gui-cs.Terminal.Gui/UnitTests/Views/ScrollBarViewTests.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using Xunit;
using Xunit.Abstractions;

namespace Terminal.Gui.ViewsTests;

public class ScrollBarViewTests {
	static HostView _hostView;
	readonly ITestOutputHelper output;
	bool _added;
	ScrollBarView _scrollBar;

	public ScrollBarViewTests (ITestOutputHelper output) => this.output = output;

	[Fact]
	[AutoInitShutdown]
	public void Horizontal_Default_Draws_Correctly ()
	{
		var width = 40;
		var height = 3;

		var super = new Window { Id = "super", Width = Dim.Fill (), Height = Dim.Fill () };
		Application.Top.Add (super);

		var sbv = new ScrollBarView {
			Id = "sbv",
			Size = width * 2,
			// BUGBUG: ScrollBarView should work if Host is null
			Host = super,
			ShowScrollIndicator = true
		};
		super.Add (sbv);
		Application.Begin (Application.Top);
		((FakeDriver)Application.Driver).SetBufferSize (width, height);

		var expected = @"
┌──────────────────────────────────────┐
│◄├────────────────┤░░░░░░░░░░░░░░░░░░►│
└──────────────────────────────────────┘";
		_ = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);

	}

	[Fact]
	[AutoInitShutdown]
	public void Vertical_Default_Draws_Correctly ()
	{
		var width = 3;
		var height = 40;

		var super = new Window { Id = "super", Width = Dim.Fill (), Height = Dim.Fill () };
		Application.Top.Add (super);

		var sbv = new ScrollBarView {
			Id = "sbv",
			Size = height * 2,
			// BUGBUG: ScrollBarView should work if Host is null
			Host = super,
			ShowScrollIndicator = true,
			IsVertical = true
		};

		super.Add (sbv);
		Application.Begin (Application.Top);
		((FakeDriver)Application.Driver).SetBufferSize (width, height);

		var expected = @"
┌─┐
│▲│
│┬│
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│┴│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│▼│
└─┘";
		_ = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);

	}

	[Fact]
	[AutoInitShutdown]
	public void Both_Default_Draws_Correctly ()
	{
		var width = 3;
		var height = 40;

		var super = new Window { Id = "super", Width = Dim.Fill (), Height = Dim.Fill () };
		Application.Top.Add (super);

		var horiz = new ScrollBarView {
			Id = "horiz",
			Size = width * 2,
			// BUGBUG: ScrollBarView should work if Host is null
			Host = super,
			ShowScrollIndicator = true,
			IsVertical = true
		};
		super.Add (horiz);

		var vert = new ScrollBarView {
			Id = "vert",
			Size = height * 2,
			// BUGBUG: ScrollBarView should work if Host is null
			Host = super,
			ShowScrollIndicator = true,
			IsVertical = true
		};
		super.Add (vert);

		Application.Begin (Application.Top);
		((FakeDriver)Application.Driver).SetBufferSize (width, height);

		var expected = @"
┌─┐
│▲│
│┬│
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│││
│┴│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│░│
│▼│
└─┘";
		_ = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);

	}

	void AddHandlers ()
	{
		if (!_added) {
			_hostView.DrawContent += _hostView_DrawContent;
			_scrollBar.ChangedPosition += _scrollBar_ChangedPosition;
			_scrollBar.OtherScrollBarView.ChangedPosition += _scrollBar_OtherScrollBarView_ChangedPosition;
		}
		_added = true;
	}

	void RemoveHandlers ()
	{
		if (_added) {
			_hostView.DrawContent -= _hostView_DrawContent;
			_scrollBar.ChangedPosition -= _scrollBar_ChangedPosition;
			_scrollBar.OtherScrollBarView.ChangedPosition -= _scrollBar_OtherScrollBarView_ChangedPosition;
		}
		_added = false;
	}

	void _hostView_DrawContent (object sender, DrawEventArgs e)
	{
		_scrollBar.Size = _hostView.Lines;
		_scrollBar.Position = _hostView.Top;
		_scrollBar.OtherScrollBarView.Size = _hostView.Cols;
		_scrollBar.OtherScrollBarView.Position = _hostView.Left;
		_scrollBar.Refresh ();
	}

	void _scrollBar_ChangedPosition (object sender, EventArgs e)
	{
		_hostView.Top = _scrollBar.Position;
		if (_hostView.Top != _scrollBar.Position) {
			_scrollBar.Position = _hostView.Top;
		}
		_hostView.SetNeedsDisplay ();
	}

