Basic viewer working

The viewer has basic capabilities, but still lacks loading
high resolution images, spacing components, and resizing correctly.

9 files changed, 504 insertions, 130 deletions

diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/Document.java b/demos/java/gsviewer/src/com/artifex/gsviewer/Document.java
index 2d5035e19..7b6f2c041 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/Document.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/Document.java
@@ -17,20 +17,34 @@ import com.artifex.gsjava.util.BytePointer;
 import com.artifex.gsjava.util.LongReference;
 import com.artifex.gsviewer.ImageUtil.ImageParams;
 
+/**
+ * A Document stores an ordered list of Pages.
+ *
+ * @author Ethan Vrhel
+ *
+ */
 public class Document implements List<Page> {
 
 	private static final Object slock = new Object();
 	private static final DocumentLoader documentLoader = new DocumentLoader();
 	private static final int format = GS_COLORS_RGB | GS_DISPLAY_DEPTH_8 | GS_DISPLAY_BIGENDIAN;
 
-	public static void loadDocumentAsync(final File file, final DocAsyncLoadCallback cb)
+	/**
+	 * Loads a document on a separate thread.
+	 *
+	 * @param file The file to load.
+	 * @param cb The callback when loading the document has finished.
+	 * @param dlb The callback signifying when progress has occurred while loading.
+	 * @throws NullPointerException When <code>cb</code> is <code>null</code>.
+	 */
+	public static void loadDocumentAsync(final File file, final DocAsyncLoadCallback cb, final DocLoadProgressCallback dlb)
 			throws NullPointerException {
 		Objects.requireNonNull(cb, "DocAsyncLoadCallback");
 		final Thread t = new Thread(() -> {
 			Document doc = null;
 			Exception exception = null;
 			try {
-				doc = new Document(file);
+				doc = new Document(file, dlb);
 			} catch (FileNotFoundException | IllegalStateException | NullPointerException e) {
 				exception = e;
 			}
@@ -41,17 +55,69 @@ public class Document implements List<Page> {
 		t.start();
 	}
 
+	/**
+	 * Loads a document on a separate thread.
+	 *
+	 * @param file The file to load.
+	 * @param cb The callback when loading the document has finished.
+	 * @throws NullPointerException When <code>cb</code> is <code>null</code>.
+	 */
+	public static void loadDocumentAsync(final File file, final DocAsyncLoadCallback cb)
+			throws NullPointerException {
+		loadDocumentAsync(file, cb, null);
+	}
+
+	/**
+	 * Loads a document on a separate thread.
+	 *
+	 * @param filename The name of the file to load.
+	 * @param cb The callback when loading the document has finished.
+	 * @param dlb The callback signifying when progress has occurred while loading.
+	 * @throws NullPointerException When <code>cb</code> is <code>null</code>.
+	 */
+	public static void loadDocumentAsync(final String filename, final DocAsyncLoadCallback cb, final DocLoadProgressCallback dlb)
+			throws NullPointerException {
+		loadDocumentAsync(new File(filename), cb, dlb);
+	}
+
+	/**
+	 * Loads a document on a separate thread.
+	 *
+	 * @param filename The name of the file to load.
+	 * @param cb The callback when loading the document has finished.
+	 * @throws NullPointerException When <code>cb</code> is <code>null</code>.
+	 */
 	public static void loadDocumentAsync(final String filename, final DocAsyncLoadCallback cb)
 			throws NullPointerException {
-		loadDocumentAsync(new File(filename), cb);
+		loadDocumentAsync(filename, cb, null);
 	}
 
 	@FunctionalInterface
 	public static interface DocAsyncLoadCallback {
 
+		/**
+		 * Called when a document has finished loading on a separate
+		 * thread.
+		 *
+		 * @param doc The document which was loaded. <code>null</code> if the document
+		 * failed to load.
+		 * @param exception An exception that ocurred while loading, <code>null</code>
+		 * if no exception was thrown.
+		 */
 		public void onDocumentLoad(Document doc, Exception exception);
 	}
 
