Этап 6

Minint.Core/Models/MinintDocument.cs

@@ -21,6 +21,13 @@ public sealed class MinintDocument
 
     public List<MinintLayer> Layers { get; }
 
+    /// <summary>
+    /// Reverse lookup cache: RgbaColor → palette index. Built lazily, invalidated
+    /// on structural palette changes (compact, clear). Call <see cref="InvalidatePaletteCache"/>
+    /// after bulk palette modifications.
+    /// </summary>
+    private Dictionary<RgbaColor, int>? _paletteCache;
+
     public MinintDocument(string name)
     {
         Name = name;
@@ -50,4 +57,48 @@ public sealed class MinintDocument
         <= 16_777_215 => 3,
         _ => 4
     };
+
+    /// <summary>
+    /// O(1) lookup of a color in the palette. Returns the index, or -1 if not found.
+    /// Lazily builds an internal dictionary on first call.
+    /// </summary>
+    public int FindColorCached(RgbaColor color)
+    {
+        var cache = EnsurePaletteCache();
+        return cache.TryGetValue(color, out int idx) ? idx : -1;
+    }
+
+    /// <summary>
+    /// Returns the index of <paramref name="color"/>. If absent, appends it to the palette
+    /// and updates the cache. O(1) amortized.
+    /// </summary>
+    public int EnsureColorCached(RgbaColor color)
+    {
+        var cache = EnsurePaletteCache();
+        if (cache.TryGetValue(color, out int idx))
+            return idx;
+
+        idx = Palette.Count;
+        Palette.Add(color);
+        cache[color] = idx;
+        return idx;
+    }
+
+    /// <summary>
+    /// Drops the reverse lookup cache. Must be called after any operation that
+    /// reorders, removes, or bulk-replaces palette entries (e.g. compact, grayscale).
+    /// </summary>
+    public void InvalidatePaletteCache() => _paletteCache = null;
+
+    private Dictionary<RgbaColor, int> EnsurePaletteCache()
+    {
+        if (_paletteCache is not null)
+            return _paletteCache;
+
+        var cache = new Dictionary<RgbaColor, int>(Palette.Count);
+        for (int i = 0; i < Palette.Count; i++)
+            cache.TryAdd(Palette[i], i); // first occurrence wins (for dupes)
+        _paletteCache = cache;
+        return cache;
+    }
 }

Minint.Core/Services/Impl/PaletteService.cs

@@ -5,26 +5,10 @@ namespace Minint.Core.Services.Impl;
 public sealed class PaletteService : IPaletteService
 {
     public int FindColor(MinintDocument document, RgbaColor color)
-    {
-        var palette = document.Palette;
-        for (int i = 0; i < palette.Count; i++)
-        {
-            if (palette[i] == color)
-                return i;
-        }
-        return -1;
-    }
+        => document.FindColorCached(color);
 
     public int EnsureColor(MinintDocument document, RgbaColor color)
-    {
-        int idx = FindColor(document, color);
-        if (idx >= 0)
-            return idx;
-
-        idx = document.Palette.Count;
-        document.Palette.Add(color);
-        return idx;
-    }
+        => document.EnsureColorCached(color);
 
     public void CompactPalette(MinintDocument document)
     {
@@ -32,19 +16,16 @@ public sealed class PaletteService : IPaletteService
         if (palette.Count <= 1)
             return;
 
-        // 1. Collect indices actually used across all layers
-        var usedIndices = new HashSet<int> { 0 }; // always keep transparent
+        var usedIndices = new HashSet<int> { 0 };
         foreach (var layer in document.Layers)
         {
             foreach (int idx in layer.Pixels)
                 usedIndices.Add(idx);
         }
 
-        // 2. Build new palette and old→new mapping
         var oldToNew = new int[palette.Count];
         var newPalette = new List<RgbaColor>(usedIndices.Count);
 
-        // Index 0 (transparent) stays at 0
         newPalette.Add(palette[0]);
         oldToNew[0] = 0;
 
@@ -55,23 +36,21 @@ public sealed class PaletteService : IPaletteService
                 oldToNew[i] = newPalette.Count;
                 newPalette.Add(palette[i]);
             }
-            // unused indices don't get a mapping — they'll never be looked up
         }
 
-        // 3. If nothing was removed, skip the remap
         if (newPalette.Count == palette.Count)
             return;
 
-        // 4. Replace palette
         palette.Clear();
         palette.AddRange(newPalette);
 
-        // 5. Remap all pixel arrays
         foreach (var layer in document.Layers)
         {
             var px = layer.Pixels;
             for (int i = 0; i < px.Length; i++)
                 px[i] = oldToNew[px[i]];
         }
+
+        document.InvalidatePaletteCache();
     }
 }

