Java desktop example: detect retina and scale accordingly

also: zoom in/out buttons

2 files changed, 98 insertions, 8 deletions

diff --git a/platform/java/example/PageCanvas.java b/platform/java/example/PageCanvas.java
index ffe3efc2..bfeca21b 100644
--- a/platform/java/example/PageCanvas.java
+++ b/platform/java/example/PageCanvas.java
@@ -9,6 +9,9 @@ public class PageCanvas extends java.awt.Canvas
 	protected Page page;
 	protected BufferedImage image;
 
+	protected float mScale = 1.0f;
+	private float mRetinaScale = 1.0f;
+
 	public static BufferedImage imageFromPixmap(Pixmap pixmap) {
 		int w = pixmap.getWidth();
 		int h = pixmap.getHeight();
@@ -23,7 +26,7 @@ public class PageCanvas extends java.awt.Canvas
 		Pixmap pixmap = new Pixmap(ColorSpace.DeviceBGR, bbox);
 		pixmap.clear(255);
 		DrawDevice dev = new DrawDevice(pixmap);
-		page.run(dev, new Matrix());
+		page.run(dev, ctm);
 		dev.destroy();
 		BufferedImage image = imageFromPixmap(pixmap);
 		pixmap.destroy();
@@ -37,9 +40,19 @@ public class PageCanvas extends java.awt.Canvas
 		return image;
 	}
 
-	public PageCanvas(Page page_) {
+	public PageCanvas(Page page_, float nativeScale) {
+		mRetinaScale = nativeScale;
+		mScale = mRetinaScale;
 		this.page = page_;
-		image = imageFromPage(page, new Matrix());
+		run();
+	}
+
+	private void run()
+	{
+		Matrix ctm = new Matrix();
+		ctm.scale(mScale);
+		image = imageFromPage(page, ctm);
+		repaint();
 	}
 
 	public Dimension getPreferredSize() {
@@ -54,7 +67,25 @@ public class PageCanvas extends java.awt.Canvas
 		return getPreferredSize();
 	}
 
-	public void paint(Graphics g) {
-		g.drawImage(image, 0, 0, null);
+	public void zoomIn() {
+		mScale += 0.25f;
+		run();
+	}
+
+	public void zoomOut() {
+	    mScale -= 0.25f;
+	    run();
 	}
+
+	public void paint(Graphics g)
+	{
+		float scale = 1.0f;
+		scale = 1/mRetinaScale;
+
+		final Graphics2D g2d = (Graphics2D)g.create(0, 0, image.getWidth(), image.getHeight());
+		g2d.scale(scale, scale);
+		g2d.drawImage(image, 0, 0, null);
+		g2d.dispose();
+	}
+
 }
diff --git a/platform/java/example/Viewer.java b/platform/java/example/Viewer.java
index 91b0fa1d..310aeb15 100644
--- a/platform/java/example/Viewer.java
+++ b/platform/java/example/Viewer.java
@@ -14,10 +14,14 @@ import java.awt.event.ActionListener;
 import java.awt.event.WindowListener;
 import java.awt.event.WindowEvent;
 import java.awt.event.ActionEvent;
+import java.awt.GraphicsEnvironment;
+import java.awt.GraphicsDevice;
+import java.awt.Toolkit;
 
 import javax.swing.JFileChooser;
 import javax.swing.filechooser.FileFilter;
 import javax.swing.JOptionPane;
+import java.lang.reflect.Field;
 
 public class Viewer extends Frame implements WindowListener, ActionListener
 {
@@ -25,19 +29,23 @@ public class Viewer extends Frame implements WindowListener, ActionListener
 	protected Panel toolbar;
 	protected PageCanvas pageCanvas;
 	protected Label pageLabel;
-	protected Button firstButton, prevButton, nextButton, lastButton;
+	protected Button firstButton, prevButton, nextButton, lastButton, zoomInButton, zoomOutButton;
 	protected int pageCount;
 	protected int pageNumber;
 