+	@FunctionalInterface
+	public static interface DocLoadProgressCallback {
+
+		/**
+		 * Called when the document has made progress while loading.
+		 *
+		 * @param progress The amount of progress (from 0 to 100).
+		 */
+		public void onDocumentProgress(int progress);
+	}
+
 	private static void initDocInstance(LongReference instanceRef) throws IllegalStateException {
 		int code = gsapi_new_instance(instanceRef, GS_NULL);
 		if (code != GS_ERROR_OK) {
@@ -76,6 +142,8 @@ public class Document implements List<Page> {
 		private int pageWidth, pageHeight, pageRaster;
 		private BytePointer pimage;
 		private List<BufferedImage> images;
+		private int progress;
+		private DocLoadProgressCallback callback;
 
 		private DocumentLoader() {
 			reset();
@@ -87,6 +155,8 @@ public class Document implements List<Page> {
 			this.pageRaster = 0;
 			this.pimage = null;
 			this.images = new LinkedList<>();
+			this.progress = 0;
+			this.callback = null;
 			return this;
 		}
 
@@ -104,6 +174,11 @@ public class Document implements List<Page> {
 		public int onDisplayPage(long handle, long device, int copies, boolean flush) {
 			byte[] data = (byte[]) pimage.toArrayNoConvert();
 			images.add(ImageUtil.createImage(data, new ImageParams(pageWidth, pageHeight, pageRaster, BufferedImage.TYPE_3BYTE_BGR)));
+
+			progress += (100 - progress) / 2;
+			if (callback != null)
+				callback.onDocumentProgress(progress);
+
 			return 0;
 		}
 	}
@@ -111,7 +186,16 @@ public class Document implements List<Page> {
 	private File file;
 	private List<Page> pages;
 
-	public Document(final File file)
+	/**
+	 * Creates and loads a new document.
+	 *
+	 * @param file The file to load.
+	 * @param loadCallback The callback to indicate when progress has occurred while loading.
+	 * @throws FileNotFoundException When <code>file</code> does not exist.
+	 * @throws IllegalStateException When Ghostscript fails to intialize or load the document.
+	 * @throws NullPointerException When <code>file</code> is <code>null</code>.
+	 */
+	public Document(final File file, final DocLoadProgressCallback loadCallback)
 			throws FileNotFoundException, IllegalStateException, NullPointerException {
 		this.file = Objects.requireNonNull(file, "file");
 		if (!file.exists())
@@ -124,6 +208,8 @@ public class Document implements List<Page> {
 			LongReference instanceRef = new LongReference();
 			initDocInstance(instanceRef);
 
+			documentLoader.callback = loadCallback;
+
 			int code = gsapi_init_with_args(instanceRef.value, gargs);
 			gsapi_exit(instanceRef.value);
 			gsapi_delete_instance(instanceRef.value);
@@ -135,13 +221,58 @@ public class Document implements List<Page> {
 			for (BufferedImage img : documentLoader.images) {
 				pages.add(new Page(img));
 			}
-		}
-	}
 
-	public Document(final String filename) throws FileNotFoundException, NullPointerException {
-		this(new File(Objects.requireNonNull(filename, "filename")));
+			if (documentLoader.callback != null)
+				documentLoader.callback.onDocumentProgress(100);
+		}
 	}
 
+	/**
+	 * Creates and loads a document from a filename.
+	 *
+	 * @param file The file to load.
+	 * @throws FileNotFoundException If the given file does not exist.
+	 * @throws NullPointerException If <code>file</code> is <code>null</code>.
+	 */
+	public Document(final File file)
+			throws FileNotFoundException, NullPointerException {
+		this(file, null);
+	}
+
+	/**
+	 * Creates and loads a document from a filename.
+	 *
+	 * @param filename The name of the file to load.
+	 * @param loadCallback The callback to indicate when progress has occurred while loading.
+	 * @throws FileNotFoundException If the given filename does not exist.
+	 * @throws NullPointerException If <code>filename</code> is <code>null</code>.
+	 */
+	public Document(final String filename, final DocLoadProgressCallback loadCallback)
+			throws FileNotFoundException, NullPointerException {
+		this(new File(Objects.requireNonNull(filename, "filename")), loadCallback);
+	}
+
+	/**
+	 * Creates and loads a document from a filename.
+	 *
+	 * @param filename The name of the file to load.
+	 * @throws FileNotFoundException If the given filename does not exist.
+	 * @throws NullPointerException If <code>filename</code> is <code>null</code>.
+	 */
+	public Document(final String filename)
+			throws FileNotFoundException, NullPointerException {
+		this(filename, null);
+	}
+
+	/**
+	 * Loads the high resolution images in a range of images.
+	 *
+	 * @param startPage The first page to load.
+	 * @param endPage The end page to load.
+	 * @throws IndexOutOfBoundsException When <code>firstPage</code> or <code>endPage</code>
+	 * are not in the document or <code>endPage</code> is less than <code>firstPage</code>.
+	 * @throws IllegalStateException When Ghostscript fails to initialize or load the document.
+	 */
 	public void loadHighRes(int startPage, int endPage) throws IndexOutOfBoundsException, IllegalStateException {
 		checkBounds(startPage, endPage);
 		final String[] gargs = { "gs", "-dNOPAUSE", "-dSAFER", "-I%rom%Resource%/Init/", "-dBATCH", "-r" + Page.PAGE_HIGH_DPI,
@@ -166,10 +297,26 @@ public class Document implements List<Page> {
 		}
 	}
 