	void _scrollBar_OtherScrollBarView_ChangedPosition (object sender, EventArgs e)
	{
		_hostView.Left = _scrollBar.OtherScrollBarView.Position;
		if (_hostView.Left != _scrollBar.OtherScrollBarView.Position) {
			_scrollBar.OtherScrollBarView.Position = _hostView.Left;
		}
		_hostView.SetNeedsDisplay ();
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Hosting_A_Null_View_To_A_ScrollBarView_Throws_ArgumentNullException ()
	{
		Assert.Throws<ArgumentNullException> ("The host parameter can't be null.",
			() => new ScrollBarView (null, true));
		Assert.Throws<ArgumentNullException> ("The host parameter can't be null.",
			() => new ScrollBarView (null, false));
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Hosting_A_Null_SuperView_View_To_A_ScrollBarView_Throws_ArgumentNullException ()
	{
		Assert.Throws<ArgumentNullException> ("The host SuperView parameter can't be null.",
			() => new ScrollBarView (new View (), true));
		Assert.Throws<ArgumentNullException> ("The host SuperView parameter can't be null.",
			() => new ScrollBarView (new View (), false));
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Hosting_Two_Vertical_ScrollBarView_Throws_ArgumentException ()
	{
		var top = new Toplevel ();
		var host = new View ();
		top.Add (host);
		var v = new ScrollBarView (host, true);
		var h = new ScrollBarView (host, true);

		Assert.Throws<ArgumentException> (() => v.OtherScrollBarView = h);
		Assert.Throws<ArgumentException> (() => h.OtherScrollBarView = v);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Hosting_Two_Horizontal_ScrollBarView_Throws_ArgumentException ()
	{
		var top = new Toplevel ();
		var host = new View ();
		top.Add (host);
		var v = new ScrollBarView (host, false);
		var h = new ScrollBarView (host, false);

		Assert.Throws<ArgumentException> (() => v.OtherScrollBarView = h);
		Assert.Throws<ArgumentException> (() => h.OtherScrollBarView = v);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Scrolling_With_Default_Constructor_Do_Not_Scroll ()
	{
		var sbv = new ScrollBarView {
			Position = 1
		};
		Assert.Equal (1, sbv.Position);
		Assert.NotEqual (0, sbv.Position);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void Hosting_A_View_To_A_ScrollBarView ()
	{
		RemoveHandlers ();

		_scrollBar = new ScrollBarView (_hostView, true);

		Application.Begin (Application.Top);

		Assert.True (_scrollBar.IsVertical);
		Assert.False (_scrollBar.OtherScrollBarView.IsVertical);

		Assert.Equal (_scrollBar.Position, _hostView.Top);
		Assert.NotEqual (_scrollBar.Size, _hostView.Lines);
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		Assert.NotEqual (_scrollBar.OtherScrollBarView.Size, _hostView.Cols);

		AddHandlers ();
		_hostView.SuperView.LayoutSubviews ();
		_hostView.Draw ();

		Assert.Equal (_scrollBar.Position, _hostView.Top);
		Assert.Equal (_scrollBar.Size, _hostView.Lines);
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		Assert.Equal (_scrollBar.OtherScrollBarView.Size, _hostView.Cols);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void ChangedPosition_Update_The_Hosted_View ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		_scrollBar.Position = 2;
		Assert.Equal (_scrollBar.Position, _hostView.Top);

		_scrollBar.OtherScrollBarView.Position = 5;
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void ChangedPosition_Scrolling ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		for (var i = 0; i < _scrollBar.Size; i++) {
			_scrollBar.Position += 1;
			Assert.Equal (_scrollBar.Position, _hostView.Top);
		}
		for (var i = _scrollBar.Size - 1; i >= 0; i--) {
			_scrollBar.Position -= 1;
			Assert.Equal (_scrollBar.Position, _hostView.Top);
		}

		for (var i = 0; i < _scrollBar.OtherScrollBarView.Size; i++) {
			_scrollBar.OtherScrollBarView.Position += i;
			Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		}
		for (var i = _scrollBar.OtherScrollBarView.Size - 1; i >= 0; i--) {
			_scrollBar.OtherScrollBarView.Position -= 1;
			Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		}
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void ChangedPosition_Negative_Value ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		_scrollBar.Position = -20;
		Assert.Equal (0, _scrollBar.Position);
		Assert.Equal (_scrollBar.Position, _hostView.Top);

