Fixes #2489. Create new ScrollBar based on a new Scroll and remove ScrollBarView/ScrollView

Terminal.Gui/Views/Scroll.cs

@@ -0,0 +1,355 @@
+//
+// Scroll.cs: Vertical or horizontal scroll
+//
+// Author: BDisp
+//
+// Licensed under the MIT license
+//
+
+namespace Terminal.Gui;
+
+/// <summary>
+///     Represents the "inside part" of a scroll bar, minus the arrows.
+/// </summary>
+public class Scroll : View
+{
+    /// <inheritdoc/>
+    public Scroll ()
+    {
+        WantContinuousButtonPressed = true;
+        ClearOnVisibleFalse = false;
+        CanFocus = false;
+        Orientation = Orientation.Vertical;
+        Width = 1;
+
+        _slider = new () { Id = "slider" };
+        Add (_slider);
+
+        Added += Scroll_Added;
+        Removed += Scroll_Removed;
+        Initialized += Scroll_Initialized;
+        DrawContent += Scroll_DrawContent;
+        MouseEvent += Scroll_MouseEvent;
+        _slider.DrawContent += Scroll_DrawContent;
+        _slider.MouseEvent += Slider_MouseEvent;
+    }
+
+    private readonly View _slider;
+    private int _lastLocation = -1;
+
+    private Orientation _orientation;
+    private int _size;
+    private int _position;
+
+    private bool _wasSliderMouse;
+
+    /// <summary>
+    ///     Determines the Orientation of the scroll.
+    /// </summary>
+    public Orientation Orientation
+    {
+        get => _orientation;
+        set
+        {
+            _orientation = value;
+            SetWidthHeight ();
+        }
+    }
+
+    /// <summary>
+    ///     The position, relative to <see cref="Size"/>, to set the scrollbar at.
+    /// </summary>
+    public int Position
+    {
+        get => _position;
+        set
+        {
+            int barSize = Orientation == Orientation.Vertical ? Frame.Height : Frame.Width;
+
+            if (value < 0 || (value > 0 && value + barSize > Size))
+            {
+                return;
+            }
+
+            StateEventArgs<int> args = OnPositionChanging (_position, value);
+
+            if (args.Cancel)
+            {
+                return;
+            }
+
+            int oldPos = _position;
+            _position = value;
+            OnPositionChanged (oldPos);
+
+            if (!_wasSliderMouse)
+            {
+                SetWidthHeight ();
+            }
+        }
+    }
+
+    /// <summary>This event is raised when the position on the scrollbar has changed.</summary>
+    public event EventHandler<StateEventArgs<int>> PositionChanged;
+
+    /// <summary>This event is raised when the position on the scrollbar is changing.</summary>
+    public event EventHandler<StateEventArgs<int>> PositionChanging;
+
+    /// <summary>
+    ///     The size of content the scroll represents.
+    /// </summary>
+    public int Size
+    {
+        get => _size;
+        set
+        {
+            int oldSize = _size;
+            _size = value;
+            OnSizeChanged (oldSize);
+            SetWidthHeight ();
+        }
+    }
+
+    /// <summary>This event is raised when the size of the scroll has changed.</summary>
+    public event EventHandler<StateEventArgs<int>> SizeChanged;
+
+    /// <inheritdoc/>
+    protected override void Dispose (bool disposing)
+    {
+        Added -= Scroll_Added;
+        Initialized -= Scroll_Initialized;
+        DrawContent -= Scroll_DrawContent;
+        MouseEvent -= Scroll_MouseEvent;
+        _slider.DrawContent -= Scroll_DrawContent;
+        _slider.MouseEvent -= Slider_MouseEvent;
+
+        base.Dispose (disposing);
+    }
+
+    /// <summary>Virtual method to invoke the <see cref="PositionChanged"/> event handler.</summary>
+    protected virtual void OnPositionChanged (int oldPos) { PositionChanged?.Invoke (this, new (oldPos, Position)); }
+
+    /// <summary>Virtual method to invoke the cancelable <see cref="PositionChanging"/> event handler.</summary>
+    protected virtual StateEventArgs<int> OnPositionChanging (int oldPos, int newPos)
+    {
+        StateEventArgs<int> args = new (oldPos, newPos);
