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Fallback fonts

No font has every character. When the main font has no glyph for a character, the library can take the glyph from another font. You list those fonts in TextOptions.FallbackFontFamilies.

Set fallback families​

using PinataLabs.Typography;

FontCollection fonts = new();
Font latin = fonts.Add("fonts/OpenSans-Regular.ttf").CreateFont(16);
FontFamily emoji = fonts.Add("fonts/TwemojiMozilla.ttf");
FontFamily japanese = fonts.Add("fonts/NotoSansJP-Regular.otf");

TextOptions options = new(latin)
{
    FallbackFontFamilies = [japanese, emoji],
};

FontRectangle size = TextMeasurer.MeasureSize("Hello δΈ–η•Œ πŸ˜€", options);

For each character, the library uses the first font in this order that has a glyph for it:

  1. The font of the run: TextOptions.Font, or the Font of the TextRun that the character is in.
  2. Each family in FallbackFontFamilies, in list order.

The library makes each fallback font at the same size and the same requested style as TextOptions.Font.

Each fallback font is shaped with its own metrics and its own OpenType tables, so a Japanese fallback font gets correct Japanese shaping inside Latin text.

When no font has the character​

If no font in the list has the character, the library uses the missing-glyph box (glyph 0) of the main font. The glyph comes to your renderer with GlyphType.Fallback, so you can find characters that the text cannot show:

public bool BeginGlyph(in FontRectangle bounds, in GlyphRendererParameters parameters)
{
    if (parameters.GlyphType == GlyphType.Fallback)
    {
        Console.WriteLine($"No font has {parameters.CodePoint}");
    }

    return true;
}

Choose fallback fonts​

  • Put the font that covers the most missing characters first. The library checks the list in order for each character.
  • Prefer fonts that are made to work together, such as the Noto family. Their sizes and baselines match, so the mixed text looks even.
  • For emoji, use a color font such as Twemoji or Noto Color Emoji with COLR glyphs. See Color fonts.
  • On a server, ship the fallback fonts with your application. Do not rely on the fonts installed on the machine. See System fonts.