		_scrollBar.OtherScrollBarView.Position = -50;
		Assert.Equal (0, _scrollBar.OtherScrollBarView.Position);
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void DrawContent_Update_The_ScrollBarView_Position ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		_hostView.Top = 3;
		_hostView.Draw ();
		Assert.Equal (_scrollBar.Position, _hostView.Top);

		_hostView.Left = 6;
		_hostView.Draw ();
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void OtherScrollBarView_Not_Null ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		Assert.NotNull (_scrollBar.OtherScrollBarView);
		Assert.NotEqual (_scrollBar, _scrollBar.OtherScrollBarView);
		Assert.Equal (_scrollBar.OtherScrollBarView.OtherScrollBarView, _scrollBar);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void ShowScrollIndicator_Check ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void KeepContentAlwaysInViewport_True ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		Assert.Equal (80, _hostView.Bounds.Width);
		Assert.Equal (25, _hostView.Bounds.Height);
		Assert.Equal (79, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal (24, _scrollBar.Bounds.Height);
		Assert.Equal (30, _scrollBar.Size);
		Assert.Equal (100, _scrollBar.OtherScrollBarView.Size);
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);

		_scrollBar.Position = 50;
		Assert.Equal (_scrollBar.Position, _scrollBar.Size - _scrollBar.Bounds.Height);
		Assert.Equal (_scrollBar.Position, _hostView.Top);
		Assert.Equal (6, _scrollBar.Position);
		Assert.Equal (6, _hostView.Top);
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);

		_scrollBar.OtherScrollBarView.Position = 150;
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _scrollBar.OtherScrollBarView.Size - _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		Assert.Equal (21, _scrollBar.OtherScrollBarView.Position);
		Assert.Equal (21, _hostView.Left);
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void KeepContentAlwaysInViewport_False ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		_scrollBar.KeepContentAlwaysInViewport = false;
		_scrollBar.Position = 50;
		Assert.Equal (_scrollBar.Position, _scrollBar.Size - 1);
		Assert.Equal (_scrollBar.Position, _hostView.Top);
		Assert.Equal (29, _scrollBar.Position);
		Assert.Equal (29, _hostView.Top);

		_scrollBar.OtherScrollBarView.Position = 150;
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _scrollBar.OtherScrollBarView.Size - 1);
		Assert.Equal (_scrollBar.OtherScrollBarView.Position, _hostView.Left);
		Assert.Equal (99, _scrollBar.OtherScrollBarView.Position);
		Assert.Equal (99, _hostView.Left);
	}

	[Fact]
	[ScrollBarAutoInitShutdown]
	public void AutoHideScrollBars_Check ()
	{
		Hosting_A_View_To_A_ScrollBarView ();

		AddHandlers ();

		_hostView.Draw ();
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.Equal ("Absolute(1)", _scrollBar.Width.ToString ());
		Assert.Equal (1, _scrollBar.Bounds.Width);
		Assert.Equal ("Combine(View(Height,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.Height.ToString ());
		Assert.Equal (24, _scrollBar.Bounds.Height);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);
		Assert.Equal ("Combine(View(Width,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.OtherScrollBarView.Width.ToString ());
		Assert.Equal (79, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal ("Absolute(1)", _scrollBar.OtherScrollBarView.Height.ToString ());
		Assert.Equal (1, _scrollBar.OtherScrollBarView.Bounds.Height);

		_hostView.Lines = 10;
		_hostView.Draw ();
		Assert.False (_scrollBar.ShowScrollIndicator);
		Assert.False (_scrollBar.Visible);
		Assert.Equal ("Absolute(1)", _scrollBar.Width.ToString ());
		Assert.Equal (1, _scrollBar.Bounds.Width);
		Assert.Equal ("Combine(View(Height,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.Height.ToString ());
		Assert.Equal (24, _scrollBar.Bounds.Height);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);
		Assert.Equal ("View(Width,HostView()(0,0,80,25))",
			_scrollBar.OtherScrollBarView.Width.ToString ());
		Assert.Equal (80, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal ("Absolute(1)", _scrollBar.OtherScrollBarView.Height.ToString ());
		Assert.Equal (1, _scrollBar.OtherScrollBarView.Bounds.Height);