Minint/Controls/PixelCanvas.cs

@@ -0,0 +1,325 @@
+using System;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
+using Avalonia.Media;
+using Avalonia.Media.Imaging;
+using Avalonia.Threading;
+
+namespace Minint.Controls;
+
+/// <summary>
+/// Custom control that renders a WriteableBitmap through a Viewport (pan/zoom).
+/// Supports nearest-neighbor scaling, pixel grid overlay, scrollbars, and mouse interaction.
+/// <para>Input model:</para>
+/// <list type="bullet">
+///   <item>Ctrl+Wheel: zoom at cursor</item>
+///   <item>Wheel: scroll vertically</item>
+///   <item>Shift+Wheel: scroll horizontally</item>
+///   <item>Touchpad two-finger scroll: free pan (Delta.X + Delta.Y)</item>
+///   <item>Middle mouse drag: pan</item>
+/// </list>
+/// </summary>
+public class PixelCanvas : Control
+{
+    #region Styled Properties
+
+    public static readonly StyledProperty<WriteableBitmap?> SourceBitmapProperty =
+        AvaloniaProperty.Register<PixelCanvas, WriteableBitmap?>(nameof(SourceBitmap));
+
+    public static readonly StyledProperty<bool> ShowGridProperty =
+        AvaloniaProperty.Register<PixelCanvas, bool>(nameof(ShowGrid), defaultValue: false);
+
+    public WriteableBitmap? SourceBitmap
+    {
+        get => GetValue(SourceBitmapProperty);
+        set => SetValue(SourceBitmapProperty, value);
+    }
+
+    public bool ShowGrid
+    {
+        get => GetValue(ShowGridProperty);
+        set => SetValue(ShowGridProperty, value);
+    }
+
+    #endregion
+
+    private readonly Viewport _viewport = new();
+    private bool _isPanning;
+    private Point _panStart;
+    private double _panStartOffsetX, _panStartOffsetY;
+    private bool _viewportInitialized;
+
+    private ScrollBar? _hScrollBar;
+    private ScrollBar? _vScrollBar;
+    private bool _suppressScrollSync;
+
+    private const double ScrollPixelsPerTick = 20.0;
+
+    public Viewport Viewport => _viewport;
+
+    static PixelCanvas()
+    {
+        AffectsRender<PixelCanvas>(SourceBitmapProperty, ShowGridProperty);
+        FocusableProperty.OverrideDefaultValue<PixelCanvas>(true);
+    }
+
+    public PixelCanvas()
+    {
+        ClipToBounds = true;
+    }
+
+    /// <summary>
+    /// Connects external ScrollBar controls. Call once after the UI is built.
+    /// </summary>
+    public void AttachScrollBars(ScrollBar horizontal, ScrollBar vertical)
+    {
+        if (_hScrollBar is not null)
+            _hScrollBar.ValueChanged -= OnHScrollChanged;
+        if (_vScrollBar is not null)
+            _vScrollBar.ValueChanged -= OnVScrollChanged;
+
+        _hScrollBar = horizontal;
+        _vScrollBar = vertical;
+
+        _hScrollBar.ValueChanged += OnHScrollChanged;
+        _vScrollBar.ValueChanged += OnVScrollChanged;
+    }
+
+    #region Rendering
+
+    public override void Render(DrawingContext context)
+    {
+        base.Render(context);
+        context.FillRectangle(Brushes.Transparent, new Rect(Bounds.Size));
+
+        var bmp = SourceBitmap;
+        if (bmp is null)
+            return;
+
+        int imgW = bmp.PixelSize.Width;
+        int imgH = bmp.PixelSize.Height;
+
+        if (!_viewportInitialized)
+        {
+            _viewport.FitToView(imgW, imgH, Bounds.Width, Bounds.Height);
+            _viewportInitialized = true;
+        }
+
+        DrawCheckerboard(context, imgW, imgH);
+
+        var destRect = _viewport.ImageScreenRect(imgW, imgH);
+        var srcRect = new Rect(0, 0, imgW, imgH);
+        RenderOptions.SetBitmapInterpolationMode(this, BitmapInterpolationMode.None);
+        context.DrawImage(bmp, srcRect, destRect);
