macOS: Fix blurry rendering on Retina displays by setting correct backing scale factor

src/Ryujinx.Common/Helpers/ObjectiveC.cs

@@ -42,6 +42,9 @@ namespace Ryujinx.Common.Helper
         [return: MarshalAs(UnmanagedType.Bool)]
         private static partial bool bool_objc_msgSend(nint receiver, Selector selector, nint param);
 
+        [LibraryImport(ObjCRuntime, EntryPoint = "objc_msgSend")]
+        private static partial double double_objc_msgSend(nint receiver, Selector selector);
+
         public readonly struct Object
         {
             public readonly nint ObjPtr;
@@ -105,6 +108,11 @@ namespace Ryujinx.Common.Helper
             {
                 return bool_objc_msgSend(ObjPtr, selector, obj.ObjPtr);
             }
+
+            public double GetDoubleFromMessage(Selector selector)
+            {
+                return double_objc_msgSend(ObjPtr, selector);
+            }
         }
 
         public readonly struct Selector

src/Ryujinx.Common/SystemInterop/ForceDpiAware.cs

@@ -1,7 +1,9 @@
+using Ryujinx.Common.Helper;
 using Ryujinx.Common.Logging;
 using System;
 using System.Globalization;
 using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 
 namespace Ryujinx.Common.SystemInterop
 {
@@ -53,6 +55,10 @@ namespace Ryujinx.Common.SystemInterop
                 {
                     userDpiScale = GdiPlusHelper.GetDpiX(nint.Zero);
                 }
+                else if (OperatingSystem.IsMacOS())
+                {
+                    userDpiScale = GetMacOSDpiScale();
+                }
                 else if (OperatingSystem.IsLinux())
                 {
                     string xdgSessionType = Environment.GetEnvironmentVariable("XDG_SESSION_TYPE")?.ToLower();
@@ -93,5 +99,27 @@ namespace Ryujinx.Common.SystemInterop
 
             return Math.Min(userDpiScale / StandardDpiScale, MaxScaleFactor);
         }
+
+        [SupportedOSPlatform("macos")]
+        private static double GetMacOSDpiScale()
+        {
+            try
+            {
+                ObjectiveC.Object screenClass = new("NSScreen");
+                ObjectiveC.Object mainScreen = screenClass.GetFromMessage("mainScreen");
+                if (mainScreen.ObjPtr != nint.Zero)
+                {
+                    double backingScale = mainScreen.GetDoubleFromMessage("backingScaleFactor");
+                    // Convert backing scale factor (e.g., 2.0) to equivalent DPI (e.g., 192).
+                    return StandardDpiScale * backingScale;
+                }
+            }
+            catch (Exception e)
+            {
+                Logger.Warning?.Print(LogClass.Application, $"Couldn't determine monitor DPI on macOS: {e.Message}");
+            }
+
+            return StandardDpiScale;
+        }
     }
 }

src/Ryujinx/UI/Renderer/EmbeddedWindow.cs

@@ -243,9 +243,18 @@ namespace Ryujinx.Ava.UI.Renderer
             // Make its renderer our metal layer.
             child.SendMessage("setWantsLayer:", 1);
             child.SendMessage("setLayer:", metalLayer);
-            metalLayer.SendMessage("setContentsScale:", Program.DesktopScaleFactor);
 
-            // Ensure the scale factor is up to date.
+            // Query the actual backing scale factor from the screen.
+            // This ensures the CAMetalLayer drawable is created at the correct
+            // pixel resolution for Retina displays, preventing blurry rendering.
+            double backingScaleFactor = GetBackingScaleFactor();
+            metalLayer.SendMessage("setContentsScale:", backingScaleFactor);
+
+            // Update DesktopScaleFactor immediately so the rest of the app
+            // (including the bounds callback) uses the correct value.
+            Program.DesktopScaleFactor = backingScaleFactor;
+
+            // Ensure the scale factor is up to date on bounds changes.
             _updateBoundsCallback = rect =>
             {
                 metalLayer.SendMessage("setContentsScale:", Program.DesktopScaleFactor);
@@ -258,6 +267,26 @@ namespace Ryujinx.Ava.UI.Renderer
             return new PlatformHandle(nsView, "NSView");
         }
 
+        [SupportedOSPlatform("macos")]
+        private static double GetBackingScaleFactor()
+        {
+            try
+            {
+                ObjectiveC.Object screenClass = new("NSScreen");
+                ObjectiveC.Object mainScreen = screenClass.GetFromMessage("mainScreen");
+                if (mainScreen.ObjPtr != nint.Zero)
+                {
+                    return mainScreen.GetDoubleFromMessage("backingScaleFactor");
+                }
+            }
+            catch
+            {
+                // Fallback to default scale if ObjC call fails.
+            }
+
+            return 2.0;
+        }
+
         [SupportedOSPlatform("Linux")]
         void DestroyLinux()
         {