SwtDisplayDevice.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 net.sf.vex.swt;

import net.sf.vex.core.DisplayDevice;

import org.eclipse.swt.widgets.Display;

/**
 * Adapts the DisplayDevice display to the current SWT display.
 */
public class SwtDisplayDevice extends DisplayDevice {

    /**
     * Class constructor.
     */
    public SwtDisplayDevice() {
        // We used to do it like this, but it turns out sometimes we did it 
        // too early and getCurrent() returned null, so now the convoluted stuff below.
//        Display display = Display.getCurrent();
//        this.horizontalPPI = display.getDPI().x;
//        this.verticalPPI = display.getDPI().y;
    }

    public int getHorizontalPPI() {
        if (!this.loaded) {
            this.load();
        }
        return this.horizontalPPI;
    }

    public int getVerticalPPI() {
        if (!this.loaded) {
            this.load();
        }
        return this.verticalPPI;
    }

    private boolean loaded = false;
    private int horizontalPPI = 72;
    private int verticalPPI = 72;
    
    private void load() {
        Display display = Display.getCurrent();
        if (display != null) {
            this.horizontalPPI = display.getDPI().x;
            this.verticalPPI = display.getDPI().y;
            this.loaded = true;
        }        
    }
    
}