+	/**
+	 * Loads the high resolution image of a singular page.
+	 *
+	 * @param page The page to load.
+	 * @throws IndexOutOfBoundsException When <code>page</code> is not in the document.
+	 * @throws IllegalStateException When Ghostscript fails to initialize or load the
+	 * images.
+	 */
 	public void loadHighRes(int page) throws IndexOutOfBoundsException, IllegalStateException {
 		loadHighRes(page, page);
 	}
 
+	/**
+	 * Loads the high resolution images of a list of pages.
+	 *
+	 * @param pages The pages to load.
+	 * @throws IndexOutOfBoundsException When any page is not a page in the document.
+	 * @throws IllegalStateException When Ghostscript fails to initialize or load the
+	 * images.
+	 */
 	public void loadHighResList(final int... pages) throws IndexOutOfBoundsException, IllegalStateException {
 		if (pages.length > 0) {
 			final StringBuilder builder = new StringBuilder();
@@ -208,6 +355,14 @@ public class Document implements List<Page> {
 		}
 	}
 
+	/**
+	 * Unloads the high resolution images in a range of pages.
+	 *
+	 * @param startPage The start page to unload the high resolution image from.
+	 * @param endPage The end page to unload the high resolution image from.
+	 * @throws IndexOutOfBoundsException When <code>startPage</code> and <code>endPage</code>
+	 * are outside document or <code>endPage</code> is less than <code>startPage</code>.
+	 */
 	public void unloadHighRes(int startPage, int endPage) throws IndexOutOfBoundsException {
 		checkBounds(startPage, endPage);
 		for (int i = startPage - 1; i < endPage; i++) {
@@ -215,12 +370,30 @@ public class Document implements List<Page> {
 		}
 	}
 
+	/**
+	 * Unloads a high resolution image at the given page.
+	 *
+	 * @param page The page to unload the high resolution image.
+	 * @throws IndexOutOfBoundsException When page is not a page in the document.
+	 */
 	public void unloadHighRes(int page) throws IndexOutOfBoundsException {
 		unloadHighRes(page, page);
 	}
 
+	/**
+	 * Unloads the document's resources. The document will be unusable after this
+	 * call.
+	 */
+	public void unload() {
+		for (Page p : pages) {
+			p.unloadLowRes();
+			p.unloadHighRes();
+		}
+		pages.clear();
+	}
+
 	private void checkBounds(int start, int end) throws IndexOutOfBoundsException {
-		if (start < 1 || start >= pages.size())
+		if (start < 1 || start > pages.size())
 			throw new IndexOutOfBoundsException("start=" + start);
 		if (end < 1 || end > pages.size())
 			throw new IndexOutOfBoundsException("end=" + end);
@@ -362,4 +535,9 @@ public class Document implements List<Page> {
 	public int hashCode() {
 		return pages.hashCode();
 	}
+
+	@Override
+	public void finalize() {
+		unload();
+	}
 }
\ No newline at end of file
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/GSFileFilter.java b/demos/java/gsviewer/src/com/artifex/gsviewer/GSFileFilter.java
index 6136e973b..acdab56ac 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/GSFileFilter.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/GSFileFilter.java
@@ -16,12 +16,12 @@ public class GSFileFilter extends FileFilter {
 		final int ind = name.lastIndexOf('.');
 		final String ext = name.substring(ind);
 		return
-			equals(ext, "pdf") ||
-			equals(ext, "eps") ||
-			equals(ext, "ps") ||
-			equals(ext, "xps") ||
-			equals(ext, "oxps") ||
-			equals(ext, "bin");
+			equals(ext, ".pdf") ||
+			equals(ext, ".eps") ||
+			equals(ext, ".ps") ||
+			equals(ext, ".xps") ||
+			equals(ext, ".oxps") ||
+			equals(ext, ".bin");
 	}
 
