feat(core): add video/display frame buffer

src/Chip8.Core/Video.cs

@@ -0,0 +1,192 @@
+using System.IO;
+
+namespace Chip8.Core;
+
+public sealed class Video
+{
+    public const int loWidth = 64;
+    public const int loHeight = 32;
+    public const int hiWidth = 128;
+    public const int hiHeight = 64;
+    public const int maxPixels = hiWidth * hiHeight;
+    public const int planeCount = 2;
+    public const int scrollStep = 4;
+
+    public int width { get; private set; } = loWidth;
+    public int height { get; private set; } = loHeight;
+    public bool hires => width == hiWidth;
+
+    readonly bool[][] plane =
+    {
+        new bool[maxPixels],
+        new bool[maxPixels],
+    };
+
+    public void reset()
+    {
+        width = loWidth;
+        height = loHeight;
+        foreach (var buffer in plane)
+        {
+            System.Array.Clear(buffer, 0, buffer.Length);
+        }
+    }
+
+    public void setResolution(bool high)
+    {
+        width = high ? hiWidth : loWidth;
+        height = high ? hiHeight : loHeight;
+        foreach (var buffer in plane)
+        {
+            System.Array.Clear(buffer, 0, buffer.Length);
+        }
+    }
+
+    public bool pixel(int planeIndex, int x, int y) => plane[planeIndex][y * width + x];
+
+    internal void writeTo(BinaryWriter writer)
+    {
+        writer.Write(width);
+        writer.Write(height);
+        for (int p = 0; p < planeCount; p++)
+        {
+            for (int cell = 0; cell < maxPixels; cell++)
+            {
+                writer.Write(plane[p][cell]);
+            }
+        }
+    }
+
+    internal void readFrom(BinaryReader reader)
+    {
+        width = reader.ReadInt32();
+        height = reader.ReadInt32();
+        for (int p = 0; p < planeCount; p++)
+        {
+            for (int cell = 0; cell < maxPixels; cell++)
+            {
+                plane[p][cell] = reader.ReadBoolean();
+            }
+        }
+    }
+
+    public int colorAt(int x, int y)
+    {
+        int index = y * width + x;
+        int color = 0;
+        for (int p = 0; p < planeCount; p++)
+        {
+            if (plane[p][index])
+            {
+                color |= 1 << p;
+            }
+        }
+        return color;
+    }
+
+    public void clear(int planeMask)
+    {
+        for (int p = 0; p < planeCount; p++)
+        {
+            if ((planeMask & (1 << p)) == 0)
+            {
+                continue;
+            }
+            for (int cell = 0; cell < width * height; cell++)
+            {
+                plane[p][cell] = false;
+            }
+        }
+    }
+
+    public void scrollDown(int rows, int planeMask) => shift(0, rows, planeMask);
+
+    public void scrollUp(int rows, int planeMask) => shift(0, -rows, planeMask);
+
+    public void scrollRight(int columns, int planeMask) => shift(columns, 0, planeMask);
+
+    public void scrollLeft(int columns, int planeMask) => shift(-columns, 0, planeMask);
+
+    void shift(int dx, int dy, int planeMask)
+    {
+        for (int p = 0; p < planeCount; p++)
+        {
+            if ((planeMask & (1 << p)) == 0)
+            {
+                continue;
+            }
+
+            bool[] buffer = plane[p];
+            var source = (bool[])buffer.Clone();
+            for (int y = 0; y < height; y++)
+            {
+                for (int x = 0; x < width; x++)
+                {
+                    int sx = x - dx;
+                    int sy = y - dy;
+                    bool value = sx >= 0 && sx < width && sy >= 0 && sy < height
+                        && source[sy * width + sx];
+                    buffer[y * width + x] = value;
+                }
+            }
+        }
+    }
+
+    public bool drawSprite(byte[] memory, int address, int originX, int originY, int rows, int planeMask, bool wrap)
+    {
+        int spriteRows = rows == 0 ? 16 : rows;
+        int bytesPerRow = rows == 0 ? 2 : 1;
+        int spriteWidth = bytesPerRow * 8;
+        int startX = originX % width;
+        int startY = originY % height;
+        bool collision = false;
+        int addr = address;
+
+        for (int p = 0; p < planeCount; p++)
+        {
+            if ((planeMask & (1 << p)) == 0)
+            {
+                continue;
+            }
+
+            bool[] buffer = plane[p];
+            for (int row = 0; row < spriteRows; row++)
+            {
+                int rowBits = 0;
+                for (int b = 0; b < bytesPerRow; b++)
+                {
+                    rowBits = (rowBits << 8) | memory[addr++ & (memory.Length - 1)];
+                }
+
+                for (int col = 0; col < spriteWidth; col++)
+                {
+                    if ((rowBits & (1 << (spriteWidth - 1 - col))) == 0)
+                    {
+                        continue;
+                    }
+
+                    int px = startX + col;
+                    int py = startY + row;
+                    if (wrap)
+                    {
+                        px %= width;
+                        py %= height;
+                    }
+                    else if (px >= width || py >= height)
+                    {
+                        continue;
+                    }
+
+                    int index = py * width + px;
+                    if (buffer[index])
+                    {
+                        collision = true;
+                    }
+                    buffer[index] ^= true;
+                }
+            }
+        }
+
+        return collision;
+    }
+}