org.eclipse.vex.core/src/org/eclipse/vex/core/internal/core/DisplayDevice.java

/*******************************************************************************
 * Copyright (c) 2004, 2008 John Krasnay and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     John Krasnay - initial API and implementation
 *******************************************************************************/
package org.eclipse.vex.core.internal.core;

/**
 * Represents a device that can display graphics. This class is subclassed for each target system.
 */
public abstract class DisplayDevice {

	public static final DisplayDevice NULL = new DisplayDevice() {
		@Override
		public int getHorizontalPPI() {
			return 0;
		}

		@Override
		public int getVerticalPPI() {
			return 0;
		}
	};

	public static final DisplayDevice _72DPI = new DisplayDevice() {
		@Override
		public int getHorizontalPPI() {
			return 72;
		}

		@Override
		public int getVerticalPPI() {
			return 72;
		}
	};

	/**
	 * Class constructor.
	 */
	public DisplayDevice() {
	}

	/**
	 * Returns the current display device.
	 */
	public static DisplayDevice getCurrent() {
		return current;
	}

	/**
	 * Returns the horizontal resolution of the device, in pixels-per-inch.
	 */
	public abstract int getHorizontalPPI();

	/**
	 * Returns the horizontal resolution of the device, in pixels-per-inch.
	 */
	public abstract int getVerticalPPI();

	/**
	 * Sets the current display device. This is typically called by the platform-specific widget;
	 *
	 * @param current
	 *            The device to use as the current device.
	 */
	public static void setCurrent(final DisplayDevice current) {
		DisplayDevice.current = current;
	}

	// ======================================================= PRIVATE

	private static DisplayDevice current = NULL;
}