DMDirc-Plugins/ui_swing/src/main/java/com/dmdirc/addons/ui_swing/components/ListScroller.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.dmdirc.addons.ui_swing.components;

import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;

import javax.swing.JList;
import javax.swing.ListModel;
import javax.swing.ListSelectionModel;

/**
 * Utility class to provide mouse wheel scrolling to a JList.
 */
public class ListScroller implements MouseWheelListener {

    /** List to scroll. */
    private final ListModel<?> model;
    /** List to scroll. */
    private final ListSelectionModel selectionModel;

    /**
     * Creates a new instance of ListScroller.
     *
     * @param list List to scroll over
     */
    public ListScroller(final JList<?> list) {
        this(list.getModel(), list.getSelectionModel());
    }

    /**
     * Creates a new instance of ListScroller. You will need to manually need to add a listener to
     * trigger the scrolling behaviour either by adding a mouse wheel listener or by triggering
     * {@link #changeFocus(boolean)}.
     *
     * @param model          List model to scroll over
     * @param selectionModel List selection model to scroll over
     */
    public ListScroller(final ListModel<?> model,
            final ListSelectionModel selectionModel) {
        this.model = model;
        this.selectionModel = selectionModel;
    }

    /**
     * Creates a new instance of ListScroller and attaches it to the specified list.
     *
     * @param list List to scroll over
     *
     * @since 0.6.6
     */
    public static void register(final JList<?> list) {
        final ListScroller scroller = new ListScroller(list);
        list.addMouseWheelListener(scroller);
    }

    /**
     * Creates a new instance of ListScroller and attaches it to the specified model and selection
     * model. You will need to manually need to add a listener to trigger the scrolling behaviour
     * either by adding a mouse wheel listener or by triggering {@link #changeFocus(boolean)}.
     *
     * @param model          List model to scroll over
     * @param selectionModel List selection model to scroll over
     *
     * @since 0.6.6
     */
    public static void register(final ListModel<?> model,
            final ListSelectionModel selectionModel) {
        new ListScroller(model, selectionModel); //NOPMD
    }

    @Override
    public void mouseWheelMoved(final MouseWheelEvent e) {
        if (e.getWheelRotation() < 0) {
            changeFocus(true);
        } else {
            changeFocus(false);
        }
    }

    /**
     * Activates the node above or below the active node in the list.
     *
     * @param direction true = up, false = down.
     */
    public void changeFocus(final boolean direction) {
        final int index;

        //are we going up or down?
        if (direction) {
            //up
            index = changeFocusUp(selectionModel.getMinSelectionIndex());
        } else {
            //down
            index = changeFocusDown(selectionModel.getMinSelectionIndex());
        }
        selectionModel.setSelectionInterval(index, index);
    }

    /**
     * Changes the list focus up.
     *
     * @param index Start index
     *
     * @return next index
     */
    private int changeFocusUp(final int index) {
        final int nextIndex;

        if (index == 0 || index == -1) {
            nextIndex = model.getSize() - 1;
        } else {
            nextIndex = index - 1;
        }

        return nextIndex;
    }

    /**
     * Changes the list focus down.
     *
     * @param index Start index
     *
     * @return next index
     */
    private int changeFocusDown(final int index) {
        final int nextIndex;

        if (index == model.getSize() - 1) {
            nextIndex = 0;
        } else {
            nextIndex = index + 1;
        }

        return nextIndex;
    }

}