Don't update MarginContainer if it already matches its parent size, update TestGame.

TODO.md

@@ -69,6 +69,18 @@
 - Make action system use an InputMap resource instead.
 - Gamepad support
 
+## Diagnostics
+
+- Implement Profiler class.
+- Generate a Speedscope report.
+- Collect reports for systems
+  - Game
+  - Render
+  - Audio
+  - ResourceManager
+  - UI
+  - Particles
+
 ## UI
 
 - ~~Layout~~
@@ -80,6 +92,8 @@
   - ~~Positioning (anchors)~~
 - ~~Move layouting to Render instead of Update, use Update for input.~~
 - Input propagation
+  - Use GridSet to efficiently query inputtable UI elements.
+  - Add element focus logic, make them focusable with action inputs.
 - Basic input elements (button, text field, toggle).
 - Styling
   - Add style settings for UI panels (for buttons, labels, etc.).

TestGame/Resources/fonts/default.fontset.toml

@@ -0,0 +1,3 @@
+[FontSet]
+
+fonts = ["Inter-Regular.ttf", "NotoSansJP-Regular.ttf"]

TestGame/TestGame.cs

@@ -20,7 +20,7 @@ public class TestGame : Game
         InitializeSystemsDefault();
 
         _uiSystem = new UISystem(Input, ResourceRef<Style>.Empty());
-        _uiSystem.RenderDebugRects = true;
+        // _uiSystem.RenderDebugRects = true;
 
         _particleSystem = new ParticleSystem();
 
@@ -42,6 +42,11 @@ public class TestGame : Game
 
         }
 
+        if (!ResourceManager.TryLoad("fonts/NotoSansJP-Regular.ttf", out _jpFont))
+        {
+
+        }
+
         ResourceManager.TryLoad("icon.png", out _icon);
         ResourceManager.TryLoad("sounds/test_sound_mono.ogg", out _sound);
 
@@ -49,6 +54,8 @@ public class TestGame : Game
         {
             throw new Exception("Failed to load emitter settings!");
         }
+
+        _defaultFontSet = new([_font, _jpFont]);
     }
 
     protected override void Ready()
@@ -56,9 +63,32 @@ public class TestGame : Game
         Input.AddInputMapping("reload", new IInputAction[] { new KeyInputAction(KeyboardKey.R) });
         _emitterId = _particleSystem.CreateEmitter(Renderer.WindowSize / 2, _fireEffect);
 
-        _frame.AddChild(_container);
+        var addButton = new Button("Add element", _defaultFontSet, () => { _container.AddChild(new Label("Hello, World!", _defaultFontSet)); });
+        addButton.Padding = new Margin(8.0f);
 
-        _uiSystem.AddElement(_frame);
+        var removeButton = new Button("Remove element", _defaultFontSet, () =>
+        {
+            if (_container.Children.Count == 0) return;
+            var lastChild = _container.Children.Last();
+            _container.RemoveChild(lastChild);
+        });
+
+        removeButton.Padding = new Margin(8.0f);
+
+        _buttonContainer.AddChild(addButton);
+        _buttonContainer.AddChild(removeButton);
+
+        var c = new VerticalContainer();
+
+        var m = new MarginContainer();
+        m.AddChild(_container);
+
+        c.AddChild(_buttonContainer);
+        c.AddChild(m);
+
+        _rootFill.AddChild(c);
+
+        _uiSystem.AddElement(_rootFill);
     }
 
 
@@ -69,32 +99,16 @@ public class TestGame : Game
             ResourceManager.Reload();
             _particleSystem!.RestartEmitter(_emitterId);
         }
-
-        if (Input.IsActionPressed("accept"))
-        {
-            _container.AddChild(new RectangleWidget(new Rect(32.0f, 32.0f), MathUtils.RandomColor()));
-        }
-
-        if (Input.IsActionPressed("cancel") && _container.Children.Count != 0)
-        {
-            var lastChild = _container.Children.Last();
-            _container.RemoveChild(lastChild);
-        }
-
-        if (Input.IsMouseButtonDown(MouseButton.Left))
-        {
-            var mousePos = Input.GetMousePosition();
-            _frame.Size = new Rect(mousePos.X, mousePos.Y);
-        }
     }
 
     protected override void Render(double deltaTime)
     {
         Renderer.ClearBackground(Color.Black);
-        foreach (var emitter in _particleSystem!.Emitters)
+
-        {
+        // foreach (var emitter in _particleSystem!.Emitters)
-            DrawEmitter(emitter);
+        // {
-        }
+        //     DrawEmitter(emitter);
+        // }
 
         Renderer.ResetTransform();
         _uiSystem.Render(Renderer);
@@ -124,25 +138,28 @@ public class TestGame : Game
     private int _emitterId;
     private ResourceRef<ParticleEmitterSettingsResource> _fireEffect;
     private ResourceRef<Font> _font;
+    private ResourceRef<Font> _jpFont;
+
+    private FontSet _defaultFontSet;
+
     private ResourceRef<Sound> _sound;
     private ResourceRef<Texture2d> _icon;
 
-    private FlexContainer _container = new(minimumSize: new Rect(64.0f, 64.0f), new())
+    private FlexContainer _container = new(minimumSize: new Rect(256.0f, 256.0f), new())
     {
         Anchor = Anchor.Center,
-        Size = new Rect(500, 300),
         Direction = FlexDirection.Column,
         Justify = JustifyContent.Start,
         Align = AlignItems.Center,
         Wrap = true,
-        Gap = 10f
+        Gap = 8.0f
     };
 
-    private Frame _frame = new();
+    [NotNull] private Label _label;
-    // private VerticalContainer _container = new(new Rect(128.0f, 64.0f), new(), 16)
+
-    // {
+    private FillContainer _rootFill = new();
-    //     ConfineToContents = true,
+    private HorizontalContainer _buttonContainer = new(16)
-    //     Anchor = Anchor.CenterLeft,
+    {
-    //     AnchorOffset = new Vector2(0.5f, 0.0f)
+        ConfineToContents = true,
-    // };
+    };
 }

Voile/GridSet.cs

@@ -0,0 +1,37 @@
+using System.Collections;
+using System.Collections.Generic;
+using System.Numerics;
+using Voile.Extensions;
+
+namespace Voile;
+
+public class GridSet<T>
+{
+    public float GridSize { get; }
+    public GridSet(float gridSize = 32.0f)
+    {
+        GridSize = gridSize;
+    }
+
+    public void Add(Vector2 position, T child)
+    {
+        var snap = Vector2.One * GridSize;
+        position = position.Snapped(snap);
+
+        if (_values.TryGetValue(position, out var list))
+        {
+            list.Add(child);
+        }
+        else
+        {
+            _values.Add(position, new List<T>());
+        }
+    }
+
+    public void Remove(T child)
+    {
+
+    }
+
+    private Dictionary<Vector2, List<T>> _values = new();
+}