+
+        if (ShowGrid && _viewport.Zoom >= 4)
+            DrawPixelGrid(context, imgW, imgH);
+
+        // Defer scrollbar sync — updating layout properties during Render is forbidden
+        int w = imgW, h = imgH;
+        Dispatcher.UIThread.Post(() => SyncScrollBars(w, h), DispatcherPriority.Render);
+    }
+
+    private void DrawCheckerboard(DrawingContext context, int imgW, int imgH)
+    {
+        var rect = _viewport.ImageScreenRect(imgW, imgH);
+        var clip = new Rect(0, 0, Bounds.Width, Bounds.Height);
+        var visible = rect.Intersect(clip);
+        if (visible.Width <= 0 || visible.Height <= 0) return;
+
+        const int checkerSize = 8;
+        var light = new SolidColorBrush(Color.FromRgb(204, 204, 204));
+        var dark = new SolidColorBrush(Color.FromRgb(170, 170, 170));
+
+        using (context.PushClip(visible))
+        {
+            context.FillRectangle(light, visible);
+
+            double startX = visible.X - ((visible.X - rect.X) % (checkerSize * 2));
+            double startY = visible.Y - ((visible.Y - rect.Y) % (checkerSize * 2));
+
+            for (double y = startY; y < visible.Bottom; y += checkerSize)
+            {
+                for (double x = startX; x < visible.Right; x += checkerSize)
+                {
+                    int col = (int)((x - rect.X) / checkerSize);
+                    int row = (int)((y - rect.Y) / checkerSize);
+                    if ((col + row) % 2 == 1)
+                        context.FillRectangle(dark, new Rect(x, y, checkerSize, checkerSize));
+                }
+            }
+        }
+    }
+
+    private void DrawPixelGrid(DrawingContext context, int imgW, int imgH)
+    {
+        var pen = new Pen(new SolidColorBrush(Color.FromArgb(60, 255, 255, 255)), 1);
+        var clip = new Rect(0, 0, Bounds.Width, Bounds.Height);
+        var imgRect = _viewport.ImageScreenRect(imgW, imgH);
+        var visible = imgRect.Intersect(clip);
+        if (visible.Width <= 0 || visible.Height <= 0) return;
+
+        var (startPx, startPy) = _viewport.ScreenToPixel(visible.X, visible.Y);
+        var (endPx, endPy) = _viewport.ScreenToPixel(visible.Right, visible.Bottom);
+        startPx = Math.Max(0, startPx);
+        startPy = Math.Max(0, startPy);
+        endPx = Math.Min(imgW, endPx + 1);
+        endPy = Math.Min(imgH, endPy + 1);
+
+        using (context.PushClip(visible))
+        {
+            for (int px = startPx; px <= endPx; px++)
+            {
+                var (sx, _) = _viewport.PixelToScreen(px, 0);
+                context.DrawLine(pen, new Point(sx, visible.Top), new Point(sx, visible.Bottom));
+            }
+
+            for (int py = startPy; py <= endPy; py++)
+            {
+                var (_, sy) = _viewport.PixelToScreen(0, py);
+                context.DrawLine(pen, new Point(visible.Left, sy), new Point(visible.Right, sy));
+            }
+        }
+    }
+
+    #endregion
+
+    #region Scrollbar Sync
+
+    private void SyncScrollBars(int imgW, int imgH)
+    {
+        if (_hScrollBar is null || _vScrollBar is null) return;
+
+        _suppressScrollSync = true;
+
+        // Scrollbar value is negated offset: increasing value = scroll right = offset decreases
+        var (hMin, hMax, hVal, hView) = _viewport.GetScrollInfo(imgW, Bounds.Width, _viewport.OffsetX);
+        _hScrollBar.Minimum = -hMax;
+        _hScrollBar.Maximum = -hMin;
+        _hScrollBar.Value = -hVal;
+        _hScrollBar.ViewportSize = hView;
+
+        var (vMin, vMax, vVal, vView) = _viewport.GetScrollInfo(imgH, Bounds.Height, _viewport.OffsetY);