		_hostView.Cols = 60;
		_hostView.Draw ();
		Assert.False (_scrollBar.ShowScrollIndicator);
		Assert.False (_scrollBar.Visible);
		Assert.Equal ("Absolute(1)", _scrollBar.Width.ToString ());
		Assert.Equal (1, _scrollBar.Bounds.Width);
		Assert.Equal ("Combine(View(Height,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.Height.ToString ());
		Assert.Equal (24, _scrollBar.Bounds.Height);
		Assert.False (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.False (_scrollBar.OtherScrollBarView.Visible);
		Assert.Equal ("View(Width,HostView()(0,0,80,25))",
			_scrollBar.OtherScrollBarView.Width.ToString ());
		Assert.Equal (80, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal ("Absolute(1)", _scrollBar.OtherScrollBarView.Height.ToString ());
		Assert.Equal (1, _scrollBar.OtherScrollBarView.Bounds.Height);

		_hostView.Lines = 40;
		_hostView.Draw ();
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.Equal ("Absolute(1)", _scrollBar.Width.ToString ());
		Assert.Equal (1, _scrollBar.Bounds.Width);
		Assert.Equal ("View(Height,HostView()(0,0,80,25))",
			_scrollBar.Height.ToString ());
		Assert.Equal (25, _scrollBar.Bounds.Height);
		Assert.False (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.False (_scrollBar.OtherScrollBarView.Visible);
		Assert.Equal ("View(Width,HostView()(0,0,80,25))",
			_scrollBar.OtherScrollBarView.Width.ToString ());
		Assert.Equal (80, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal ("Absolute(1)", _scrollBar.OtherScrollBarView.Height.ToString ());
		Assert.Equal (1, _scrollBar.OtherScrollBarView.Bounds.Height);

		_hostView.Cols = 120;
		_hostView.Draw ();
		Assert.True (_scrollBar.ShowScrollIndicator);
		Assert.True (_scrollBar.Visible);
		Assert.Equal ("Absolute(1)", _scrollBar.Width.ToString ());
		Assert.Equal (1, _scrollBar.Bounds.Width);
		Assert.Equal ("Combine(View(Height,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.Height.ToString ());
		Assert.Equal (24, _scrollBar.Bounds.Height);
		Assert.True (_scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (_scrollBar.OtherScrollBarView.Visible);
		Assert.Equal ("Combine(View(Width,HostView()(0,0,80,25))-Absolute(1))",
			_scrollBar.OtherScrollBarView.Width.ToString ());
		Assert.Equal (79, _scrollBar.OtherScrollBarView.Bounds.Width);
		Assert.Equal ("Absolute(1)", _scrollBar.OtherScrollBarView.Height.ToString ());
		Assert.Equal (1, _scrollBar.OtherScrollBarView.Bounds.Height);
	}

	[Fact]
	public void Constructor_ShowBothScrollIndicator_False_And_IsVertical_True_Refresh_Does_Not_Throws_An_Object_Null_Exception ()
	{
		var exception = Record.Exception (() => {
			Application.Init (new FakeDriver ());
			var top = Application.Top;
			var win = new Window {
				X = 0,
				Y = 0,
				Width = Dim.Fill (),
				Height = Dim.Fill ()
			};
			var source = new List<string> ();
			for (var i = 0; i < 50; i++) {
				source.Add ($"item {i}");
			}
			var listView = new ListView (source) {
				X = 0,
				Y = 0,
				Width = Dim.Fill (),
				Height = Dim.Fill ()
			};
			win.Add (listView);
			var newScrollBarView = new ScrollBarView (listView, true, false) {
				KeepContentAlwaysInViewport = true
			};
			win.Add (newScrollBarView);
			newScrollBarView.ChangedPosition += (s, e) => {
				listView.TopItem = newScrollBarView.Position;
				if (listView.TopItem != newScrollBarView.Position) {
					newScrollBarView.Position = listView.TopItem;
				}
				Assert.Equal (newScrollBarView.Position, listView.TopItem);
				listView.SetNeedsDisplay ();
			};
			listView.DrawContent += (s, e) => {
				newScrollBarView.Size = listView.Source.Count;
				Assert.Equal (newScrollBarView.Size, listView.Source.Count);
				newScrollBarView.Position = listView.TopItem;
				Assert.Equal (newScrollBarView.Position, listView.TopItem);
				newScrollBarView.Refresh ();
			};
			top.Ready += (s, e) => {
				newScrollBarView.Position = 45;
				Assert.Equal (newScrollBarView.Position, newScrollBarView.Size - listView.TopItem + (listView.TopItem - listView.Bounds.Height));
				Assert.Equal (newScrollBarView.Position, listView.TopItem);
				Assert.Equal (27, newScrollBarView.Position);
				Assert.Equal (27, listView.TopItem);
				Application.RequestStop ();
			};
			top.Add (win);
			Application.Run ();
			Application.Shutdown ();
		});