Voile/Source/Color.cs

@@ -0,0 +1,301 @@
+namespace Voile
+{
+    // Based on https://github.com/ppr-game/PPR/blob/engine/PER.Util/src/Color.cs
+    /// <summary>
+    /// A record struct representing a color.
+    /// </summary>
+    public record struct Color
+    {
+        public static readonly Color AliceBlue = new(0xF0F8FF);
+        public static readonly Color AntiqueWhite = new(0xFAEBD7);
+        public static readonly Color Aqua = new(0x00FFFF);
+        public static readonly Color Aquamarine = new(0x7FFFD4);
+        public static readonly Color Azure = new(0xF0FFFF);
+        public static readonly Color Beige = new(0xF5F5DC);
+        public static readonly Color Bisque = new(0xFFE4C4);
+        public static readonly Color Black = new(0x000000);
+        public static readonly Color BlanchedAlmond = new(0xFFEBCD);
+        public static readonly Color Blue = new(0x0000FF);
+        public static readonly Color BlueViolet = new(0x8A2BE2);
+        public static readonly Color Brown = new(0xA52A2A);
+        public static readonly Color BurlyWood = new(0xDEB887);
+        public static readonly Color CadetBlue = new(0x5F9EA0);
+        public static readonly Color Chartreuse = new(0x7FFF00);
+        public static readonly Color Chocolate = new(0xD2691E);
+        public static readonly Color Coral = new(0xFF7F50);
+        public static readonly Color CornflowerBlue = new(0x6495ED);
+        public static readonly Color Cornsilk = new(0xFFF8DC);
+        public static readonly Color Crimson = new(0xDC143C);
+        public static readonly Color Cyan = new(0x00FFFF);
+        public static readonly Color DarkBlue = new(0x00008B);
+        public static readonly Color DarkCyan = new(0x008B8B);
+        public static readonly Color White = new(0xFFFFFF);
+        public static readonly Color Green = new(0x00FF00);
+        public static readonly Color Red = new(0xFF0000);
+        public static readonly Color DarkGoldenRod = new(0xB8860B);
+        public static readonly Color DarkGray = new(0xA9A9A9);
+        public static readonly Color DarkGreen = new(0x006400);
+        public static readonly Color DarkKhaki = new(0xBDB76B);
+        public static readonly Color DarkMagenta = new(0x8B008B);
+        public static readonly Color DarkOliveGreen = new(0x556B2F);
+        public static readonly Color DarkOrange = new(0xFF8C00);
+        public static readonly Color DarkOrchid = new(0x9932CC);
+        public static readonly Color DarkRed = new(0x8B0000);
+        public static readonly Color DarkSalmon = new(0xE9967A);
+        public static readonly Color DarkSeaGreen = new(0x8FBC8F);
+        public static readonly Color DarkSlateBlue = new(0x483D8B);
+        public static readonly Color DarkSlateGray = new(0x2F4F4F);
+        public static readonly Color DarkTurquoise = new(0x00CED1);
+        public static readonly Color DarkViolet = new(0x9400D3);
+        public static readonly Color DeepPink = new(0xFF1493);
+        public static readonly Color DeepSkyBlue = new(0x00BFFF);
+        public static readonly Color DimGray = new(0x696969);
+        public static readonly Color DodgerBlue = new(0x1E90FF);
+        public static readonly Color FireBrick = new(0xB22222);
+        public static readonly Color FloralWhite = new(0xFFFAF0);
+        public static readonly Color ForestGreen = new(0x228B22);
+        public static readonly Color Gainsboro = new(0xDCDCDC);
+        public static readonly Color GhostWhite = new(0xF8F8FF);
+        public static readonly Color Gold = new(0xFFD700);
+        public static readonly Color GoldenRod = new(0xDAA520);
+        public static readonly Color Gray = new(0x808080);
+        public static readonly Color GreenYellow = new(0xADFF2F);
+        public static readonly Color HoneyDew = new(0xF0FFF0);
+        public static readonly Color HotPink = new(0xFF69B4);
+        public static readonly Color IndianRed = new(0xCD5C5C);
+        public static readonly Color Indigo = new(0x4B0082);
+        public static readonly Color Ivory = new(0xFFFFF0);
+        public static readonly Color Khaki = new(0xF0E68C);
+        public static readonly Color Lavender = new(0xE6E6FA);
+        public static readonly Color LavenderBlush = new(0xFFF0F5);
+        public static readonly Color LawnGreen = new(0x7CFC00);
+        public static readonly Color LemonChiffon = new(0xFFFACD);
+        public static readonly Color LightBlue = new(0xADD8E6);
+        public static readonly Color LightCoral = new(0xF08080);
+        public static readonly Color LightCyan = new(0xE0FFFF);
+        public static readonly Color LightGoldenRodYellow = new(0xFAFAD2);
+        public static readonly Color LightGray = new(0xD3D3D3);
+        public static readonly Color LightGreen = new(0x90EE90);
+        public static readonly Color LightPink = new(0xFFB6C1);
+        public static readonly Color LightSalmon = new(0xFFA07A);
+        public static readonly Color LightSeaGreen = new(0x20B2AA);
+        public static readonly Color LightSkyBlue = new(0x87CEFA);
+        public static readonly Color LightSlateGray = new(0x778899);
+        public static readonly Color LightSteelBlue = new(0xB0C4DE);
+        public static readonly Color LightYellow = new(0xFFFFE0);
+        public static readonly Color Lime = new(0x00FF00);
+        public static readonly Color LimeGreen = new(0x32CD32);
+        public static readonly Color Linen = new(0xFAF0E6);
+        public static readonly Color Magenta = new(0xFF00FF);
+        public static readonly Color Maroon = new(0x800000);
+        public static readonly Color MediumAquaMarine = new(0x66CDAA);
+        public static readonly Color MediumBlue = new(0x0000CD);
+        public static readonly Color MediumOrchid = new(0xBA55D3);
+        public static readonly Color MediumPurple = new(0x9370DB);
+        public static readonly Color MediumSeaGreen = new(0x3CB371);
+        public static readonly Color MediumSlateBlue = new(0x7B68EE);
+        public static readonly Color MediumSpringGreen = new(0x00FA9A);
+        public static readonly Color MediumTurquoise = new(0x48D1CC);
+        public static readonly Color MediumVioletRed = new(0xC71585);
+        public static readonly Color MidnightBlue = new(0x191970);
+        public static readonly Color MintCream = new(0xF5FFFA);
+        public static readonly Color MistyRose = new(0xFFE4E1);
+        public static readonly Color Moccasin = new(0xFFE4B5);
+        public static readonly Color NavajoWhite = new(0xFFDEAD);
+        public static readonly Color Navy = new(0x000080);
+        public static readonly Color OldLace = new(0xFDF5E6);
+        public static readonly Color Olive = new(0x808000);
+        public static readonly Color OliveDrab = new(0x6B8E23);
+        public static readonly Color Orange = new(0xFFA500);
+        public static readonly Color OrangeRed = new(0xFF4500);
+        public static readonly Color Orchid = new(0xDA70D6);
+        public static readonly Color PaleGoldenRod = new(0xEEE8AA);
+        public static readonly Color PaleGreen = new(0x98FB98);
+        public static readonly Color PaleTurquoise = new(0xAFEEEE);
+        public static readonly Color PaleVioletRed = new(0xDB7093);
+        public static readonly Color PapayaWhip = new(0xFFEFD5);
+        public static readonly Color PeachPuff = new(0xFFDAB9);
+        public static readonly Color Peru = new(0xCD853F);
+        public static readonly Color Pink = new(0xFFC0CB);
+        public static readonly Color Plum = new(0xDDA0DD);