+        _vScrollBar.Minimum = -vMax;
+        _vScrollBar.Maximum = -vMin;
+        _vScrollBar.Value = -vVal;
+        _vScrollBar.ViewportSize = vView;
+
+        _suppressScrollSync = false;
+    }
+
+    private void OnHScrollChanged(object? sender, RangeBaseValueChangedEventArgs e)
+    {
+        if (_suppressScrollSync) return;
+        var (imgW, imgH) = GetImageSize();
+        _viewport.SetOffset(-e.NewValue, _viewport.OffsetY,
+                            imgW, imgH, Bounds.Width, Bounds.Height);
+        InvalidateVisual();
+    }
+
+    private void OnVScrollChanged(object? sender, RangeBaseValueChangedEventArgs e)
+    {
+        if (_suppressScrollSync) return;
+        var (imgW, imgH) = GetImageSize();
+        _viewport.SetOffset(_viewport.OffsetX, -e.NewValue,
+                            imgW, imgH, Bounds.Width, Bounds.Height);
+        InvalidateVisual();
+    }
+
+    #endregion
+
+    #region Mouse Input
+
+    private (int W, int H) GetImageSize()
+    {
+        var bmp = SourceBitmap;
+        return bmp is not null ? (bmp.PixelSize.Width, bmp.PixelSize.Height) : (0, 0);
+    }
+
+    protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
+    {
+        base.OnPointerWheelChanged(e);
+        var (imgW, imgH) = GetImageSize();
+        if (imgW == 0) return;
+
+        bool ctrl = (e.KeyModifiers & KeyModifiers.Control) != 0;
+        bool shift = (e.KeyModifiers & KeyModifiers.Shift) != 0;
+
+        if (ctrl)
+        {
+            var pos = e.GetPosition(this);
+            _viewport.ZoomAtPoint(pos.X, pos.Y, e.Delta.Y,
+                                  imgW, imgH, Bounds.Width, Bounds.Height);
+        }
+        else
+        {
+            double dx = e.Delta.X * ScrollPixelsPerTick;
+            double dy = e.Delta.Y * ScrollPixelsPerTick;
+
+            if (shift && Math.Abs(e.Delta.X) < 0.001)
+            {
+                dx = dy;
+                dy = 0;
+            }
+
+            _viewport.Pan(dx, dy, imgW, imgH, Bounds.Width, Bounds.Height);
+        }
+
+        InvalidateVisual();
+        e.Handled = true;
+    }
+
+    protected override void OnPointerPressed(PointerPressedEventArgs e)
+    {
+        base.OnPointerPressed(e);
+
+        if (e.GetCurrentPoint(this).Properties.IsMiddleButtonPressed)
+        {
+            _isPanning = true;
+            _panStart = e.GetPosition(this);
+            _panStartOffsetX = _viewport.OffsetX;
+            _panStartOffsetY = _viewport.OffsetY;
+            e.Handled = true;
+        }
+    }
+
+    protected override void OnPointerMoved(PointerEventArgs e)
+    {
+        base.OnPointerMoved(e);
+
+        if (_isPanning)
+        {
+            var pos = e.GetPosition(this);
+            var (imgW, imgH) = GetImageSize();
+            _viewport.SetOffset(
+                _panStartOffsetX + (pos.X - _panStart.X),
+                _panStartOffsetY + (pos.Y - _panStart.Y),
+                imgW, imgH, Bounds.Width, Bounds.Height);
+            InvalidateVisual();
+            e.Handled = true;
+        }
+    }
+
+    protected override void OnPointerReleased(PointerReleasedEventArgs e)
+    {
+        base.OnPointerReleased(e);
+
+        if (_isPanning && e.InitialPressMouseButton == MouseButton.Middle)
+        {
+            _isPanning = false;
+            e.Handled = true;
+        }
+    }
+
+    #endregion
+
+    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+    {
+        base.OnPropertyChanged(change);
+
+        if (change.Property == SourceBitmapProperty)
+            _viewportInitialized = false;
+    }
+}

