smile.swing.table.MultiColumnSortTableHeaderCellRenderer Maven / Gradle / Ivy

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/*
 * Copyright (c) 2010-2021 Haifeng Li. All rights reserved.
 *
 * Smile is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Smile 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Smile.  If not, see .
 */

package smile.swing.table;

import javax.swing.Icon;
import javax.swing.JTable;
import javax.swing.RowSorter;
import javax.swing.UIManager;

import smile.swing.AlphaIcon;

/**
 * An extension of
 * DefaultTableHeaderCellRenderer that paints sort icons on the
 * header of each sorted column with varying opacity.
 *
 * @author Haifeng Li
 */
@SuppressWarnings("serial")
public class MultiColumnSortTableHeaderCellRenderer extends DefaultTableHeaderCellRenderer {

    private float alpha;

    /**
     * Constructs a
     * MultisortTableHeaderCellRenderer with a default alpha of
     * 0.5.
     */
    public MultiColumnSortTableHeaderCellRenderer() {
        this(0.5F);
    }

    /**
     * Constructs a
     * MultisortTableHeaderCellRenderer with the specified alpha. A
     * lower value represents greater contrast between icons, while a higher
     * value can make more sort icons visible.
     *
     * @param alpha the opacity, in the range 0.0F to 1.0F. Recommended range:
     * 0.5F to 0.7F.
     */
    public MultiColumnSortTableHeaderCellRenderer(float alpha) {
        this.alpha = alpha;
    }

    /**
     * Overridden to return an icon suitable to a sorted column, or null if the
     * column is unsorted. The icon for the primary sorted column is fully
     * opaque, and the opacity is reduced by a factor of
     * alpha for each subsequent sort index.
     *
     * @param table the JTable.
     * @param column the column index.
     * @return the sort icon with appropriate opacity, or null if the column is
     * unsorted.
     */
    @Override
    public Icon getIcon(JTable table, int column) {
        float computedAlpha = 1.0F;
        for (RowSorter.SortKey sortKey : table.getRowSorter().getSortKeys()) {
            if (table.convertColumnIndexToView(sortKey.getColumn()) == column) {
                switch (sortKey.getSortOrder()) {
                    case ASCENDING:
                        return new AlphaIcon(UIManager.getIcon("Table.ascendingSortIcon"), computedAlpha);
                    case DESCENDING:
                        return new AlphaIcon(UIManager.getIcon("Table.descendingSortIcon"), computedAlpha);
                        
                    default:
                        // Just to remove unmatched case warning
                }
            }
            computedAlpha *= alpha;
        }
        return null;
    }
}