+        public static readonly Color PowderBlue = new(0xB0E0E6);
+        public static readonly Color Purple = new(0x800080);
+        public static readonly Color RebeccaPurple = new(0x663399);
+        public static readonly Color RosyBrown = new(0xBC8F8F);
+        public static readonly Color RoyalBlue = new(0x4169E1);
+        public static readonly Color SaddleBrown = new(0x8B4513);
+        public static readonly Color Salmon = new(0xFA8072);
+        public static readonly Color SandyBrown = new(0xF4A460);
+        public static readonly Color SeaGreen = new(0x2E8B57);
+        public static readonly Color Seashell = new(0xFFF5EE);
+        public static readonly Color Sienna = new(0xA0522D);
+        public static readonly Color Silver = new(0xC0C0C0);
+        public static readonly Color SkyBlue = new(0x87CEEB);
+        public static readonly Color SlateBlue = new(0x6A5ACD);
+        public static readonly Color SlateGray = new(0x708090);
+        public static readonly Color Snow = new(0xFFFAFA);
+        public static readonly Color SpringGreen = new(0x00FF7F);
+        public static readonly Color SteelBlue = new(0x4682B4);
+        public static readonly Color Tan = new(0xD2B48C);
+        public static readonly Color Teal = new(0x008080);
+        public static readonly Color Thistle = new(0xD8BFD8);
+        public static readonly Color Tomato = new(0xFF6347);
+        public static readonly Color Turquoise = new(0x40E0D0);
+        public static readonly Color Violet = new(0xEE82EE);
+        public static readonly Color Wheat = new(0xF5DEB3);
+        public static readonly Color WhiteSmoke = new(0xF5F5F5);
+        public static readonly Color Yellow = new(0xFFFF00);
+        public static readonly Color YellowGreen = new(0x9ACD32);
+
+        /// <summary>
+        /// Red component of this <see cref="Color"/>.
+        /// </summary>
+        public byte R { get; set; }
+        /// <summary>
+        /// Green component of this <see cref="Color"/>.
+        /// </summary>
+        public byte G { get; set; }
+        /// <summary>
+        /// Blue component of this <see cref="Color"/>.
+        /// </summary>
+        public byte B { get; set; }
+        /// <summary>
+        /// Alpha component of this <see cref="Color"/>.
+        /// </summary>/// <summary>
+        /// Gets the color as a 32-bit ARGB integer in the format 0xAARRGGBB.
+        /// </summary>
+        public byte A { get; set; } = 255;
+
+        /// <summary>
+        /// Gets the color as a 32-bit ARGB integer in the format 0xAARRGGBB.
+        /// </summary>
+        public int Argb
+        {
+            get
+            {
+                int a = A << 24;
+                int r = R << 16;
+                int g = G << 8;
+                int b = B;
+
+                return a | r | g | b;
+            }
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Color"/> struct using float RGB(A) values between 0 and 1.
+        /// </summary>
+        /// <param name="r">The red component (0.0 to 1.0).</param>
+        /// <param name="g">The green component (0.0 to 1.0).</param>
+        /// <param name="b">The blue component (0.0 to 1.0).</param>
+        /// <param name="a">The alpha component (0.0 to 1.0), default is 1.0 (fully opaque).</param>
+        public Color(float r, float g, float b, float a = 1.0f)
+        {
+            R = (byte)Math.Clamp(r * 255, 0, 255);
+            G = (byte)Math.Clamp(g * 255, 0, 255);
+            B = (byte)Math.Clamp(b * 255, 0, 255);
+            A = (byte)Math.Clamp(a * 255, 0, 255);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Color"/> struct using byte RGB(A) values.
+        /// </summary>
+        /// <param name="r">The red component (0 to 255).</param>
+        /// <param name="g">The green component (0 to 255).</param>
+        /// <param name="b">The blue component (0 to 255).</param>
+        /// <param name="a">The alpha component (0 to 255), default is 255 (fully opaque).</param>
+        public Color(byte r, byte g, byte b, byte a = 255)
+        {
+            R = r;
+            G = g;
+            B = b;
+            A = a;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Color"/> struct using a hexadecimal value.
+        /// </summary>
+        /// <param name="hex">
+        /// A 24-bit (RRGGBB) or 32-bit (AARRGGBB) integer representing the color.
+        /// Alpha is assumed to be 255 if not included.
+        /// </param>
+        public Color(int hex)
+        {
+            A = 255;  // Default alpha to 255 if not provided
+            B = (byte)(hex & 0xFF);
+            G = (byte)((hex >> 8) & 0xFF);
+            R = (byte)((hex >> 16) & 0xFF);
+            if (hex > 0xFFFFFF)  // If the hex value includes alpha
+            {
+                A = (byte)((hex >> 24) & 0xFF);
+            }
+        }
+
+        /// <summary>
+        /// Parses a color from a hexadecimal string in the format "#RRGGBB" or "#AARRGGBB".
+        /// </summary>
+        /// <param name="hex">The hex string representing the color.</param>
+        /// <returns>A <see cref="Color"/> instance parsed from the string.</returns>
+        /// <exception cref="ArgumentException">Thrown if the format is invalid.</exception>
+        public static Color FromHexString(string hex)
+        {
+            if (hex.StartsWith("#"))
+            {
+                hex = hex[1..];
+            }
+
+            if (hex.Length == 6)
+            {
+                int rgb = int.Parse(hex, System.Globalization.NumberStyles.HexNumber);
+                return new Color(rgb);
+            }
+            else if (hex.Length == 8)
+            {
+                int rgba = int.Parse(hex, System.Globalization.NumberStyles.HexNumber);
+                return new Color(rgba);
+            }
+            else
+            {
+                throw new ArgumentException("Invalid hex color format. Use #RRGGBB or #RRGGBBAA.");
+            }
+        }
+
+        /// <summary>
+        /// Returns a lightened version of the color by interpolating toward white.
+        /// </summary>
+        /// <param name="amount">A value from 0.0 (no change) to 1.0 (fully white).</param>
+        /// <returns>A lighter <see cref="Color"/>.</returns>
+        public Color Lightened(float amount)
+        {
+            var result = this;
+            result.R = (byte)Math.Min(255, R + (255 - R) * amount);
+            result.G = (byte)Math.Min(255, G + (255 - G) * amount);
+            result.B = (byte)Math.Min(255, B + (255 - B) * amount);
+            return result;
+        }
+
+        /// <summary>
+        /// Returns a darkened version of the color by interpolating toward black.
+        /// </summary>
+        /// <param name="amount">A value from 0.0 (no change) to 1.0 (fully black).</param>
+        /// <returns>A darker <see cref="Color"/>.</returns>
+        public Color Darkened(float amount)
+        {
+            var result = this;
+            result.R = (byte)(R * (1.0f - amount));
+            result.G = (byte)(G * (1.0f - amount));
+            result.B = (byte)(B * (1.0f - amount));
+            return result;
+        }
+
+        /// <summary>
+        /// Converts this color to a <see cref="System.Drawing.Color"/>.
+        /// </summary>
+        /// <returns>A <see cref="System.Drawing.Color"/> with equivalent ARGB values.</returns>
+        public System.Drawing.Color ToSystemColor()
+        {
+            var result = System.Drawing.Color.FromArgb(Argb);
+            return result;
+        }
+    }
+}

