Add MarginContainer, mark parent elements dirty when child gets marked dirty too.

TestGame/TestGame.cs

@@ -56,9 +56,10 @@ public class TestGame : Game
         Input.AddInputMapping("reload", new IInputAction[] { new KeyInputAction(KeyboardKey.R) });
         _emitterId = _particleSystem.CreateEmitter(Renderer.WindowSize / 2, _fireEffect);
 
-        _frame.AddChild(_container);
+        _fillContainer.AddChild(_marginContainer);
+        _marginContainer.AddChild(_container);
 
-        _uiSystem.AddElement(_frame);
+        _uiSystem.AddElement(_fillContainer);
     }
 
 
@@ -84,7 +85,7 @@ public class TestGame : Game
         if (Input.IsMouseButtonDown(MouseButton.Left))
         {
             var mousePos = Input.GetMousePosition();
-            _frame.Size = new Rect(mousePos.X, mousePos.Y);
+            _fillContainer.Size = new Rect(mousePos.X, mousePos.Y);
         }
     }
 
@@ -130,19 +131,19 @@ public class TestGame : Game
     private FlexContainer _container = new(minimumSize: new Rect(64.0f, 64.0f), 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();
-    // private VerticalContainer _container = new(new Rect(128.0f, 64.0f), new(), 16)
+    private FillContainer _fillContainer = new();
+    private MarginContainer _marginContainer = new(new Margin(32.0f))
+    {
+    };
+    // private HorizontalContainer _container = new(new Rect(128.0f, 64.0f), new(), 16)
     // {
     //     ConfineToContents = true,
-    //     Anchor = Anchor.CenterLeft,
-    //     AnchorOffset = new Vector2(0.5f, 0.0f)
     // };
 }

Voile/Source/Resources/Resource.cs

@@ -1,3 +1,4 @@
+using System.Diagnostics.CodeAnalysis;
 using Voile.Resources;
 
 namespace Voile
@@ -32,7 +33,7 @@ namespace Voile
         /// </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(out T? value)
+        public bool TryGetValue([NotNullWhen(true)] out T? value)
         {
             value = ResourceManager.GetResource<T>(Guid);
             return value != null;

Voile/Source/UI/Containers/Container.cs

@@ -44,7 +44,6 @@ public abstract class Container : UIElement, IParentableElement
         {
             if (child is not IUpdatableElement updatable) continue;
 
-            updatable.MarkDirty();
             updatable.Update();
 
             if (child is IAnchorableElement anchorable)
@@ -61,6 +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>
@@ -96,7 +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

@@ -3,16 +3,17 @@ using Voile.Rendering;
 namespace Voile.UI.Containers;
 
 /// <summary>
-/// A frame is a special container that occupies the entire available size of the parent.
+/// 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 Frame : Container
+public class FillContainer : Container
 {
-    public Frame()
+    public FillContainer()
     {
 
     }
 
-    public Frame(Rect minimumSize) : base(minimumSize)
+    public FillContainer(Rect minimumSize) : base(minimumSize)
     {
 
     }

Voile/Source/UI/Containers/MarginContainer.cs

@@ -0,0 +1,78 @@
+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 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;
+
+        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/UIElement.cs

@@ -23,8 +23,6 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
         get => _size;
         set
         {
-            _size = value;
-
             if (value.Width < MinimumSize.Width)
             {
                 _size.Width = MinimumSize.Width;
@@ -35,8 +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;
@@ -44,7 +47,15 @@ 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"/>.

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)
     {
@@ -50,22 +52,44 @@ public class UISystem : IUpdatableSystem, IRenderableSystem
         {
             if (element is IRenderableElement renderable)
             {
-                renderable.Render(renderer, _style.Value);
-
-                if (!RenderDebugRects) return;
-                renderable.DrawSize(renderer);
+                // TODO: normally you'd load a default style if the one supplied is empty,
+                // but for now this will do.
+                if (!_style.TryGetValue(out var value))
+                {
+                    value = new Style(string.Empty);
                 }
 
-            if (element is IParentableElement parentable)
-            {
-                foreach (var child in parentable.Children)
-                {
-                    if (child is not IRenderableElement renderableChild) continue;
+                renderable.Render(renderer, value);
+            }
+        }
 
         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);
+            }
         }
     }
 

Voile/Source/Utils/Color.cs

@@ -147,11 +147,28 @@ namespace Voile
         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
@@ -165,6 +182,13 @@ namespace Voile
             }
         }
 
+        /// <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);
@@ -173,6 +197,13 @@ namespace Voile
             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;
@@ -181,6 +212,13 @@ namespace Voile
             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
@@ -193,7 +231,13 @@ namespace Voile
             }
         }
 
-        public static readonly Color FromHexString(string hex)
+        /// <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("#"))
             {
@@ -216,6 +260,11 @@ namespace Voile
             }
         }
 
+        /// <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;
@@ -225,6 +274,11 @@ namespace Voile
             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;
@@ -234,6 +288,10 @@ namespace Voile
             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);