convert the leaderboard form as well

Author: Morilli

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevos.cs

@@ -200,7 +200,7 @@ private void BuildMenu(ToolStripItemCollection raDropDownItems)
 			var viewLboardListItem = new ToolStripMenuItem("View Leaderboard List");
 			viewLboardListItem.Click += (_, _) =>
 			{
-				_lboardListForm.OnFrameAdvance(true);
+				_lboardListForm.OnFrameAdvance();
 				_lboardListForm.Show();
 			};
 			raDropDownItems.Add(viewLboardListItem);

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevosAchievementListForm.cs

@@ -11,7 +11,7 @@ namespace BizHawk.Client.EmuHawk
 	public partial class RCheevosAchievementListForm : Form
 	{
 		private RCheevos.Cheevo[] _cheevos;
-		private RCheevosAchievementForm[] _cheevoForms;
+		private RCheevosAchievementForm[] _cheevoForms = [ ];
 		private Func<uint, string> _getCheevoProgress;
 		private Func<bool> _isHardcodeMode;
 
@@ -21,7 +21,6 @@ public RCheevosAchievementListForm()
 		{
 			InitializeComponent();
 			FormClosing += RCheevosAchievementListForm_FormClosing;
-			_cheevoForms = Array.Empty<RCheevosAchievementForm>();
 			using var temp = new RCheevosAchievementForm(null);
 			_controlHeight = temp.Height + temp.Margin.Bottom + temp.Margin.Top;
 			flowLayoutPanel1.BoundScrollBar = vScrollBar1;

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevosLeaderboardForm.cs

@@ -7,18 +7,32 @@ namespace BizHawk.Client.EmuHawk
 	/// </summary>
 	public partial class RCheevosLeaderboardForm : Form
 	{
-		private readonly RCheevos.LBoard _lboard;
+		private RCheevos.LBoard _lboard;
 
-		public RCheevosLeaderboardForm(RCheevos.LBoard lboard)
+		public RCheevosLeaderboardForm()
 		{
 			InitializeComponent();
+			TopLevel = false;
+			Show();
+		}
+
+		public bool UpdateLBoard(RCheevos.LBoard lboard)
+		{
+			bool updated = _lboard != lboard;
+
+			_lboard = lboard;
+
 			titleBox.Text = lboard.Title;
 			descriptionBox.Text = lboard.Description;
-			scoreBox.Text = lboard.Score;
 			lowerIsBetterBox.Checked = lboard.LowerIsBetter;
-			_lboard = lboard;
-			TopLevel = false;
-			Show();
+
+			if (scoreBox.Text != _lboard.Score)
+			{
+				scoreBox.Text = _lboard.Score;
+				updated = true;
+			}
+
+			return updated;
 		}
 
 		public void OnFrameAdvance()

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevosLeaderboardListForm.Designer.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using System.Windows.Forms;
 
@@ -9,18 +10,18 @@ namespace BizHawk.Client.EmuHawk
 	/// </summary>
 	public partial class RCheevosLeaderboardListForm : Form
 	{
-		public bool IsShown { get; private set; }
+		private RCheevos.LBoard[] _lboards;
+		private RCheevosLeaderboardForm[] _lboardForms = [ ];
 
-		private RCheevosLeaderboardForm[] _lboardForms;
-		private int _updateCooldown;
+		private readonly int _controlHeight;
 
 		public RCheevosLeaderboardListForm()
 		{
 			InitializeComponent();
 			FormClosing += RCheevosLeaderboardListForm_FormClosing;
-			Shown += (_, _) => IsShown = true;
-			_lboardForms = Array.Empty<RCheevosLeaderboardForm>();
-			_updateCooldown = 5; // only update every 5 frames / 12 fps (as this is rather expensive to update)
+			using var temp = new RCheevosLeaderboardForm();
+			_controlHeight = temp.Height + temp.Margin.Bottom + temp.Margin.Top;
+			flowLayoutPanel1.BoundScrollBar = vScrollBar1;
 		}
 