Voile/Source/Extensions/Vector2Extensions.cs

@@ -8,5 +8,31 @@ namespace Voile.Extensions
         {
             return new Vector2((float)MathUtils.Lerp(a.X, b.X, t), (float)MathUtils.Lerp(a.Y, b.Y, t));
         }
+
+        public static Vector2 Snapped(this Vector2 a, Vector2 snap)
+        {
+            var x = a.X % snap.X;
+            var y = a.Y % snap.Y;
+
+            if (x == 0)
+            {
+                x = a.X;
+            }
+            else
+            {
+                x = a.X - x;
+            }
+
+            if (y == 0)
+            {
+                y = a.Y;
+            }
+            else
+            {
+                y = a.Y - y;
+            }
+
+            return new Vector2(x, y);
+        }
     }
 }

Voile/Source/Rect.cs

@@ -1,4 +1,4 @@
-namespace Voile.UI;
+namespace Voile;
 
 /// <summary>
 /// Represents a rectangle. Used to determine widget confines for UI layout.

Voile/Source/Rendering/RaylibRenderSystem.cs

@@ -81,7 +81,7 @@ namespace Voile.Rendering
                 Raylib.InitWindow((int)_windowSize.X, (int)_windowSize.Y, windowSettings.Title);
             }
 
-            // Raylib.SetWindowState(windowFlags);
+            Raylib.SetWindowState(windowFlags);
         }
 
         // TODO
@@ -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.
+            string ext = ".ttf";
-            int fontChars = 250; // TODO: control this dynamically to not load the entire font.
+            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/Rendering/RenderSystem.cs

@@ -256,7 +256,7 @@ namespace Voile.Rendering
     {
         public string Title;
         public Vector2 Size = new Vector2(1280, 720);
-        public bool Resizable { get; set; }
+        public bool Resizable { get; set; } = true;
 
         public WindowSettings(string title, Vector2 size)
         {

Voile/Source/Resources/Font.cs

@@ -1,9 +1,26 @@
+using System.Numerics;
+
+using FreeTypeSharp;
+using static FreeTypeSharp.FT;
+using static FreeTypeSharp.FT_LOAD;
+
 namespace Voile;
 
+public struct Glyph
+{
+    public int TextureId { get; set; } = -1;
+    public float Width { get; set; }
+    public float Height { get; set; }
+    public Vector2 Bearing { get; set; }
+    public int Advance { get; set; }
+
+    public Glyph() { }
+}
+
 /// <summary>
 /// Represents font data.
 /// </summary>
-public class Font : Resource
+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.
@@ -14,8 +31,162 @@ public class Font : Resource
     public byte[]? Buffer { get; private set; }
     public long BufferSize { get; set; }
 
+    public bool Dirty => _dirty;
+
+    internal float UnitsPerEm;
+
+    internal nint FacePtr;
+    internal nint LibraryPtr;
+
+    internal List<int> Codepoints => _glyphs.Keys.ToList();
+
     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);
+        }
+    }
+
+    /// <summary>
+    /// Measures a given string using the font metrics.
+    /// </summary>
+    /// <param name="text">Text to measure.</param>
+    /// <returns>A <see cref="Rect"/> with the sizes of a given text using this font.</returns>
+    public Rect Measure(string text)
+    {
+        if (string.IsNullOrEmpty(text))
+            return Rect.Zero;
+
+        float totalWidth = 0;
+        float maxAscent = 0;
+        float maxDescent = 0;
+
+        for (int i = 0; i < text.Length; i++)
+        {
+            char c = text[i];
+            Glyph glyph = GetGlyph(c);
+
+            totalWidth += glyph.Advance;
+
+            float ascent = glyph.Bearing.Y;
+            float descent = glyph.Height - glyph.Bearing.Y;
+
+            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 (!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;
+
+        // 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_Set_Pixel_Sizes(face, 0, (uint)Size);
+        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;
+        var metrics = glyph->metrics;
+
+        return new Glyph
+        {
+            Width = metrics.width >> 6,
+            Height = metrics.height >> 6,
+            Bearing = new Vector2(metrics.horiBearingX >> 6, metrics.horiBearingY >> 6),
+            Advance = (int)metrics.horiAdvance >> 6,
+        };
+    }
+
+    public void MarkUpdated()
+    {
+        _dirty = false;
+    }
+
+    private bool _dirty;
+    private Dictionary<int, Glyph> _glyphs = new();
 }

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();
+}

Voile/Source/Resources/Loaders/FontLoader.cs

@@ -1,6 +1,11 @@
 
+using System.Numerics;
+using FreeTypeSharp;
 using Voile.VFS;
 
+using static FreeTypeSharp.FT;
+using static FreeTypeSharp.FT_LOAD;
+
 namespace Voile.Resources;
 
 public class FontLoader : ResourceLoader<Font>
@@ -10,7 +15,6 @@ public class FontLoader : ResourceLoader<Font>
         ".ttf"
     };
 
-
     protected override Font LoadResource(string path)
     {
         using Stream stream = VirtualFileSystem.Read(path);
@@ -21,6 +25,30 @@ public class FontLoader : ResourceLoader<Font>
 
         result.BufferSize = bytesRead;
 
+        LoadFaceData(result);
+        result.LoadAsciiData();
+
         return result;
     }
+
+    private unsafe void LoadFaceData(Font font)
+    {
+        FT_LibraryRec_* lib;
+        FT_Error error = FT_Init_FreeType(&lib);
+        if (error != 0)
+            throw new Exception("Failed to init FreeType");
+
+        font.LibraryPtr = (nint)lib;
+
+        fixed (byte* data = font.Buffer)
+        {
+            FT_FaceRec_* face;
+            error = FT_New_Memory_Face(lib, data, (nint)font.BufferSize, 0, &face);
+            if (error != 0)
+                throw new Exception("Failed to load font face");
+
+            font.UnitsPerEm = face->units_per_EM;
+            font.FacePtr = (nint)face;
+        }
+    }
 }

Voile/Source/Resources/Loaders/ResourceLoader.cs

@@ -65,7 +65,12 @@ namespace Voile.Resources
             var resource = ResourceManager.LoadedResources[resourceGuid];
 
             ResourceManager.RemoveResource(resourceGuid);
-            resource.Dispose();
+
+            if (resource is IDisposable disposable)
+            {
+                disposable.Dispose();
+            }
+
 
             return true;
         }

Voile/Source/Resources/Resource.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics.CodeAnalysis;
 using Voile.Resources;
 
 namespace Voile
@@ -13,11 +14,35 @@ namespace Voile
         /// </summary>
         public readonly Guid Guid = Guid.Empty;
         public bool HasValue => Guid != Guid.Empty;
-        /// <summary>
-        /// Retrieve a reference.
-        /// </summary>
-        public T Value => ResourceManager.GetResource<T>(Guid);
 