 	@Override
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/Main.java b/demos/java/gsviewer/src/com/artifex/gsviewer/Main.java
index b1c3014e9..e8c63b7af 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/Main.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/Main.java
@@ -1,10 +1,5 @@
 package com.artifex.gsviewer;
 
-import java.io.File;
-import java.io.FileNotFoundException;
-import java.io.IOException;
-
-import javax.imageio.ImageIO;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.UnsupportedLookAndFeelException;
@@ -13,34 +8,17 @@ import com.artifex.gsviewer.gui.ViewerWindow;
 
 public class Main {
 
-	public static void main(String[] args) throws FileNotFoundException {
+	public static void main(String[] args) {
 		try {
 			UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
 		} catch (ClassNotFoundException | InstantiationException | IllegalAccessException
-				| UnsupportedLookAndFeelException e1) {
-			e1.printStackTrace();
+				| UnsupportedLookAndFeelException e) {
+			System.err.println("Failed to set Look and Feel: " + e);
 		}
 
-		ViewerWindow win = new ViewerWindow(new ViewerGUIListenerImpl());
+		ViewerWindow win = new ViewerWindow(new ViewerController());
 		SwingUtilities.invokeLater(() -> {
 			win.setVisible(true);
 		});
-
-
-		//Document doc = new Document("010104_momentum_concepts.pdf");
-		//doc.loadHighRes(1, 3);
-		//doc.unloadHighRes(2);
-		//doc.loadHighResList(1, 2, 3);
-
-		//int pageNum = 1;
-		//for (Page page : doc) {
-		//	try {
-		//		ImageIO.write(page.getDisplayableImage(), "PNG", new File("page-" + pageNum + ".png"));
-		//	} catch (IOException e) {
-		//		System.err.println("Failed to write page " + pageNum);
-		//	}
-		//	pageNum++;
-		//}
-
 	}
 }
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/Page.java b/demos/java/gsviewer/src/com/artifex/gsviewer/Page.java
index 3bb0be37e..63b716cad 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/Page.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/Page.java
@@ -1,11 +1,26 @@
 package com.artifex.gsviewer;
 
+import java.awt.Dimension;
 import java.awt.image.BufferedImage;
 import com.artifex.gsviewer.ImageUtil.ImageParams;
 
+/**
+ * A Page represents an individual page within a Document. It stores a high resolution image
+ * and a low resolution preview image.
+ *
+ * @author Ethan Vrhel
+ *
+ */
 public class Page {
 
+	/**
+	 * The high-resolution DPI to use.
+	 */
 	public static final int PAGE_HIGH_DPI = 72;
+
+	/**
+	 * The low-resolution DPI to use.
+	 */
 	public static final int PAGE_LOW_DPI = 10;
 
 	private BufferedImage lowRes;
@@ -56,6 +71,11 @@ public class Page {
 		}
 	}
 
+	public void unloadAll() {
+		unloadLowRes();
+		unloadHighRes();
+	}
+
 	public BufferedImage getLowResImage() {
 		return lowRes;
 	}
@@ -68,6 +88,29 @@ public class Page {
 		return highRes == null ? lowRes : highRes;
 	}
 
+	public Dimension getLowResSize() {
+		return lowRes == null ? null : new Dimension(lowRes.getWidth(), lowRes.getHeight());
+	}
+
+	public Dimension getHighResSize() {
+		return highRes == null ? null : new Dimension(highRes.getWidth(), highRes.getHeight());
+	}
+
+	public Dimension getDisplayableSize() {
+		return highRes == null ? getLowResSize() : getHighResSize();
+	}
+
+	public Dimension getSize() {
+		Dimension size = getHighResSize();
+		if (size != null)
+			return size;
+		size = getLowResSize();
+		if (size == null)
+			return new Dimension(0, 0);
+		return new Dimension(size.width * PAGE_HIGH_DPI / PAGE_LOW_DPI,
+				size.height * PAGE_HIGH_DPI / PAGE_LOW_DPI);
+	}
+
 	@Override
 	public String toString() {
 		return "Page[lowResLoaded=" + (lowRes != null) + ",highResLoaded=" + (highRes != null) + "]";
@@ -93,7 +136,6 @@ public class Page {
 