+	private float retinaScale;
+
 	public Viewer(Document doc_) {
 		super("MuPDF");
 
+		retinaScale = getRetinaScale();
+		
 		this.doc = doc_;
 
 		pageCount = doc.countPages();
 		pageNumber = 0;
 
-		setSize(600, 900);
+		setSize(1200, 900);
 		setTitle("MuPDF: " + doc.getMetaData(Document.META_INFO_TITLE));
 
 		toolbar = new Panel();
@@ -50,12 +58,18 @@ public class Viewer extends Frame implements WindowListener, ActionListener
 		nextButton.addActionListener(this);
 		lastButton = new Button(">|");
 		lastButton.addActionListener(this);
+		zoomInButton = new Button("+");
+		zoomInButton.addActionListener(this);
+		zoomOutButton = new Button("-");
+		zoomOutButton.addActionListener(this);
 		pageLabel = new Label();
 
 		toolbar.add(firstButton);
 		toolbar.add(prevButton);
 		toolbar.add(nextButton);
 		toolbar.add(lastButton);
+		toolbar.add(zoomInButton);
+		toolbar.add(zoomOutButton);
 		toolbar.add(pageLabel);
 
 		add(toolbar, BorderLayout.NORTH);
@@ -69,7 +83,7 @@ public class Viewer extends Frame implements WindowListener, ActionListener
 		pageLabel.setText("Page " + (pageNumber + 1) + " / " + pageCount);
 		if (pageCanvas != null)
 			remove(pageCanvas);
-		pageCanvas = new PageCanvas(doc.loadPage(pageNumber));
+		pageCanvas = new PageCanvas(doc.loadPage(pageNumber), retinaScale);
 		add(pageCanvas, BorderLayout.CENTER);
 		validate();
 	}
@@ -80,19 +94,30 @@ public class Viewer extends Frame implements WindowListener, ActionListener
 
 		if (source == firstButton)
 			pageNumber = 0;
+
 		if (source == lastButton)
 			pageNumber = pageCount - 1;
+
 		if (source == prevButton) {
 			pageNumber = pageNumber - 1;
 			if (pageNumber < 0)
 				pageNumber = 0;
 		}
+
 		if (source == nextButton) {
 			pageNumber = pageNumber + 1;
 			if (pageNumber >= pageCount)
 				pageNumber = pageCount - 1;
 		}
 
+		if (source == zoomInButton) {
+			pageCanvas.zoomIn();
+		}
+
+		if (source == zoomOutButton) {
+			pageCanvas.zoomOut();
+		}
+
 		if (pageNumber != oldPageNumber)
 			stuff();
 	}
@@ -200,4 +225,38 @@ public class Viewer extends Frame implements WindowListener, ActionListener
 	{
 		JOptionPane.showMessageDialog(null, infoMessage, "InfoBox: " + titleBar, JOptionPane.INFORMATION_MESSAGE);
 	}
+
+	public float getRetinaScale()
+	{
+		//  first try Oracle's VM (we should also test for 1.7.0_40 or higher)
+		final String vendor = System.getProperty("java.vm.vendor");
+		boolean isOracle = vendor != null && vendor.toLowerCase().contains("Oracle".toLowerCase());
+		if (isOracle)
+		{
+			GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
+			final GraphicsDevice device = env.getDefaultScreenDevice();
+			try {
+				Field field = device.getClass().getDeclaredField("scale");
+				if (field != null) {
+					field.setAccessible(true);
+					Object scale = field.get(device);
+					if (scale instanceof Integer && ((Integer)scale).intValue() == 2) {
+						return 2.0f;
+					}
+				}
+			}
+			catch (Exception ignore) {
+			}
+			return 1.0f;
+		}
+
+		//  try Apple VM
+		final Float scaleFactor = (Float)Toolkit.getDefaultToolkit().getDesktopProperty("apple.awt.contentScaleFactor");
+		if (scaleFactor != null && scaleFactor.intValue() == 2) {
+			return 2.0f;
+		}
+
+		return 1.0f;
+	}
+
 }