+        /// <summary>
+        /// Retrieves a <see cref="Resource"/>.<br />
+        /// This will throw an <see cref="InvalidOperationException"/> if the resource wasn't loaded or is invalid. <br />
+        /// You can check if resource was loaded with <see cref="HasValue"/>, or consider using <see cref="TryGetValue"/>.
+        /// </summary> 
+        public T Value => ResourceManager.GetResource<T>(Guid)
+            ?? throw new InvalidOperationException($"Resource with GUID {Guid} is not loaded or invalid.");
+
+        /// <summary>
+        /// Retrieves a resource or <c>null</c> if the resource wasn't loaded or is invalid.
+        /// </summary>
+        public T? ValueOrNull => ResourceManager.GetResource<T>(Guid);
+
+        /// <summary>
+        /// Tries to retrieve a <see cref="Resource"/>.
+        /// </summary>
+        /// <param name="value">An instance of a retrieved <see cref="Resource"/>.</param>
+        /// <returns><c>true</c> if the resource was successfully retrieved, otherwise <c>false</c>.</returns>
+        public bool TryGetValue([NotNullWhen(true)] out T? value)
+        {
+            value = ResourceManager.GetResource<T>(Guid);
+            return value != null;
+        }
+
+        /// <summary>
+        /// Create an empty <see cref="ResourceRef"/>.
+        /// </summary>
+        /// <returns></returns>
         public static ResourceRef<T> Empty()
         {
             return new ResourceRef<T>(Guid.Empty);
@@ -27,12 +52,34 @@ namespace Voile
         {
             Guid = guid;
         }
+
+        public override bool Equals(object? obj)
+        {
+            return obj is ResourceRef<T> other && Guid.Equals(other.Guid);
+        }
+
+        public override int GetHashCode()
+        {
+            return Guid.GetHashCode();
+        }
+
+        public static bool operator ==(ResourceRef<T>? left, ResourceRef<T>? right)
+        {
+            if (ReferenceEquals(left, right)) return true;
+            if (left is null || right is null) return false;
+            return left.Guid == right.Guid;
+        }
+
+        public static bool operator !=(ResourceRef<T>? left, ResourceRef<T>? right)
+        {
+            return !(left == right);
+        }
     }
 
     /// <summary>
     /// Represents data usable by Voile.
     /// </summary>
-    public abstract class Resource : IDisposable
+    public abstract class Resource
     {
         /// <summary>
         /// Path to this resource.
@@ -43,9 +90,21 @@ namespace Voile
         {
             Path = path;
         }
+    }
 
-        public void Dispose()
+    /// <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();
     }
 }

Voile/Source/Resources/ResourceManager.cs

@@ -231,7 +231,7 @@ namespace Voile.Resources
         /// </summary>
         /// <param name="path">Path to the resource.</param>
         /// <returns>True if a resource at the specified path is loaded, otherwise false.</returns>
-        public bool IsResourceLoaded(string path) => _resourcePathMap.ContainsKey(path);
+        public static bool IsResourceLoaded(string path) => _resourcePathMap.ContainsKey(path);
 
         /// <summary>
         /// Adds a resource loader associated with a resource type.

Voile/Source/UI/Anchor.cs

@@ -2,23 +2,76 @@ using System.Numerics;
 
 namespace Voile.UI;
 
+/// <summary>
+/// Specifies predefined anchor points used to position UI elements relative to their parent container.
+/// </summary>
 public enum Anchor
 {
+    /// <summary>
+    /// Anchors the element to the top-left corner of the parent.
+    /// </summary>
     TopLeft,
+
+    /// <summary>
+    /// Anchors the element to the top-center of the parent.
+    /// </summary>
     TopCenter,
+
+    /// <summary>
+    /// Anchors the element to the top-right corner of the parent.
+    /// </summary>
     TopRight,
+
+    /// <summary>
+    /// Anchors the element to the center-left edge of the parent.
+    /// </summary>
     CenterLeft,
+
+    /// <summary>
+    /// Anchors the element to the exact center of the parent.
+    /// </summary>
     Center,
+
+    /// <summary>
+    /// Anchors the element to the center-right edge of the parent.
+    /// </summary>
     CenterRight,
+
+    /// <summary>
+    /// Anchors the element to the bottom-left corner of the parent.
+    /// </summary>
     BottomLeft,
+
+    /// <summary>
+    /// Anchors the element to the bottom-center of the parent.
+    /// </summary>
     BottomCenter,
+
+    /// <summary>
+    /// Anchors the element to the bottom-right corner of the parent.
+    /// </summary>
     BottomRight,
     Fill
 }
 
-
+/// <summary>
+/// Provides extension methods for calculating anchored positions of UI elements.
+/// </summary>
 public static class AnchorExtensions
 {
+    /// <summary>
+    /// Calculates the offset position for an element based on the specified <see cref="Anchor"/>.
+    /// </summary>
+    /// <param name="anchor">The anchor mode to use.</param>
+    /// <param name="parentPosition">The absolute position of the parent container (top-left corner).</param>
+    /// <param name="parentRect">The bounding rectangle of the parent container.</param>
+    /// <param name="elementRect">The size of the element being anchored.</param>
+    /// <returns>
+    /// A <see cref="Vector2"/> representing the local offset position where the element should be placed inside the parent.
+    /// </returns>
+    /// <remarks>
+    /// The result is the relative offset from the parent's origin, not a global position.
+    /// </remarks>
     public static Vector2 Calculate(this Anchor anchor, Vector2 parentPosition, Rect parentRect, Rect elementRect)
     {
         var size = new Vector2(elementRect.Width, elementRect.Height);

Voile/Source/UI/Containers/Container.cs

@@ -3,7 +3,6 @@ using Voile.Rendering;
 
 namespace Voile.UI.Containers;
 
-// TODO: make Container extend Widget, it already implements similar behaviors. 
 /// <summary>
 /// A base class for all UI containers, used to position and rendering child <see cref="IElement">s.
 /// </summary>
@@ -45,7 +44,6 @@ public abstract class Container : UIElement, IParentableElement
         {
             if (child is not IUpdatableElement updatable) continue;
 
-            updatable.MarkDirty();
             updatable.Update();
 
             if (child is IAnchorableElement anchorable)
@@ -62,6 +60,18 @@ public abstract class Container : UIElement, IParentableElement
         }
     }
 
+    public override void MarkDirty()
+    {
+        base.MarkDirty();
+
+        foreach (var child in _children)
+        {
+            if (child is not IUpdatableElement updatable) continue;
+
+            updatable.MarkDirty();
+        }
+    }
+
     /// <summary>
     /// Called when this <see cref="Container"/> has to rearrange its children.
     /// </summary>
@@ -97,7 +107,12 @@ public abstract class Container : UIElement, IParentableElement
         float finalWidth = MathF.Max(occupiedWidth, _minimumSize.Width);
         float finalHeight = MathF.Max(occupiedHeight, _minimumSize.Height);
 
-        Size = new Rect(finalWidth, finalHeight);
+        var finalSize = new Rect(finalWidth, finalHeight);
+
+        if (finalSize != Size)
+        {
+            Size = finalSize;
+        }
 
         if (_minimumSize > Size)
         {

Voile/Source/UI/Containers/FillContainer.cs

@@ -0,0 +1,58 @@
+using Voile.Rendering;
+
+namespace Voile.UI.Containers;
+
+/// <summary>
+/// A special container that occupies the entire available size of the parent. <br />
+/// Usually used as a root element for the UI system.
+/// </summary>
+public class FillContainer : Container
+{
+    public FillContainer()
+    {
+
+    }
+
+    public FillContainer(Rect minimumSize) : base(minimumSize)
+    {
+
+    }
+
+    public override void Arrange()
+    {
+
+    }
+
+    public override void Render(RenderSystem renderer, Style style)
+    {
+        base.Render(renderer, style);
+
+        Rect parentSize;
+
+        if (Parent != null)
+        {
+            parentSize = Parent.Size;
+        }
+        else
+        {
+            var windowSize = renderer.WindowSize;
+            var windowRect = new Rect(windowSize.X, windowSize.Y);
+
+            parentSize = windowRect;
+        }
+
+        if (_lastParentSize != parentSize)
+        {
+            Size = parentSize;
+            _lastParentSize = parentSize;
+        }
+    }
+
+    protected override void OnUpdate()
+    {
+        base.OnUpdate();
+        Size = _lastParentSize;
+    }
+
+    private Rect _lastParentSize = Rect.Zero;
+}