 	@Override
 	public void finalize() {
-		unloadLowRes();
-		unloadHighRes();
+		unloadAll();
 	}
 }
\ No newline at end of file
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/StdIO.java b/demos/java/gsviewer/src/com/artifex/gsviewer/StdIO.java
index 68912954e..4a3951074 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/StdIO.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/StdIO.java
@@ -4,6 +4,13 @@ import com.artifex.gsjava.callbacks.IStdErrFunction;
 import com.artifex.gsjava.callbacks.IStdInFunction;
 import com.artifex.gsjava.callbacks.IStdOutFunction;
 
+/**
+ * Implementation of <code>IStdOutFunction</code>, <code>IStdErrFunction</code>, and
+ * <code>IStdInFunction</code> to get IO data from Ghostscript.
+ *
+ * @author Ethan Vrhel
+ *
+ */
 public class StdIO implements IStdOutFunction, IStdErrFunction, IStdInFunction {
 
 	@Override
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerController.java b/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerController.java
new file mode 100644
index 000000000..6353d5849
--- /dev/null
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerController.java
@@ -0,0 +1,93 @@
+package com.artifex.gsviewer;
+
+import java.awt.Point;
+import java.io.File;
+
+import javax.swing.JFileChooser;
+import javax.swing.JOptionPane;
+
+import com.artifex.gsviewer.gui.ViewerGUIListener;
+import com.artifex.gsviewer.gui.ViewerWindow;
+
+public class ViewerController implements ViewerGUIListener {
+
+	private ViewerWindow source;
+	private Document currentDocument;
+
+	public void open(final File file) {
+		if (currentDocument != null)
+			close();
+		Document.loadDocumentAsync(file, (final Document doc, final Exception exception) -> {
+			source.setLoadProgress(0);
+			if (exception != null) {
+				JOptionPane.showMessageDialog(source, exception.toString(),
+						"Failed to load", JOptionPane.ERROR_MESSAGE);
+			} else {
+				System.out.println("Loaded document");
+				this.currentDocument = doc;
+				source.loadDocumentToViewer(doc);
+			}
+		}, (int progress) -> {
+			source.setLoadProgress(progress);
+		});
+	}
+
+	public void close() {
+		if (currentDocument != null) {
+			source.loadDocumentToViewer(null);
+			currentDocument.unload();
+			currentDocument = null;
+		}
+	}
+
+	public Document getCurrentDocument() {
+		return currentDocument;
+	}
+
+	@Override
+	public void onViewerAdd(ViewerWindow source) {
+		this.source = source;
+	}
+
+	@Override
+	public void onPageChange(int oldPage, int newPage) {
+		System.out.println("Page change: " + oldPage + " to " + newPage);
+	}
+
+	@Override
+	public void onZoomChange(double oldZoom, double newZoom) {
+		System.out.println("Zoom change: " + oldZoom + " to " + newZoom);
+	}
+
+	@Override
+	public void onScrollChange(Point oldScroll, Point newScroll) {
+		System.out.println("Scroll change: " + oldScroll + " to " + newScroll);
+	}
+
+	@Override
+	public void onOpenFile() {
+		JFileChooser chooser = new JFileChooser();
+		chooser.setFileFilter(GSFileFilter.INSTANCE);
+		chooser.setCurrentDirectory(new File("").getAbsoluteFile());
+		int status = chooser.showOpenDialog(source);
+		if (status == JFileChooser.APPROVE_OPTION)
+			open(chooser.getSelectedFile());
+	}
+
+	@Override
+	public void onCloseFile() {
+		close();
+	}
+
+	@Override
+	public void onClosing() {
+		source.dispose();
+		System.exit(0);
+	}
+
+	@Override
+	public void onSettingsOpen() {
+		System.out.println("Settings open");
+	}
+
+}
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerGUIListenerImpl.java b/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerGUIListenerImpl.java
deleted file mode 100644
index 108be1974..000000000
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/ViewerGUIListenerImpl.java
+++ /dev/null
@@ -1,67 +0,0 @@
-package com.artifex.gsviewer;
-
-import java.awt.Point;
-import java.io.File;
-
-import javax.swing.JFileChooser;
-import javax.swing.JOptionPane;
-
-import com.artifex.gsviewer.gui.ViewerGUIListener;
-import com.artifex.gsviewer.gui.ViewerWindow;
-
-public class ViewerGUIListenerImpl implements ViewerGUIListener {
-
-	@Override
-	public void onPageChange(ViewerWindow source, int oldPage, int newPage) {
-		System.out.println("Page change: " + oldPage + " to " + newPage);
-	}
-
-	@Override
-	public void onZoomChange(ViewerWindow source, double oldZoom, double newZoom) {
-		System.out.println("Zoom change: " + oldZoom + " to " + newZoom);
-	}
-
-	@Override
-	public void onScrollChange(ViewerWindow source, Point oldScroll, Point newScroll) {
-		System.out.println("Scroll change: " + oldScroll + " to " + newScroll);
-	}
-
-	@Override
-	public void onOpenFile(ViewerWindow source) {
-		System.out.println("Open file");
-		JFileChooser chooser = new JFileChooser();
-		chooser.setFileFilter(GSFileFilter.INSTANCE);
-		chooser.setCurrentDirectory(new File("").getAbsoluteFile());
-		int status = chooser.showOpenDialog(source);
-		if (status == JFileChooser.APPROVE_OPTION) {
-			File toOpen = chooser.getSelectedFile();
-			System.out.println("To open: " + toOpen.getAbsolutePath());
-			Document.loadDocumentAsync(toOpen, (final Document doc, final Exception exception) -> {
-				if (exception != null) {
-					JOptionPane.showMessageDialog(source, exception.toString(),
-							"Failed to load", JOptionPane.ERROR_MESSAGE);
-				} else {
-					System.out.println("Loaded document");
-				}
-			});
-		}
-	}
-
-	@Override
-	public void onCloseFile(ViewerWindow source) {
-		System.out.println("Close file");
-	}
-
-	@Override
-	public void onClosing(ViewerWindow source) {
-		System.out.println("Closing");
-		source.dispose();
-		System.exit(0);
-	}
-
-	@Override
-	public void onSettingsOpen(ViewerWindow source) {
-		System.out.println("Settings open");
-	}
-
-}
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerGUIListener.java b/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerGUIListener.java
index f56bbc5cb..7acaa587b 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerGUIListener.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerGUIListener.java
@@ -4,17 +4,19 @@ import java.awt.Point;
 
