feat(layout): UIContext.FindLayoutProblems reports clipped and overflowing controls

src/Forma/Label.cs

@@ -28,13 +28,15 @@ public enum LabelTextFit
     /// <summary>The result of <see cref="Label.TextFit"/>: the fit and the measured and available text sizes.</summary>
     public readonly struct LabelTextFitInfo
     {
+        /// <summary>Creates a fit result.</summary>
         public LabelTextFitInfo(LabelTextFit fit, Vector2 measured, Vector2 available)
         {
             Fit = fit;
             Measured = measured;
             Available = available;
         }
 
+        /// <summary>How the text relates to its box.</summary>
         public LabelTextFit Fit { get; }
         /// <summary>The size the text needs (wrapped to the available width when the label autowraps).</summary>
         public Vector2 Measured { get; }

src/Forma/LayoutProblems.cs

@@ -0,0 +1,173 @@
+// Copyright (c) 2026 Igor Hipólito Vieira
+// SPDX-License-Identifier: MIT
+
+using System;
+using System.Collections.Generic;
+using Microsoft.Xna.Framework;
+
+namespace Forma
+{
+    /// <summary>What kind of layout problem <see cref="UIContext.FindLayoutProblems(Control, LayoutProblemOptions)"/> found.</summary>
+    [Flags]
+    public enum LayoutProblemKind
+    {
+        /// <summary>No kind selected.</summary>
+        None = 0,
+        /// <summary>A label or button's text needs more room than its box has and is cut off or drawn past it.</summary>
+        TextClipped = 1,
+        /// <summary>An autowrapping label's wrapped lines are taller than its box.</summary>
+        TextWrappedPastBox = 2,
+        /// <summary>A control extends past the bounds of its parent.</summary>
+        ChildOutsideParent = 4,
+        /// <summary>A control extends past the viewport.</summary>
+        OutsideViewport = 8,
+        /// <summary>A control extends past an ancestor that clips its contents.</summary>
+        ClippedByAncestor = 16,
+        /// <summary>Every kind.</summary>
+        All = TextClipped | TextWrappedPastBox | ChildOutsideParent | OutsideViewport | ClippedByAncestor,
+    }
+
+    /// <summary>Selects what <see cref="UIContext.FindLayoutProblems(Control, LayoutProblemOptions)"/> reports.</summary>
+    public sealed class LayoutProblemOptions
+    {
+        /// <summary>Creates options that report every kind with a one pixel tolerance.</summary>
+        public LayoutProblemOptions() { }
+
+        /// <summary>The kinds to report. Default: all.</summary>
+        public LayoutProblemKind Kinds { get; set; } = LayoutProblemKind.All;
+        /// <summary>How many pixels a control may extend past its box before it counts. Default 1.</summary>
+        public float Tolerance { get; set; } = 1f;
+        /// <summary>Whether to ignore controls that scroll or clip their content by design (scroll containers, lists, data grids, tabs, text fields). Default true.</summary>
+        public bool IgnoreScrollingContainers { get; set; } = true;
+    }
+
+    /// <summary>One clipped or overflowing control.</summary>
+    public sealed class LayoutProblem
+    {
+        /// <summary>Creates a finding.</summary>
+        public LayoutProblem(LayoutProblemKind kind, Control control, Vector2 overflow, string message)
+        {
+            Kind = kind;
+            Control = control ?? throw new ArgumentNullException(nameof(control));
+            Overflow = overflow;
+            Message = message;
+        }
+
+        /// <summary>What kind of problem this is.</summary>
+        public LayoutProblemKind Kind { get; }
+        /// <summary>The control that has the problem.</summary>
+        public Control Control { get; }
+        /// <summary>The control's name (<c>x:Name</c> or <c>id</c>), or an empty string.</summary>
+        public string Name => Control.Name ?? string.Empty;
+        /// <summary>The control's style classes, space separated.</summary>
+        public string Classes => string.Join(" ", Control.Classes);
+        /// <summary>Where the control was authored (<c>file:line</c>) when the view carries it in the <c>origin</c> data attribute; otherwise empty.</summary>
+        public string Origin => Control.GetData("origin") ?? string.Empty;
+        /// <summary>How far the control extends past its box, per axis, in layout pixels.</summary>
+        public Vector2 Overflow { get; }
+        /// <summary>A sentence describing the problem, naming the control.</summary>
+        public string Message { get; }
+        /// <summary>The message.</summary>
+        public override string ToString() => Message;
+    }
+
+    public partial class UIContext
+    {
+        /// <summary>Finds text that does not fit its box and controls that extend past their parent, an ancestor's clip or the viewport.</summary>
+        /// <param name="root">The control to inspect, with its descendants.</param>
+        /// <param name="options">What to report; null reports everything with a one pixel tolerance.</param>
+        public IReadOnlyList<LayoutProblem> FindLayoutProblems(Control root, LayoutProblemOptions options = null)
+        {
+            if (root == null) throw new ArgumentNullException(nameof(root));
+            options ??= new LayoutProblemOptions();
+            Layout();
+            var problems = new List<LayoutProblem>();
+            var viewport = new Rectangle(0, 0, (int)MathF.Round(ViewportSize.X), (int)MathF.Round(ViewportSize.Y));
+            Walk(root, root, viewport, options, problems);