Voile/Source/UI/Containers/Frame.cs

@@ -1,19 +0,0 @@
-namespace Voile.UI.Containers;
-
-public class Frame : Container
-{
-    public Frame()
-    {
-
-    }
-
-    public Frame(Rect minimumSize) : base(minimumSize)
-    {
-        
-    }
-
-    public override void Arrange()
-    {
-
-    }
-}

Voile/Source/UI/Containers/MarginContainer.cs

@@ -0,0 +1,88 @@
+using System.Numerics;
+
+namespace Voile.UI.Containers;
+
+/// <summary>
+/// Represents the margin offsets applied around an element.
+/// </summary>
+public struct Margin
+{
+    public float Left;
+    public float Right;
+    public float Top;
+    public float Bottom;
+
+    public Margin(float uniform)
+    {
+        Left = Right = Top = Bottom = uniform;
+    }
+
+    public Margin(float horizontal, float vertical)
+    {
+        Left = Right = horizontal;
+        Top = Bottom = vertical;
+    }
+
+    public Margin(float left, float right, float top, float bottom)
+    {
+        Left = left;
+        Right = right;
+        Top = top;
+        Bottom = bottom;
+    }
+
+    public static Margin Zero => new Margin(0);
+
+    public static Rect operator +(Margin margin, Rect rect) =>
+        new Rect(rect.Width + margin.Left + margin.Right,
+                 rect.Height + margin.Top + margin.Bottom);
+
+    public static Rect operator +(Rect rect, Margin margin) =>
+        margin + rect;
+}
+
+public class MarginContainer : Container
+{
+    /// <summary>
+    /// The margin to apply around the contents of this container.
+    /// </summary>
+    public Margin Margin { get; set; }
+
+    /// <summary>
+    /// Specifies if this <see cref="MarginContainer"/> will fill to parent size.
+    /// </summary>
+    public bool Fill { get; set; } = true;
+
+    public MarginContainer() : this(new Margin()) { }
+
+    public MarginContainer(Margin margin)
+    {
+        Margin = margin;
+    }
+
+    protected override void OnUpdate()
+    {
+        base.OnUpdate();
+        if (Parent == null) return;
+
+        if (Size != Parent.Size)
+        {
+            Size = Parent.Size;
+        }
+    }
+
+    public override void Arrange()
+    {
+        foreach (var child in Children)
+        {
+            var newPosition = new Vector2(Margin.Left, Margin.Top);
+            var newSize = new Rect(
+                Size.Width - Margin.Left - Margin.Right,
+                Size.Height - Margin.Top - Margin.Bottom
+            );
+
+            child.Size = newSize;
+            child.LocalPosition = newPosition;
+        }
+    }
+}

Voile/Source/UI/IElement.cs

@@ -1,9 +1,11 @@
 using System.Numerics;
-using Voile.Input;
 using Voile.Rendering;
 
 namespace Voile.UI;
 
+/// <summary>
+/// Represents a basic UI element with position and size information.
+/// </summary>
 public interface IElement
 {
     /// <summary>
@@ -16,6 +18,9 @@ public interface IElement
     public Rect Size { get; set; }
 }
 
+/// <summary>
+/// Represents a UI element that can contain child elements.
+/// </summary>
 public interface IParentableElement
 {
     /// <summary>
@@ -34,6 +39,10 @@ public interface IParentableElement
     public void RemoveChild(UIElement child);
 }
 
+/// <summary>
+/// Represents a UI element that can provide a minimum size constraint.<br />
+/// Implement this interface if your UI element is expected to be resizeable.
+/// </summary>
 public interface IResizeableElement
 {
     /// <summary>
@@ -42,10 +51,13 @@ public interface IResizeableElement
     public abstract Rect MinimumSize { get; }
 }
 
+/// <summary>
+/// Represents a UI element that supports updates when its state changes.
+/// </summary>
 public interface IUpdatableElement
 {
     /// <summary>
-    /// Specifies if this element's properties have changed, making it necessary to update it.
+    /// Gets a value indicating whether the element's state has changed and needs to be updated.
     /// </summary>
     public bool Dirty { get; }
     /// <summary>
@@ -58,6 +70,9 @@ public interface IUpdatableElement
     void MarkDirty();
 }
 
+/// <summary>
+/// Represents a UI element that can be rendered to the screen.
+/// </summary>
 public interface IRenderableElement
 {
     /// <summary>
@@ -77,6 +92,9 @@ public interface IRenderableElement
     public void DrawSize(RenderSystem renderer);
 }
 
+/// <summary>
+/// Represents a UI element that can receive and process user input.
+/// </summary>
 public interface IInputElement
 {
     /// <summary>
@@ -90,9 +108,23 @@ public interface IInputElement
     void Input(UIInputContext action);
 }
 
+/// <summary>
+/// Represents a UI element that supports positional anchoring within a parent.
+/// </summary>
 public interface IAnchorableElement
 {
+    /// <summary>
+    /// Gets or sets the anchor point relative to the parent container.
+    /// </summary>
     public Anchor Anchor { get; set; }
+    /// <summary>
+    /// Gets or sets an additional offset to apply after anchoring, in pixels.
+    /// </summary>
     public Vector2 AnchorOffset { get; set; }
+    /// <summary>
+    /// Applies the current anchor settings based on the parent's position and size.
+    /// </summary>
+    /// <param name="parentPosition">The parent's top-left global position.</param>
+    /// <param name="parentRect">The bounding rectangle of the parent container.</param>
     public void ApplyAnchor(Vector2 parentPosition, Rect parentRect);
 }

Voile/Source/UI/UIElement.cs

@@ -3,6 +3,9 @@ using Voile.Rendering;
 
 namespace Voile.UI;
 
+/// <summary>
+/// Base class for all UI elements. 
+/// </summary>
 public abstract class UIElement : IElement, IRenderableElement, IResizeableElement, IUpdatableElement, IAnchorableElement
 {
     public bool Visible { get; set; } = true;
@@ -10,13 +13,16 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
     public Vector2 LocalPosition { get; set; } = Vector2.Zero;
     public Vector2 GlobalPosition => _parent?.GlobalPosition + LocalPosition ?? LocalPosition;
 
+    /// <summary>
+    /// Parent <see cref="UIElement"/> of this element.
+    /// </summary>
+    public UIElement? Parent => _parent;
+
     public Rect Size
     {
         get => _size;
         set
         {
-            _size = value;
-
             if (value.Width < MinimumSize.Width)
             {
                 _size.Width = MinimumSize.Width;
@@ -27,8 +33,13 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
                 _size.Height = MinimumSize.Height;
             }
 
+            if (_size != value)
+            {
                 MarkDirty();
             }
+
+            _size = value;
+        }
     }
     public Vector2 AnchorOffset { get; set; } = Vector2.Zero;
     public Anchor Anchor { get; set; } = Anchor.TopLeft;
@@ -36,11 +47,24 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
     public abstract Rect MinimumSize { get; }
     public bool Dirty => _dirty;
 
-    public virtual void MarkDirty() => _dirty = true;
+    public virtual void MarkDirty()
+    {
+        if (Parent != null && !Parent.Dirty)
+        {
+            Parent.MarkDirty();
+        }
 