 public interface ViewerGUIListener {
 
-	public void onPageChange(ViewerWindow source, int oldPage, int newPage);
+	public void onViewerAdd(ViewerWindow source);
 
-	public void onZoomChange(ViewerWindow source, double oldZoom, double newZoom);
+	public void onPageChange(int oldPage, int newPage);
 
-	public void onScrollChange(ViewerWindow source, Point oldScroll, Point newScroll);
+	public void onZoomChange(double oldZoom, double newZoom);
 
-	public void onOpenFile(ViewerWindow source);
+	public void onScrollChange(Point oldScroll, Point newScroll);
 
-	public void onCloseFile(ViewerWindow source);
+	public void onOpenFile();
 
-	public void onClosing(ViewerWindow source);
+	public void onCloseFile();
 
-	public void onSettingsOpen(ViewerWindow source);
+	public void onClosing();
+
+	public void onSettingsOpen();
 }
diff --git a/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerWindow.java b/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerWindow.java
index ca144d683..49932244c 100644
--- a/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerWindow.java
+++ b/demos/java/gsviewer/src/com/artifex/gsviewer/gui/ViewerWindow.java
@@ -1,5 +1,23 @@
 package com.artifex.gsviewer.gui;
 
+import java.awt.Color;
+import java.awt.Dimension;
+import java.awt.FlowLayout;
+import java.awt.Graphics;
+import java.awt.Image;
+import java.awt.image.BufferedImage;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+import javax.swing.Box;
+import javax.swing.BoxLayout;
+import javax.swing.JPanel;
+import javax.swing.RepaintManager;
+
+import com.artifex.gsviewer.Document;
+import com.artifex.gsviewer.Page;
+
 /**
  * Auto-generated form using NetBeans.
  */
@@ -11,6 +29,10 @@ public class ViewerWindow extends javax.swing.JFrame {
 	private int currentPage, maxPage;
 	private double currentZoom;
 
+	private Document loadedDocument;
+	private List<PagePanel> viewerPagePanels;
+	private List<PagePanel> miniViewerPagePanels;
+
 	/**
 	 * Creates new form ViewerWindow
 	 */
@@ -20,10 +42,13 @@ public class ViewerWindow extends javax.swing.JFrame {
 
 	public ViewerWindow(final ViewerGUIListener listener) {
 		initComponents();
-		this.guiListener = listener;
 		this.currentPage = 0;
 		this.maxPage = 0;
 		this.currentZoom = 1.0;
+		this.viewerPagePanels = new ArrayList<>();
+		this.miniViewerPagePanels = new ArrayList<>();
+
+		setGUIListener(listener);
 	}
 
