Fix float marshalling for sampler LOD on ARM64

- Ensures correct LOD max clamp setting on Apple Silicon by using
  explicit float P/Invoke to avoid ABI issues with objc_msgSend

Author: al6uiz

src/MewVG.Metal/Interop/Metal.cs

@@ -129,6 +129,7 @@ public static class Sel
         public static readonly nint SetMinFilter = ObjCRuntime.RegisterSelector("setMinFilter:");
         public static readonly nint SetMagFilter = ObjCRuntime.RegisterSelector("setMagFilter:");
         public static readonly nint SetMipFilter = ObjCRuntime.RegisterSelector("setMipFilter:");
+        public static readonly nint SetLodMaxClamp = ObjCRuntime.RegisterSelector("setLodMaxClamp:");
         public static readonly nint SetSAddressMode = ObjCRuntime.RegisterSelector("setSAddressMode:");
         public static readonly nint SetTAddressMode = ObjCRuntime.RegisterSelector("setTAddressMode:");
 

src/MewVG.Metal/Interop/ObjCRuntime.cs

@@ -85,6 +85,15 @@ public static unsafe partial class ObjCRuntime
     [LibraryImport(LibObjC, EntryPoint = "objc_msgSend")]
     public static partial void SendMessageNoReturn(nint receiver, nint selector, double arg1);
 
+    // Use DllImport (not LibraryImport) for the float overload. LibraryImport's
+    // source-generated marshalling for float was observed to corrupt subsequent
+    // objc_msgSend calls on Apple Silicon (ARM64) — float failed to reliably land
+    // in the s0 floating-point register. DllImport defers to the runtime's standard
+    // platform ABI which handles float correctly on both ARM64 (s0) and x86_64
+    // (xmm0). Single signature covers both architectures.
+    [DllImport(LibObjC, EntryPoint = "objc_msgSend")]
+    public static extern void SendMessageFloat(nint receiver, nint selector, float arg1);
+
     [LibraryImport(LibObjC, EntryPoint = "objc_msgSend")]
     public static partial void SendMessageNoReturn(nint receiver, nint selector, MTLClearColor arg1);
 

src/MewVG.Metal/MNVGcontext.cs

@@ -2335,6 +2335,9 @@ public int CreateTexture(int type, int width, int height, int imageFlags, ReadOn
         if ((imageFlags & (int)NVGimageFlags.GenerateMipmaps) != 0)
         {
             ObjCRuntime.SendMessage(samplerDescriptor, MetalSelectors.setMipFilter, (ulong)MTLSamplerMipFilter.Linear);
+            // Use explicit float P/Invoke — LibraryImport float overload appears to
+            // mishandle the ARM64 ABI here, breaking subsequent text sampler creation.
+            ObjCRuntime.SendMessageFloat(samplerDescriptor, Metal.Sel.SetLodMaxClamp, 2.0f);
         }
 
         var repeatX = (imageFlags & (int)NVGimageFlags.RepeatX) != 0;