Initial commit.

Terminal.Gui/Views/NumericUpDown.cs

@@ -0,0 +1,178 @@
+using System.ComponentModel;
+using Terminal.Gui;
+
+/// <summary>
+///     Enables the user to increase or decrease a value by clicking on the up or down buttons.
+/// </summary>
+/// <remarks>
+///     Supports the following types: <see cref="int"/>, <see cref="long"/>, <see cref="float"/>, <see cref="double"/>,
+///     <see cref="decimal"/>.
+///     Supports only one digit of precision.
+/// </remarks>
+public class NumericUpDown<T> : View
+{
+    private readonly Button _down;
+
+    // TODO: Use a TextField instead of a Label
+    private readonly View _number;
+    private readonly Button _up;
+
+    public NumericUpDown ()
+    {
+        Type type = typeof (T);
+
+        if (!(type == typeof (int) || type == typeof (long) || type == typeof (float) || type == typeof (double) || type == typeof (decimal)))
+        {
+            // Support object for AllViewsTester
+            if (type != typeof (object))
+            {
+                throw new InvalidOperationException ("T must be a numeric type that supports addition and subtraction.");
+            }
+        }
+
+        Width = Dim.Auto (DimAutoStyle.Content); //Dim.Function (() => Digits + 2); // button + 3 for number + button
+        Height = Dim.Auto (DimAutoStyle.Content);
+
+        _down = new ()
+        {
+            Height = 1,
+            Width = 1,
+            NoPadding = true,
+            NoDecorations = true,
+            Title = $"{Glyphs.DownArrow}",
+            WantContinuousButtonPressed = true,
+            CanFocus = false,
+            ShadowStyle = ShadowStyle.None
+        };
+
+        _number = new ()
+        {
+            Text = Value?.ToString () ?? "Err",
+            X = Pos.Right (_down),
+            Y = Pos.Top (_down),
+            Width = Dim.Func (() => Digits),
+            Height = 1,
+            TextAlignment = Alignment.Center,
+            CanFocus = true
+        };
+
+        _up = new ()
+        {
+            X = Pos.AnchorEnd (),
+            Y = Pos.Top (_number),
+            Height = 1,
+            Width = 1,
+            NoPadding = true,
+            NoDecorations = true,
+            Title = $"{Glyphs.UpArrow}",
+            WantContinuousButtonPressed = true,
+            CanFocus = false,
+            ShadowStyle = ShadowStyle.None
+        };
+
+        CanFocus = true;
+
+        _down.Accept += OnDownButtonOnAccept;
+        _up.Accept += OnUpButtonOnAccept;
+
+        Add (_down, _number, _up);
+
+        AddCommand (
+                    Command.ScrollUp,
+                    () =>
+                    {
+                        if (type == typeof (object))
+                        {
+                            return false;
+                        }
+
+                        Value = (dynamic)Value + 1;
+                        _number.Text = Value?.ToString () ?? string.Empty;
+
+                        return true;
+                    });
+
+        AddCommand (
+                    Command.ScrollDown,
+                    () =>
+                    {
+                        if (type == typeof (object))
+                        {
+                            return false;
+                        }
+
+                        Value = (dynamic)Value - 1;
+                        _number.Text = Value.ToString () ?? string.Empty;
+
+                        return true;
+                    });
+
+        KeyBindings.Add (Key.CursorUp, Command.ScrollUp);
+        KeyBindings.Add (Key.CursorDown, Command.ScrollDown);
+
+        return;
+
+        void OnDownButtonOnAccept (object s, HandledEventArgs e) { InvokeCommand (Command.ScrollDown); }
+
+        void OnUpButtonOnAccept (object s, HandledEventArgs e) { InvokeCommand (Command.ScrollUp); }
+    }
+
+    private void _up_Enter (object sender, FocusEventArgs e) { throw new NotImplementedException (); }
+
+    private T _value;
+
+    /// <summary>
+    ///     The value that will be incremented or decremented.
+    /// </summary>
+    public T Value
+    {
+        get => _value;
+        set
+        {
+            if (_value.Equals (value))
+            {
+                return;
+            }
+
+            T oldValue = value;
+            CancelEventArgs<T> args = new (ref _value, ref value);
+            ValueChanging?.Invoke (this, args);
+
+            if (args.Cancel)
+            {
+                return;
+            }
+
+            _value = value;
+            _number.Text = _value.ToString ();
+            ValueChanged?.Invoke (this, new (ref _value));
+        }
+    }
+
+    /// <summary>
+    ///     Fired when the value is about to change. Set <see cref="CancelEventArgs{T}.Cancel"/> to true to prevent the change.
+    /// </summary>
+    [CanBeNull]
+    public event EventHandler<CancelEventArgs<T>> ValueChanging;
+
+    /// <summary>
+    ///     Fired when the value has changed.
+    /// </summary>
+    [CanBeNull]
+    public event EventHandler<EventArgs<T>> ValueChanged;
+
+    /// <summary>
+    ///     The number of digits to display. The <see cref="View.Viewport"/> will be resized to fit this number of characters
+    ///     plus the buttons. The default is 3.
+    /// </summary>
+    public int Digits { get; set; } = 3;
+}
+
+
+/// <summary>
+///     Enables the user to increase or decrease an <see langword="int"/> by clicking on the up or down buttons.
+/// </summary>
+public class NumericUpDown : NumericUpDown<int>
+{
+
+}