MenuButton.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.menubutton;

import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.Document;
import com.google.gwt.resources.client.ClientBundle;
import com.google.gwt.resources.client.CssResource;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.FocusWidget;

import org.vectomatic.dom.svg.ui.SVGResource;

import java.util.List;
import java.util.Optional;

import static com.google.gwt.dom.client.NativeEvent.BUTTON_LEFT;
import static java.util.Optional.ofNullable;

/** Button with popup menu. */
public class MenuButton extends FlowPanel {

    private static final Resources RESOURCES;

    protected final ItemsProvider itemsProvider;

    private final Timer showMenuTimer;

    private ActionHandler actionHandler;
    private ItemsList     menu;

    public MenuButton(SafeHtml content, ItemsProvider itemsProvider) {
        super();

        this.itemsProvider = itemsProvider;

        addStyleName(RESOURCES.css().menuButton());

        showMenuTimer = new Timer() {
            @Override
            public void run() {
                showMenu();
            }
        };

        final FocusWidget mainButton = new MainButton(content);
        final FocusWidget dropButton = new DropButton();

        add(mainButton);
        add(dropButton);

        attachMouseEventHandlers(mainButton);
        attachMouseEventHandlers(dropButton);
    }

    private void attachMouseEventHandlers(FocusWidget widget) {
        widget.addMouseOutHandler(event -> showMenuTimer.cancel());
        widget.addMouseUpHandler(event -> showMenuTimer.cancel());
        widget.addMouseDownHandler(event -> {
            if (event.getNativeButton() == BUTTON_LEFT) {
                showMenuTimer.schedule(1000);
            } else {
                showMenuTimer.cancel();
            }
        });
    }

    public Optional<ActionHandler> getActionHandler() {
        return ofNullable(actionHandler);
    }

    /** Set {@link ActionHandler} to handle {@link MenuItem}s selection. */
    public void setActionHandler(ActionHandler actionHandler) {
        this.actionHandler = actionHandler;
    }

    private void showMenu() {
        final List<MenuItem> items = itemsProvider.getItems();

        if (!items.isEmpty()) {
            menu = new ItemsList(items, itemsProvider, RESOURCES, null);
            getActionHandler().ifPresent(handler -> menu.setActionHandler(handler));
            menu.setPopupPosition(getAbsoluteLeft(), getAbsoluteTop() + getOffsetHeight());
            menu.show();
        }
    }

    public interface Resources extends ClientBundle {

        @Source({"button.css", "org/eclipse/che/ide/api/ui/style.css"})
        Css css();

        @Source("arrowIcon.svg")
        SVGResource arrowIcon();
    }

    public interface Css extends CssResource {

        String menuButton();

        String button();

        String mainButton();

        String dropButton();

        String popupPanel();

        String expandedImage();

        String popupItem();

        String popupItemOver();

        String arrow();

        String label();
    }

    private class MainButton extends FocusWidget {

        MainButton(SafeHtml content) {
            super(Document.get().createDivElement());

            getElement().setInnerSafeHtml(content);

            addStyleName(RESOURCES.css().button());
            addStyleName(RESOURCES.css().mainButton());

            addClickHandler(event -> {
                if (menu != null && menu.isShowing()) {
                    return;
                }

                final Optional<MenuItem> defaultItem = itemsProvider.getDefaultItem();

                if (defaultItem.isPresent()) {
                    getActionHandler().ifPresent(actionHandler -> actionHandler.onAction(defaultItem.get()));
                } else {
                    showMenu();
                }
            });
        }
    }

    private class DropButton extends FocusWidget {

        DropButton() {
            super(Document.get().createDivElement());

            addStyleName(RESOURCES.css().button());
            addStyleName(RESOURCES.css().dropButton());

            final FlowPanel marker = new FlowPanel();
            marker.getElement().appendChild(RESOURCES.arrowIcon().getSvg().getElement());
            marker.addStyleName(RESOURCES.css().expandedImage());

            getElement().appendChild(marker.getElement());

            addClickHandler(event -> {
                if (menu == null || !menu.isShowing()) {
                    showMenu();
                }
            });
        }
    }

    static {
        RESOURCES = GWT.create(Resources.class);
        RESOURCES.css().ensureInjected();
    }
}