Fix : Fix controller Stick visualizer perfomance (#119)

This PR aims to fix a bug inside the settings window that caused the Controller Stick visualizer to run at extremely degraded performance when the selected profile had a rainbow LED configuration:
Old behaviour : <video src="/attachments/1915ab74-6e1b-4e2f-9182-820cbed5359b" title="Screen Recording 2026-05-30 105859" controls></video>
New / updated behaviour : <video src="/attachments/dd293402-19e7-439e-8aa6-114d4ee22404" title="Screen Recording 2026-05-30 110338" controls></video>

The issue was that the input settings page automatically subscribed controllers to rainbow LED updates when a saved profile with rainbow LEDs enabled was loaded.
Reopening input settings on a non-default controller profile could immediately start the rainbow LED update loop from the settings UI, which caused the stick visualizer to become sluggish or jittery on affected controllers. The preview handler is now only registered when the rainbow LED option is changed in the settings UI, and it uses a stable handler so duplicate callbacks are not stacked.

Reviewed-on: https://git.ryujinx.app/projects/Ryubing/pulls/119

src/Ryujinx/UI/ViewModels/Input/ControllerInputViewModel.cs

@@ -2,6 +2,7 @@ using Avalonia.Svg.Skia;
 using CommunityToolkit.Mvvm.ComponentModel;
 using Ryujinx.Ava.UI.Models.Input;
 using Ryujinx.Ava.UI.Views.Input;
+using Ryujinx.Common.Helper;
 using Ryujinx.Common.Utilities;
 using Ryujinx.UI.Views.Input;
 
@@ -59,32 +60,46 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
         public partial SvgImage Image { get; set; }
         public InputViewModel ParentModel { get; }
 
+        private readonly RefEvent<System.Drawing.Color>.Handler _rainbowLedHandler;
+
         public ControllerInputViewModel(InputViewModel model, GamepadInputConfig config, StickVisualizer visualizer)
         {
             ParentModel = model;
             Visualizer = visualizer;
+            _rainbowLedHandler = SetRainbowLed;
+
             model.NotifyChangesEvent += OnParentModelChanged;
             OnParentModelChanged();
-            config.PropertyChanged += (_, args) =>
+            config.PropertyChanged += OnConfigPropertyChanged;
-            {
-                if (args.PropertyName is nameof(Config.UseRainbowLed))
-                {
-                    if (Config is { UseRainbowLed: true, TurnOffLed: false, EnableLedChanging: true })
-                        Rainbow.Updated += (ref color) => ParentModel.SelectedGamepad.SetLed((uint)color.ToArgb());
-                    else
-                    {
-                        Rainbow.Reset();
-
-                        if (Config.TurnOffLed)
-                            ParentModel.SelectedGamepad.ClearLed();
-                        else
-                            ParentModel.SelectedGamepad.SetLed(Config.LedColor.ToUInt32());
-                    }
-                }
-            };
             Config = config;
         }
 
+        private void OnConfigPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs args)
+        {
+            if (args.PropertyName is nameof(Config.UseRainbowLed))
+            {
+                if (Config is { UseRainbowLed: true, TurnOffLed: false, EnableLedChanging: true })
+                {
+                    Rainbow.Updated -= _rainbowLedHandler;
+                    Rainbow.Updated += _rainbowLedHandler;
+                }
+                else
+                {
+                    Rainbow.Reset();
+
+                    if (Config.TurnOffLed)
+                        ParentModel.SelectedGamepad.ClearLed();
+                    else
+                        ParentModel.SelectedGamepad.SetLed(Config.LedColor.ToUInt32());
+                }
+            }
+        }
+
+        private void SetRainbowLed(ref System.Drawing.Color color)
+        {
+            ParentModel.SelectedGamepad.SetLed((uint)color.ToArgb());
+        }
+
         public async void ShowMotionConfig()
         {
             await MotionInputView.Show(this);

src/Ryujinx/UI/ViewModels/Input/InputViewModel.cs

@@ -23,7 +23,6 @@ using Ryujinx.Input.SDL3;
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Drawing;
 using System.IO;
 using System.Linq;
 using System.Text.Json;
@@ -81,10 +80,6 @@ namespace Ryujinx.Ava.UI.ViewModels.Input
 
                 field = value;
 
-                if ((field?.Features & GamepadFeaturesFlag.Led) != 0 &&
-                    ConfigViewModel is ControllerInputViewModel { Config.UseRainbowLed: true })
-                    Rainbow.Updated += (ref Color color) => field.SetLed((uint)color.ToArgb());
-
                 OnPropertiesChanged(nameof(HasLed), nameof(CanClearLed));
             }
         }