Minint/Controls/Viewport.cs

@@ -0,0 +1,119 @@
+using System;
+using Avalonia;
+
+namespace Minint.Controls;
+
+/// <summary>
+/// Manages zoom level and pan offset for the pixel canvas.
+/// Provides screen↔pixel coordinate transforms.
+/// </summary>
+public sealed class Viewport
+{
+    public double Zoom { get; set; } = 1.0;
+    public double OffsetX { get; set; }
+    public double OffsetY { get; set; }
+
+    public const double MinZoom = 0.25;
+    public const double MaxZoom = 128.0;
+
+    /// <summary>
+    /// Zoom base per 1.0 unit of wheel delta. Actual factor = Pow(base, |delta|).
+    /// Touchpad nudge (delta ~0.1) → ~1.01×, mouse tick (delta 1.0) → 1.10×, fast (3.0) → 1.33×.
+    /// </summary>
+    private const double ZoomBase = 1.10;
+
+    public (int X, int Y) ScreenToPixel(double screenX, double screenY) =>
+        ((int)Math.Floor((screenX - OffsetX) / Zoom),
+         (int)Math.Floor((screenY - OffsetY) / Zoom));
+
+    public (double X, double Y) PixelToScreen(int pixelX, int pixelY) =>
+        (pixelX * Zoom + OffsetX,
+         pixelY * Zoom + OffsetY);
+
+    public Rect ImageScreenRect(int imageWidth, int imageHeight) =>
+        new(OffsetX, OffsetY, imageWidth * Zoom, imageHeight * Zoom);
+
+    /// <summary>
+    /// Zooms keeping the point under cursor fixed.
+    /// Uses the actual magnitude of <paramref name="delta"/> for proportional zoom.
+    /// </summary>
+    public void ZoomAtPoint(double screenX, double screenY, double delta,
+                            int imageWidth, int imageHeight, double controlWidth, double controlHeight)
+    {
+        double absDelta = Math.Abs(delta);
+        double factor = delta > 0 ? Math.Pow(ZoomBase, absDelta) : 1.0 / Math.Pow(ZoomBase, absDelta);
+        double newZoom = Math.Clamp(Zoom * factor, MinZoom, MaxZoom);
+        if (Math.Abs(newZoom - Zoom) < 1e-12) return;
+
+        double pixelX = (screenX - OffsetX) / Zoom;
+        double pixelY = (screenY - OffsetY) / Zoom;
+        Zoom = newZoom;
+        OffsetX = screenX - pixelX * Zoom;
+        OffsetY = screenY - pixelY * Zoom;
+
+        ClampOffset(imageWidth, imageHeight, controlWidth, controlHeight);
+    }
+
+    /// <summary>
+    /// Pans by screen-space delta, then clamps so the image can't be scrolled out of view.
+    /// </summary>
+    public void Pan(double deltaX, double deltaY,
+                    int imageWidth, int imageHeight, double controlWidth, double controlHeight)
+    {
+        OffsetX += deltaX;
+        OffsetY += deltaY;
+        ClampOffset(imageWidth, imageHeight, controlWidth, controlHeight);
+    }
+
+    /// <summary>
+    /// Sets offset directly (e.g. from middle-mouse drag), then clamps.
+    /// </summary>
+    public void SetOffset(double offsetX, double offsetY,
+                          int imageWidth, int imageHeight, double controlWidth, double controlHeight)
+    {
+        OffsetX = offsetX;
+        OffsetY = offsetY;
+        ClampOffset(imageWidth, imageHeight, controlWidth, controlHeight);
+    }
+
+    /// <summary>
+    /// Ensures at least <c>minVisible</c> pixels of the image remain on screen on each edge.
+    /// </summary>
+    public void ClampOffset(int imageWidth, int imageHeight, double controlWidth, double controlHeight)
+    {
+        double extentW = imageWidth * Zoom;
+        double extentH = imageHeight * Zoom;
+
+        double minVisH = Math.Max(32, Math.Min(controlWidth, extentW) * 0.10);
+        double minVisV = Math.Max(32, Math.Min(controlHeight, extentH) * 0.10);
+
+        // Image right edge must be >= minVisH from left of control
+        // Image left edge must be <= controlWidth - minVisH from left
+        OffsetX = Math.Clamp(OffsetX, minVisH - extentW, controlWidth - minVisH);
+        OffsetY = Math.Clamp(OffsetY, minVisV - extentH, controlHeight - minVisV);
+    }
+
+    public void FitToView(int imageWidth, int imageHeight, double controlWidth, double controlHeight)
+    {
+        if (imageWidth <= 0 || imageHeight <= 0 || controlWidth <= 0 || controlHeight <= 0)
+            return;
+
+        double scaleX = controlWidth / imageWidth;
+        double scaleY = controlHeight / imageHeight;
+        Zoom = Math.Max(1.0, Math.Floor(Math.Min(scaleX, scaleY)));
+
+        OffsetX = (controlWidth - imageWidth * Zoom) / 2.0;
+        OffsetY = (controlHeight - imageHeight * Zoom) / 2.0;
+    }
+
+    public (double Min, double Max, double Value, double ViewportSize)
+        GetScrollInfo(int imageSize, double controlSize, double offset)
+    {
+        double extent = imageSize * Zoom;
+        double minVis = Math.Max(32, Math.Min(controlSize, extent) * 0.10);
+        double min = minVis - extent;
+        double max = controlSize - minVis;
+        double viewportSize = Math.Min(controlSize, extent);
+        return (min, max, offset, viewportSize);
+    }
+}

Minint/Minint.csproj

@@ -3,6 +3,7 @@
     <OutputType>WinExe</OutputType>
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <BuiltInComInteropSupport>true</BuiltInComInteropSupport>
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <AvaloniaUseCompiledBindingsByDefault>true</AvaloniaUseCompiledBindingsByDefault>