+        _dirty = true;
+    }
+
+    /// <summary>
+    /// Sets a parent element for this <see cref="UIElement"/>.
+    /// </summary>
+    /// <param name="parent">Element to parent this <see cref="UIElement"/> to.</param>
     public void SetParent(UIElement parent)
     {
         _parent = parent;
+        MarkDirty();
     }
 
     public void Update()

Voile/Source/UI/UISystem.cs

@@ -9,6 +9,8 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
     public IReadOnlyList<IElement> Elements => _elements;
 
     public bool RenderDebugRects { get; set; }
+    public Color DebugSizeRectColor { get; set; } = Color.Red;
+    public Color DebugDirtyRectColor { get; set; } = new Color(1.0f, 1.0f, 0.0f, 0.5f);
 
     public UISystem(InputSystem inputSystem)
     {
@@ -29,7 +31,11 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
         _elements = elements;
     }
 
-    public void AddElement(UIElement element) => _elements.Add(element);
+    public void AddElement(UIElement element)
+    {
+        _elements.Add(element);
+        _inputElementIndices.Add(element.GlobalPosition, _elements.Count - 1);
+    }
     public void RemoveElement(UIElement element) => _elements.Remove(element);
 
     public void Update(double deltaTime)
@@ -50,22 +56,44 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
         {
             if (element is IRenderableElement renderable)
             {
-                renderable.Render(renderer, _style.Value);
+                // TODO: normally you'd load a default style if the one supplied is empty,
-
+                // but for now this will do.
-                if (!RenderDebugRects) return;
+                if (!_style.TryGetValue(out var value))
-                renderable.DrawSize(renderer);
+                {
+                    value = new Style(string.Empty);
                 }
 
-            if (element is IParentableElement parentable)
+                renderable.Render(renderer, value);
-            {
+            }
-                foreach (var child in parentable.Children)
+        }
-                {
-                    if (child is not IRenderableElement renderableChild) continue;
 
         if (!RenderDebugRects) return;
-                    renderableChild.DrawSize(renderer);
+
+        foreach (var element in _elements)
+        {
+            if (element is not UIElement uiElement) continue;
+            DrawDebugForElement(renderer, uiElement);
         }
     }
+
+    private void DrawDebugForElement(RenderSystem renderer, UIElement element)
+    {
+        var size = new Vector2(element.Size.Width, element.Size.Height);
+        renderer.SetTransform(element.GlobalPosition, Vector2.Zero);
+        renderer.DrawRectangleOutline(size, DebugSizeRectColor);
+
+        if (element.Dirty)
+        {
+            renderer.DrawRectangle(size, DebugDirtyRectColor);
+        }
+
+        if (element is IParentableElement parentableElement)
+        {
+            foreach (var child in parentableElement.Children)
+            {
+                if (child is not UIElement childElement) continue;
+                DrawDebugForElement(renderer, childElement);
+            }
         }
     }
 
@@ -122,6 +150,8 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
         {
             var element = elements[i];
 
+            // if (!element.ContainsPoint(context.MousePosition)) continue;
+
             if (element is IInputElement inputElement && !inputElement.IgnoreInput)
             {
                 inputElement.Input(context);
@@ -143,5 +173,7 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
     private List<UIElement> _elements = new();
     private InputSystem _input;
 
+    private GridSet<int> _inputElementIndices = new();
+
     private Vector2 _lastMousePosition = Vector2.Zero;
 }

Voile/Source/UI/Widgets/Button.cs

@@ -1,6 +1,8 @@
 using System.Numerics;
 using Voile.Input;
 using Voile.Rendering;
+using Voile.Resources;
+using Voile.UI.Containers;
 
 namespace Voile.UI.Widgets;
 
@@ -17,13 +19,42 @@ public enum ButtonState
 /// </summary>
 public class Button : Widget
 {
-    public string Label { get; set; } = "Button";
+    public string Text
-    public override Rect MinimumSize => new Rect(Width: 128.0f, Height: 64.0f);
-
-    public Button(string label, Action pressedAction)
     {
-        Label = label;
+        get => _text; set
+        {
+            _text = value;
+            MarkDirty();
+        }
+    }
+    public override Rect MinimumSize => Padding + _textSize;
+
+    /// <summary>
+    /// <see cref="FontSet"/> to use with this button.
+    /// </summary>
+    public FontSet FontSet { get; set; } = new();
+    public Margin Padding { get; set; } = Margin.Zero;
+
+    public Button(string text, ResourceRef<Font> fontOverride, Action pressedAction)
+    {
+        _text = text;
         _pressedAction = pressedAction;
+
+        FontSet.AddFont(fontOverride);
+
+        MarkDirty();
+        Update();
+    }
+
+    public Button(string text, FontSet fontSet, Action pressedAction)
+    {
+        _text = text;
+        _pressedAction = pressedAction;
+
+        FontSet = fontSet;
+
+        MarkDirty();
+        Update();
     }
 
     public override void Render(RenderSystem renderer, Style style)
@@ -31,17 +62,46 @@ public class Button : Widget
         // TODO: use a button color from style.
         renderer.SetTransform(GlobalPosition, Vector2.Zero);
         renderer.DrawRectangle(new Vector2(MinimumSize.Width, MinimumSize.Height), new Color(0.25f, 0.25f, 0.25f));
+
+        var textPosition = new Vector2(GlobalPosition.X + Padding.Left, GlobalPosition.Y + Padding.Top);
+        renderer.SetTransform(textPosition, Vector2.Zero);
+        renderer.DrawText(_suitableFont, _text, Color.White);
     }
 
     protected override void OnInput(UIInputContext action)
     {
-
+        if (action.MouseReleased && ContainsPoint(action.MousePosition))
+        {
+            _pressedAction?.Invoke();
+        }
     }
 
     protected override void OnUpdate()
     {
-        throw new NotImplementedException();
+        ResourceRef<Font> fontRef = ResourceRef<Font>.Empty();
+        foreach (var c in _text)
+        {
+            if (FontSet.TryGetFontFor(c, out var fallbackFont))
+            {
+                if (fallbackFont != fontRef)
+                {
+                    fontRef = fallbackFont;
+                }
+            }
+        }
+
+        _suitableFont = fontRef;
+
+        var font = _suitableFont.Value;
+        _textSize = font.Measure(_text);
+
+        Size = Padding + _textSize;
     }
 
     private Action _pressedAction;
+
+    private ResourceRef<Font> _suitableFont = ResourceRef<Font>.Empty();
+
+    private string _text = "Hello, World!";
+    private Rect _textSize = Rect.Zero;
 }

Voile/Source/UI/Widgets/Label.cs

@@ -1,43 +1,85 @@
 using System.Numerics;
 using Voile.Input;
 using Voile.Rendering;
+using Voile.Resources;
 
 namespace Voile.UI.Widgets;
 
 public class Label : Widget
 {
-    public override Rect MinimumSize => throw new NotImplementedException();
+    public override Rect MinimumSize => _textSize;
 