 	/**
@@ -267,7 +292,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 			currentPage = Math.max(currentPage - 1, 1);
 			pageNumberField.setText(new StringBuilder().append(currentPage).toString());
 			if (guiListener != null)
-				guiListener.onPageChange(this, oldPage, currentPage);
+				guiListener.onPageChange(oldPage, currentPage);
 		} else {
 			pageNumberField.setText(new StringBuilder().append(0).toString());
 		}
@@ -279,7 +304,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 			currentPage = Math.min(currentPage + 1, maxPage);
 			pageNumberField.setText(new StringBuilder().append(currentPage).toString());
 			if (guiListener != null)
-				guiListener.onPageChange(this, oldPage, currentPage);
+				guiListener.onPageChange(oldPage, currentPage);
 		} else {
 			pageNumberField.setText(new StringBuilder().append(0).toString());
 		}
@@ -287,7 +312,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 
 	private void formWindowClosing(java.awt.event.WindowEvent evt) {// GEN-FIRST:event_formWindowClosing
 		if (guiListener != null)
-			guiListener.onClosing(this);
+			guiListener.onClosing();
 	}// GEN-LAST:event_formWindowClosing
 
 	private void pageNumberFieldKeyPressed(java.awt.event.KeyEvent evt) {// GEN-FIRST:event_pageNumberFieldKeyPressed
@@ -300,7 +325,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 				final int oldPage = currentPage;
 				this.currentPage = newPage;
 				if (guiListener != null)
-					guiListener.onPageChange(this, oldPage, currentPage);
+					guiListener.onPageChange(oldPage, currentPage);
 			} catch (IllegalArgumentException e) {
 				System.err.println(new StringBuilder().append("Invalid page number \"").
 						append(text).append('\"').toString());
@@ -315,7 +340,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 		final double oldZoom = currentZoom;
 		this.currentZoom = sliderValue;
 		if (guiListener != null && oldZoom != currentZoom)
-			guiListener.onZoomChange(this, oldZoom, currentZoom);
+			guiListener.onZoomChange(oldZoom, currentZoom);
 	}// GEN-LAST:event_zoomSliderMouseReleased
 
 	private void increaseZoomButtonActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_increaseZoomButtonActionPerformed
@@ -323,7 +348,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 		this.currentZoom = Math.min(Math.ceil((oldZoom * 10) + 1) / 10, 2.0);
 		zoomSlider.setValue((int)(currentZoom * 50));
 		if (guiListener != null && oldZoom != currentZoom)
-			guiListener.onZoomChange(this, oldZoom, currentZoom);
+			guiListener.onZoomChange(oldZoom, currentZoom);
 	}// GEN-LAST:event_increaseZoomButtonActionPerformed
 
 	private void decreaseZoomButtonActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_decreaseZoomButtonActionPerformed
@@ -331,27 +356,27 @@ public class ViewerWindow extends javax.swing.JFrame {
 		this.currentZoom = Math.max(Math.floor((oldZoom * 10) - 1) / 10, 0.0);
 		zoomSlider.setValue((int)(currentZoom * 50));
 		if (guiListener != null && oldZoom != currentZoom)
-			guiListener.onZoomChange(this, oldZoom, currentZoom);
+			guiListener.onZoomChange(oldZoom, currentZoom);
 	}// GEN-LAST:event_decreaseZoomButtonActionPerformed
 
 	private void openMenuActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_openMenuActionPerformed
 		if (guiListener != null)
-			guiListener.onOpenFile(this);
+			guiListener.onOpenFile();
 	}// GEN-LAST:event_openMenuActionPerformed
 
 	private void closeMenuItemActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_closeMenuItemActionPerformed
 		if (guiListener != null)
-			guiListener.onCloseFile(this);
+			guiListener.onCloseFile();
 	}// GEN-LAST:event_closeMenuItemActionPerformed
 
 	private void exitMenuItemActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_exitMenuItemActionPerformed
 		if (guiListener != null)
-			guiListener.onClosing(this);
+			guiListener.onClosing();
 	}// GEN-LAST:event_exitMenuItemActionPerformed
 
 	private void settingsMenuItemActionPerformed(java.awt.event.ActionEvent evt) {// GEN-FIRST:event_settingsMenuItemActionPerformed
 		if (guiListener != null)
-			guiListener.onSettingsOpen(this);
+			guiListener.onSettingsOpen();
 	}// GEN-LAST:event_settingsMenuItemActionPerformed
 