Minint/ViewModels/EditorViewModel.cs

@@ -0,0 +1,163 @@
+using System;
+using System.Collections.ObjectModel;
+using Avalonia;
+using Avalonia.Media.Imaging;
+using CommunityToolkit.Mvvm.ComponentModel;
+using Minint.Core.Models;
+using Minint.Core.Services;
+using Minint.Core.Services.Impl;
+
+namespace Minint.ViewModels;
+
+public partial class EditorViewModel : ViewModelBase
+{
+    private readonly ICompositor _compositor = new Compositor();
+    private readonly IPaletteService _paletteService = new PaletteService();
+
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(HasContainer))]
+    [NotifyPropertyChangedFor(nameof(Title))]
+    private MinintContainer? _container;
+
+    [ObservableProperty]
+    private MinintDocument? _activeDocument;
+
+    [ObservableProperty]
+    private MinintLayer? _activeLayer;
+
+    private bool _suppressDocumentSync;
+
+    [ObservableProperty]
+    private WriteableBitmap? _canvasBitmap;
+
+    [ObservableProperty]
+    private bool _showGrid;
+
+    /// <summary>
+    /// Path of the currently open file, or null for unsaved new containers.
+    /// </summary>
+    [ObservableProperty]
+    [NotifyPropertyChangedFor(nameof(Title))]
+    private string? _filePath;
+
+    public bool HasContainer => Container is not null;
+
+    public string Title => FilePath is not null
+        ? $"Minint — {System.IO.Path.GetFileName(FilePath)}"
+        : Container is not null
+            ? "Minint — Untitled"
+            : "Minint";
+
+    public ObservableCollection<MinintDocument> Documents { get; } = [];
+    public ObservableCollection<MinintLayer> Layers { get; } = [];
+
+    public void NewContainer(int width, int height)
+    {
+        var c = new MinintContainer(width, height);
+        c.AddNewDocument("Document 1");
+        LoadContainer(c, null);
+    }
+
+    public void LoadContainer(MinintContainer container, string? path)
+    {
+        Container = container;
+        FilePath = path;
+
+        Documents.Clear();
+        foreach (var doc in container.Documents)
+            Documents.Add(doc);
+
+        SelectDocument(container.Documents.Count > 0 ? container.Documents[0] : null);
+    }
+
+    /// <summary>
+    /// Called by CommunityToolkit when ActiveDocument property changes (e.g. from ListBox binding).
+    /// </summary>
+    partial void OnActiveDocumentChanged(MinintDocument? value)
+    {
+        if (_suppressDocumentSync) return;
+        SyncLayersAndCanvas(value);
+    }
+
+    public void SelectDocument(MinintDocument? doc)
+    {
+        _suppressDocumentSync = true;
+        ActiveDocument = doc;
+        _suppressDocumentSync = false;
+
+        SyncLayersAndCanvas(doc);
+    }
+
+    private void SyncLayersAndCanvas(MinintDocument? doc)
+    {
+        Layers.Clear();
+        if (doc is not null)
+        {
+            foreach (var layer in doc.Layers)
+                Layers.Add(layer);
+            ActiveLayer = doc.Layers.Count > 0 ? doc.Layers[0] : null;
+        }
+        else
+        {
+            ActiveLayer = null;
+        }
+
+        RefreshCanvas();
+    }
+
+    public void RefreshCanvas()
+    {
+        if (Container is null || ActiveDocument is null)
+        {
+            CanvasBitmap = null;
+            return;
+        }
+
+        int w = Container.Width;
+        int h = Container.Height;
+        uint[] argb = _compositor.Composite(ActiveDocument, w, h);
+
+        var bmp = new WriteableBitmap(
+            new PixelSize(w, h),
+            new Vector(96, 96),
+            Avalonia.Platform.PixelFormat.Bgra8888);
+
+        using (var fb = bmp.Lock())
+        {
+            unsafe
+            {
+                var dst = new Span<uint>((void*)fb.Address, w * h);
+                for (int i = 0; i < argb.Length; i++)
+                {
+                    // argb[i] is 0xAARRGGBB, need premultiplied BGRA for the bitmap
+                    uint px = argb[i];
+                    byte a = (byte)(px >> 24);
+                    byte r = (byte)((px >> 16) & 0xFF);
+                    byte g = (byte)((px >> 8) & 0xFF);
+                    byte b = (byte)(px & 0xFF);
+
+                    if (a == 255)
+                    {
+                        dst[i] = px; // ARGB layout == BGRA in LE memory, alpha=255 → no premul needed
+                    }
+                    else if (a == 0)
+                    {
+                        dst[i] = 0;
+                    }
+                    else
+                    {
+                        r = (byte)(r * a / 255);
+                        g = (byte)(g * a / 255);
+                        b = (byte)(b * a / 255);
+                        dst[i] = (uint)(b | (g << 8) | (r << 16) | (a << 24));
+                    }
+                }
+            }
+        }
+
+        CanvasBitmap = bmp;
+    }
+
+    public ICompositor Compositor => _compositor;
+    public IPaletteService PaletteService => _paletteService;
+}

