feat: add FilterableCheckBoxColumn.cs

src/DynamicTreeDataGrid/Models/Columns/FilterableCheckBoxColumn.cs

@@ -0,0 +1,86 @@
+using System.Linq.Expressions;
+
+using Avalonia.Controls;
+using Avalonia.Controls.Models.TreeDataGrid;
+using Avalonia.Experimental.Data;
+
+namespace DynamicTreeDataGrid.Models.Columns;
+
+/// <summary>
+/// A column in an <see cref="ITreeDataGridSource"/> which displays a check box.
+/// Direct port of <see cref="CheckBoxColumn{TModel}"/> that adds filtering and visbility.
+/// </summary>
+/// <typeparam name="TModel">The model type.</typeparam>
+public class FilterableCheckBoxColumn<TModel> : FilterableColumnBase<TModel, bool?>
+    where TModel : class {
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FilterableCheckBoxColumn{TModel}"/> class.
+    /// Direct port of <see cref="CheckBoxColumn{TModel}"/> that adds filtering and visbility.
+    /// </summary>
+    /// <param name="header">The column header.</param>
+    /// <param name="getter">
+    /// An expression which given a row model, returns a boolean cell value for the column.
+    /// </param>
+    /// <param name="setter">
+    /// A method which given a row model and a cell value, writes the cell value to the
+    /// row model. If not supplied then the column will be read-only.
+    /// </param>
+    /// <param name="width">
+    /// The column width. If null defaults to <see cref="GridLength.Auto"/>.
+    /// </param>
+    /// <param name="options">Additional column options.</param>
+    public FilterableCheckBoxColumn(object? header,
+                                    Expression<Func<TModel, bool>> getter,
+                                    Action<TModel, bool>? setter = null,
+                                    GridLength? width = null,
+                                    CheckBoxColumnOptions<TModel>? options = null) : base(header, ToNullable(getter),
+        ToNullable(getter, setter), width, options) { }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FilterableCheckBoxColumn{TModel}"/> class that
+    /// displays a three-state check box.
+    /// Direct port of <see cref="CheckBoxColumn{TModel}"/> that adds filtering and visbility.
+    /// </summary>
+    /// <param name="header">The column header.</param>
+    /// <param name="getter">
+    /// An expression which given a row model, returns a nullable boolean cell value for the
+    /// column.
+    /// </param>
+    /// <param name="setter">
+    /// A method which given a row model and a cell value, writes the cell value to the
+    /// row model. If not supplied then the column will be read-only.
+    /// </param>
+    /// <param name="width">
+    /// The column width. If null defaults to <see cref="GridLength.Auto"/>.
+    /// </param>
+    /// <param name="options">Additional column options.</param>
+    public FilterableCheckBoxColumn(object? header,
+                                    Expression<Func<TModel, bool?>> getter,
+                                    Action<TModel, bool?>? setter = null,
+                                    GridLength? width = null,
+                                    CheckBoxColumnOptions<TModel>? options = null) : base(header, getter, setter, width,
+        options ?? new()) {
+        IsThreeState = true;
+    }
+
+    public bool IsThreeState { get; }
+
+    public override ICell CreateCell(IRow<TModel> row) {
+        return new CheckBoxCell(CreateBindingExpression(row.Model), Binding.Write is null, IsThreeState);
+    }
+
+    private static Func<TModel, bool?> ToNullable(Expression<Func<TModel, bool>> getter) {
+        var c = getter.Compile();
+        return x => c(x);
+    }
+
+    private static TypedBinding<TModel, bool?> ToNullable(Expression<Func<TModel, bool>> getter,
+                                                          Action<TModel, bool>? setter) {
+        var g = Expression.Lambda<Func<TModel, bool?>>(Expression.Convert(getter.Body, typeof(bool?)),
+            getter.Parameters);
+
+        return setter is null
+            ? TypedBinding<TModel>.OneWay(g)
+            : TypedBinding<TModel>.TwoWay(g, (m, v) => setter(m, v ?? false));
+    }
+}