Fixes #4869. Add ListView<T> with typed Value, SelectedItem, Index

Examples/UICatalog/Scenarios/GenericListView.cs

@@ -0,0 +1,208 @@
+#nullable enable
+using System.Collections.ObjectModel;
+using System.Text;
+
+namespace UICatalog.Scenarios;
+
+[ScenarioMetadata ("Generic ListView<T>", "Demonstrates ListView<T> with typed Value, SelectedItem, Index, and RowRender for custom row coloring")]
+[ScenarioCategory ("Controls")]
+[ScenarioCategory ("ListView")]
+public class GenericListView : Scenario
+{
+    private ListView<Country>? _listView;
+    private ObservableCollection<string> _eventList = [];
+    private ListView? _eventListView;
+    private Label? _nameLabel;
+    private Label? _capitalLabel;
+    private Label? _populationLabel;
+    private Label? _indexLabel;
+    private CheckBox? _cancelNextCb;
+    private bool _cancelNext;
+
+    /// <inheritdoc/>
+    public override void Main ()
+    {
+        ConfigurationManager.Enable (ConfigLocations.All);
+        using IApplication app = Application.Create ();
+        app.Init ();
+
+        using Window appWindow = new () { Title = GetQuitKeyAndName () };
+
+        ObservableCollection<Country> countries =
+        [
+            new ("Australia", "Canberra", 26_000_000),
+            new ("Brazil", "Brasília", 215_000_000),
+            new ("Canada", "Ottawa", 38_000_000),
+            new ("Denmark", "Copenhagen", 5_900_000),
+            new ("Egypt", "Cairo", 104_000_000),
+            new ("France", "Paris", 68_000_000),
+            new ("Germany", "Berlin", 84_000_000),
+            new ("Hungary", "Budapest", 9_700_000),
+            new ("India", "New Delhi", 1_428_000_000),
+            new ("Japan", "Tokyo", 124_000_000)
+        ];
+
+        // -- Cancel checkbox --------------------------------------------------
+        _cancelNextCb = new CheckBox
+        {
+            X = 0,
+            Y = 0,
+            Text = "C_ancel next selection change"
+        };
+        _cancelNextCb.ValueChanging += (_, args) => _cancelNext = args.NewValue == CheckState.Checked;
+        appWindow.Add (_cancelNextCb);
+
+        // -- ListView<Country> ------------------------------------------------
+        _listView = new ListView<Country>
+        {
+            Title = "_Countries",
+            X = 0,
+            Y = Pos.Bottom (_cancelNextCb) + 1,
+            Width = 22,
+            Height = Dim.Fill (),
+            BorderStyle = LineStyle.Single
+        };
+        _listView.SetSource (countries);
+        appWindow.Add (_listView);
+
+        // Build highlight scheme by inheriting the resolved scheme and only
+        // overriding foreground colors so the background stays theme-consistent.
+        Scheme baseScheme = _listView.GetScheme ();
+        Scheme highlightScheme = new ()
+        {
+            Normal = baseScheme.Normal with { Foreground = Color.BrightRed },
+            Focus  = baseScheme.Focus  with { Foreground = Color.BrightRed, Style = TextStyle.Bold }
+        };
+
+        // Use RowRender to color rows with population > 100M (demonstrates
+        // how to achieve per-row coloring without a ColorGetter delegate).
