Implement full canvas compositing and redraw only on state change

Utils/ChangedPropertiesTracker.cs

@@ -1,29 +1,49 @@
 
+using System.Collections.Generic;
 using System.ComponentModel;
+using System.Linq;
 
 namespace RemSox.Utils;
 
 public abstract class ChangedPropertiesTracker : INotifyPropertyChanged
 {
-    private readonly Dictionary<string, object?> changedProperties = [];
+    private readonly Dictionary<string, object?> properties = [];
+    private readonly HashSet<string> changedPropertyNames = [];
 
-    public IReadOnlyDictionary<string, object?> ChangedProperties => changedProperties;
+    public IReadOnlyDictionary<string, object?> ChangedProperties
+    {
+        get
+        {
+            var changes = new Dictionary<string, object?>();
+            foreach (var name in changedPropertyNames)
+            {
+                if (properties.TryGetValue(name, out var value))
+                {
+                    changes[name] = value;
+                }
+            }
+            return changes;
+        }
+    }
+
+    public IReadOnlyDictionary<string, object?> AllProperties => properties;
 
     public event PropertyChangedEventHandler? PropertyChanged;
 
-    public bool AnyPropertyChanged => changedProperties.Count > 0;
+    public bool AnyPropertyChanged => changedPropertyNames.Count > 0;
 
     protected void SetProperty<T>(string name, ref T field, T value)
     {
         if (!EqualityComparer<T>.Default.Equals(field, value))
         {
             field = value;
-            changedProperties[name] = value;
+            properties[name] = value;
+            changedPropertyNames.Add(name);
             PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
         }
     }
 
-    public void ClearChangedProperties() => changedProperties.Clear();
+    public void ClearChangedProperties() => changedPropertyNames.Clear();
 
-    public bool IsPropertyChanged(string name) => changedProperties.ContainsKey(name);
+    public bool IsPropertyChanged(string name) => changedPropertyNames.Contains(name);
 }