perf(ui): retain shaped report text

src/AcDream.App/UI/Layout/UiTextLayoutCache.cs

@@ -0,0 +1,115 @@
+using System.Numerics;
+using AcDream.App.Rendering;
+
+namespace AcDream.App.UI.Layout;
+
+/// <summary>
+/// Retains the shaped line projection of one <see cref="UiText"/> value.
+/// Controllers publish semantic content; the cache reshapes only when that
+/// content or the text widget's layout/font inputs change.
+/// </summary>
+internal sealed class UiTextLayoutCache<T>
+{
+    private readonly UiText _target;
+    private readonly Func<UiText, T, IReadOnlyList<UiText.Line>> _shape;
+    private readonly IEqualityComparer<T> _comparer;
+    private readonly Func<T>? _source;
+    private T _value = default!;
+    private bool _hasValue;
+    private bool _shaped;
+    private IReadOnlyList<UiText.Line> _lines = Array.Empty<UiText.Line>();
+    private float _width;
+    private float _padding;
+    private Vector4 _defaultColor;
+    private UiDatFont? _datFont;
+    private BitmapFont? _bitmapFont;
+    private IReadOnlyList<Vector4>? _fontColorPalette;
+
+    public UiTextLayoutCache(
+        UiText target,
+        Func<UiText, T, IReadOnlyList<UiText.Line>> shape,
+        T initialValue,
+        IEqualityComparer<T>? comparer = null)
+        : this(target, shape, source: null, comparer, initialize: true)
+    {
+        SetValue(initialValue);
+    }
+
+    public UiTextLayoutCache(
+        UiText target,
+        Func<UiText, T, IReadOnlyList<UiText.Line>> shape,
+        Func<T> source,
+        IEqualityComparer<T>? comparer = null)
+        : this(
+            target,
+            shape,
+            source ?? throw new ArgumentNullException(nameof(source)),
+            comparer,
+            initialize: true)
+    {
+    }
+
+    private UiTextLayoutCache(
+        UiText target,
+        Func<UiText, T, IReadOnlyList<UiText.Line>> shape,
+        Func<T>? source,
+        IEqualityComparer<T>? comparer,
+        bool initialize)
+    {
+        _ = initialize;
+        _target = target ?? throw new ArgumentNullException(nameof(target));
+        _shape = shape ?? throw new ArgumentNullException(nameof(shape));
+        _source = source;
+        _comparer = comparer ?? EqualityComparer<T>.Default;
+    }
+
+    public Func<IReadOnlyList<UiText.Line>> Provider => GetLines;
+
+    public void SetValue(T value)
+    {
+        if (_hasValue && _comparer.Equals(_value, value))
+            return;
+
+        _value = value;
+        _hasValue = true;
+        _shaped = false;
+    }
+
+    public void Invalidate() => _shaped = false;
+
+    public IReadOnlyList<UiText.Line> GetLines()
+    {
+        if (_source is not null)
+            SetValue(_source());
+
+        if (!_hasValue)
+            return Array.Empty<UiText.Line>();
+
+        if (!_shaped || LayoutChanged())
+        {
+            CaptureLayout();
+            _lines = _shape(_target, _value);
+            _shaped = true;
+        }
+
+        return _lines;
+    }
+
+    private bool LayoutChanged()
+        => _width != _target.Width
+           || _padding != _target.Padding
+           || _defaultColor != _target.DefaultColor
+           || !ReferenceEquals(_datFont, _target.DatFont)
+           || !ReferenceEquals(_bitmapFont, _target.Font)
+           || !ReferenceEquals(_fontColorPalette, _target.FontColorPalette);
+
+    private void CaptureLayout()
+    {
+        _width = _target.Width;
+        _padding = _target.Padding;
+        _defaultColor = _target.DefaultColor;
+        _datFont = _target.DatFont;
+        _bitmapFont = _target.Font;
+        _fontColorPalette = _target.FontColorPalette;
+    }
+}