Font fallbacks.

Voile/Source/Resources/FontSet.cs

@@ -0,0 +1,45 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace Voile.Resources;
+
+/// <summary>
+/// Contains a set of multiple fonts. Used to fetch fonts based on availability of glyphs.
+/// </summary>
+public class FontSet
+{
+    public FontSet() { }
+
+    public FontSet(IEnumerable<ResourceRef<Font>> fonts)
+    {
+        _fonts = fonts.ToList();
+    }
+
+    public void AddFont(ResourceRef<Font> font) => _fonts.Add(font);
+
+    /// <summary>
+    /// Tries to get a suitable font that has a given character.
+    /// </summary>
+    /// <param name="c">Character to get a suitable font for.</param>
+    /// <param name="result">Font that contains this character.</param>
+    /// <returns><c>true</c> if a font that contains this character exists, <c>false</c> otherwise.</returns>
+    public bool TryGetFontFor(char c, [NotNullWhen(true)] out ResourceRef<Font>? result)
+    {
+        result = ResourceRef<Font>.Empty();
+        foreach (var fontRef in _fonts)
+        {
+            if (!fontRef.TryGetValue(out var font))
+            {
+                return false;
+            }
+
+            if (font.HasGlyph(c))
+            {
+                result = fontRef;
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private List<ResourceRef<Font>> _fonts = new();
+}