feat(ui): improve BestFitViewerForm navigation and reduce flicker

Add third row (5x3 grid, 15 items/page), remove 50-result cap so all
candidates are pageable, start maximized, replace page label with
editable textbox for direct page entry, center nav controls, and
eliminate flicker on page change via DoubleBuffered + WM_SETREDRAW.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest/Forms/BestFitViewerForm.Designer.cs

@@ -17,7 +17,8 @@ namespace OpenNest.Forms
             this.navPanel = new System.Windows.Forms.Panel();
             this.btnPrev = new System.Windows.Forms.Button();
             this.btnNext = new System.Windows.Forms.Button();
-            this.lblPage = new System.Windows.Forms.Label();
+            this.txtPage = new System.Windows.Forms.TextBox();
+            this.lblPageCount = new System.Windows.Forms.Label();
             this.navPanel.SuspendLayout();
             this.SuspendLayout();
             //
@@ -32,16 +33,18 @@ namespace OpenNest.Forms
             this.gridPanel.Dock = System.Windows.Forms.DockStyle.Fill;
             this.gridPanel.Location = new System.Drawing.Point(0, 0);
             this.gridPanel.Name = "gridPanel";
-            this.gridPanel.RowCount = 2;
+            this.gridPanel.RowCount = 3;
-            this.gridPanel.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 50F));
+            this.gridPanel.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.33F));
-            this.gridPanel.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 50F));
+            this.gridPanel.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.34F));
+            this.gridPanel.RowStyles.Add(new System.Windows.Forms.RowStyle(System.Windows.Forms.SizeType.Percent, 33.33F));
             this.gridPanel.Size = new System.Drawing.Size(1200, 764);
             this.gridPanel.TabIndex = 0;
             //
             // navPanel
             //
             this.navPanel.Controls.Add(this.btnPrev);
-            this.navPanel.Controls.Add(this.lblPage);
+            this.navPanel.Controls.Add(this.txtPage);
+            this.navPanel.Controls.Add(this.lblPageCount);
             this.navPanel.Controls.Add(this.btnNext);
             this.navPanel.Dock = System.Windows.Forms.DockStyle.Bottom;
             this.navPanel.Location = new System.Drawing.Point(0, 764);
@@ -51,31 +54,44 @@ namespace OpenNest.Forms
             //
             // btnPrev
             //
+            this.btnPrev.Anchor = System.Windows.Forms.AnchorStyles.Top;
             this.btnPrev.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
-            this.btnPrev.Location = new System.Drawing.Point(4, 4);
+            this.btnPrev.Location = new System.Drawing.Point(480, 4);
             this.btnPrev.Name = "btnPrev";
             this.btnPrev.Size = new System.Drawing.Size(80, 28);
             this.btnPrev.TabIndex = 0;
             this.btnPrev.Text = "<  Prev";
             this.btnPrev.Click += new System.EventHandler(this.btnPrev_Click);
             //
-            // lblPage
+            // txtPage
             //
-            this.lblPage.Dock = System.Windows.Forms.DockStyle.Fill;
+            this.txtPage.Anchor = System.Windows.Forms.AnchorStyles.Top;
-            this.lblPage.Name = "lblPage";
+            this.txtPage.Location = new System.Drawing.Point(564, 7);
-            this.lblPage.Size = new System.Drawing.Size(1200, 36);
+            this.txtPage.Name = "txtPage";
-            this.lblPage.TabIndex = 1;
+            this.txtPage.Size = new System.Drawing.Size(40, 20);
-            this.lblPage.Text = "Page 1 / 1";
+            this.txtPage.TabIndex = 1;
-            this.lblPage.TextAlign = System.Drawing.ContentAlignment.MiddleCenter;
+            this.txtPage.Text = "1";
+            this.txtPage.TextAlign = System.Windows.Forms.HorizontalAlignment.Center;
+            this.txtPage.KeyDown += new System.Windows.Forms.KeyEventHandler(this.txtPage_KeyDown);
+            //
+            // lblPageCount
+            //
+            this.lblPageCount.Anchor = System.Windows.Forms.AnchorStyles.Top;
+            this.lblPageCount.Location = new System.Drawing.Point(606, 4);
+            this.lblPageCount.Name = "lblPageCount";
+            this.lblPageCount.Size = new System.Drawing.Size(50, 28);
+            this.lblPageCount.TabIndex = 2;
+            this.lblPageCount.Text = "/ 1";
+            this.lblPageCount.TextAlign = System.Drawing.ContentAlignment.MiddleLeft;
             //
             // btnNext
             //
-            this.btnNext.Anchor = System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Right;
+            this.btnNext.Anchor = System.Windows.Forms.AnchorStyles.Top;
             this.btnNext.FlatStyle = System.Windows.Forms.FlatStyle.Flat;
-            this.btnNext.Location = new System.Drawing.Point(1116, 4);
+            this.btnNext.Location = new System.Drawing.Point(660, 4);
             this.btnNext.Name = "btnNext";
             this.btnNext.Size = new System.Drawing.Size(80, 28);
-            this.btnNext.TabIndex = 2;
+            this.btnNext.TabIndex = 3;
             this.btnNext.Text = "Next  >";
             this.btnNext.Click += new System.EventHandler(this.btnNext_Click);
             //
@@ -90,7 +106,9 @@ namespace OpenNest.Forms
             this.Name = "BestFitViewerForm";
             this.StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
             this.Text = "Best-Fit Viewer";
+            this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
             this.navPanel.ResumeLayout(false);
+            this.navPanel.PerformLayout();
             this.ResumeLayout(false);
         }
 