		Assert.Null (exception);
	}

	[Fact]
	public void Constructor_ShowBothScrollIndicator_False_And_IsVertical_False_Refresh_Does_Not_Throws_An_Object_Null_Exception ()
	{
		// BUGBUG: v2 - Tig broke these tests; @bdisp help?
		//var exception = Record.Exception (() => {
		Application.Init (new FakeDriver ());

		var top = Application.Top;

		var win = new Window {
			X = 0,
			Y = 0,
			Width = Dim.Fill (),
			Height = Dim.Fill ()
		};

		var source = new List<string> ();

		for (var i = 0; i < 50; i++) {
			var text = $"item {i} - ";
			for (var j = 0; j < 160; j++) {
				var col = j.ToString ();
				text += col.Length == 1 ? col [0] : col [1];
			}
			source.Add (text);
		}

		var listView = new ListView (source) {
			X = 0,
			Y = 0,
			Width = Dim.Fill (),
			Height = Dim.Fill ()
		};
		win.Add (listView);

		var newScrollBarView = new ScrollBarView (listView, false, false) {
			KeepContentAlwaysInViewport = true
		};
		win.Add (newScrollBarView);

		newScrollBarView.ChangedPosition += (s, e) => {
			listView.LeftItem = newScrollBarView.Position;
			if (listView.LeftItem != newScrollBarView.Position) {
				newScrollBarView.Position = listView.LeftItem;
			}
			Assert.Equal (newScrollBarView.Position, listView.LeftItem);
			listView.SetNeedsDisplay ();
		};

		listView.DrawContent += (s, e) => {
			newScrollBarView.Size = listView.Maxlength;
			Assert.Equal (newScrollBarView.Size, listView.Maxlength);
			newScrollBarView.Position = listView.LeftItem;
			Assert.Equal (newScrollBarView.Position, listView.LeftItem);
			newScrollBarView.Refresh ();
		};

		top.Ready += (s, e) => {
			newScrollBarView.Position = 100;
			//Assert.Equal (newScrollBarView.Position, newScrollBarView.Size - listView.LeftItem + (listView.LeftItem - listView.Bounds.Width));
			Assert.Equal (newScrollBarView.Position, listView.LeftItem);
			//Assert.Equal (92, newScrollBarView.Position);
			//Assert.Equal (92, listView.LeftItem);
			Application.RequestStop ();
		};

		top.Add (win);

		Application.Run ();

		Application.Shutdown ();
		//});

		//Assert.Null (exception);
	}

	[Fact]
	[AutoInitShutdown]
	public void Internal_Tests ()
	{
		var top = Application.Top;
		Assert.Equal (new Rect (0, 0, 80, 25), top.Bounds);
		var view = new View { Width = Dim.Fill (), Height = Dim.Fill () };
		top.Add (view);
		var sbv = new ScrollBarView (view, true);
		top.Add (sbv);
		Assert.Equal (view, sbv.Host);
		sbv.Size = 40;
		sbv.Position = 0;
		sbv.OtherScrollBarView.Size = 100;
		sbv.OtherScrollBarView.Position = 0;

		// Host bounds is not empty.
		Assert.True (sbv.CanScroll (10, out var max, sbv.IsVertical));
		Assert.Equal (10, max);
		Assert.True (sbv.OtherScrollBarView.CanScroll (10, out max, sbv.OtherScrollBarView.IsVertical));
		Assert.Equal (10, max);

		Application.Begin (top);

