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Utilities for use in developing GWT applications.
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//
// $Id$
//
// OOO GWT Utils - utilities for creating GWT applications
// Copyright (C) 2009-2010 Three Rings Design, Inc., All Rights Reserved
// http://code.google.com/p/ooo-gwt-utils/
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

package com.threerings.gwt.util;

import java.util.ArrayList;
import java.util.List;

import com.google.common.base.Function;
import com.google.gwt.event.logical.shared.CloseEvent;
import com.google.gwt.event.logical.shared.CloseHandler;
import com.google.gwt.user.client.ui.PopupPanel;
import com.google.gwt.user.client.ui.Widget;

import com.threerings.gwt.ui.Popups;

/**
 * Maintains a stack of {@link PopupPanel}s. When a new panel is pushed onto the stack, the
 * currently visible panel is hidden and the new panel is shown. When the new panel is closed, the
 * previous panel on the stack is restored to view.
 */
public class PopupStack
{
    /** A value indicating whether or not a popup is currently showing. */
    public final Value popupShowing;

    public PopupStack ()
    {
        this.popupShowing = _showingPopup.map(new Function() {
            public Boolean apply (PopupPanel panel) {
                return (panel != null);
            }
        });
    }

    /**
     * Pushes any currently showing popup onto the stack and displays the supplied popup. The popup
     * will be made visible via a call to {@link PopupPanel#center}.
     */
    public void show (PopupPanel popup)
    {
        show(popup, null);
    }

    /**
     * Pushes any currently showing popup onto the stack and displays the supplied popup. The popup
     * will centered horizontally in the page and centered vertically around the supplied widget.
     */
    public void show (PopupPanel popup, Widget onCenter)
    {
        // determine the ypos of our onCenter target in case it's in the currently popped up popup,
        // because after we hide that popup we won't be able to compute it
        int ypos = (onCenter == null) ? 0 :
            (onCenter.getAbsoluteTop() + onCenter.getOffsetHeight()/2);

        PopupPanel showing = _showingPopup.get();
        if (showing != null) {
            // null _showingPopup before hiding to avoid triggering the close handler logic
            _popups.add(showing);
            _showingPopup.update(null);
            showing.hide(true);
        }

        if (onCenter == null) {
            popup.center(); // this will show the popup
        } else {
            Popups.centerOn(popup, ypos).show();
        }

        // now that we've centered and shown our popup (which may have involved showing, hiding and
        // showing it again), we can add a close handler and listen for it to actually close
        popup.addCloseHandler(new CloseHandler() {
            public void onClose (CloseEvent event) {
                if (_showingPopup.get() == event.getTarget()) {
                    if (_popups.size() > 0) {
                        _showingPopup.update(_popups.remove(_popups.size()-1));
                        _showingPopup.get().show();
                    } else {
                        _showingPopup.update(null);
                    }
                }
            }
        });
        _showingPopup.update(popup);
    }

    /**
     * Clears out the stack completely, removing all pending popups and clearing any currently
     * showing popup.
     */
    public void clear ()
    {
        _popups.clear();
        if (_showingPopup.get() != null) {
            _showingPopup.get().hide(true);
            _showingPopup.update(null);
        }
    }

    protected Value _showingPopup = Value.create(null);
    protected List _popups = new ArrayList();
}