-    public string Text { get; set; } = "Hello World!";
+    public string Text
-
-    public Label(string text)
     {
-        Text = text;
+        get => _text; set
+        {
+            _text = value;
+            MarkDirty();
         }
+    }
+
+    /// <summary>
+    /// <see cref="FontSet"/> to use with this label.
+    /// </summary>
+    public FontSet FontSet { get; set; } = new();
 
     public Label(string text, ResourceRef<Font> fontOverride)
     {
-        Text = text;
+        _text = text;
-        _fontOverride = fontOverride;
+
+        FontSet.AddFont(fontOverride);
+
+        MarkDirty();
+        Update();
+    }
+
+    public Label(string text, FontSet fontSet)
+    {
+        _text = text;
+
+        FontSet = fontSet;
+
+        MarkDirty();
+        Update();
     }
 
     protected override void OnInput(UIInputContext action)
     {
-        throw new NotImplementedException();
+
     }
 
     public override void Render(RenderSystem renderer, Style style)
     {
         // TODO: use style here.
-        if (!_fontOverride.HasValue) return;
+
         renderer.SetTransform(GlobalPosition, Vector2.Zero);
-        renderer.DrawText(_fontOverride, Text, Color.White);
+        renderer.DrawText(_suitableFont, _text, Color.White);
     }
 
     protected override void OnUpdate()
     {
-        throw new NotImplementedException();
+        ResourceRef<Font> fontRef = ResourceRef<Font>.Empty();
+        foreach (var c in _text)
+        {
+            if (FontSet.TryGetFontFor(c, out var fallbackFont))
+            {
+                if (fallbackFont != fontRef)
+                {
+                    fontRef = fallbackFont;
+                }
+            }
         }
 
-    private ResourceRef<Font> _fontOverride = ResourceRef<Font>.Empty();
+        _suitableFont = fontRef;
+
+        var font = _suitableFont.Value;
+        _textSize = font.Measure(_text);
+
+        Size = _textSize;
+    }
+
+    private ResourceRef<Font> _suitableFont = ResourceRef<Font>.Empty();
+
+    private string _text = "Hello, World!";
+    private Rect _textSize = Rect.Zero;
 }

Voile/Source/Utils/Color.cs

@@ -1,130 +0,0 @@
-namespace Voile
-{
-    // Based on https://github.com/ppr-game/PPR/blob/engine/PER.Util/src/Color.cs
-    /// <summary>
-    /// A record struct representing a color.
-    /// </summary>
-    public record struct Color
-    {
-        // TODO: add more HTML colors.
-        public static Color AliceBlue = new(0xF0F8FF);
-        public static Color AntiqueWhite = new(0xFAEBD7);
-        public static Color Aqua = new(0x00FFFF);
-        public static Color Aquamarine = new(0x7FFFD4);
-        public static Color Azure = new(0xF0FFFF);
-        public static Color Beige = new(0xF5F5DC);
-        public static Color Bisque = new(0xFFE4C4);
-        public static Color Black = new(0x000000);
-        public static Color BlanchedAlmond = new(0xFFEBCD);
-        public static Color Blue = new(0x0000FF);
-        public static Color BlueViolet = new(0x8A2BE2);
-        public static Color Brown = new(0xA52A2A);
-        public static Color BurlyWood = new(0xDEB887);
-        public static Color CadetBlue = new(0x5F9EA0);
-        public static Color Chartreuse = new(0x7FFF00);
-        public static Color Chocolate = new(0xD2691E);
-        public static Color Coral = new(0xFF7F50);
-        public static Color CornflowerBlue = new(0x6495ED);
-        public static Color Cornsilk = new(0xFFF8DC);
-        public static Color Crimson = new(0xDC143C);
-        public static Color Cyan = new(0x00FFFF);
-        public static Color DarkBlue = new(0x00008B);
-        public static Color DarkCyan = new(0x008B8B);
-        public static Color White = new(0xFFFFFF);
-        public static Color Green = new(0x00FF00);
-        public static Color Red = new(0xFF0000);
-
-        public byte R { get; set; }
-        public byte G { get; set; }
-        public byte B { get; set; }
-        public byte A { get; set; } = 255;
-
-        public int Argb
-        {
-            get
-            {
-                int a = A << 24;
-                int r = R << 16;
-                int g = G << 8;
-                int b = B;
-
-                return a | r | g | b;
-            }
-        }
-
-        public Color(float r, float g, float b, float a = 1.0f)
-        {
-            R = (byte)Math.Clamp(r * 255, 0, 255);
-            G = (byte)Math.Clamp(g * 255, 0, 255);
-            B = (byte)Math.Clamp(b * 255, 0, 255);
-            A = (byte)Math.Clamp(a * 255, 0, 255);
-        }
-
-        public Color(byte r, byte g, byte b, byte a = 255)
-        {
-            R = r;
-            G = g;
-            B = b;
-            A = a;
-        }
-
-        public Color(int hex)
-        {
-            A = 255;  // Default alpha to 255 if not provided
-            B = (byte)(hex & 0xFF);
-            G = (byte)((hex >> 8) & 0xFF);
-            R = (byte)((hex >> 16) & 0xFF);
-            if (hex > 0xFFFFFF)  // If the hex value includes alpha
-            {
-                A = (byte)((hex >> 24) & 0xFF);
-            }
-        }
-
-        public static Color FromHexString(string hex)
-        {
-            if (hex.StartsWith("#"))
-            {
-                hex = hex[1..];
-            }
-
-            if (hex.Length == 6)
-            {
-                int rgb = int.Parse(hex, System.Globalization.NumberStyles.HexNumber);
-                return new Color(rgb);
-            }
-            else if (hex.Length == 8)
-            {
-                int rgba = int.Parse(hex, System.Globalization.NumberStyles.HexNumber);
-                return new Color(rgba);
-            }
-            else
-            {
-                throw new ArgumentException("Invalid hex color format. Use #RRGGBB or #RRGGBBAA.");
-            }
-        }
-
-        public Color Lightened(float amount)
-        {
-            var result = this;
-            result.R = (byte)Math.Min(255, R + (255 - R) * amount);
-            result.G = (byte)Math.Min(255, G + (255 - G) * amount);
-            result.B = (byte)Math.Min(255, B + (255 - B) * amount);
-            return result;
-        }
-
-        public Color Darkened(float amount)
-        {
-            var result = this;
-            result.R = (byte)(R * (1.0f - amount));
-            result.G = (byte)(G * (1.0f - amount));
-            result.B = (byte)(B * (1.0f - amount));
-            return result;
-        }
-
-        public System.Drawing.Color ToSystemColor()
-        {
-            var result = System.Drawing.Color.FromArgb(Argb);
-            return result;
-        }
-    }
-}

Voile/Voile.csproj

@@ -9,6 +9,7 @@
     </PropertyGroup>
 
     <ItemGroup>
+        <PackageReference Include="FreeTypeSharp" Version="3.0.0" />
         <PackageReference Include="Silk.NET.WebGPU" Version="2.20.0" />
         <PackageReference Include="Silk.NET.WebGPU.Native.WGPU" Version="2.20.0" />
         <PackageReference Include="Silk.NET.Windowing" Version="2.20.0" />
@@ -16,8 +17,6 @@
         <PackageReference Include="Tommy" Version="3.1.2" />
         <PackageReference Include="ImGui.NET" Version="1.89.4" />
         <PackageReference Include="Raylib-cs" Version="7.0.1" />
-        <PackageReference Include="SharpFont" Version="4.0.1" />
-        <PackageReference Include="SixLabors.Fonts" Version="1.0.0-beta19" />
         <PackageReference Include="StbImageSharp" Version="2.27.13" />
         <PackageReference Include="StbVorbisSharp" Version="1.22.4" />
     </ItemGroup>