		// They are visible so they are drawn.
		Assert.True (sbv.Visible);
		Assert.True (sbv.OtherScrollBarView.Visible);
		top.LayoutSubviews ();
		// Now the host bounds is not empty.
		Assert.True (sbv.CanScroll (10, out max, sbv.IsVertical));
		Assert.Equal (10, max);
		Assert.True (sbv.OtherScrollBarView.CanScroll (10, out max, sbv.OtherScrollBarView.IsVertical));
		Assert.Equal (10, max);
		Assert.True (sbv.CanScroll (50, out max, sbv.IsVertical));
		Assert.Equal (40, sbv.Size);
		Assert.Equal (16, max); // 16+25=41
		Assert.True (sbv.OtherScrollBarView.CanScroll (150, out max, sbv.OtherScrollBarView.IsVertical));
		Assert.Equal (100, sbv.OtherScrollBarView.Size);
		Assert.Equal (21, max); // 21+80=101
		Assert.True (sbv.Visible);
		Assert.True (sbv.OtherScrollBarView.Visible);
		sbv.KeepContentAlwaysInViewport = false;
		sbv.OtherScrollBarView.KeepContentAlwaysInViewport = false;
		Assert.True (sbv.CanScroll (50, out max, sbv.IsVertical));
		Assert.Equal (39, max);
		Assert.True (sbv.OtherScrollBarView.CanScroll (150, out max, sbv.OtherScrollBarView.IsVertical));
		Assert.Equal (99, max);
		Assert.True (sbv.Visible);
		Assert.True (sbv.OtherScrollBarView.Visible);
	}

	[Fact]
	[AutoInitShutdown]
	public void Hosting_ShowBothScrollIndicator_Invisible ()
	{
		var textView = new TextView {
			Width = Dim.Fill (),
			Height = Dim.Fill (),
			Text = "This is the help text for the Second Step.\n\nPress the button to see a message box.\n\nEnter name too."
		};
		var win = new Window {
			Width = Dim.Fill (),
			Height = Dim.Fill ()
		};
		win.Add (textView);

		var scrollBar = new ScrollBarView (textView, true);

		scrollBar.ChangedPosition += (s, e) => {
			textView.TopRow = scrollBar.Position;
			if (textView.TopRow != scrollBar.Position) {
				scrollBar.Position = textView.TopRow;
			}
			textView.SetNeedsDisplay ();
		};

		scrollBar.OtherScrollBarView.ChangedPosition += (s, e) => {
			textView.LeftColumn = scrollBar.OtherScrollBarView.Position;
			if (textView.LeftColumn != scrollBar.OtherScrollBarView.Position) {
				scrollBar.OtherScrollBarView.Position = textView.LeftColumn;
			}
			textView.SetNeedsDisplay ();
		};

		scrollBar.VisibleChanged += (s, e) => {
			if (scrollBar.Visible && textView.RightOffset == 0) {
				textView.RightOffset = 1;
			} else if (!scrollBar.Visible && textView.RightOffset == 1) {
				textView.RightOffset = 0;
			}
		};

		scrollBar.OtherScrollBarView.VisibleChanged += (s, e) => {
			if (scrollBar.OtherScrollBarView.Visible && textView.BottomOffset == 0) {
				textView.BottomOffset = 1;
			} else if (!scrollBar.OtherScrollBarView.Visible && textView.BottomOffset == 1) {
				textView.BottomOffset = 0;
			}
		};

		textView.LayoutComplete += (s, e) => {
			scrollBar.Size = textView.Lines;
			scrollBar.Position = textView.TopRow;
			if (scrollBar.OtherScrollBarView != null) {
				scrollBar.OtherScrollBarView.Size = textView.Maxlength;
				scrollBar.OtherScrollBarView.Position = textView.LeftColumn;
			}
			scrollBar.LayoutSubviews ();
			scrollBar.Refresh ();
		};
		Application.Top.Add (win);

		Application.Begin (Application.Top);
		((FakeDriver)Application.Driver).SetBufferSize (45, 20);

		Assert.True (scrollBar.AutoHideScrollBars);
		Assert.False (scrollBar.ShowScrollIndicator);
		Assert.False (scrollBar.OtherScrollBarView.ShowScrollIndicator);
		Assert.Equal (5, textView.Lines);
		Assert.Equal (42, textView.Maxlength);
		Assert.Equal (0, textView.LeftColumn);
		Assert.Equal (0, scrollBar.Position);
		Assert.Equal (0, scrollBar.OtherScrollBarView.Position);
		var expected = @"
┌───────────────────────────────────────────┐
│This is the help text for the Second Step. │
│                                           │
│Press the button to see a message box.     │
│                                           │
│Enter name too.                            │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
│                                           │
└───────────────────────────────────────────┘
";

		var pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
		Assert.Equal (new Rect (0, 0, 45, 20), pos);

		textView.WordWrap = true;
		((FakeDriver)Application.Driver).SetBufferSize (26, 20);
		Application.Refresh ();