 	// Variables declaration - do not modify//GEN-BEGIN:variables
@@ -378,8 +403,63 @@ public class ViewerWindow extends javax.swing.JFrame {
 	private javax.swing.JSlider zoomSlider;
 	// End of variables declaration//GEN-END:variables
 
+	private class PagePanel extends JPanel {
+
+		private static final long serialVersionUID = 1L;
+
+		private static final int	VIEWER_MODE = 0,
+									MINI_VIEWER_MODE = 1;
+
+		private Object lock;
+		private Page page;
+		private int mode;
+
+		private PagePanel(final Page page, final Dimension size, final int mode) {
+			this.lock = new Object();
+			this.page = page;
+			this.mode = mode;
+			setPreferredSize(size);
+
+			setBackground(Color.WHITE);
+
+			pack();
+		}
+
+		@Override
+		public void paintComponent(Graphics g) {
+			super.paintComponent(g);
+			synchronized (lock) {
+				if (page != null) {
+					Dimension size = getSize();
+					BufferedImage img;
+					switch (mode) {
+					case VIEWER_MODE:
+						img = page.getDisplayableImage();
+						if (img != null)
+							g.drawImage(img.getScaledInstance(size.width, size.height, Image.SCALE_FAST), 0, 0, this);
+						break;
+					case MINI_VIEWER_MODE:
+						img = page.getLowResImage();
+						if (img != null)
+							g.drawImage(img, 0, 0, this);
+						break;
+					default:
+						throw new IllegalStateException("Illegal mode");
+					}
+				}
+			}
+		}
+
+		@Override
+		public void invalidate() {
+			super.invalidate();
+			System.out.println("Invalidated!");
+		}
+	}
+
 	public void setGUIListener(final ViewerGUIListener listener) {
 		this.guiListener = listener;
+		listener.onViewerAdd(this);
 	}
 
 	public void setPage(final int newPage) {
@@ -389,7 +469,7 @@ public class ViewerWindow extends javax.swing.JFrame {
 			final int oldPage = currentPage;
 			currentPage = newPage;
 			if (guiListener != null)
-				guiListener.onPageChange(this, oldPage, currentPage);
+				guiListener.onPageChange(oldPage, currentPage);
 		} catch (IllegalArgumentException e) {
 			System.err.println(new StringBuilder().append("Invalid page number \"").
 					append(newPage).append('\"').toString());
@@ -401,4 +481,65 @@ public class ViewerWindow extends javax.swing.JFrame {
 	public void setMaxPage(final int max) {
 		this.maxPage = max;
 	}
+
+	public void setLoadProgress(final int progress) {
+		progressBar.setValue(progress);
+	}
+
+	public void loadDocumentToViewer(final Document document) {
+		if (document == null) {
+			unloadViewerDocument();
+			return;
+		}
+
+		for (final PagePanel panel : viewerPagePanels) {
+			synchronized (panel.lock) {
+				panel.page = null;
+			}
+		}
+		viewerContentPane.removeAll();
+		viewerPagePanels.clear();
+
+		for (final PagePanel panel : miniViewerPagePanels) {
+			synchronized (panel.lock) {
+				panel.page = null;
+			}
+		}
+		miniViewerContentPane.removeAll();
+		viewerPagePanels.clear();
+
+		this.loadedDocument = document;
+
+		setResizable(false);
+
+		viewerContentPane.setLayout(new BoxLayout(viewerContentPane, BoxLayout.Y_AXIS));
+
+		for (final Page page : document) {
+			final PagePanel panel = new PagePanel(page, page.getSize(), PagePanel.VIEWER_MODE);
+			viewerContentPane.add(panel);
+			viewerContentPane.add(Box.createVerticalStrut(10));
+
+			viewerPagePanels.add(panel);
+		}
+
+		miniViewerContentPane.setLayout(new BoxLayout(miniViewerContentPane, BoxLayout.Y_AXIS));
+
+		for (final Page page : document) {
+			final PagePanel panel = new PagePanel(page, page.getLowResSize(), PagePanel.MINI_VIEWER_MODE);
+			miniViewerContentPane.add(panel);
+			miniViewerContentPane.add(Box.createVerticalStrut(10));
+
+			miniViewerPagePanels.add(panel);
+		}
+
+		setResizable(true);
+	}
+
+	public void unloadViewerDocument() {
+		this.loadedDocument = null;
+	}
+
+	public Document getLoadedDocument() {
+		return loadedDocument;
+	}
 }