WIP: use kerning for text measuring.

TestGame/TestGame.cs

@@ -73,7 +73,7 @@ public class TestGame : Game
 
         if (Input.IsActionPressed("accept"))
         {
-            _container.AddChild(new Label("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.", _font));
+            _container.AddChild(new Label("Hello, World!", _font));
         }
 
         if (Input.IsActionPressed("cancel") && _container.Children.Count != 0)

Voile/Source/Resources/Font.cs

@@ -31,6 +31,8 @@ public class Font : Resource, IDisposable
     public byte[]? Buffer { get; private set; }
     public long BufferSize { get; set; }
 
+    internal float UnitsPerEm;
+
     internal nint FacePtr;
     internal nint LibraryPtr;
 
@@ -78,9 +80,10 @@ public class Font : Resource, IDisposable
         float maxAscent = 0;
         float maxDescent = 0;
 
-        foreach (char c in text)
+        for (int i = 0; i < text.Length; i++)
         {
-            var glyph = GetGlyph(c);
+            char c = text[i];
+            Glyph glyph = GetGlyph(c);
 
             totalWidth += glyph.Advance;
 
@@ -89,15 +92,43 @@ public class Font : Resource, IDisposable
 
             if (ascent > maxAscent)
                 maxAscent = ascent;
-
             if (descent > maxDescent)
                 maxDescent = descent;
+
+            if (i > 0)
+            {
+                char prevChar = text[i - 1];
+                totalWidth += GetKerning(prevChar, c);
+            }
         }
 
         float totalHeight = maxAscent + maxDescent;
         return new Rect(totalWidth, totalHeight);
     }
 
+    public int GetKerning(char left, char right)
+    {
+        unsafe
+        {
+            if (FacePtr == IntPtr.Zero)
+                return 0;
+
+            FT_FaceRec_* face = (FT_FaceRec_*)FacePtr;
+
+            uint leftIndex = FT_Get_Char_Index(face, left);
+            uint rightIndex = FT_Get_Char_Index(face, right);
+
+            if (leftIndex == 0 || rightIndex == 0)
+                return 0;
+
+            FT_Vector_ kerning;
+            if (FT_Get_Kerning(face, leftIndex, rightIndex, FT_Kerning_Mode_.FT_KERNING_DEFAULT, &kerning) != 0)
+                return 0;
+
+            return (int)kerning.x;
+        }
+    }
+
     public Glyph GetGlyph(char character)
     {
         if (_glyphs.TryGetValue(character, out var glyph))
@@ -128,7 +159,7 @@ public class Font : Resource, IDisposable
             Width = metrics.width >> 6,
             Height = metrics.height >> 6,
             Bearing = new Vector2(metrics.horiBearingX >> 6, metrics.horiBearingY >> 6),
-            Advance = (int)glyph->advance.x >> 6,
+            Advance = (int)metrics.horiAdvance >> 6,
         };
     }
 

Voile/Source/Resources/Loaders/FontLoader.cs

@@ -47,6 +47,7 @@ public class FontLoader : ResourceLoader<Font>
             if (error != 0)
                 throw new Exception("Failed to load font face");
 
+            font.UnitsPerEm = face->units_per_EM;
             font.FacePtr = (nint)face;
         }
     }