void checkCharacter(int charCode) {
    if (texture == null || !indexGlyphMap.containsKey(charCode)) {
        Pixmap pixmap = new Pixmap(512, 512, Pixmap.Format.RGBA8888);

        if (texture != null) {
            if (!(texture.getTextureData() instanceof PixmapTextureData))
                texture.getTextureData().prepare();
            Pixmap o = texture.getTextureData().consumePixmap();
            pixmap.drawPixmap(o, 0, 0);
            texture.getTextureData().disposePixmap();
            texture.dispose();
        }

        FreeTypeFontGenerator.GlyphAndBitmap glyphAndBitmap = fontGenerator.generateGlyphAndBitmap(charCode, 96, false); // Font size 96
        Pixmap gPixmap = glyphAndBitmap.bitmap.getPixmap(Pixmap.Format.RGBA8888, Color.WHITE, 1.8f); // Convert FreeType bitmap to Pixmap with WHITE color and 1.8 gamma
        pixmap.drawPixmap(gPixmap, textureCurX, textureCurY);

        Glyph glyph = new Glyph();

        ftFace.loadChar(charCode, FreeType.FT_LOAD_DEFAULT);
        glyph.width = glyphAndBitmap.glyph.width;
        glyph.height = glyphAndBitmap.glyph.height;
        glyph.u = textureCurX / 512f;
        glyph.v = textureCurY / 512f;
        glyph.u2 = (textureCurX + gPixmap.getWidth()) / 512f;
        glyph.v2 = (textureCurY + gPixmap.getHeight()) / 512f;
        glyph.bearingX = ftFace.getGlyph().getBitmapLeft();
        glyph.bearingY = ftFace.getGlyph().getBitmapTop();

        textureCurX += gPixmap.getWidth();
        indexGlyphMap.put(charCode, glyph);

        PixmapIO.writePNG(Gdx.files.local("characters.png"), pixmap);
        texture = new Texture(pixmap);
    }
}
...
float curX = 400;
float curY = 300;
for (int i = 0; i < glyphInfos.length; i++) {
    if (!indexCharMap.containsKey(glyphInfos[i].codepoint))
        break;
    int charCode = indexCharMap.get(glyphInfos[i].codepoint, 0);
    checkCharacter(charCode); // Create the character if it doesn't exist
    
    Glyph glyph = indexGlyphMap.get(charCode);
    GridPoint2 advance = glyphPositions[i].advance;
    GridPoint2 offset = glyphPositions[i].offset;
    float xa = advance.x/64f;
    float ya = advance.y/64f;
    float xo = offset.x/64f;
    float yo = offset.y/64f;

    float x = curX + xo + glyph.bearingX;
    float y = curY + yo + glyph.bearingY;
    batch.drawTexture(texture, glyph.u, glyph.v2, glyph.u2, glyph.v, x, y, glyph.width, glyph.height); // Draw
    curX += xa;
    curY += ya;
}

buffer = Harfbuzz.createBuffer();
buffer.addText("Hello, World!");
buffer.guessSegmentProperties();

FreeType.Library ftLib = FreeType.initFreeType();
ftFace = ftLib.newFace(Gdx.files.internal("Vazirmatn-Regular.ttf"), 0);
ftFace.setCharSize(0,96*64, 64, 64);
Harfbuzz.Font font = Harfbuzz.createFTFont(ftFace.address);
font.shape(
    buffer,
    "kern",
    "liga",
    "clig",
    "frac",
    "calt"
);

glyphInfos = buffer.getGlyphInfos();
glyphPositions = buffer.getGlyphPositions();

float x = curX + xo + glyph.bearingX;
float y = curY + yo - (glyph.height - glyph.bearingY); // Before: curY + yo + glyph.bearingY;