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 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions
 * and the following disclaimer.
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package org.openjdk.jmc.ui.misc;

import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;

import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.graphics.PaletteData;
import org.eclipse.swt.widgets.Display;
import org.openjdk.jmc.ui.UIPlugin;
import org.openjdk.jmc.ui.common.util.Environment;
import org.openjdk.jmc.ui.preferences.PreferenceConstants;

public class AwtCanvas {
	private ImageData imageDataSWT;
	private BufferedImage imageAWT;

	private static final double X_SCALE = (Display.getCurrent().getDPI().x) / Environment.getNormalDPI();
	private static final double Y_SCALE = (Display.getCurrent().getDPI().y) / Environment.getNormalDPI();

	public boolean hasImage(int width, int height) {
		return (imageDataSWT != null) && (imageDataSWT.width == width) && (imageDataSWT.height == height);
	}

	public Graphics2D getGraphics(int width, int height) {
		if ((imageDataSWT == null) || (imageDataSWT.width != width) || (imageDataSWT.height != height)) {
			imageAWT = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
			PaletteData vpPalette = new PaletteData(0xff, 0xff00, 0xff0000);
			int scanlinePad = width * 3;
			byte[] byteData = ((DataBufferByte) imageAWT.getRaster().getDataBuffer()).getData();
			imageDataSWT = new ImageData(width, height, 24, vpPalette, scanlinePad, byteData);
			Graphics2D graphicsAWT = imageAWT.createGraphics();
			setAntiAliasing(graphicsAWT);
			graphicsAWT.setFont(new Font("OptionPane.font", Font.PLAIN, 12)); //$NON-NLS-1$
			fixDPI(graphicsAWT);
			return graphicsAWT;
		} else {
			Graphics2D graphicsAWT = imageAWT.createGraphics();
			setAntiAliasing(graphicsAWT);
			graphicsAWT.setFont(new Font("OptionPane.font", Font.PLAIN, 12)); //$NON-NLS-1$
			graphicsAWT.clearRect(0, 0, width, height);
			fixDPI(graphicsAWT);
			return graphicsAWT;
		}
	}
	
	private void setAntiAliasing(Graphics2D ctx) {
		Boolean antiAliasing = UIPlugin.getDefault().getPreferenceStore().getBoolean(PreferenceConstants.P_ANTI_ALIASING);
		if (antiAliasing) {
			ctx.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
		} else {
			ctx.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF);
		}
	}

	private void fixDPI(Graphics2D ctx) {
		AffineTransform defaultTransform = ctx.getDeviceConfiguration().getDefaultTransform();
		defaultTransform.scale(X_SCALE, Y_SCALE);
		ctx.setTransform(defaultTransform);
	}

	public void paint(PaintEvent e, int x, int y) {
		try {
			Image img = new Image(e.display, imageDataSWT);
			e.gc.drawImage(img, x, y);
			img.dispose();
		} catch (ArrayIndexOutOfBoundsException ex) {
			// Workaround for image construction bug
		}
	}
}