+        _listView.RowRender += (_, args) =>
+        {
+            if (args.Row < countries.Count && countries [args.Row].Population > 100_000_000)
+            {
+                bool isSelected = args.Row == _listView.Index;
+                args.RowAttribute = isSelected ? highlightScheme.Focus : highlightScheme.Normal;
+            }
+        };
+
+        // -- Detail panel -----------------------------------------------------
+        FrameView detailPanel = new ()
+        {
+            Title = "_Selected",
+            X = Pos.Right (_listView) + 1,
+            Y = Pos.Top (_listView),
+            Width = Dim.Fill (),
+            Height = 9
+        };
+        appWindow.Add (detailPanel);
+
+        Label nameTitleLbl = new () { X = 1, Y = 1, Text = "Name:      " };
+        detailPanel.Add (nameTitleLbl);
+        _nameLabel = new () { X = Pos.Right (nameTitleLbl), Y = 1, Width = Dim.Fill (1), Text = "(none)" };
+        detailPanel.Add (_nameLabel);
+
+        Label capitalTitleLbl = new () { X = 1, Y = 2, Text = "Capital:   " };
+        detailPanel.Add (capitalTitleLbl);
+        _capitalLabel = new () { X = Pos.Right (capitalTitleLbl), Y = 2, Width = Dim.Fill (1), Text = "" };
+        detailPanel.Add (_capitalLabel);
+
+        Label populationTitleLbl = new () { X = 1, Y = 3, Text = "Population:" };
+        detailPanel.Add (populationTitleLbl);
+        _populationLabel = new () { X = Pos.Right (populationTitleLbl), Y = 3, Width = Dim.Fill (1), Text = "" };
+        detailPanel.Add (_populationLabel);
+
+        Label indexTitleLbl = new () { X = 1, Y = 5, Text = "Index:     " };
+        detailPanel.Add (indexTitleLbl);
+        _indexLabel = new () { X = Pos.Right (indexTitleLbl), Y = 5, Width = Dim.Fill (1), Text = "" };
+        detailPanel.Add (_indexLabel);
+
+        // -- Event log --------------------------------------------------------
+        _eventList = [];
+        _eventListView = new ListView
+        {
+            Title = "_Events",
+            X = Pos.Right (_listView) + 1,
+            Y = Pos.Bottom (detailPanel) + 1,
+            Width = Dim.Fill (),
+            Height = Dim.Fill (),
+            Source = new ListWrapper<string> (_eventList),
+            BorderStyle = LineStyle.Single
+        };
+        appWindow.Add (_eventListView);
+
+        // -- Wire events ------------------------------------------------------
+        _listView.ValueChanging += OnValueChanging;
+        _listView.ValueChanged += OnValueChanged;
+
+        app.Run (appWindow);
+    }
+
+    private void OnValueChanging (object? sender, ValueChangingEventArgs<Country?> args)
+    {
+        if (_cancelNext)
+        {
+            args.Handled = true;
+            _cancelNext = false;
+
+            if (_cancelNextCb is not null)
+            {
+                _cancelNextCb.Value = CheckState.UnChecked;
+            }
+
+            LogEvent ($"ValueChanging CANCELLED: {FormatCountry (args.CurrentValue)} -> {FormatCountry (args.NewValue)}");
+
+            return;
+        }
+
+        LogEvent ($"ValueChanging: {FormatCountry (args.CurrentValue)} -> {FormatCountry (args.NewValue)}");
+    }
+
+    private void OnValueChanged (object? sender, ValueChangedEventArgs<Country?> args)
+    {
+        UpdateDetail (args.NewValue);
+        LogEvent ($"ValueChanged:  {FormatCountry (args.OldValue)} -> {FormatCountry (args.NewValue)}");
+    }
+
+    private void UpdateDetail (Country? country)
+    {
+        if (_nameLabel is null)
+        {
+            return;
+        }
+
+        if (country is null)
+        {
+            _nameLabel.Text = "(none)";
+            _capitalLabel!.Text = "";
+            _populationLabel!.Text = "";
+            _indexLabel!.Text = "";
+
+            return;
+        }
+
+        _nameLabel.Text = country.Name;
+        _capitalLabel!.Text = country.Capital;
+        _populationLabel!.Text = $"{country.Population:N0}";
+        _indexLabel!.Text = _listView?.Index?.ToString () ?? "";
+    }
+
+    private void LogEvent (string message)
+    {
+        _eventList.Add (message);
+
+        if (_eventListView is not null)
+        {
+            _eventListView.MoveEnd ();
+        }
+    }
+
+    private static string FormatCountry (Country? c) => c is null ? "null" : c.Name;
+}
+
+/// <summary>A simple record used to demonstrate <see cref="ListView{T}"/>.</summary>
+internal record Country (string Name, string Capital, int Population)
+{
+    // Overriding ToString() so ListView<Country> displays the country name
+    // without needing an AspectGetter delegate.
+    public override string ToString () => Name;
+}