Minint/ViewModels/MainWindowViewModel.cs

@@ -1,6 +1,124 @@
-namespace Minint.ViewModels;
+using System;
+using System.IO;
+using System.Linq;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Platform.Storage;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Minint.Infrastructure.Serialization;
+
+namespace Minint.ViewModels;
 
 public partial class MainWindowViewModel : ViewModelBase
 {
-    public string Greeting { get; } = "Welcome to Avalonia!";
+    private readonly MinintSerializer _serializer = new();
+
+    private static readonly FilePickerFileType MinintFileType = new("Minint Files")
+    {
+        Patterns = ["*.minint"],
+    };
+
+    [ObservableProperty]
+    private EditorViewModel _editor = new();
+
+    [ObservableProperty]
+    private string _statusText = "Ready";
+
+    /// <summary>
+    /// Set by the view so that file dialogs can use the correct parent window.
+    /// </summary>
+    public TopLevel? Owner { get; set; }
+
+    [RelayCommand]
+    private void NewFile()
+    {
+        Editor.NewContainer(64, 64);
+        StatusText = "New 64×64 container created.";
+    }
+
+    [RelayCommand]
+    private async Task OpenFileAsync()
+    {
+        if (Owner?.StorageProvider is not { } sp) return;
+
+        var files = await sp.OpenFilePickerAsync(new FilePickerOpenOptions
+        {
+            Title = "Open .minint file",
+            FileTypeFilter = [MinintFileType],
+            AllowMultiple = false,
+        });
+
+        if (files.Count == 0) return;
+
+        var file = files[0];
+        try
+        {
+            await using var stream = await file.OpenReadAsync();
+            var container = _serializer.Read(stream);
+            var path = file.TryGetLocalPath();
+            Editor.LoadContainer(container, path);
+            StatusText = $"Opened {file.Name}";
+        }
+        catch (Exception ex)
+        {
+            StatusText = $"Error opening file: {ex.Message}";
+        }
+    }
+
+    [RelayCommand]
+    private async Task SaveFileAsync()
+    {
+        if (Editor.Container is null) return;
+
+        if (Editor.FilePath is not null)
+        {
+            await SaveToPathAsync(Editor.FilePath);
+        }
+        else
+        {
+            await SaveFileAsAsync();
+        }
+    }
+
+    [RelayCommand]
+    private async Task SaveFileAsAsync()
+    {
+        if (Owner?.StorageProvider is not { } sp || Editor.Container is null) return;
+
+        var file = await sp.SaveFilePickerAsync(new FilePickerSaveOptions
+        {
+            Title = "Save .minint file",
+            DefaultExtension = "minint",
+            FileTypeChoices = [MinintFileType],
+            SuggestedFileName = Editor.FilePath is not null
+                ? Path.GetFileName(Editor.FilePath) : "untitled.minint",
+        });
+
+        if (file is null) return;
+
+        var path = file.TryGetLocalPath();
+        if (path is null)
+        {
+            StatusText = "Error: could not resolve file path.";
+            return;
+        }
+
+        await SaveToPathAsync(path);
+    }
+
+    private async Task SaveToPathAsync(string path)
+    {
+        try
+        {
+            await using var fs = File.Create(path);
+            _serializer.Write(fs, Editor.Container!);
+            Editor.FilePath = path;
+            StatusText = $"Saved {Path.GetFileName(path)}";
+        }
+        catch (Exception ex)
+        {
+            StatusText = $"Error saving file: {ex.Message}";
+        }
+    }
 }

Minint/Views/MainWindow.axaml

@@ -1,20 +1,95 @@
 <Window xmlns="https://github.com/avaloniaui"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:vm="using:Minint.ViewModels"
+        xmlns:controls="using:Minint.Controls"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
-        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+        mc:Ignorable="d" d:DesignWidth="1024" d:DesignHeight="700"
         x:Class="Minint.Views.MainWindow"
         x:DataType="vm:MainWindowViewModel"
         Icon="/Assets/avalonia-logo.ico"
-        Title="Minint">
+        Title="{Binding Editor.Title}"
+        Width="1024" Height="700">
 
     <Design.DataContext>
-        <!-- This only sets the DataContext for the previewer in an IDE,
-             to set the actual DataContext for runtime, set the DataContext property in code (look at App.axaml.cs) -->
         <vm:MainWindowViewModel/>
     </Design.DataContext>
 
-    <TextBlock Text="{Binding Greeting}" HorizontalAlignment="Center" VerticalAlignment="Center"/>
+    <DockPanel>
+        <!-- Menu bar -->
+        <Menu DockPanel.Dock="Top">
+            <MenuItem Header="_File">
+                <MenuItem Header="_New" Command="{Binding NewFileCommand}" HotKey="Ctrl+N"/>
+                <MenuItem Header="_Open…" Command="{Binding OpenFileCommand}" HotKey="Ctrl+O"/>
+                <Separator/>
+                <MenuItem Header="_Save" Command="{Binding SaveFileCommand}" HotKey="Ctrl+S"/>
+                <MenuItem Header="Save _As…" Command="{Binding SaveFileAsCommand}" HotKey="Ctrl+Shift+S"/>
+            </MenuItem>
+            <MenuItem Header="_View">
+                <MenuItem Header="Pixel _Grid" ToggleType="CheckBox"
+                          IsChecked="{Binding Editor.ShowGrid}" HotKey="Ctrl+G"/>
+            </MenuItem>
+        </Menu>
 
