DropdownMenu.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.dropdown;

import com.google.gwt.core.client.GWT;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.IsWidget;
import com.google.gwt.user.client.ui.PopupPanel;
import com.google.gwt.user.client.ui.ScrollPanel;

import static com.google.gwt.user.client.ui.PopupPanel.AnimationType.ROLL_DOWN;

/** Menu for {@link DropdownList}. */
class DropdownMenu extends PopupPanel {

    private static final DropdownListResources RESOURCES = GWT.create(DropdownListResources.class);

    /** Maximum amount of widgets that should visible without scrolling. */
    private static final int MAX_VISIBLE_WIDGETS = 7;
    /** Amount of pixels reserved for displaying one widget. */
    private static final int CHILD_WIDGET_HEIGHT = 22;

    private final DropdownList dropdownList;
    private final FlowPanel    contentPanel;

    /** Stores true if dropdown menu's width should be always synchronized with the dropdown header's width. */
    private boolean widthsSynced;

    /**
     * Creates new dropdown menu.
     *
     * @param dropdownList
     *         a dropdown list to which the menu should be bound
     * @param syncWidths
     *         specifies whether this dropdown menu's width always should be the same as the given {@code dropdownList}'s width
     */
    DropdownMenu(DropdownList dropdownList, boolean syncWidths) {
        super(true);

        this.dropdownList = dropdownList;
        widthsSynced = syncWidths;
        if (syncWidths) {
            Window.addResizeHandler(e -> setWidth(dropdownList.getElement().getClientWidth() + "px"));
        }

        removeStyleName("gwt-PopupPanel");
        addStyleName(RESOURCES.dropdownListCss().menu());

        addAutoHidePartner(dropdownList.getElement());
        setAnimationEnabled(true);
        setAnimationType(ROLL_DOWN);

        contentPanel = new FlowPanel();
        contentPanel.ensureDebugId("dropdown-list-content-panel");

        add(new ScrollPanel(contentPanel));
    }

    void toggleMenuVisibility() {
        if (isShowing()) {
            hide();
        } else {
            if (widthsSynced) {
                setWidth(dropdownList.getElement().getClientWidth() + "px");
            }

            showRelativeTo(dropdownList);
        }
    }

    void addWidget(IsWidget widget) {
        contentPanel.insert(widget, 0);
        adaptMenuHeight();
    }

    void removeWidget(IsWidget widget) {
        contentPanel.remove(widget);
        adaptMenuHeight();
    }

    void removeAllWidgets() {
        contentPanel.clear();
        adaptMenuHeight();
    }

    /** Adapts menu's height depending on the amount of the child widgets. */
    private void adaptMenuHeight() {
        final int visibleRowsCount = Math.min(MAX_VISIBLE_WIDGETS, contentPanel.getWidgetCount());
        final int dropdownPanelHeight = CHILD_WIDGET_HEIGHT * visibleRowsCount;

        setHeight(dropdownPanelHeight + "px");
    }
}