@@ -98,6 +116,7 @@ namespace OpenNest.Forms
         private System.Windows.Forms.Panel navPanel;
         private System.Windows.Forms.Button btnPrev;
         private System.Windows.Forms.Button btnNext;
-        private System.Windows.Forms.Label lblPage;
+        private System.Windows.Forms.TextBox txtPage;
+        private System.Windows.Forms.Label lblPageCount;
     }
 }

OpenNest/Forms/BestFitViewerForm.cs

@@ -1,18 +1,24 @@
 using OpenNest.Controls;
 using OpenNest.Engine.BestFit;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Drawing;
+using System.Runtime.InteropServices;
 using System.Windows.Forms;
 
 namespace OpenNest.Forms
 {
     public partial class BestFitViewerForm : Form
     {
+        private const int WM_SETREDRAW = 0x000B;
+
+        [DllImport("user32.dll")]
+        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
+
         private const int Columns = 5;
-        private const int Rows = 2;
+        private const int Rows = 3;
         private const int ItemsPerPage = Columns * Rows;
-        private const int MaxResults = 50;
 
         private static readonly Color KeptColor = Color.FromArgb(0, 0, 100);
         private static readonly Color DroppedColor = Color.FromArgb(100, 0, 0);
@@ -34,6 +40,7 @@ namespace OpenNest.Forms
         {
             this.drawing = drawing;
             this.plate = plate;
+            DoubleBuffered = true;
             InitializeComponent();
             Shown += BestFitViewerForm_Shown;
         }
@@ -88,9 +95,8 @@ namespace OpenNest.Forms
                 if (r.Keep) keptCount++;
             }
 
-            var count = System.Math.Min(totalResults, MaxResults);
+            results = all;
-            results = all.GetRange(0, count);
+            pageCount = System.Math.Max(1, (int)System.Math.Ceiling(results.Count / (double)ItemsPerPage));
-            pageCount = System.Math.Max(1, (int)System.Math.Ceiling(count / (double)ItemsPerPage));
 
             sw.Stop();
             totalSeconds = sw.Elapsed.TotalSeconds;
@@ -102,6 +108,9 @@ namespace OpenNest.Forms
             var start = page * ItemsPerPage;
             var count = System.Math.Min(ItemsPerPage, results.Count - start);
 
+            SendMessage(gridPanel.Handle, WM_SETREDRAW, IntPtr.Zero, IntPtr.Zero);
+            try
+            {
                 gridPanel.SuspendLayout();
                 gridPanel.Controls.Clear();
 
@@ -118,10 +127,17 @@ namespace OpenNest.Forms
                 }
 
                 gridPanel.ResumeLayout(true);
+            }
+            finally
+            {
+                SendMessage(gridPanel.Handle, WM_SETREDRAW, (IntPtr)1, IntPtr.Zero);
+                gridPanel.Invalidate(true);
+            }
 
             btnPrev.Enabled = currentPage > 0;
             btnNext.Enabled = currentPage < pageCount - 1;
-            lblPage.Text = string.Format("Page {0} / {1}", currentPage + 1, pageCount);
+            txtPage.Text = (currentPage + 1).ToString();
+            lblPageCount.Text = string.Format("/ {0}", pageCount);
 
             Text = string.Format("Best-Fit Viewer — {0} candidates ({1} kept) | Compute: {2:F1}s | Total: {3:F1}s | Showing {4}-{5} of {6}",
                 totalResults, keptCount, computeSeconds, totalSeconds,
@@ -139,6 +155,18 @@ namespace OpenNest.Forms
                 ShowPage(newPage);
         }
 
+        private void txtPage_KeyDown(object sender, KeyEventArgs e)
+        {
+            if (e.KeyCode == Keys.Enter)
+            {
+                e.SuppressKeyPress = true;
+                if (int.TryParse(txtPage.Text, out var page) && page >= 1 && page <= pageCount)
+                    ShowPage(page - 1);
+                else
+                    txtPage.Text = (currentPage + 1).ToString();
+            }
+        }
+
         private BestFitCell CreateCell(BestFitResult result, Drawing drawing, int rank)
         {
             var bgColor = result.Keep ? KeptColor : DroppedColor;