		Assert.True (textView.WordWrap);
		Assert.True (scrollBar.AutoHideScrollBars);
		Assert.Equal (7, textView.Lines);
		Assert.Equal (22, textView.Maxlength);
		Assert.Equal (0, textView.LeftColumn);
		Assert.Equal (0, scrollBar.Position);
		Assert.Equal (0, scrollBar.OtherScrollBarView.Position);
		expected = @"
┌────────────────────────┐
│This is the help text   │
│for the Second Step.    │
│                        │
│Press the button to     │
│see a message box.      │
│                        │
│Enter name too.         │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
│                        │
└────────────────────────┘
";

		pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
		Assert.Equal (new Rect (0, 0, 26, 20), pos);

		((FakeDriver)Application.Driver).SetBufferSize (10, 10);
		Application.Refresh ();

		Assert.True (textView.WordWrap);
		Assert.True (scrollBar.AutoHideScrollBars);
		Assert.Equal (20, textView.Lines);
		Assert.Equal (7, textView.Maxlength);
		Assert.Equal (0, textView.LeftColumn);
		Assert.Equal (0, scrollBar.Position);
		Assert.Equal (0, scrollBar.OtherScrollBarView.Position);
		Assert.True (scrollBar.ShowScrollIndicator);
		expected = @"
┌────────┐
│This   ▲│
│is the ┬│
│help   ││
│text   ┴│
│for    ░│
│the    ░│
│Second ░│
│Step.  ▼│
└────────┘
";

		pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
		Assert.Equal (new Rect (0, 0, 10, 10), pos);
	}

	[Fact]
	[AutoInitShutdown]
	public void ContentBottomRightCorner_Not_Redraw_If_Both_Size_Equal_To_Zero ()
	{
		var text = "This is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test";
		var label = new Label (text);
		Application.Top.Add (label);

		var sbv = new ScrollBarView (label, true) {
			Size = 100
		};
		sbv.OtherScrollBarView.Size = 100;
		Application.Begin (Application.Top);

		Assert.Equal (100, sbv.Size);
		Assert.Equal (100, sbv.OtherScrollBarView.Size);
		Assert.True (sbv.ShowScrollIndicator);
		Assert.True (sbv.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (sbv.Visible);
		Assert.True (sbv.OtherScrollBarView.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes▲
This is a tes┬
This is a tes┴
This is a tes░
This is a tes▼
◄├─┤░░░░░░░░► 
", output);

		sbv.Size = 0;
		sbv.OtherScrollBarView.Size = 0;
		Assert.Equal (0, sbv.Size);
		Assert.Equal (0, sbv.OtherScrollBarView.Size);
		Assert.False (sbv.ShowScrollIndicator);
		Assert.False (sbv.OtherScrollBarView.ShowScrollIndicator);
		Assert.False (sbv.Visible);
		Assert.False (sbv.OtherScrollBarView.Visible);
		Application.Top.Draw ();
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a test
This is a test
This is a test
This is a test
This is a test
This is a test
", output);

		sbv.Size = 50;
		sbv.OtherScrollBarView.Size = 50;
		Assert.Equal (50, sbv.Size);
		Assert.Equal (50, sbv.OtherScrollBarView.Size);
		Assert.True (sbv.ShowScrollIndicator);
		Assert.True (sbv.OtherScrollBarView.ShowScrollIndicator);
		Assert.True (sbv.Visible);
		Assert.True (sbv.OtherScrollBarView.Visible);
		Application.Top.Draw ();
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes▲
This is a tes┬
This is a tes┴
This is a tes░
This is a tes▼
◄├──┤░░░░░░░► 
", output);

	}

	[Fact]
	[AutoInitShutdown]
	public void ContentBottomRightCorner_Not_Redraw_If_One_Size_Equal_To_Zero ()
	{
		var text = "This is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test";
		var label = new Label (text);
		Application.Top.Add (label);

		var sbv = new ScrollBarView (label, true, false) {
			Size = 100
		};
		Application.Begin (Application.Top);

		Assert.Equal (100, sbv.Size);
		Assert.Null (sbv.OtherScrollBarView);
		Assert.True (sbv.ShowScrollIndicator);
		Assert.True (sbv.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes▲
This is a tes┬
This is a tes┴
This is a tes░
This is a tes░
This is a tes▼
", output);

		sbv.Size = 0;
		Assert.Equal (0, sbv.Size);
		Assert.False (sbv.ShowScrollIndicator);
		Assert.False (sbv.Visible);
		Application.Top.Draw ();
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a test
This is a test
This is a test
This is a test
This is a test
This is a test
", output);
	}

