org.eclipse.swt.widgets.Item.java Source code

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/*******************************************************************************
 * Copyright (c) 2000, 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.swt.widgets;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.*;

/**
 * This class is the abstract superclass of all non-windowed
 * user interface objects that occur within specific controls.
 * For example, a tree will contain tree items.
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>(none)</dd>
 * <dt><b>Events:</b></dt>
 * <dd>(none)</dd>
 * </dl>
 *
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 */

public abstract class Item extends Widget {
    String text;
    Image image;
    /**
     * Maximum number of characters Windows can reliably display in one line.
     * Mac and Linux can display more but we are limited by windows here.
     */
    static final int TEXT_LIMIT = 8192;

    static final String ELLIPSIS = "...";

    /**
     * Constructs a new instance of this class given its parent
     * and a style value describing its behavior and appearance.
     * The item is added to the end of the items maintained by its parent.
     * <p>
     * The style value is either one of the style constants defined in
     * class <code>SWT</code> which is applicable to instances of this
     * class, or must be built by <em>bitwise OR</em>'ing together
     * (that is, using the <code>int</code> "|" operator) two or more
     * of those <code>SWT</code> style constants. The class description
     * lists the style constants that are applicable to the class.
     * Style bits are also inherited from superclasses.
     * </p>
     *
     * @param parent a widget which will be the parent of the new instance (cannot be null)
     * @param style the style of item to construct
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
     * </ul>
     *
     * @see SWT
     * @see Widget#getStyle
     */
    public Item(Widget parent, int style) {
        super(parent, style);
        text = "";
    }

    /**
     * Constructs a new instance of this class given its parent
     * and a style value describing its behavior and appearance,
     * and the index at which to place it in the items maintained
     * by its parent.
     * <p>
     * The style value is either one of the style constants defined in
     * class <code>SWT</code> which is applicable to instances of this
     * class, or must be built by <em>bitwise OR</em>'ing together
     * (that is, using the <code>int</code> "|" operator) two or more
     * of those <code>SWT</code> style constants. The class description
     * lists the style constants that are applicable to the class.
     * Style bits are also inherited from superclasses.
     * </p>
     *
     * @param parent a widget which will be the parent of the new instance (cannot be null)
     * @param style the style of item to construct
     * @param index the zero-relative index at which to store the receiver in its parent
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
     *    <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the parent (inclusive)</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
     * </ul>
     *
     * @see SWT
     * @see Widget#getStyle
     */
    public Item(Widget parent, int style, int index) {
        this(parent, style);
    }

    @Override
    protected void checkSubclass() {
        /* Do Nothing - Subclassing is allowed */
    }

    /**
     * Returns the receiver's image if it has one, or null
     * if it does not.
     *
     * @return the receiver's image
     *
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     */
    public Image getImage() {
        checkWidget();
        return image;
    }

    @Override
    String getNameText() {
        return getText();
    }

    /**
     * Returns the receiver's text, which will be an empty
     * string if it has never been set.
     *
     * @return the receiver's text
     *
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     */
    public String getText() {
        checkWidget();
        return text;
    }

    @Override
    void releaseWidget() {
        super.releaseWidget();
        text = null;
        image = null;
    }

    /**
     * Sets the receiver's image to the argument, which may be
     * null indicating that no image should be displayed.
     *
     * @param image the image to display on the receiver (may be null)
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_INVALID_ARGUMENT - if the image has been disposed</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     */
    public void setImage(Image image) {
        checkWidget();
        if (image != null && image.isDisposed())
            error(SWT.ERROR_INVALID_ARGUMENT);
        this.image = image;
    }

    /**
     * Sets the receiver's text.
     * <p>
     * Note: If control characters like '\n', '\t' etc. are used
     * in the string, then the behavior is platform dependent.
     * </p>
     * @param string the new text
     *
     * @exception IllegalArgumentException <ul>
     *    <li>ERROR_NULL_ARGUMENT - if the text is null</li>
     * </ul>
     * @exception SWTException <ul>
     *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
     *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
     * </ul>
     */
    public void setText(String string) {
        checkWidget();
        if (string == null)
            error(SWT.ERROR_NULL_ARGUMENT);
        text = string;
        if ((state & HAS_AUTO_DIRECTION) != 0) {
            updateTextDirection(AUTO_TEXT_DIRECTION);
        }
    }

    boolean updateTextDirection(int textDirection) {
        /*
         * textDirection argument passed here is either (1) AUTO_TEXT_DIRECTION, or
         * (2) 0 (i.e. match orientation) or FLIP_TEXT_DIRECTION (mismatch orientation).
         */
        if (textDirection == AUTO_TEXT_DIRECTION) {
            state |= HAS_AUTO_DIRECTION;
            textDirection = (style ^ BidiUtil.resolveTextDirection(text)) == 0 ? 0 : SWT.FLIP_TEXT_DIRECTION;
        } else {
            state &= ~HAS_AUTO_DIRECTION;
        }
        if (((style & SWT.FLIP_TEXT_DIRECTION) ^ textDirection) != 0) {
            style ^= SWT.FLIP_TEXT_DIRECTION;
            return true;
        }
        return textDirection == AUTO_TEXT_DIRECTION;
    }

}