+            return problems;
+        }
+
+        private static void Walk(Control control, Control root, Rectangle viewport, LayoutProblemOptions options, List<LayoutProblem> problems)
+        {
+            if (!control.Visible) return;
+            var box = control.Bounds;
+            if (box.Width > 0 && box.Height > 0)
+            {
+                CheckText(control, options, problems);
+                var visual = control.VisualBounds;
+                if (!ReferenceEquals(control, root))
+                {
+                    var scrolled = options.IgnoreScrollingContainers && AnyAncestor(control, IsScrolling);
+                    if (!scrolled)
+                    {
+                        if ((options.Kinds & LayoutProblemKind.OutsideViewport) != 0 && Past(visual, viewport, options.Tolerance) is { } outside)
+                            problems.Add(new LayoutProblem(LayoutProblemKind.OutsideViewport, control, outside, Describe(control, $"extends {Format(outside)} past the {viewport.Width}x{viewport.Height} viewport")));
+                        if ((options.Kinds & LayoutProblemKind.ClippedByAncestor) != 0 && FirstClippingAncestor(control, root) is { } clip && Past(visual, clip.VisualBounds, options.Tolerance) is { } clipped)
+                            problems.Add(new LayoutProblem(LayoutProblemKind.ClippedByAncestor, control, clipped, Describe(control, $"extends {Format(clipped)} past {clip.GetType().Name} '{clip.Name}' that clips it")));
+                        else if ((options.Kinds & LayoutProblemKind.ChildOutsideParent) != 0 && control.VisualParent is { } parent && !parent.ClipContents && Past(visual, parent.VisualBounds, options.Tolerance) is { } beyond)
+                            problems.Add(new LayoutProblem(LayoutProblemKind.ChildOutsideParent, control, beyond, Describe(control, $"extends {Format(beyond)} past its parent {parent.GetType().Name} '{parent.Name}'")));
+                    }
+                }
+            }
+
+            foreach (var child in control.Children) Walk(child, root, viewport, options, problems);
+        }
+
+        private static void CheckText(Control control, LayoutProblemOptions options, List<LayoutProblem> problems)
+        {
+            if (control is Label label)
+            {
+                var info = label.TextFit;
+                if (info.Fit != LabelTextFit.Clipped) return;
+                var wrapped = label.AutowrapMode != LabelAutowrapMode.Off;
+                var kind = wrapped ? LayoutProblemKind.TextWrappedPastBox : LayoutProblemKind.TextClipped;
+                if ((options.Kinds & kind) == 0 || (info.Overflow.X <= options.Tolerance && info.Overflow.Y <= options.Tolerance)) return;
+                problems.Add(new LayoutProblem(kind, control, info.Overflow,
+                    Describe(control, $"text \"{Shorten(label.Text)}\" needs {info.Measured.X:0}x{info.Measured.Y:0} but has {info.Available.X:0}x{info.Available.Y:0}")));
+            }
+            else if (control is BaseButton button && (options.Kinds & LayoutProblemKind.TextClipped) != 0)
+            {
+                var minimum = button.GetMinimumSize();
+                var overflow = new Vector2(Math.Max(0, minimum.X - control.Size.X), Math.Max(0, minimum.Y - control.Size.Y));
+                if (overflow.X > options.Tolerance || overflow.Y > options.Tolerance)
+                    problems.Add(new LayoutProblem(LayoutProblemKind.TextClipped, control, overflow,
+                        Describe(control, $"button \"{Shorten(button.Text)}\" needs {minimum.X:0}x{minimum.Y:0} but has {control.Size.X:0}x{control.Size.Y:0}")));
+            }
+        }
+
+        private static Vector2? Past(Rectangle box, Rectangle limit, float tolerance)
+        {
+            var x = Math.Max(Math.Max(0, limit.Left - box.Left), Math.Max(0, box.Right - limit.Right));
+            var y = Math.Max(Math.Max(0, limit.Top - box.Top), Math.Max(0, box.Bottom - limit.Bottom));
+            return x > tolerance || y > tolerance ? new Vector2(x, y) : (Vector2?)null;
+        }
+
+        private static Control FirstClippingAncestor(Control control, Control root)
+        {
+            for (var ancestor = control.VisualParent; ancestor != null; ancestor = ancestor.VisualParent)
+            {
+                if (ancestor.ClipContents && !IsScrolling(ancestor)) return ancestor;
+                if (ReferenceEquals(ancestor, root)) break;
+            }
+
+            return null;
+        }
+
+        private static bool AnyAncestor(Control control, Func<Control, bool> predicate)
+        {
+            for (var parent = control.VisualParent; parent != null; parent = parent.VisualParent)
+                if (predicate(parent)) return true;
+            return false;
+        }
+
+        private static bool IsScrolling(Control control) =>
+            control is ScrollContainer or ListBox or DataGrid or ItemsControl or TabContainer or LineEdit or TextEdit;
+
+        private static string Describe(Control control, string what) =>
+            $"{control.GetType().Name}{(string.IsNullOrEmpty(control.Name) ? string.Empty : " '" + control.Name + "'")}{(control.Classes.Count > 0 ? " (" + string.Join(" ", control.Classes) + ")" : string.Empty)} {what}.";
+
+        private static string Format(Vector2 overflow) => $"{overflow.X:0}x{overflow.Y:0}px";
+
+        private static string Shorten(string text) => text == null ? string.Empty : text.Length <= 40 ? text : text.Substring(0, 37) + "...";
+    }
+}

