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Apache POI - Java API To Access Microsoft Format Files
There is a newer version: 5.3.0
/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You 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.
==================================================================== */

package org.apache.poi.hssf.usermodel;

import java.awt.Font;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

/**
 * Allows the user to lookup the font metrics for a particular font without
 * actually having the font on the system. The font details are loaded as a
 * resource from the POI jar file (or classpath) and should be contained in path
 * "/font_metrics.properties". The font widths are for a 10 point version of the
 * font. Use a multiplier for other sizes.
 */
final class StaticFontMetrics {
    private static final Logger LOGGER = LogManager.getLogger(StaticFontMetrics.class);
    /** The font metrics property file we're using */
    private static Properties fontMetricsProps;
    /** Our cache of font details we've already looked up */
    private static final Map fontDetailsMap = new HashMap<>();

    private StaticFontMetrics() {}

    /**
     * Retrieves the fake font details for a given font.
     *
     * @param font
     *            the font to lookup.
     * @return the fake font.
     */
    public static synchronized FontDetails getFontDetails(Font font) {
        // If we haven't already identified out font metrics file,
        // figure out which one to use and load it
        if (fontMetricsProps == null) {
            try {
                fontMetricsProps = loadMetrics();
            } catch (IOException e) {
                throw new IllegalStateException("Could not load font metrics", e);
            }
        }

        // Grab the base name of the font they've asked about
        String fontName = font.getName();

        // Some fonts support plain/bold/italic/bolditalic variants
        // Others have different font instances for bold etc
        // (eg font.dialog.plain.* vs font.Californian FB Bold.*)
        String fontStyle = "";
        if (font.isPlain()) {
            fontStyle += "plain";
        }
        if (font.isBold()) {
            fontStyle += "bold";
        }
        if (font.isItalic()) {
            fontStyle += "italic";
        }

        // Do we have a definition for this font with just the name?
        // If not, check with the font style added
        String fontHeight = FontDetails.buildFontHeightProperty(fontName);
        String styleHeight = FontDetails.buildFontHeightProperty(fontName + "." + fontStyle);

        if (fontMetricsProps.get(fontHeight) == null
            && fontMetricsProps.get(styleHeight) != null) {
            // Need to add on the style to the font name
            fontName += "." + fontStyle;
        }

        // Get the details on this font
        FontDetails fontDetails = fontDetailsMap.get(fontName);
        if (fontDetails == null) {
            fontDetails = FontDetails.create(fontName, fontMetricsProps);
            fontDetailsMap.put(fontName, fontDetails);
        }
        return fontDetails;
    }

    private static Properties loadMetrics() throws IOException {
        // Check to see if the font metric file was specified
        // as a system property
        File propFile = null;
        try {
            String propFileName = System.getProperty("font.metrics.filename");
            if (propFileName != null) {
                propFile = new File(propFileName);
                if (!propFile.exists()) {
                    LOGGER.atWarn().log("font_metrics.properties not found at path {}", propFile.getAbsolutePath());
                    propFile = null;
                }
            }
        } catch (SecurityException e) {
            LOGGER.atWarn().withThrowable(e).log("Can't access font.metrics.filename system property");
        }

        try (InputStream metricsIn = (propFile != null)
                ? Files.newInputStream(propFile.toPath())
                : FontDetails.class.getResourceAsStream("/font_metrics.properties")
        )  {
            // Use the built-in font metrics file off the classpath
            if (metricsIn == null) {
                String err = "font_metrics.properties not found in classpath";
                throw new IOException(err);
            }

            Properties props = new Properties();
            props.load(metricsIn);
            return props;
        }
    }
}