Implemenmted rendering priorities

Core/Video/SmsVdp.cs

@@ -9,6 +9,7 @@ namespace Core.Video
         public byte[] CRAM { get; private set; } = new byte[0x20];   // 32 Bytes Color Palette
         public byte[] Registers { get; private set; } = new byte[16]; // 11 Hardware Control Registers
         public int[] FrameBuffer { get; private set; } = new int[256 * 192];
+        private bool[] _priorityBuffer = new bool[256 * 192]; // Tracks priority pixels!
 
         // The Control Port State Machine (Port 0xBF)
         private bool _isSecondControlByte = false;
@@ -131,18 +132,19 @@ namespace Core.Video
         private void RenderBackground()
         {
             ushort nameTableBase = (ushort)((Registers[2] & 0x0E) << 10);
-
             byte scrollX = Registers[8];
             byte scrollY = Registers[9];
 
-            bool lockRowScroll = (Registers[0] & 0x80) != 0; // Top 2 rows (Y < 16)
+            bool lockRowScroll = (Registers[0] & 0x80) != 0;
-            bool lockColScroll = (Registers[0] & 0x40) != 0; // Right 8 columns (X >= 192)
+            bool lockColScroll = (Registers[0] & 0x40) != 0;
+
+            // Clear the priority mask for the new frame!
+            Array.Clear(_priorityBuffer, 0, _priorityBuffer.Length);
 
             for (int screenY = 0; screenY < 192; screenY++)
             {
                 for (int screenX = 0; screenX < 256; screenX++)
                 {
-                    // Apply Vertical Scrolling (Depends on X for column locking!)
                     int effectiveScrollY = scrollY;
                     if (lockColScroll && screenX >= 192) effectiveScrollY = 0;
 
@@ -150,7 +152,6 @@ namespace Core.Video
                     int row = vdpY / 8;
                     int tileY = vdpY % 8;
 
-                    // Apply Horizontal Scrolling (Depends on Y for row locking!)
                     int effectiveScrollX = scrollX;
                     if (lockRowScroll && screenY < 16) effectiveScrollX = 0;
 
@@ -158,31 +159,34 @@ namespace Core.Video
                     int col = vdpX / 8;
                     int tileX = vdpX % 8;
 
-                    // 1. Read the 16-bit Tile instruction from the Name Table
+                    // 1. Read the 16-bit Tile instruction
                     ushort nameTableAddr = (ushort)(nameTableBase + (row * 64) + (col * 2));
                     byte lowByte = VRAM[nameTableAddr];
                     byte highByte = VRAM[nameTableAddr + 1];
                     ushort tileData = (ushort)((highByte << 8) | lowByte);
 
-                    // 2. Extract Tile Index and Palette Info
+                    // 2. EXTRACT ALL THE HARDWARE BITS!
                     int tileIndex = tileData & 0x01FF;
-                    bool useSpritePalette = (tileData & 0x0800) != 0;
+                    bool flipH = (tileData & 0x0200) != 0;          // Bit 9
+                    bool flipV = (tileData & 0x0400) != 0;          // Bit 10
+                    bool useSpritePalette = (tileData & 0x0800) != 0; // Bit 11
+                    bool priority = (tileData & 0x1000) != 0;       // Bit 12
 
-                    // 3. Find the tile data in VRAM
+                    // 3. Apply Vertical Flip (Read from the bottom of the tile instead of the top)
+                    int readY = flipV ? (7 - tileY) : tileY;
                     ushort tileAddress = (ushort)(tileIndex * 32);
 
-                    // 4. Fetch the 4 bitplanes
+                    byte bp0 = VRAM[tileAddress + (readY * 4) + 0];
-                    byte bp0 = VRAM[tileAddress + (tileY * 4) + 0];
+                    byte bp1 = VRAM[tileAddress + (readY * 4) + 1];
-                    byte bp1 = VRAM[tileAddress + (tileY * 4) + 1];
+                    byte bp2 = VRAM[tileAddress + (readY * 4) + 2];
-                    byte bp2 = VRAM[tileAddress + (tileY * 4) + 2];
+                    byte bp3 = VRAM[tileAddress + (readY * 4) + 3];
-                    byte bp3 = VRAM[tileAddress + (tileY * 4) + 3];
 
