Move some FreeType operations to Font itself, add lazy loading for Glyph data, remove IDisposable from base Resource.

Voile/Source/Resources/Font.cs

@@ -1,5 +1,9 @@
 using System.Numerics;
 
+using FreeTypeSharp;
+using static FreeTypeSharp.FT;
+using static FreeTypeSharp.FT_LOAD;
+
 namespace Voile;
 
 public struct Glyph
@@ -16,7 +20,7 @@ public struct Glyph
 /// <summary>
 /// Represents font data.
 /// </summary>
-public class Font : Resource
+public class Font : Resource, IDisposable
 {
     /// <summary>
     /// Internal handle for the font. If it got successfully loaded into the GPU, the value will be other than -1.
@@ -27,11 +31,37 @@ public class Font : Resource
     public byte[]? Buffer { get; private set; }
     public long BufferSize { get; set; }
 
+    internal nint FacePtr;
+    internal nint LibraryPtr;
+
     public Font(string path, byte[] buffer) : base(path)
     {
         Buffer = buffer;
     }
 
+    public void Dispose()
+    {
+        unsafe
+        {
+            if (FacePtr != IntPtr.Zero)
+                FT_Done_Face((FT_FaceRec_*)FacePtr);
+
+            if (LibraryPtr != IntPtr.Zero)
+                FT_Done_FreeType((FT_LibraryRec_*)LibraryPtr);
+        }
+    }
+
+    /// <summary>
+    /// Loads a basic ASCII charset for this font.
+    /// </summary>
+    public void LoadAsciiData()
+    {
+        for (char c = ' '; c < 127; c++)
+        {
+            GetGlyph(c);
+        }
+    }
+
     public void Measure(string text)
     {
         foreach (char c in text)
@@ -40,9 +70,14 @@ public class Font : Resource
         }
     }
 
-    internal void AddGlyph(char c, Glyph glyph)
+    public Glyph GetGlyph(char character)
     {
-        _glyphs.Add(c, glyph);
+        if (_glyphs.TryGetValue(character, out var glyph))
+            return glyph;
+
+        var loaded = LoadGlyph(character);
+        _glyphs[character] = loaded;
+        return loaded;
     }
 
     internal void GetGlyphBoundingBox(Glyph glyph)
@@ -50,5 +85,26 @@ public class Font : Resource
 
     }
 
+    private unsafe Glyph LoadGlyph(char character)
+    {
+        var face = (FT_FaceRec_*)FacePtr;
+
+        // TODO: for now, we're loading glyphs for metrics, but when implementing WebGPU rendering, we want to somehow render them to SDF or bitmap.
+        FT_Error error = FT_Load_Char(face, character, FT_LOAD_NO_BITMAP);
+        if (error != 0)
+            throw new Exception($"Failed to load glyph for '{character}'");
+
+        var glyph = face->glyph;
+        var bitmap = glyph->bitmap;
+
+        return new Glyph
+        {
+            Width = bitmap.width,
+            Height = bitmap.rows,
+            Bearing = new Vector2(glyph->bitmap_left, glyph->bitmap_top),
+            Advance = (int)glyph->advance.x >> 6,
+        };
+    }
+
     private Dictionary<char, Glyph> _glyphs = new();
 }

Voile/Source/Resources/Loaders/FontLoader.cs

@@ -1,12 +1,10 @@
 
 using System.Numerics;
-using System.Runtime.InteropServices;
 using FreeTypeSharp;
 using Voile.VFS;
 
 using static FreeTypeSharp.FT;
 using static FreeTypeSharp.FT_LOAD;
-using static FreeTypeSharp.FT_Render_Mode_;
 
 namespace Voile.Resources;
 
@@ -28,67 +26,28 @@ public class FontLoader : ResourceLoader<Font>
         result.BufferSize = bytesRead;
 
         LoadFaceData(result);
+        result.LoadAsciiData();
 
         return result;
     }
 
     private unsafe void LoadFaceData(Font font)
     {
-        LoadFreeType();
+        FT_LibraryRec_* lib;
+        FT_Error error = FT_Init_FreeType(&lib);
+        if (error != 0)
+            throw new Exception("Failed to init FreeType");
 
-        fixed (FT_LibraryRec_** lib = &_lib)
+        font.LibraryPtr = (nint)lib;
+
+        fixed (byte* data = font.Buffer)
         {
-            fixed (FT_FaceRec_* face = &_face)
+            FT_FaceRec_* face;
-            {
+            error = FT_New_Memory_Face(lib, data, (nint)font.BufferSize, 0, &face);
-                FT_Error error;
+            if (error != 0)
+                throw new Exception("Failed to load font face");
 
-                var buffer = new Memory<byte>(font.Buffer);
+            font.FacePtr = (nint)face;
-                var handle = buffer.Pin();
-
-                error = FT_New_Memory_Face(*lib, (byte*)handle.Pointer, (nint)font.BufferSize, 0, &face);
-                error = FT_Set_Pixel_Sizes(face, 0, (uint)font.Size);
-
-                error = FT_Select_Charmap(face, FT_Encoding_.FT_ENCODING_UNICODE);
-
-                uint gid;
-                var charcode = FT_Get_First_Char(face, &gid);
-
-                while (gid != 0)
-                {
-                    Console.WriteLine($"Codepoint: {(char)charcode}, gid {gid}");
-                    charcode = FT_Get_Next_Char(face, charcode, &gid);
-                }
-
-                error = FT_Load_Char(face, 'F', FT_LOAD_NO_BITMAP);
-
-                var metrics = face->glyph->metrics;
-
-                font.AddGlyph('F', new Glyph()
-                {
-                    Width = metrics.width >> 6,
-                    Height = metrics.height >> 6,
-                    Bearing = new Vector2(metrics.horiBearingX >> 6, metrics.horiBearingY >> 6),
-                    Advance = (int)metrics.horiAdvance >> 6,
-                });
-
-                FT_Done_Face(face);
-                FT_Done_FreeType(*lib);
-            }
         }
     }
-
-    private unsafe void LoadFreeType()
-    {
-        fixed (FT_LibraryRec_** lib = &_lib)
-        {
-            FT_Error error;
-            if (_lib == null)
-            {
-                error = FT_Init_FreeType(lib);
-            }
-        }
-    }
-
-    private unsafe FT_LibraryRec_* _lib;
-    private unsafe FT_FaceRec_ _face;
 }

Voile/Source/Resources/Resource.cs

@@ -57,7 +57,7 @@ namespace Voile
     /// <summary>
     /// Represents data usable by Voile.
     /// </summary>
-    public abstract class Resource : IDisposable
+    public abstract class Resource
     {
         /// <summary>
         /// Path to this resource.
@@ -68,9 +68,5 @@ namespace Voile
         {
             Path = path;
         }
-
-        public void Dispose()
-        {
-        }
     }
 }