+        PositionChanging?.Invoke (this, args);
+
+        return args;
+    }
+
+    /// <summary>Virtual method to invoke the <see cref="SizeChanged"/> event handler.</summary>
+    protected void OnSizeChanged (int oldSize) { SizeChanged?.Invoke (this, new (oldSize, Size)); }
+
+    private int GetPositionFromSliderLocation (int location)
+    {
+        if (Frame.Height == 0 || Frame.Width == 0)
+        {
+            return 0;
+        }
+
+        int barSize = Orientation == Orientation.Vertical ? Frame.Height : Frame.Width;
+
+        return Math.Min (location * Size / barSize, Size - barSize);
+    }
+
+    private (int Location, int Dimension) GetSliderLocationDimensionFromPosition ()
+    {
+        if (Frame.Height == 0 || Frame.Width == 0)
+        {
+            return new (0, 0);
+        }
+
+        int barSize = Orientation == Orientation.Vertical ? Frame.Height : Frame.Width;
+        int location;
+        int dimension;
+
+        if (Size > 0)
+        {
+            dimension = Math.Min (Math.Max (barSize * barSize / Size, 1), barSize);
+
+            // Ensure the Position is valid
+            if (Position > 0 && Position + barSize > Size)
+            {
+                Position = Size - barSize;
+            }
+
+            location = Math.Min (Position * barSize / Size, barSize - dimension);
+
+            if (Position == Size - barSize && location + dimension < barSize)
+            {
+                location = barSize - dimension;
+            }
+        }
+        else
+        {
+            location = 0;
+            dimension = barSize;
+        }
+
+        return new (location, dimension);
+    }
+
+    private void Parent_LayoutComplete (object sender, LayoutEventArgs e)
+    {
+        if (!_wasSliderMouse)
+        {
+            SetWidthHeight ();
+        }
+        else
+        {
+            _wasSliderMouse = false;
+        }
+    }
+
+    private void Parent_MouseEnter (object sender, MouseEventEventArgs e) { OnMouseEnter (e.MouseEvent); }
+
+    private void Parent_MouseLeave (object sender, MouseEventEventArgs e) { OnMouseLeave (e.MouseEvent); }
+
+    private void Scroll_Added (object sender, SuperViewChangedEventArgs e)
+    {
+        View parent = e.Parent is Adornment adornment ? adornment.Parent : e.Parent;
+
+        parent.LayoutComplete += Parent_LayoutComplete;
+        parent.MouseEnter += Parent_MouseEnter;
+        parent.MouseLeave += Parent_MouseLeave;
+    }
+
+    private void Scroll_DrawContent (object sender, DrawEventArgs e) { SetColorSchemeWithSuperview (sender as View); }
+
+    private void Scroll_Initialized (object sender, EventArgs e) { SetWidthHeight (); }
+
+    private void Scroll_MouseEvent (object sender, MouseEventEventArgs e)
+    {
+        MouseEvent me = e.MouseEvent;
+        int location = Orientation == Orientation.Vertical ? me.Position.Y : me.Position.X;
+        int barSize = Orientation == Orientation.Vertical ? Frame.Height : Frame.Width;
+
+        (int topLeft, int bottomRight) sliderPos = _orientation == Orientation.Vertical
+                                                       ? new (_slider.Frame.Y, _slider.Frame.Bottom - 1)
+                                                       : new (_slider.Frame.X, _slider.Frame.Right - 1);
+
+        if (me.Flags == MouseFlags.Button1Pressed && location < sliderPos.topLeft)
+        {
+            Position = Math.Max (Position - barSize, 0);
+        }
+        else if (me.Flags == MouseFlags.Button1Pressed && location > sliderPos.bottomRight)
+        {
+            Position = Math.Min (Position + barSize, Size - barSize);
+        }
+    }
+
+    private void Scroll_Removed (object sender, SuperViewChangedEventArgs e)
+    {
+        if (e.Parent is { })
+        {
+            View parent = e.Parent is Adornment adornment ? adornment.Parent : e.Parent;
+
+            parent.LayoutComplete -= Parent_LayoutComplete;
+            parent.MouseEnter -= Parent_MouseEnter;