	[Fact]
	[AutoInitShutdown]
	public void ShowScrollIndicator_False_Must_Also_Set_Visible_To_False_To_Not_Respond_To_Events ()
	{
		var clicked = false;
		var text = "This is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test";
		var label = new Label (text) { Width = 14, Height = 5 };
		var btn = new Button (14, 0, "Click Me!");
		btn.Clicked += (s, e) => clicked = true;
		Application.Top.Add (label, btn);

		var sbv = new ScrollBarView (label, true, false) {
			Size = 5
		};
		Application.Begin (Application.Top);

		Assert.Equal (5, sbv.Size);
		Assert.Null (sbv.OtherScrollBarView);
		Assert.False (sbv.ShowScrollIndicator);
		Assert.False (sbv.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@$"
This is a test{CM.Glyphs.LeftBracket} Click Me! {CM.Glyphs.RightBracket}
This is a test             
This is a test             
This is a test             
This is a test             ", output);

		Application.OnMouseEvent (new MouseEventEventArgs (new MouseEvent {
			X = 15,
			Y = 0,
			Flags = MouseFlags.Button1Clicked
		}));

		Assert.Null (Application.MouseGrabView);
		Assert.True (clicked);

		clicked = false;

		sbv.Visible = true;
		Assert.Equal (5, sbv.Size);
		Assert.False (sbv.ShowScrollIndicator);
		Assert.True (sbv.Visible);
		Application.Top.Draw ();
		Assert.False (sbv.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@$"
This is a test{CM.Glyphs.LeftBracket} Click Me! {CM.Glyphs.RightBracket}
This is a test             
This is a test             
This is a test             
This is a test             ", output);

		Application.OnMouseEvent (new MouseEventEventArgs (new MouseEvent {
			X = 15,
			Y = 0,
			Flags = MouseFlags.Button1Clicked
		}));

		Assert.Null (Application.MouseGrabView);
		Assert.True (clicked);
		Assert.Equal (5, sbv.Size);
		Assert.False (sbv.ShowScrollIndicator);
		Assert.False (sbv.Visible);
	}

	[Fact]
	[AutoInitShutdown]
	public void ClearOnVisibleFalse_Gets_Sets ()
	{
		var text = "This is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test\nThis is a test";
		var label = new Label (text);
		Application.Top.Add (label);

		var sbv = new ScrollBarView (label, true, false) {
			Size = 100,
			ClearOnVisibleFalse = false
		};
		Application.Begin (Application.Top);

		Assert.True (sbv.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes▲
This is a tes┬
This is a tes┴
This is a tes░
This is a tes░
This is a tes▼
", output);

		sbv.Visible = false;
		Assert.False (sbv.Visible);
		Application.Top.Draw ();
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a test
This is a test
This is a test
This is a test
This is a test
This is a test
", output);

		sbv.Visible = true;
		Assert.True (sbv.Visible);
		Application.Top.Draw ();
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes▲
This is a tes┬
This is a tes┴
This is a tes░
This is a tes░
This is a tes▼
", output);

		sbv.ClearOnVisibleFalse = true;
		sbv.Visible = false;
		Assert.False (sbv.Visible);
		TestHelpers.AssertDriverContentsWithFrameAre (@"
This is a tes
This is a tes
This is a tes
This is a tes
This is a tes
This is a tes
", output);
	}

	// This class enables test functions annotated with the [InitShutdown] attribute
	// to have a function called before the test function is called and after.
	// 
	// This is necessary because a) Application is a singleton and Init/Shutdown must be called
	// as a pair, and b) all unit test functions should be atomic.
	[AttributeUsage (AttributeTargets.Class | AttributeTargets.Method)]
	public class ScrollBarAutoInitShutdownAttribute : AutoInitShutdownAttribute {
		public override void Before (MethodInfo methodUnderTest)
		{
			base.Before (methodUnderTest);

			_hostView = new HostView {
				Width = Dim.Fill (),
				Height = Dim.Fill (),
				Top = 0,
				Lines = 30,
				Left = 0,
				Cols = 100
			};

			Application.Top.Add (_hostView);
		}

		public override void After (MethodInfo methodUnderTest)
		{
			_hostView = null;
			base.After (methodUnderTest);
		}
	}

	public class HostView : View {
		public int Top { get; set; }

		public int Lines { get; set; }

		public int Left { get; set; }

		public int Cols { get; set; }
	}
}