-                    // 5. Extract color index
+                    // 4. Apply Horizontal Flip (Shift from right-to-left instead of left-to-right)
-                    int shift = 7 - tileX;
+                    int readX = flipH ? tileX : (7 - tileX);
-                    int colorIndex = ((bp0 >> shift) & 1) |
+                    int colorIndex = ((bp0 >> readX) & 1) |
-                                     (((bp1 >> shift) & 1) << 1) |
+                                     (((bp1 >> readX) & 1) << 1) |
-                                     (((bp2 >> shift) & 1) << 2) |
+                                     (((bp2 >> readX) & 1) << 2) |
-                                     (((bp3 >> shift) & 1) << 3);
+                                     (((bp3 >> readX) & 1) << 3);
 
                     int paletteOffset = useSpritePalette ? 16 : 0;
                     byte smsColor = CRAM[paletteOffset + colorIndex];
@@ -191,7 +195,16 @@ namespace Core.Video
                     int g = ((smsColor >> 2) & 0x03) * 85;
                     int b = ((smsColor >> 4) & 0x03) * 85;
 
-                    FrameBuffer[(screenY * 256) + screenX] = (255 << 24) | (r << 16) | (g << 8) | b;
+                    int screenAddress = (screenY * 256) + screenX;
+                    FrameBuffer[screenAddress] = (255 << 24) | (r << 16) | (g << 8) | b;
+
+                    // 5. FLAG THE PRIORITY PIXEL!
+                    // If this tile has priority AND the pixel isn't transparent (color 0), 
+                    // tell the sprite renderer not to draw over it!
+                    if (priority && colorIndex != 0)
+                    {
+                        _priorityBuffer[screenAddress] = true;
+                    }
                 }
             }
         }
@@ -262,6 +275,9 @@ namespace Core.Video
                         // If the color index is 0, DO NOT draw it! Let the background show through.
                         if (colorIndex == 0) continue;
 
+                        // If the background tile at this exact pixel claimed priority, hide the sprite!
+                        if (_priorityBuffer[(screenY * 256) + screenX]) continue;
+
                         // Sprites ALWAYS use the second half of CRAM (Palette 1: Indices 16-31)
                         byte smsColor = CRAM[16 + colorIndex];
 

Desktop/DebuggerForm.cs

@@ -10,9 +10,9 @@ namespace Desktop
     {
         private readonly Z80 _cpu;
         private readonly SmsMemoryBus _memoryBus;
-        private readonly Form1 _mainForm;
+        private readonly ParsonsForm1 _mainForm;
 
-        public DebuggerForm(Z80 cpu, SmsMemoryBus memoryBus, Form1 mainForm)
+        public DebuggerForm(Z80 cpu, SmsMemoryBus memoryBus, ParsonsForm1 mainForm)
         {
             InitializeComponent();
             _cpu = cpu;
@@ -103,9 +103,9 @@ namespace Desktop
             lblIE.Text = $"Interrupt Mode: {_cpu.InterruptMode}";
             lblFlags.Text = $"Flags: {_cpu.GetFlagsString()}";
             lblTStates.Text = $"T-States: {_cpu.TotalTStates}";
-            //lblFrames.Text = $"Frames Rendered: {_mainForm.TotalFrameCount}";
+            lblFrames.Text = $"Frames Rendered: {_mainForm.TotalFrameCount}";
-            //lblFrameTime.Text = $"Frame Time: {((float)_mainForm.FrameTime):F1}ms";
+            lblFrameTime.Text = $"Frame Time: {((float)_mainForm.FrameTime):F1}ms";
-            //lblFPS.Text = $"FPS: {_mainForm.FramesPerSecond:F2}";
+            lblFPS.Text = $"FPS: {_mainForm.FramesPerSecond:F2}";
             UpdateMemoryView();
             UpdateStackView();
             UpdateDisassemblyView();

