PopupKeyDownListener.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * 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:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.ide.ui.popup;

import org.eclipse.che.ide.util.dom.Elements;
import com.google.gwt.core.client.Scheduler;
import com.google.gwt.core.client.Scheduler.ScheduledCommand;
import com.google.gwt.event.dom.client.KeyCodes;

import elemental.dom.Element;
import elemental.events.Event;
import elemental.events.EventListener;
import elemental.events.KeyboardEvent;

public class PopupKeyDownListener implements EventListener {

    /**
     * The related opopup widget.
     */
    private final PopupWidget<?> popupWidget;

    /**
     * The list element (contains the items).
     */
    private final Element listElement;

    public PopupKeyDownListener(final PopupWidget<?> popupWidget, final Element listElement) {
        this.popupWidget = popupWidget;
        this.listElement = listElement;
    }

    @Override
    public void handleEvent(final Event evt) {
        if (evt instanceof KeyboardEvent) {
            final KeyboardEvent keyEvent = (KeyboardEvent) evt;
            switch (keyEvent.getKeyCode()) {
                case KeyCodes.KEY_ESCAPE:
                    Scheduler.get().scheduleDeferred(new ScheduledCommand() {
                        @Override
                        public void execute() {
                            popupWidget.hide();
                        }
                    });
                    break;
                case KeyCodes.KEY_DOWN:
                    focusNext();
                    break;
                case KeyCodes.KEY_UP:
                    focusPrevious();
                    break;
                case KeyCodes.KEY_HOME:
                    focusFirst();
                    break;
                case KeyCodes.KEY_END:
                    focusLast();
                    break;
                case KeyCodes.KEY_ENTER:
                    evt.preventDefault();
                    evt.stopImmediatePropagation();
                    validateItem();
                    break;
                default:
            }
        }
    }

    /**
     * Focus the next item in the list, or the first item if we are already at the last.
     * In the case the list doesn't currently have focus, focus the first element.
     */
    private void focusNext() {
        final Element current = Elements.getDocument().getActiveElement();
        if (current.getParentElement().isEqualNode(listElement)) {
            final Element next = current.getNextElementSibling();
            if (next != null) {
                next.focus();
            } else {
                focusFirst();
            }
        } else {
            // we don't actually have focus, focus the first element
            focusFirst();
        }
    }

    /**
     * Focus the previous item in the list, or the last item if we are already at the first.
     * In the case the list doesn't currently have focus, focus the first element.
     */
    private void focusPrevious() {
        final Element current = Elements.getDocument().getActiveElement();
        if (current.getParentElement().isEqualNode(listElement)) {
            final Element prev = current.getPreviousElementSibling();
            if (prev != null) {
                prev.focus();
            } else {
                focusLast();
            }
        } else {
            // we don't actually have focus, focus the first element
            focusFirst();
        }
    }

    /**
     * Focus the first item in the list (if any).
     */
    private void focusFirst() {
        if (this.listElement.hasChildNodes()) {
            this.listElement.getFirstElementChild().focus();
        }
    }

    /**
     * Focus the last item in the list (if any).
     */
    private void focusLast() {
        if (this.listElement.hasChildNodes()) {
            this.listElement.getLastElementChild().focus();
        }
    }

    /**
     * Activates the currently selected item.
     */
    private void validateItem() {
        final Element current = Elements.getDocument().getActiveElement();
        if (current.getParentElement().isEqualNode(listElement)) {
            this.popupWidget.validateItem(current);
        }
    }
}