Synnefo

/*

 * Copyright 2011 GRNET S.A. All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or

 * without modification, are permitted provided that the following

 * conditions are met:

 *

 *   1. Redistributions of source code must retain the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer.

 *

 *   2. Redistributions in binary form must reproduce the above

 *      copyright notice, this list of conditions and the following

 *      disclaimer in the documentation and/or other materials

 *      provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED

 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

 * POSSIBILITY OF SUCH DAMAGE.

 *

 * The views and conclusions contained in the software and

 * documentation are those of the authors and should not be

 * interpreted as representing official policies, either expressed

 * or implied, of GRNET S.A.

 */

package gr.grnet.pithos.web.client.components;

import com.google.gwt.event.dom.client.ClickEvent;

import com.google.gwt.event.dom.client.ClickHandler;

import com.google.gwt.event.logical.shared.ValueChangeEvent;

import com.google.gwt.event.logical.shared.ValueChangeHandler;

import com.google.gwt.event.shared.HandlerRegistration;

import com.google.gwt.user.client.DOM;

import com.google.gwt.user.client.Element;

import com.google.gwt.user.client.ui.FocusWidget;

import com.google.gwt.user.client.ui.HasValue;

/**

 * Checkbox with three states (checked, unchecked and undefined).

 *

 */

public class TristateCheckBox extends FocusWidget implements HasValue<Boolean> {

    private static final String UNCHECKED_IMG = "images/tristate_unchecked.gif";

    private static final String UNKNOWN_IMG = "images/tristate_intermediate.gif";

    private static final String CHECKED_IMG = "images/tristate_checked.gif";

    private final Element buttonElement = DOM.createElement("input");

    private boolean valueChangeHandlerInitialized;

    private Boolean value;

    private Boolean initialValue;

    public TristateCheckBox(final Boolean state) {

        DOM.setElementProperty(buttonElement, "type", "image");

        setElement(buttonElement);

        setStyleName("tristateCheckbox");

        DOM.setElementAttribute(buttonElement, "src", UNCHECKED_IMG);

        addClickHandler(new ClickHandler() {

                        @Override

                        public void onClick(ClickEvent event) {

                final String img = DOM.getElementAttribute(buttonElement, "src");

                String newImg;

                if (img.endsWith(UNCHECKED_IMG))

                                        newImg = CHECKED_IMG;

                                else if (img.endsWith(UNKNOWN_IMG))

                                        newImg = UNCHECKED_IMG;

                                else if (img.endsWith(CHECKED_IMG))

                                        if (initialValue==null) // Only show unknown choice if there is a reason for it

                                                newImg = UNKNOWN_IMG;

                                        else

                                                newImg = UNCHECKED_IMG;

                                else

                                        throw new IllegalArgumentException("unknown checkbox state");

                DOM.setElementAttribute(buttonElement, "src", newImg);

            }

        });

        setState(state);

        initialValue = state;

    }

    public void setState(final Boolean state) {

            DOM.setElementAttribute(buttonElement, "src", state == null ?

                            UNKNOWN_IMG : state.booleanValue() ? CHECKED_IMG : UNCHECKED_IMG);

    }

    public Boolean getState() {

        final String img = DOM.getElementAttribute(buttonElement, "src");

        if (img.endsWith(UNCHECKED_IMG))

                        return Boolean.FALSE;

                else if (img.endsWith(UNKNOWN_IMG))

                        return null;

                else if (img.endsWith(CHECKED_IMG))

                        return Boolean.TRUE;

                else

                        throw new IllegalArgumentException("unknown checkbox state");

    }

    @Override

        public Boolean getValue() {

        return value;

    }

    @Override

        public void setValue(final Boolean _value) {

        value = _value;

    }

    @Override

        public HandlerRegistration addValueChangeHandler(

            ValueChangeHandler<Boolean> handler) {

            // Is this the first value change handler? If so, time to add handlers

            if (!valueChangeHandlerInitialized) {

                    ensureDomEventHandlers();

                    valueChangeHandlerInitialized = true;

            }

            return addHandler(handler, ValueChangeEvent.getType());

          }

    protected void ensureDomEventHandlers() {

        addClickHandler(new ClickHandler() {

                @Override

                        public void onClick(ClickEvent event) {

                        ValueChangeEvent.fire(TristateCheckBox.this, getValue());

                }

        });

    }

    @Override

        public void setValue(Boolean _value, boolean fireEvents) {

        Boolean oldValue = getValue();

        setValue(_value);

        if (_value.equals(oldValue))

                        return;

        if (fireEvents)

                        ValueChangeEvent.fire(this, _value);

    }

}