Request for Feedback: Improving Startup Latency in X11 (#16033)

* Improve: X11 Startup time with asynchronous Gfx Startup

Before: 80-100
After: 66-81

* Changed: Move CursorFactory Back to its Place

* Changed: An alternative attempt with lazy cursor generation.

src/Avalonia.X11/X11CursorFactory.cs

@@ -1,13 +1,10 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Runtime.InteropServices;
 using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Input;
 using Avalonia.Platform;
 using Avalonia.Platform.Internal;
-using Avalonia.SourceGenerator;
-using Avalonia.Utilities;
 
 #nullable enable
 
@@ -50,15 +47,14 @@ namespace Avalonia.X11
                 {StandardCursorType.TopRightCorner, CursorFontShape.XC_top_right_corner},
             };
 
-        [GenerateEnumValueList]
-        private static partial CursorFontShape[] GetAllCursorShapes();
-        
         public X11CursorFactory(IntPtr display)
         {
             _display = display;
             _nullCursor = GetNullCursor(display);
-            _cursors = GetAllCursorShapes()
-                .ToDictionary(id => id, id => XLib.XCreateFontCursor(_display, id));
+            
+            // 78 = number of items in CursorFontShape enum
+            // Unlikely to change, but, do we have a Src Gen for this?
+            _cursors = new Dictionary<CursorFontShape, IntPtr>(78);
         }
 
         public ICursorImpl GetCursor(StandardCursorType cursorType)
@@ -71,8 +67,8 @@ namespace Avalonia.X11
             else
             {
                 handle = s_mapping.TryGetValue(cursorType, out var shape)
-                ? _cursors[shape]
-                : _cursors[CursorFontShape.XC_left_ptr];
+                ? GetCursorHandleLazy(shape)
+                : GetCursorHandleLazy(CursorFontShape.XC_left_ptr);
             }
             return new CursorImpl(handle);
         }
@@ -144,6 +140,14 @@ namespace Avalonia.X11
             
             public IFramebufferRenderTarget CreateFramebufferRenderTarget() => new FuncFramebufferRenderTarget(Lock);
         }
+        
+        private nint GetCursorHandleLazy(CursorFontShape shape)
+        {
+            if (!_cursors.TryGetValue(shape, out var handle))
+                _cursors[shape] = handle = XLib.XCreateFontCursor(_display, shape);
+
+            return handle;
+        }
     }
 
     internal class CursorImpl : ICursorImpl

src/Avalonia.X11/X11Platform.cs

@@ -2,8 +2,6 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
-using System.Runtime.InteropServices;
-using Avalonia.Controls;
 using Avalonia.Controls.Platform;
 using Avalonia.FreeDesktop;
 using Avalonia.FreeDesktop.DBusIme;