ch.unifr.pai.twice.mousecontrol.client.TouchPadScrollWidget.java Source code

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Here is the source code for ch.unifr.pai.twice.mousecontrol.client.TouchPadScrollWidget.java

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package ch.unifr.pai.twice.mousecontrol.client;

/*
 * Copyright 2013 Oliver Schmid
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.HTML;
import com.google.gwt.user.client.ui.ScrollPanel;

/**
 * An implementation of the mouse pointer control based on scroll. This is e.g. required for e-readers or other rather exotic devices which are not providing
 * appropriate mouse and / or touch events.
 * 
 * @author Oliver Schmid
 * 
 */
public class TouchPadScrollWidget extends TouchPadWidget {

    private final HTML spacer = new HTML();
    private final ScrollPanel scroller = new ScrollPanel();

    Timer updater;
    int currentScreenX;
    int currentScreenY;

    public TouchPadScrollWidget() {
        super(false);
        scroller.setHeight("100%");
        scroller.setWidth("100%");
        add(scroller);
        scroller.add(spacer);
        updater = new Timer() {

            @Override
            public void run() {
                currentScreenX = spacer.getOffsetWidth() - scroller.getHorizontalScrollPosition()
                        - scroller.getOffsetWidth();
                currentScreenY = spacer.getOffsetHeight() - scroller.getVerticalScrollPosition()
                        - scroller.getOffsetHeight();
            }
        };

    }

    /*
     * (non-Javadoc)
     * @see ch.unifr.pai.twice.mousecontrol.client.TouchPadWidget#getX()
     */
    @Override
    protected int getX() {
        return currentScreenX;
    }

    /*
     * (non-Javadoc)
     * @see ch.unifr.pai.twice.mousecontrol.client.TouchPadWidget#getY()
     */
    @Override
    protected int getY() {
        return currentScreenY;
    }

    /*
     * (non-Javadoc)
     * @see ch.unifr.pai.twice.mousecontrol.client.TouchPadWidget#updateScreenDimensions()
     */
    @Override
    protected void updateScreenDimensions() {
        spacer.setWidth((scroller.getOffsetWidth() + screenWidth) + "px");
        spacer.setHeight((scroller.getOffsetHeight() + screenHeight) + "px");
    }

    /*
     * (non-Javadoc)
     * @see ch.unifr.pai.twice.mousecontrol.client.TouchPadWidget#start()
     */
    @Override
    public void start() {
        super.start();
        updater.scheduleRepeating(MOVEMENTUPDATEINTERVAL);
    }

    /*
     * (non-Javadoc)
     * @see ch.unifr.pai.twice.mousecontrol.client.TouchPadWidget#stop()
     */
    @Override
    public void stop() {
        super.stop();
        updater.cancel();
    }

}