+        <!-- Status bar -->
+        <Border DockPanel.Dock="Bottom" Background="{DynamicResource SystemControlBackgroundChromeMediumLowBrush}"
+                Padding="8,2">
+            <TextBlock Text="{Binding StatusText}" FontSize="12"/>
+        </Border>
+
+        <!-- Main content: left panel, canvas, right panel -->
+        <Grid ColumnDefinitions="180,*,180">
+
+            <!-- Left panel: documents -->
+            <Border Grid.Column="0" BorderBrush="{DynamicResource SystemControlForegroundBaseMediumLowBrush}"
+                    BorderThickness="0,0,1,0" Padding="4">
+                <DockPanel>
+                    <TextBlock DockPanel.Dock="Top" Text="Documents" FontWeight="SemiBold" Margin="0,0,0,4"/>
+                    <ListBox ItemsSource="{Binding Editor.Documents}"
+                             SelectedItem="{Binding Editor.ActiveDocument}"
+                             SelectionMode="Single">
+                        <ListBox.ItemTemplate>
+                            <DataTemplate>
+                                <TextBlock Text="{Binding Name}"/>
+                            </DataTemplate>
+                        </ListBox.ItemTemplate>
+                    </ListBox>
+                </DockPanel>
+            </Border>
+
+            <!-- Center: canvas with scrollbars -->
+            <Grid Grid.Column="1" RowDefinitions="*,Auto" ColumnDefinitions="*,Auto">
+                <Border Grid.Row="0" Grid.Column="0" Background="#FF1E1E1E" ClipToBounds="True">
+                    <controls:PixelCanvas x:Name="Canvas"
+                                           SourceBitmap="{Binding Editor.CanvasBitmap}"
+                                           ShowGrid="{Binding Editor.ShowGrid}"/>
+                </Border>
+                <ScrollBar x:Name="HScroll" Grid.Row="1" Grid.Column="0"
+                           Orientation="Horizontal"/>
+                <ScrollBar x:Name="VScroll" Grid.Row="0" Grid.Column="1"
+                           Orientation="Vertical"/>
+            </Grid>
+
+            <!-- Right panel: layers -->
+            <Border Grid.Column="2" BorderBrush="{DynamicResource SystemControlForegroundBaseMediumLowBrush}"
+                    BorderThickness="1,0,0,0" Padding="4">
+                <DockPanel>
+                    <TextBlock DockPanel.Dock="Top" Text="Layers" FontWeight="SemiBold" Margin="0,0,0,4"/>
+                    <ListBox ItemsSource="{Binding Editor.Layers}"
+                             SelectedItem="{Binding Editor.ActiveLayer}"
+                             SelectionMode="Single">
+                        <ListBox.ItemTemplate>
+                            <DataTemplate>
+                                <StackPanel Orientation="Horizontal" Spacing="4">
+                                    <CheckBox IsChecked="{Binding IsVisible}" MinWidth="0"/>
+                                    <TextBlock Text="{Binding Name}" VerticalAlignment="Center"/>
+                                </StackPanel>
+                            </DataTemplate>
+                        </ListBox.ItemTemplate>
+                    </ListBox>
+                </DockPanel>
+            </Border>
+
+        </Grid>
+    </DockPanel>
 </Window>

Minint/Views/MainWindow.axaml.cs

@@ -1,4 +1,8 @@
+using System;
 using Avalonia.Controls;
+using Avalonia.Controls.Primitives;
+using Minint.Controls;
+using Minint.ViewModels;
 
 namespace Minint.Views;
 
@@ -8,4 +12,23 @@ public partial class MainWindow : Window
     {
         InitializeComponent();
     }
+
+    protected override void OnOpened(EventArgs e)
+    {
+        base.OnOpened(e);
+
+        var canvas = this.FindControl<PixelCanvas>("Canvas");
+        var hScroll = this.FindControl<ScrollBar>("HScroll");
+        var vScroll = this.FindControl<ScrollBar>("VScroll");
+
+        if (canvas is not null && hScroll is not null && vScroll is not null)
+            canvas.AttachScrollBars(hScroll, vScroll);
+    }
+
+    protected override void OnDataContextChanged(EventArgs e)
+    {
+        base.OnDataContextChanged(e);
+        if (DataContext is MainWindowViewModel vm)
+            vm.Owner = this;
+    }
 }