 		private void DisposeLboardForms()
@@ -33,16 +34,17 @@ private void DisposeLboardForms()
 
 		public void Restart(IEnumerable<RCheevos.LBoard> lboards)
 		{
+			_lboards = lboards.ToArray();
 			flowLayoutPanel1.Controls.Clear();
-			DisposeLboardForms();
-			_lboardForms = lboards.Select(lboard => new RCheevosLeaderboardForm(lboard)).ToArray();
-			flowLayoutPanel1.Controls.AddRange(_lboardForms);
+
+			RCheevosLeaderboardListForm_SizeChanged(this, EventArgs.Empty);
+			vScrollBar1.Value = 0;
+			vScrollBar1.Maximum = _controlHeight * _lboards.Length;
+
 		}
 
-		public void OnFrameAdvance(bool forceUpdate = false)
+		public void OnFrameAdvance()
 		{
-			if (--_updateCooldown > 0 && !forceUpdate) return;
-			_updateCooldown = 5;
 			foreach (var lb in _lboardForms)
 			{
 				lb.OnFrameAdvance();
@@ -53,7 +55,55 @@ private void RCheevosLeaderboardListForm_FormClosing(object sender, FormClosingE
 		{
 			Hide();
 			e.Cancel = true;
-			IsShown = false;
+		}
+
+		private void UpdateForms()
+		{
+			int firstIndex = vScrollBar1.Value / _controlHeight;
+			int indexOffset = vScrollBar1.Value % _controlHeight;
+			while (firstIndex > _lboards.Length - _lboardForms.Length)
+			{
+				firstIndex--;
+				indexOffset += _controlHeight;
+			}
+			flowLayoutPanel1.SuspendDrawing();
+			flowLayoutPanel1.SuspendLayout();
+			bool refresh = flowLayoutPanel1.AutoScrollPosition.Y != -indexOffset;
+			for (int i = 0; i < _lboardForms.Length; i++)
+			{
+				refresh |= _lboardForms[i].UpdateLBoard(_lboards[firstIndex + i]);
+			}
+			flowLayoutPanel1.AutoScrollPosition = new Point(0, indexOffset);
+			flowLayoutPanel1.ResumeLayout();
+			flowLayoutPanel1.ResumeDrawing();
+			if (refresh)
+			{
+				Refresh();
+			}
+		}
+
+		private void vScrollBar1_ValueChanged(object sender, EventArgs e) => UpdateForms();
+
+		private int DisplayedItems()
+		{
+			return Math.Min((int) Math.Ceiling((double) flowLayoutPanel1.Height / _controlHeight) + 1, _lboards.Length);
+		}
+
+		private void RCheevosLeaderboardListForm_SizeChanged(object sender, EventArgs e)
+		{
+			if (flowLayoutPanel1.Controls.Count != DisplayedItems())
+			{
+				flowLayoutPanel1.Controls.Clear();
+				DisposeLboardForms();
+				_lboardForms = new RCheevosLeaderboardForm[DisplayedItems()];
+				for (int i = 0; i < DisplayedItems(); i++)
+				{
+					_lboardForms[i] = new RCheevosLeaderboardForm();
+				}
+				flowLayoutPanel1.Controls.AddRange(_lboardForms);
+			}
+
+			UpdateForms();
 		}
 	}
 }

src/BizHawk.Client.EmuHawk/RetroAchievements/RCheevosLeaderboardListForm.cs

@@ -1,4 +1,5 @@
-using System.Windows.Forms;
+using System.ComponentModel;
+using System.Windows.Forms;
 
 using BizHawk.Common.NumberExtensions;
 
@@ -7,6 +8,8 @@ namespace BizHawk.Client.EmuHawk;
 public class VirtualizedFlowLayoutPanel : FlowLayoutPanel
 {
 	private VScrollBar? _boundScrollBar;
+	[Browsable(false)]
+	[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
 	public VScrollBar BoundScrollBar
 	{
 		get => _boundScrollBar!;