src/Forma/UIContext.cs

@@ -20,7 +20,7 @@ public enum InputModality { Pointer, Touch, Keyboard, Gamepad }
     /// Owns a UI tree's input state, focus and rendering. Add it to a Game's update/draw loop, or use
     /// <see cref="UIComponent"/> for the usual game component integration.
     /// </summary>
-    public sealed class UIContext : IDisposable
+    public sealed partial class UIContext : IDisposable
     {
         internal int OwnerThreadId { get; } = Environment.CurrentManagedThreadId;
         internal IDisposable ModalSessionOwner { get; set; }

src/Forma/Xaml/PseudoLocalizer.cs

@@ -11,6 +11,9 @@ namespace Forma.Xaml
     /// <summary>Options for <see cref="PseudoLocalizer"/>.</summary>
     public sealed class PseudoLocaleOptions
     {
+        /// <summary>Creates the default options: 40% longer, accented, in markers, left to right.</summary>
+        public PseudoLocaleOptions() { }
+
         /// <summary>How much longer each string becomes, as a fraction of its length (0.4 is 40% longer). Default 0.4.</summary>
         public double ExpansionFactor { get; set; } = 0.4;
         /// <summary>Replaces plain letters with accented ones, so text that assumes ASCII widths or a font without accents shows up.</summary>

