change the chooseFiles() method signature to support pre-selected
  files, a starting folder, and style attributes.
* Add style constants to FileListWidget.

Normally, we would deprecate the old method signatures for backwards
compatibility, but since no scijava-common release has occurred since
this API was introduced, we are free to change it.

Signed-off-by: Curtis Rueden <ctrueden@wisc.edu>

Author: imagejan

src/main/java/org/scijava/ui/DefaultUIService.java

@@ -321,15 +321,15 @@ public File chooseFile(final File file, final String style) {
 	}
 
 	@Override
-	public File[] chooseFiles(File[] files, FileFilter filter) {
+	public File[] chooseFiles(File parent, File[] files, FileFilter filter, String style) {
 		final UserInterface ui = getDefaultUI();
-		return ui == null ? null : ui.chooseFiles(files, filter);
+		return ui == null ? null : ui.chooseFiles(parent, files, filter, style);
 	}
 
 	@Override
-	public List<File> chooseFiles(List<File> fileList, FileFilter filter) {
+	public List<File> chooseFiles(File parent, List<File> fileList, FileFilter filter, String style) {
 		final UserInterface ui = getDefaultUI();
-		return ui == null ? null : ui.chooseFiles(fileList, filter);
+		return ui == null ? null : ui.chooseFiles(parent, fileList, filter, style);
 	}
 
 	@Override

src/main/java/org/scijava/ui/FileListPreprocessor.java

@@ -56,7 +56,9 @@ public void process(final Module module) {
 		final File[] files = fileInput.getValue(module);
 
 		// show file chooser dialog box
-		final File[] result = uiService.chooseFiles(files, null);
+		// TODO decide how to create filter from style attributes
+		// TODO retrieve parent folder??
+		final File[] result = uiService.chooseFiles(null, files, null, fileInput.getWidgetStyle());
 		if (result == null) {
 			cancel("");
 			return;

src/main/java/org/scijava/ui/UIService.java

@@ -304,7 +304,7 @@ DialogPrompt.Result showDialog(String message, String title,
 	 * @param files The initial value displayed in the file chooser prompt.
 	 * @param filter A filter allowing to restrict the choice of files
 	 */
-	File[] chooseFiles(File[] files, FileFilter filter);
+	File[] chooseFiles(File parent, File[] files, FileFilter filter, String style);
 
 	/**
 	 * Prompts the user to select one or multiple files.
@@ -315,7 +315,7 @@ DialogPrompt.Result showDialog(String message, String title,
 	 * @param fileList The initial value displayed in the file chooser prompt.
 	 * @param filter A filter allowing to restrict the choice of files
 	 */
-	List<File> chooseFiles(List<File> fileList, FileFilter filter);
+	List<File> chooseFiles(File parent, List<File> fileList, FileFilter filter, String style);
 
 	/**
 	 * Displays a popup context menu for the given display at the specified

src/main/java/org/scijava/ui/UserInterface.java

@@ -191,26 +191,30 @@ default File chooseFile(String title, File file, String style) {
 	/**
 	 * Prompts the user to choose a list of files.
 	 *
+	 * @param parent Parent folder for file selection
 	 * @param files The initial value displayed in the file chooser prompt.
 	 * @param filter A filter allowing to restrict file choice.
+	 * @param style File selection style (files, directories, or both) and optional filters
 	 * @return The selected {@link File}s chosen by the user, or null if the
 	 *         user cancels the prompt.
 	 */
-	default File[] chooseFiles(File[] files, FileFilter filter) {
+	default File[] chooseFiles(File parent, File[] files, FileFilter filter, String style) {
 		throw new UnsupportedOperationException();
 	}
 
 	/**
 	 * Prompts the user to choose a list of files.
 	 *
+	 * @param parent Parent folder for file selection
 	 * @param fileList The initial value displayed in the file chooser prompt.
 	 * @param filter A filter allowing to restrict file choice.
+	 * @param style File selection style (files, directories, or both) and optional filters
 	 * @return The selected {@link File}s chosen by the user, or null if the
 	 *         user cancels the prompt.
 	 */
-	default List<File> chooseFiles(List<File> fileList, FileFilter filter) {
+	default List<File> chooseFiles(File parent, List<File> fileList, FileFilter filter, String style) {
 		final File[] initialFiles = fileList.toArray(new File[fileList.size()]);
-		final File[] chosenFiles = chooseFiles(initialFiles, filter);
+		final File[] chosenFiles = chooseFiles(parent, initialFiles, filter, style);
 		return chosenFiles == null ? null : Arrays.asList(chosenFiles);
 	}
 

src/main/java/org/scijava/widget/FileListWidget.java

@@ -34,5 +34,24 @@
 import java.io.File;
 
 public interface FileListWidget<U> extends InputWidget<File[], U> {
-	// NB: No changes to interface.
+	/**
+	 * Widget style to allow file selection only
+	 * 
+	 * @see org.scijava.plugin.Parameter#style()
+	 */
+	String FILES_ONLY = "files";
+
+	/**
+	 * Widget style to allow directory selection only
+	 * 
+	 * @see org.scijava.plugin.Parameter#style()
+	 */
+	String DIRECTORIES_ONLY = "directories";
+
+	/**
+	 * Widget style to allow selection of both files and directories
+	 * 
+	 * @see org.scijava.plugin.Parameter#style()
+	 */
+	String FILES_AND_DIRECTORIES = "both";
 }