Show fallback glyph if its not present in the font, add Japanese font to TestGame.

Voile/Source/Rendering/RaylibRenderSystem.cs

@@ -244,6 +244,12 @@ namespace Voile.Rendering
                 LoadFont(font);
             }
 
+            if (font.Dirty && font.Handle != -1)
+            {
+                UnloadFont(font);
+                LoadFont(font);
+            }
+
             var rayFont = _fontPool[font.Handle];
 
             Raylib.DrawTextPro(rayFont, text, transformPosition, transformPivot, transformRotation, font.Size, 0.0f, VoileColorToRaylibColor(color));
@@ -268,10 +274,10 @@ namespace Voile.Rendering
         {
             Raylib_cs.Font fontRay;
 
-            string ext = ".ttf"; // TODO: don't use a hardcoded extension.
-            int fontChars = 250; // TODO: control this dynamically to not load the entire font.
+            string ext = ".ttf";
+            int fontChars = font.Codepoints.Count;
 
-            fontRay = Raylib.LoadFontFromMemory(ext, font.Buffer, font.Size, null, fontChars);
+            fontRay = Raylib.LoadFontFromMemory(ext, font.Buffer, font.Size, font.Codepoints.ToArray(), fontChars);
 
             Raylib.GenTextureMipmaps(ref fontRay.Texture);
             Raylib.SetTextureFilter(fontRay.Texture, TextureFilter.Bilinear);
@@ -281,6 +287,14 @@ namespace Voile.Rendering
             font.Handle = _fontPool.Count - 1;
         }
 
+        private void UnloadFont(Font font)
+        {
+            var fontRay = _fontPool[font.Handle];
+            Raylib.UnloadFont(fontRay);
+
+            _fontPool.RemoveAt(font.Handle);
+        }
+
         private void LoadTexture(Texture2d texture)
         {
             Image image = new();

Voile/Source/Resources/Font.cs

@@ -20,7 +20,7 @@ public struct Glyph
 /// <summary>
 /// Represents font data.
 /// </summary>
-public class Font : Resource, IDisposable
+public class Font : Resource, IUpdatableResource, IDisposable
 {
     /// <summary>
     /// Internal handle for the font. If it got successfully loaded into the GPU, the value will be other than -1.
@@ -31,6 +31,8 @@ public class Font : Resource, IDisposable
     public byte[]? Buffer { get; private set; }
     public long BufferSize { get; set; }
 
+    public bool Dirty => _dirty;
+
     internal float UnitsPerEm;
 
     internal nint FacePtr;
@@ -131,14 +133,31 @@ public class Font : Resource, IDisposable
 
     public Glyph GetGlyph(char character)
     {
+        if (!HasGlyph(character))
+        {
+            _glyphs.TryGetValue('?', out var defGlyph);
+            return defGlyph;
+        }
         if (_glyphs.TryGetValue(character, out var glyph))
             return glyph;
 
         var loaded = LoadGlyph(character);
         _glyphs[character] = loaded;
+
+        _dirty = true;
+
         return loaded;
     }
 
+    public bool HasGlyph(char character)
+    {
+        unsafe
+        {
+            var face = (FT_FaceRec_*)FacePtr;
+            return FT_Get_Char_Index(face, character) != 0;
+        }
+    }
+
     private unsafe Glyph LoadGlyph(char character)
     {
         var face = (FT_FaceRec_*)FacePtr;
@@ -163,5 +182,11 @@ public class Font : Resource, IDisposable
         };
     }
 
+    public void MarkUpdated()
+    {
+        _dirty = false;
+    }
+
+    private bool _dirty;
     private Dictionary<int, Glyph> _glyphs = new();
 }

Voile/Source/Resources/Resource.cs

@@ -69,4 +69,20 @@ namespace Voile
             Path = path;
         }
     }
+
+    /// <summary>
+    /// Represents a Resource that requires systems to react to its changes.
+    /// </summary>
+    public interface IUpdatableResource
+    {
+        /// <summary>
+        /// Gets a value indicating whether this resource's state has changed and needs to be reloaded.
+        /// </summary>
+        bool Dirty { get; }
+
+        /// <summary>
+        /// Marks this resource as updated.
+        /// </summary>
+        void MarkUpdated();
+    }
 }