Source: \loaders\bitmapFontParser.js

    import * as path from 'path';
import { utils } from '../core';
import { Resource } from 'resource-loader';
import { BitmapText } from '../extras';

/**
 * Register a BitmapText font from loader resource.
 *
 * @function parseBitmapFontData
 * @memberof PIXI.loaders
 * @param {PIXI.loaders.Resource} resource - Loader resource.
 * @param {PIXI.Texture} texture - Reference to texture.
 */
export function parse(resource, texture)
{
    resource.bitmapFont = BitmapText.registerFont(resource.data, texture);
}

export default function ()
{
    return function bitmapFontParser(resource, next)
    {
        // skip if no data or not xml data
        if (!resource.data || resource.type !== Resource.TYPE.XML)
        {
            next();

            return;
        }

        // skip if not bitmap font data, using some silly duck-typing
        if (resource.data.getElementsByTagName('page').length === 0
            || resource.data.getElementsByTagName('info').length === 0
            || resource.data.getElementsByTagName('info')[0].getAttribute('face') === null
        )
        {
            next();

            return;
        }

        let xmlUrl = !resource.isDataUrl ? path.dirname(resource.url) : '';

        if (resource.isDataUrl)
        {
            if (xmlUrl === '.')
            {
                xmlUrl = '';
            }

            if (this.baseUrl && xmlUrl)
            {
                // if baseurl has a trailing slash then add one to xmlUrl so the replace works below
                if (this.baseUrl.charAt(this.baseUrl.length - 1) === '/')
                {
                    xmlUrl += '/';
                }

                // remove baseUrl from xmlUrl
                xmlUrl = xmlUrl.replace(this.baseUrl, '');
            }
        }

        // if there is an xmlUrl now, it needs a trailing slash. Ensure that it does if the string isn't empty.
        if (xmlUrl && xmlUrl.charAt(xmlUrl.length - 1) !== '/')
        {
            xmlUrl += '/';
        }

        const textureUrl = xmlUrl + resource.data.getElementsByTagName('page')[0].getAttribute('file');

        if (utils.TextureCache[textureUrl])
        {
            // reuse existing texture
            parse(resource, utils.TextureCache[textureUrl]);
            next();
        }
        else
        {
            const loadOptions = {
                crossOrigin: resource.crossOrigin,
                loadType: Resource.LOAD_TYPE.IMAGE,
                metadata: resource.metadata.imageMetadata,
                parentResource: resource,
            };

            // load the texture for the font
            this.add(`${resource.name}_image`, textureUrl, loadOptions, (res) =>
            {
                parse(resource, res.texture);
                next();
            });
        }
    };
}