Replace string element render types with RenderCommandType enum, decompose UI elements (Button, CheckBox, chrome) into drawing primitives via ToPrimitives(), emit per-element commands on flush, and move composite into IRenderSource.

UI/GUI/UIEelements/UIEelement.cs

@@ -1,3 +1,4 @@
+using RemSox.UI.GUI.Rendering;
 using RemSox.Utils;
 
 using System.Drawing;
@@ -6,6 +7,8 @@ namespace RemSox.UI.GUI.UIEelements;
 
 public abstract class UIElement(string type) : ChangedPropertiesTracker
 {
+    public const int PrimitiveIdShift = 6;
+
     public int Id { get; init; }
 
     public string Type { get; set; } = type;
@@ -15,4 +18,10 @@ public abstract class UIElement(string type) : ChangedPropertiesTracker
         get;
         set => SetProperty(nameof(Position), ref field, value);
     }
+
+    /// <summary> Expands this UI element into drawing primitives. </summary>
+    public abstract IEnumerable<RenderCommand> ToPrimitives(int windowId);
+
+    /// <summary> Builds a stable primitive ID from element ID and sub-index. </summary>
+    protected int PrimitiveId(int subIndex) => (Id << PrimitiveIdShift) | subIndex;
 }