Desktop/Form1.Designer.cs

@@ -1,6 +1,6 @@
 namespace Desktop
 {
-    partial class Form1
+    partial class ParsonsForm1
     {
         /// <summary>
         ///  Required designer variable.
@@ -49,7 +49,7 @@
             // 
             pbScreen.Location = new Point(12, 36);
             pbScreen.Name = "pbScreen";
-            pbScreen.Size = new Size(762, 672);
+            pbScreen.Size = new Size(768, 576);
             pbScreen.SizeMode = PictureBoxSizeMode.Zoom;
             pbScreen.TabIndex = 1;
             pbScreen.TabStop = false;
@@ -60,7 +60,7 @@
             menuStrip1.Items.AddRange(new ToolStripItem[] { fileToolStripMenuItem, viewToolStripMenuItem, machineToolStripMenuItem, helpToolStripMenuItem });
             menuStrip1.Location = new Point(0, 0);
             menuStrip1.Name = "menuStrip1";
-            menuStrip1.Size = new Size(785, 33);
+            menuStrip1.Size = new Size(791, 33);
             menuStrip1.TabIndex = 2;
             menuStrip1.Text = "menuStrip1";
             // 
@@ -75,27 +75,27 @@
             // 
             openToolStripMenuItem.DropDownItems.AddRange(new ToolStripItem[] { includedToolStripMenuItem, selectROMToolStripMenuItem1 });
             openToolStripMenuItem.Name = "openToolStripMenuItem";
-            openToolStripMenuItem.Size = new Size(270, 34);
+            openToolStripMenuItem.Size = new Size(158, 34);
             openToolStripMenuItem.Text = "Open";
             // 
             // includedToolStripMenuItem
             // 
             includedToolStripMenuItem.Name = "includedToolStripMenuItem";
-            includedToolStripMenuItem.Size = new Size(270, 34);
+            includedToolStripMenuItem.Size = new Size(218, 34);
             includedToolStripMenuItem.Text = "Included";
             includedToolStripMenuItem.Click += includedToolStripMenuItem_Click;
             // 
             // selectROMToolStripMenuItem1
             // 
             selectROMToolStripMenuItem1.Name = "selectROMToolStripMenuItem1";
-            selectROMToolStripMenuItem1.Size = new Size(270, 34);
+            selectROMToolStripMenuItem1.Size = new Size(218, 34);
             selectROMToolStripMenuItem1.Text = "Select ROM...";
             selectROMToolStripMenuItem1.Click += selectROMToolStripMenuItem_Click;
             // 
             // exitToolStripMenuItem
             // 
             exitToolStripMenuItem.Name = "exitToolStripMenuItem";
-            exitToolStripMenuItem.Size = new Size(270, 34);
+            exitToolStripMenuItem.Size = new Size(158, 34);
             exitToolStripMenuItem.Text = "Exit";
             exitToolStripMenuItem.Click += exitToolStripMenuItem_Click;
             // 
@@ -140,16 +140,16 @@
             aboutToolStripMenuItem.Size = new Size(164, 34);
             aboutToolStripMenuItem.Text = "About";
             // 
-            // Form1
+            // ParsonsForm1
             // 
             AutoScaleDimensions = new SizeF(10F, 25F);
             AutoScaleMode = AutoScaleMode.Font;
-            ClientSize = new Size(785, 719);
+            ClientSize = new Size(791, 622);
             Controls.Add(pbScreen);
             Controls.Add(menuStrip1);
             MainMenuStrip = menuStrip1;
             Margin = new Padding(4);
-            Name = "Form1";
+            Name = "ParsonsForm1";
             Text = "Form1";
             ((System.ComponentModel.ISupportInitialize)pbScreen).EndInit();
             menuStrip1.ResumeLayout(false);

Desktop/Form1.cs

@@ -1,22 +1,26 @@
+using System.Diagnostics;
+using System.Drawing.Imaging;
 using System.Reflection;
 using System.Reflection.PortableExecutable;
-using Core;
-using System.Threading.Tasks;
-using System.Drawing.Imaging;
 using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 using System.Windows.Forms;
+using Core;
 
 namespace Desktop
 {
-    public partial class Form1 : Form
+    public partial class ParsonsForm1 : Form
     {
         private SmsMachine _machine = null!;
         private DebuggerForm _debugger;
         private Bitmap _screenBitmap = new Bitmap(256, 192, PixelFormat.Format32bppArgb);
-
         private Task _emulatorTask;
-
+        private double TargetFrameTime = 16.667f;
-
+        public int TotalFrameCount = 0;
+        public double FrameTime { get; private set; } = 0;
+        public double FramesPerSecond { get; private set; } = 0;
+        private string _currentRomName = "No ROM";
+        private Stopwatch _stopwatch = new System.Diagnostics.Stopwatch();
         public bool IsRunning { get; private set; } = false;
 
         public ushort? Breakpoint
@@ -25,9 +29,10 @@ namespace Desktop
             set { if (_machine != null) _machine.Breakpoint = value; }
         }
 
-        public Form1()
+        public ParsonsForm1()
         {
             InitializeComponent();
+            this.Text = $"Parsons Master System 2026 - {_currentRomName}";
             _machine = new SmsMachine();
 
