/*
 * Copyright (c) 2010, 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javafx.scene.control;

import javafx.scene.control.skin.LabelSkin;
import com.sun.javafx.scene.NodeHelper;

import javafx.beans.property.ObjectProperty;
import javafx.beans.property.ObjectPropertyBase;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.WritableValue;
import javafx.css.StyleableProperty;
import javafx.scene.AccessibleRole;
import javafx.scene.Node;

/**
 * Label is a non-editable text control. A Label is useful for displaying
 * text that is required to fit within a specific space, and thus may need
 * to use an ellipsis or truncation to size the string to fit. Labels also are
 * useful in that they can have mnemonics which, if used, will send focus to
 * the Control listed as the target of the <code>labelFor</code> property.
 * <p>
 * Label sets focusTraversable to false.
 * </p>
 *
 * <p>Example:
 * <pre><code>Label label = new Label("a label");</code></pre>
 *
 * <img src="doc-files/Label.png" alt="Image of the Label control">
 *
 * @since JavaFX 2.0
 */
public class Label extends Labeled {

    /* *************************************************************************
     *                                                                         *
     * Constructors                                                            *
     *                                                                         *
     **************************************************************************/

    /**
     * Creates an empty label
     */
    public Label() {
        initialize();
    }

    /**
     * Creates Label with supplied text.
     * @param text null text is treated as the empty string
     */
    public Label(String text) {
        super(text);
        initialize();
    }

    /**
     * Creates a Label with the supplied text and graphic.
     * @param text null text is treated as the empty string
     * @param graphic a null graphic is acceptable
     */
    public Label(String text, Node graphic) {
        super(text, graphic);
        initialize();
    }

    private void initialize() {
        getStyleClass().setAll("label");
        setAccessibleRole(AccessibleRole.TEXT);
        // Labels are not focus traversable, unlike most other UI Controls.
        // focusTraversable is styleable through css. Calling setFocusTraversable
        // makes it look to css like the user set the value and css will not
        // override. Initializing focusTraversable by calling set on the
        // CssMetaData ensures that css will be able to override the value.
        ((StyleableProperty<Boolean>)(WritableValue<Boolean>)focusTraversableProperty()).applyStyle(null, Boolean.FALSE);
    }

    /* *************************************************************************
     *                                                                         *
     * Properties                                                              *
     *                                                                         *
     **************************************************************************/

    private ChangeListener<Boolean> mnemonicStateListener = (observable, oldValue, newValue) -> {
        NodeHelper.showMnemonicsProperty(Label.this).setValue(newValue);
    };

    /**
     * A Label can act as a label for a different Control or
     * Node. This is used for Mnemonics and Accelerator parsing.
     * This allows setting of the target Node.
     * @return the Node that this label is to be associated with
     */
    public ObjectProperty<Node> labelForProperty() {
        if (labelFor == null) {
            labelFor = new ObjectPropertyBase<Node>() {
                Node oldValue = null;
                @Override protected void invalidated() {
                    if (oldValue != null) {
                        NodeHelper.getNodeAccessor().setLabeledBy(oldValue, null);
                        NodeHelper.showMnemonicsProperty(oldValue).removeListener(mnemonicStateListener);
                    }
                    final Node node = get();
                    if (node != null) {
                        NodeHelper.getNodeAccessor().setLabeledBy(node, Label.this);
                        NodeHelper.showMnemonicsProperty(node).addListener(mnemonicStateListener);
                        NodeHelper.setShowMnemonics(Label.this, NodeHelper.isShowMnemonics(node));
                    } else {
                        NodeHelper.setShowMnemonics(Label.this, false);
                    }
                    oldValue = node;
                }

                @Override public Object getBean() {
                    return Label.this;
                }

                @Override public String getName() {
                    return "labelFor";
                }
            };

        }
        return labelFor;
    }
    private ObjectProperty<Node> labelFor;

    public final void setLabelFor(Node value) { labelForProperty().setValue(value); }
    public final Node getLabelFor() { return labelFor == null ? null : labelFor.getValue(); }

    /* *************************************************************************
     *                                                                         *
     * Methods                                                                 *
     *                                                                         *
     **************************************************************************/

    /** {@inheritDoc} */
    @Override protected Skin<?> createDefaultSkin() {
        return new LabelSkin(this);
    }

    /* *************************************************************************
     *                                                                         *
     * CSS Support                                                             *
     *                                                                         *
     **************************************************************************/

    /**
     * Returns the initial focus traversable state of this control, for use
     * by the JavaFX CSS engine to correctly set its initial value. This method
     * is overridden as by default UI controls have focus traversable set to true,
     * but that is not appropriate for this control.
     *
     * @since 9
     */
    @Override protected Boolean getInitialFocusTraversable() {
        return Boolean.FALSE;
    }

}