tests/Forma.Tests/LayoutProblemsTest.cs

@@ -0,0 +1,134 @@
+// Copyright (c) 2026 Igor Hipólito Vieira
+// SPDX-License-Identifier: MIT
+
+using System.Linq;
+using Microsoft.Xna.Framework;
+
+namespace Forma.Tests
+{
+    [TestFixture]
+    public sealed class LayoutProblemsTest
+    {
+        private static UIFontFace Face() => UIFontFace.FromProjectFile(TestContext.CurrentContext.TestDirectory, "Fonts/Inter_Regular.ttf");
+
+        private static (UIContext Context, Control Root) Host(Vector2 viewport, params Control[] children)
+        {
+            var context = new UIContext { ViewportSize = viewport };
+            var root = new Control { Size = viewport };
+            foreach (var child in children) root.AddChild(child);
+            context.Add(root);
+            return (context, root);
+        }
+
+        private static Label TextLabel(UIFontFace face, string text, Vector2 position, Vector2 size, Action<Label> configure = null)
+        {
+            var label = new Label { Text = text, UIFont = new DynamicUIFont(face, 16), Padding = new Thickness(0), Position = position, Size = size };
+            configure?.Invoke(label);
+            return label;
+        }
+
+        [Test]
+        public void AViewThatFits_HasNoProblems()
+        {
+            using var face = Face();
+            var (context, root) = Host(new Vector2(400, 300), TextLabel(face, "Save", new Vector2(10, 10), new Vector2(200, 40)));
+            using var _ = context;
+
+            Assert.That(context.FindLayoutProblems(root), Is.Empty);
+        }
+
+        [Test]
+        public void ClippedText_IsReported_WithItsNameClassesAndOverflow()
+        {
+            using var face = Face();
+            var label = TextLabel(face, "Auto-place Spawn Points and everything else", new Vector2(10, 10), new Vector2(80, 40));
+            label.Name = "Menu";
+            label.Classes.Add("trace-text");
+            var (context, root) = Host(new Vector2(400, 300), label);
+            using var _ = context;
+
+            var problem = context.FindLayoutProblems(root).Single(p => p.Kind == LayoutProblemKind.TextClipped);
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(problem.Control, Is.SameAs(label));
+                Assert.That(problem.Name, Is.EqualTo("Menu"));
+                Assert.That(problem.Classes, Is.EqualTo("trace-text"));
+                Assert.That(problem.Overflow.X, Is.GreaterThan(0));
+                Assert.That(problem.Message, Does.Contain("Menu").And.Contain("Auto-place"));
+            });
+        }
+
+        [Test]
+        public void WrappedLinesTallerThanTheBox_AreTextWrappedPastBox()
+        {
+            using var face = Face();
+            var label = TextLabel(face, "Select an object in the map or the list to edit it.", new Vector2(10, 10), new Vector2(120, 20), l => l.Autowrap = true);
+            var (context, root) = Host(new Vector2(400, 300), label);
+            using var _ = context;
+
+            var problems = context.FindLayoutProblems(root);
+
+            Assert.That(problems.Select(p => p.Kind), Does.Contain(LayoutProblemKind.TextWrappedPastBox));
+        }
+
+        [Test]
+        public void AControlPastItsParent_IsChildOutsideParent_AndPastAClippingAncestor_IsClippedByAncestor()
+        {
+            var inner = new ColorRect { Position = new Vector2(80, 80), Size = new Vector2(50, 50) };
+            var plain = new Control { Position = new Vector2(10, 10), Size = new Vector2(100, 100) };
+            plain.AddChild(inner);
+            var clipped = new ColorRect { Position = new Vector2(80, 0), Size = new Vector2(50, 20) };
+            var clipper = new Control { Position = new Vector2(200, 10), Size = new Vector2(100, 100), ClipContents = true };
+            clipper.AddChild(clipped);
+            var (context, root) = Host(new Vector2(400, 300), plain, clipper);
+            using var _ = context;
+
+            var problems = context.FindLayoutProblems(root);
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(problems.Any(p => p.Kind == LayoutProblemKind.ChildOutsideParent && ReferenceEquals(p.Control, inner)), Is.True);
+                Assert.That(problems.Any(p => p.Kind == LayoutProblemKind.ClippedByAncestor && ReferenceEquals(p.Control, clipped)), Is.True);
+            });
+        }
+
+        [Test]
+        public void AControlPastTheViewport_IsOutsideViewport()
+        {
+            var wide = new ColorRect { Position = new Vector2(300, 10), Size = new Vector2(200, 20) };
+            var (context, root) = Host(new Vector2(400, 300), wide);
+            using var _ = context;
+
+            var problem = context.FindLayoutProblems(root).Single(p => p.Kind == LayoutProblemKind.OutsideViewport);
+
+            Assert.That(problem.Overflow.X, Is.EqualTo(100).Within(1));
+        }
+
+        [Test]
+        public void ContentOfAScrollContainer_IsNotReported_ByDefault()
+        {
+            var scroll = new ScrollContainer { Position = new Vector2(10, 10), Size = new Vector2(100, 100) };
+            scroll.AddChild(new ColorRect { Size = new Vector2(400, 400) });
+            var (context, root) = Host(new Vector2(400, 300), scroll);
+            using var _ = context;
+
+            Assert.That(context.FindLayoutProblems(root), Is.Empty);
+        }
+
+        [Test]
+        public void TheKindsOption_FiltersWhatIsReported_AndResultsAreStable()
+        {
+            var wide = new ColorRect { Position = new Vector2(300, 10), Size = new Vector2(200, 20) };
+            var (context, root) = Host(new Vector2(400, 300), wide);
+            using var _ = context;
+            var only = new LayoutProblemOptions { Kinds = LayoutProblemKind.TextClipped };
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(context.FindLayoutProblems(root, only), Is.Empty);
+                Assert.That(context.FindLayoutProblems(root).Select(p => p.ToString()), Is.EqualTo(context.FindLayoutProblems(root).Select(p => p.ToString())));
+            });
+        }
+    }
+}