             PopulateIncludedRomsMenu();
@@ -46,32 +51,81 @@ namespace Desktop
 
             // Update the PictureBox
             pbScreen.Image = _screenBitmap;
+            TotalFrameCount++;
         }
 
         public void StartEmulator()
         {
             if (IsRunning) return;
             IsRunning = true;
+            TotalFrameCount = 0;
+
+            double TargetFrameTime = 1000.0 / 60.0;
+
             _emulatorTask = Task.Run(() =>
             {
+                _stopwatch.Restart();
+
+                double nextFrameTargetTime = _stopwatch.Elapsed.TotalMilliseconds + TargetFrameTime;
+                double lastFpsUpdate = _stopwatch.Elapsed.TotalMilliseconds;
+                int framesThisSecond = 0;
+
                 while (IsRunning)
                 {
+                    // Mark exactly when the emulator starts thinking
+                    double frameStartTime = _stopwatch.Elapsed.TotalMilliseconds;
+
+                    // 1. Do the heavy lifting (Z80 and VDP)
                     _machine.RunFrame();
 
-                    Invoke((System.Windows.Forms.MethodInvoker)delegate { DrawScreen(); });
+                    // 2. FIRE AND FORGET! Tell Windows to draw, but DO NOT WAIT for it to finish!
+                    BeginInvoke((System.Windows.Forms.MethodInvoker)delegate { DrawScreen(); });
 
-                    // Safety catch: If we hit a breakpoint while running, stop the loop!
+                    // 3. Safety catch
                     if (_machine.Breakpoint.HasValue && _machine.Cpu.PC == _machine.Breakpoint.Value)
                     {
                         IsRunning = false;
+                        BeginInvoke((System.Windows.Forms.MethodInvoker)delegate { _debugger?.uiUpdateTimer_Tick(null, EventArgs.Empty); });
+                        break;
+                    }
 
-                        // Optional: Force the debugger UI to update immediately so you see it!
+                    // 4. Calculate TRUE Frame Time (Compute Time) BEFORE we go to sleep!
-                        Invoke((System.Windows.Forms.MethodInvoker)delegate { _debugger?.uiUpdateTimer_Tick(null, EventArgs.Empty); });
+                    FrameTime = _stopwatch.Elapsed.TotalMilliseconds - frameStartTime;
+
+                    // --- HIGH PRECISION THROTTLE ---
+                    while (_stopwatch.Elapsed.TotalMilliseconds < nextFrameTargetTime)
+                    {
+                        if (nextFrameTargetTime - _stopwatch.Elapsed.TotalMilliseconds > 2.0)
+                        {
+                            Thread.Sleep(1);
                         }
                         else
                         {
-                        // Only throttle the speed if we are actively running
+                            Thread.SpinWait(10);
-                        Thread.Sleep(8);
+                        }
+                    }
+
+                    // --- METRICS MATH ---
+                    double currentTime = _stopwatch.Elapsed.TotalMilliseconds;
+                    TotalFrameCount++;
+                    framesThisSecond++;
+
+                    if (currentTime - lastFpsUpdate >= 1000.0)
+                    {
+                        FramesPerSecond = framesThisSecond / ((currentTime - lastFpsUpdate) / 1000.0);
+                        framesThisSecond = 0;
+                        lastFpsUpdate = currentTime;
+
+                        BeginInvoke((System.Windows.Forms.MethodInvoker)delegate {
+                            this.Text = $"Parsons Master System - {_currentRomName} [FPS/FT: {FramesPerSecond:F0}/{FrameTime:F1}]";
+                        });
+                    }
+
+                    nextFrameTargetTime += TargetFrameTime;
+
+                    if (currentTime > nextFrameTargetTime + TargetFrameTime)
+                    {
+                        nextFrameTargetTime = currentTime + TargetFrameTime;
                     }
                 }
             });
@@ -102,8 +156,8 @@ namespace Desktop
             // 3. Jam it into the Sega Mapper
             _machine.LoadCartridge(rom);
 
-            // 4. Update the Window title so it looks professional
+            _currentRomName = Path.GetFileNameWithoutExtension(filePath);
-            this.Text = $"Parsons Master System 2026 - {Path.GetFileNameWithoutExtension(filePath)}";
+            this.Text = $"Parsons Master System - {_currentRomName}";
 
             // 5. Turn the power on!
 

Desktop/Program.cs

@@ -11,7 +11,7 @@ namespace Desktop
             // To customize application configuration such as set high DPI settings or default font,
             // see https://aka.ms/applicationconfiguration.
             ApplicationConfiguration.Initialize();
-            Application.Run(new Form1());
+            Application.Run(new ParsonsForm1());
         }
     }
 }