1. Code Samples
  2. Text
  3. Font Registry

Load fonts on demand with the FontMissing event

View as Markdown

FontText

This sample shows how to start with an empty font registry and add only the fonts a design actually uses, at the moment it asks for them. When a font is requested by a PostScript name that is not registered, CustomFontRegistry raises the FontMissing event; the handler looks the name up in the application's own font catalog and adds the file with CustomFontRegistry.Add, and the request then succeeds. A server with a large font library no longer has to parse every font at startup.

Code Snippet

// The application's font catalog: PostScript names and their files. Nothing is loaded yet.
var catalog = new Dictionary<string, string>
{
    ["Lobster"] = "Lobster.ttf",
    ["Jost-Regular"] = "Jost-Regular.ttf",
    ["Montserrat-Medium"] = "Montserrat-Medium.ttf",
};

using (var fontRegistry = new CustomFontRegistry())
{
    fontRegistry.FontMissing += (sender, e) =>
    {
        if (catalog.TryGetValue(e.PostscriptName, out var fileName))
        {
            Console.WriteLine("Loading {0} from {1}", e.PostscriptName, fileName);
            e.FontRegistry.Add(fileName);
        }
    };

    using (var bitmap = new Bitmap(500, 200, PixelFormat.Format24bppRgb, RgbColor.White))
    using (var graphics = bitmap.GetGraphics())
    {
        graphics.FontRegistry = fontRegistry;

        // Each font is added the first time it is asked for.
        var title = new PlainText("Summer Sale", graphics.CreateFont("Lobster", 60f))
        {
            Position = new System.Drawing.PointF(250, 95),
            Alignment = TextAlignment.Center,
            Brush = new SolidBrush(new RgbColor(214, 69, 65)),
        };

        var subtitle = new PlainText("Up to 50% off all items", graphics.CreateFont("Jost-Regular", 24f))
        {
            Position = new System.Drawing.PointF(250, 150),
            Alignment = TextAlignment.Center,
        };

        graphics.DrawText(title);
        graphics.DrawText(subtitle);

        bitmap.Save("LoadFontsOnDemand.png");
    }

    Console.WriteLine("Fonts in the registry: {0} of {1}", fontRegistry.Fonts.Count, catalog.Count);
}

Input

Lobster.ttf

Download

Jost-Regular.ttf

Download

Montserrat-Medium.ttf

Download

Output

LoadFontsOnDemand.png

LoadFontsOnDemand.png

LoadFontsOnDemand.txt

Loading Lobster from Lobster.ttf
Loading Jost-Regular from Jost-Regular.ttf
Fonts in the registry: 2 of 3

Used APIs