org.eclipse.nebula.widgets.nattable.extension.poi/src/org/eclipse/nebula/widgets/nattable/extension/poi/HSSFExcelExporter.java

/*******************************************************************************
 * Copyright (c) 2012, 2020 Original authors and others.
 *
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     Original authors and others - initial API and implementation
 ******************************************************************************/
package org.eclipse.nebula.widgets.nattable.extension.poi;

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

import org.apache.poi.hssf.usermodel.HSSFPalette;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.Workbook;
import org.eclipse.nebula.widgets.nattable.export.FileOutputStreamProvider;
import org.eclipse.nebula.widgets.nattable.export.IOutputStreamProvider;
import org.eclipse.swt.graphics.Color;

public class HSSFExcelExporter extends PoiExcelExporter {

    private List<Color> colorIndex = new ArrayList<>();

    public HSSFExcelExporter() {
        super(new FileOutputStreamProvider("table_export.xls", new String[] { "Excel Workbook (*.xls)" }, new String[] { "*.xls" })); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
    }

    public HSSFExcelExporter(IOutputStreamProvider outputStreamProvider) {
        super(outputStreamProvider);
    }

    @Override
    protected Workbook createWorkbook() {
        this.colorIndex = new ArrayList<>();
        return new HSSFWorkbook();
    }

    @Override
    protected void setFillForegroundColor(CellStyle xlCellStyle, Color swtColor) {
        xlCellStyle.setFillForegroundColor(getColorIndex(swtColor));
    }

    @Override
    protected void setFontColor(Font xlFont, Color swtColor) {
        xlFont.setColor(getColorIndex(swtColor));
    }

    /**
     * Note: The Excel HSSF format only supports a maximum of 56 custom colors.
     * If you have more than that number of colors, bad things will happen when
     * you try to export.
     */
    private short getColorIndex(Color swtColor) {
        if (!this.colorIndex.contains(swtColor)) {
            this.colorIndex.add(swtColor);

            HSSFPalette palette = ((HSSFWorkbook) this.xlWorkbook)
                    .getCustomPalette();

            palette.setColorAtIndex(
                    (short) (55 - this.colorIndex.indexOf(swtColor)),
                    (byte) swtColor.getRed(), (byte) swtColor.getGreen(),
                    (byte) swtColor.getBlue());
        }

        return (short) (55 - this.colorIndex.indexOf(swtColor));
    }

}