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/*******************************************************************************
 * Copyright (c) 2008 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.layout;

import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.FontMetrics;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Control;

import org.eclipse.jface.dialogs.Dialog;

/**
 * PixelConverter performs various conversions from device-independent units
 * (such as DLUs or characters) to pixels. It can be associated with a control or
 * a font. In the case of a control, the font used by the control at the time
 * the PixelConverter is created is used for the pixel calculations. In the case
 * of a specific font, the supplied font is used for the calculations.
 * 
 * The control and/or font must not be disposed at the time the PixelConverter
 * is created.
 * 
 * @since 3.5
 */
public class PixelConverter {

  private final FontMetrics fontMetrics;

  /**
   * Create a PixelConverter which will convert device-independent units to
   * pixels using the font of the specified control.
   * 
   * @param control
   *            the control whose font should be used for pixel conversions.
   *            Note that the font used by the control at the time this
   *            constructor is called is the font that will be used for all
   *            calculations. If the font of the specified control is changed
   *            after this PixelConverter is created, then the conversions
   *            from this instance will not produce the desired effect.
   */
  public PixelConverter(Control control) {
    this(control.getFont());
  }

  /**
   * Create a PixelConverter which will convert device-independent units to
   * pixels using the specified font.
   * 
   * @param font
   *            the font that should be used for pixel conversions.
   */
  public PixelConverter(Font font) {
    GC gc = new GC(font.getDevice());
    gc.setFont(font);
    fontMetrics = gc.getFontMetrics();
    gc.dispose();
  }

  /**
   * Returns the number of pixels corresponding to the height of the given
   * number of characters.
   * 
   * @param chars
   *            the number of characters
   * @return the number of pixels
   */
  public int convertHeightInCharsToPixels(int chars) {
    return Dialog.convertHeightInCharsToPixels(fontMetrics, chars);
  }

  /**
   * Returns the number of pixels corresponding to the given number of
   * horizontal dialog units.
   * 
   * @param dlus
   *            the number of horizontal dialog units
   * @return the number of pixels
   */
  public int convertHorizontalDLUsToPixels(int dlus) {
    return Dialog.convertHorizontalDLUsToPixels(fontMetrics, dlus);
  }

  /**
   * Returns the number of pixels corresponding to the given number of
   * vertical dialog units.
   * 
   * @param dlus
   *            the number of vertical dialog units
   * @return the number of pixels
   */
  public int convertVerticalDLUsToPixels(int dlus) {
    return Dialog.convertVerticalDLUsToPixels(fontMetrics, dlus);
  }

  /**
   * Returns the number of pixels corresponding to the width of the given
   * number of characters.
   * 
   * @param chars
   *            the number of characters
   * @return the number of pixels
   */
  public int convertWidthInCharsToPixels(int chars) {
    return Dialog.convertWidthInCharsToPixels(fontMetrics, chars);
  }

}
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