Updated graphics renderer to allow for pixel perfect resizing

Desktop/Form1.Designer.cs

@@ -28,7 +28,6 @@
         /// </summary>
         private void InitializeComponent()
         {
-            picScreen = new PictureBox();
             menuStrip1 = new MenuStrip();
             fileToolStripMenuItem = new ToolStripMenuItem();
             openToolStripMenuItem = new ToolStripMenuItem();
@@ -44,20 +43,9 @@
             resetToolStripMenuItem1 = new ToolStripMenuItem();
             optionsToolStripMenuItem = new ToolStripMenuItem();
             HighSpeedToolStripMenuItem = new ToolStripMenuItem();
-            ((System.ComponentModel.ISupportInitialize)picScreen).BeginInit();
             menuStrip1.SuspendLayout();
             SuspendLayout();
             // 
-            // picScreen
-            // 
-            picScreen.BackColor = Color.Black;
-            picScreen.Location = new Point(10, 26);
-            picScreen.Name = "picScreen";
-            picScreen.Size = new Size(720, 576);
-            picScreen.SizeMode = PictureBoxSizeMode.Zoom;
-            picScreen.TabIndex = 0;
-            picScreen.TabStop = false;
-            // 
             // menuStrip1
             // 
             menuStrip1.ImageScalingSize = new Size(24, 24);
@@ -163,7 +151,7 @@
             // HighSpeedToolStripMenuItem
             // 
             HighSpeedToolStripMenuItem.Name = "HighSpeedToolStripMenuItem";
-            HighSpeedToolStripMenuItem.Size = new Size(224, 26);
+            HighSpeedToolStripMenuItem.Size = new Size(170, 26);
             HighSpeedToolStripMenuItem.Text = "High Speed";
             HighSpeedToolStripMenuItem.Click += btnHighSpeedToggle_Click;
             // 
@@ -172,13 +160,11 @@
             AutoScaleDimensions = new SizeF(8F, 20F);
             AutoScaleMode = AutoScaleMode.Font;
             ClientSize = new Size(738, 608);
-            Controls.Add(picScreen);
             Controls.Add(menuStrip1);
             KeyPreview = true;
             MainMenuStrip = menuStrip1;
             Name = "Form1";
             Text = "Parsons Sinclair ZX Spectrum 48K - 2026";
-            ((System.ComponentModel.ISupportInitialize)picScreen).EndInit();
             menuStrip1.ResumeLayout(false);
             menuStrip1.PerformLayout();
             ResumeLayout(false);
@@ -186,8 +172,6 @@
         }
 
         #endregion
-
-        private PictureBox picScreen;
         private MenuStrip menuStrip1;
         private ToolStripMenuItem fileToolStripMenuItem;
         private ToolStripMenuItem openToolStripMenuItem;

Desktop/Form1.cs

@@ -18,6 +18,7 @@ namespace Desktop
         private TapManager _tapManager = null!;
         private DebuggerForm? _debugger = null;
         private BeeperDevice _beeper = null!;
+        private Bitmap _screenBitmap = null!;
         private string _baseTitle = "";
         private bool _isRunning = false;
         private bool _isPaused = false;
@@ -34,6 +35,8 @@ namespace Desktop
         public Form1()
         {
             InitializeComponent();
+            this.DoubleBuffered = true;
+            this.ResizeRedraw = true;
             InitializeEmulator();
         }
 
@@ -173,7 +176,10 @@ namespace Desktop
                                     {
                                         this.BeginInvoke((MethodInvoker)delegate
                                         {
-                                            UpdateScreenBitmap();
+                                            UpdateScreenBitmap(); // Your existing method that writes the ULA data to _screenBitmap
+
+                                            this.Invalidate(); // Tells Windows: "The bitmap changed, please run OnPaint()!"
+
                                             this.Text = $"{_baseTitle} - FPS: {FramesPerSecond:F1}";
                                         });
                                     }
@@ -181,10 +187,13 @@ namespace Desktop
                                 }
                                 else
                                 {
-                                    this.Invoke((MethodInvoker)delegate
+                                    this.BeginInvoke((MethodInvoker)delegate
                                     {
-                                        UpdateScreenBitmap();
+                                        UpdateScreenBitmap(); // Your existing method that writes the ULA data to _screenBitmap
-                                        this.Text = $"{_baseTitle} - FPS: {FramesPerSecond:F1} - Tape Loaded: {tapeLoaded.ToString()}";
+
+                                        this.Invalidate(); // Tells Windows: "The bitmap changed, please run OnPaint()!"
+
+                                        this.Text = $"{_baseTitle} - FPS: {FramesPerSecond:F1}";
                                     });
                                 }
 
@@ -225,6 +234,40 @@ namespace Desktop
             });
         }
 
+        protected override void OnPaint(PaintEventArgs e)
+        {
+            base.OnPaint(e);
+
+            // If we don't have a screen bitmap yet, just paint the background black and exit
+            if (_screenBitmap == null)
+            {
+                e.Graphics.Clear(Color.Black);
+                return;
+            }
+
+            // 1. Calculate the scaling factor to fit the window while preserving aspect ratio
+            float scaleX = (float)this.ClientSize.Width / _screenBitmap.Width;
+            float scaleY = (float)this.ClientSize.Height / _screenBitmap.Height;
+            float scale = Math.Min(scaleX, scaleY); // Pick the smallest scale so it fits inside
+
+            int newWidth = (int)(_screenBitmap.Width * scale);
+            int newHeight = (int)(_screenBitmap.Height * scale);
+
+            // 2. Center the image horizontally and vertically (Pillarboxing/Letterboxing)
+            int posX = (this.ClientSize.Width - newWidth) / 2;
+            int posY = (this.ClientSize.Height - newHeight) / 2;
+
+            // 3. RETRO MAGIC: Force Nearest-Neighbor interpolation for razor-sharp pixels!
+            e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.NearestNeighbor;
+
+            // PixelOffsetMode.Half is a GDI+ trick required to make NearestNeighbor perfectly accurate
+            e.Graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.Half;
+
+            // 4. Paint the black borders (if any) and draw the screen
+            e.Graphics.Clear(Color.Black);
+            e.Graphics.DrawImage(_screenBitmap, posX, posY, newWidth, newHeight);
+        }
+
         private void HandleInstantTapeLoad()
         {
             byte[] block = _tapManager.GetNextBlock(); // Your original Queue.Dequeue() method
@@ -271,7 +314,7 @@ namespace Desktop
             _cpu.SP++;
             _cpu.PC = (ushort)((pcHigh << 8) | pcLow);
         }
-        
+
 
         private void UpdateScreenBitmap()
         {
@@ -286,8 +329,14 @@ namespace Desktop
             Marshal.Copy(_ula.FrameBuffer, 0, bmpData.Scan0, _ula.FrameBuffer.Length);
             bmp.UnlockBits(bmpData);
 
-            if (picScreen.Image != null) picScreen.Image.Dispose();
+            // Dispose of the old frame to prevent massive RAM leaks!
-            picScreen.Image = bmp;
+            if (_screenBitmap != null)
+            {
+                _screenBitmap.Dispose();
+            }
+
+            // Save the new frame so OnPaint() can draw it
+            _screenBitmap = bmp;
         }
 
         private void loadTAPToolStripMenuItem_Click(object sender, EventArgs e)