org.eclipse.jface.layout.PixelConverter.java Source code

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Here is the source code for org.eclipse.jface.layout.PixelConverter.java

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/*******************************************************************************
 * Copyright (c) 2008, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * 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);
    }

}