Этап 5

Minint/ViewModels/EditorViewModel.cs

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+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;
+
+    /// <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;
+}