+            parent.MouseLeave -= Parent_MouseLeave;
+        }
+    }
+
+    private static void SetColorSchemeWithSuperview (View view)
+    {
+        if (view.SuperView is { })
+        {
+            View parent = view.SuperView is Adornment adornment ? adornment.Parent : view.SuperView;
+
+            if (view.Id == "slider")
+            {
+                view.ColorScheme = new () { Normal = new (parent.ColorScheme.Normal.Foreground, parent.ColorScheme.Normal.Foreground) };
+            }
+            else
+            {
+                view.ColorScheme = parent.ColorScheme;
+            }
+        }
+    }
+
+    private void SetSliderText ()
+    {
+        TextDirection = Orientation == Orientation.Vertical ? TextDirection.TopBottom_LeftRight : TextDirection.LeftRight_TopBottom;
+
+        Text = string.Concat (
+                              Enumerable.Repeat (
+                                                 Glyphs.Stipple.ToString (),
+                                                 Frame.Width * Frame.Height));
+        _slider.TextDirection = Orientation == Orientation.Vertical ? TextDirection.TopBottom_LeftRight : TextDirection.LeftRight_TopBottom;
+
+        _slider.Text = string.Concat (
+                                      Enumerable.Repeat (
+                                                         Glyphs.ContinuousMeterSegment.ToString (),
+                                                         _slider.Frame.Width * _slider.Frame.Height));
+    }
+
+    private void SetWidthHeight ()
+    {
+        if (!IsInitialized)
+        {
+            return;
+        }
+
+        (int Location, int Dimension) slider = GetSliderLocationDimensionFromPosition ();
+        _slider.X = Orientation == Orientation.Vertical ? 0 : slider.Location;
+        _slider.Y = Orientation == Orientation.Vertical ? slider.Location : 0;
+        _slider.Width = Orientation == Orientation.Vertical ? Dim.Fill () : slider.Dimension;
+        _slider.Height = Orientation == Orientation.Vertical ? slider.Dimension : Dim.Fill ();
+
+        SetSliderText ();
+    }
+
+    private void Slider_MouseEvent (object sender, MouseEventEventArgs e)
+    {
+        MouseEvent me = e.MouseEvent;
+        int location = Orientation == Orientation.Vertical ? me.Position.Y : me.Position.X;
+        int barSize = Orientation == Orientation.Vertical ? Frame.Height : Frame.Width;
+        int offset = _lastLocation > -1 ? location - _lastLocation : 0;
+
+        if (me.Flags == MouseFlags.Button1Pressed)
+        {
+            if (Application.MouseGrabView != sender as View)
+            {
+                Application.GrabMouse (sender as View);
+                _lastLocation = location;
+            }
+        }
+        else if (me.Flags == (MouseFlags.Button1Pressed | MouseFlags.ReportMousePosition))
+        {
+            if (Orientation == Orientation.Vertical)
+            {
+                if (_slider.Frame.Y + offset >= 0 && _slider.Frame.Y + offset + _slider.Frame.Height <= barSize)
+                {
+                    _wasSliderMouse = true;
+                    _slider.Y = _slider.Frame.Y + offset;
+                    Position = GetPositionFromSliderLocation (_slider.Frame.Y);
+                }
+            }
+            else
+            {
+                if (_slider.Frame.X + offset >= 0 && _slider.Frame.X + offset + _slider.Frame.Width <= barSize)
+                {
+                    _wasSliderMouse = true;
+                    _slider.X = _slider.Frame.X + offset;
+                    Position = GetPositionFromSliderLocation (_slider.Frame.X);
+                }
+            }
+        }
+        else if (me.Flags == MouseFlags.Button1Released)
+        {
+            _lastLocation = -1;
+
+            if (Application.MouseGrabView == sender as View)
+            {
+                Application.UngrabMouse ();
+            }
+        }
+        else
+        {
+            return;
+        }
+
+        e.Handled = true;
+    }
+}