UI: add a VRR VSync mode using the FifoRelaxed present mode

Add a new VSyncMode.Vrr that selects the FifoRelaxed Vulkan present mode,
letting the display's variable refresh rate (G-Sync/FreeSync) drive the
refresh in fullscreen and smoothing a fluctuating frame rate without
tearing. Reachable by cycling the status-bar VSync button; shown in green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Ryujinx.Common/Configuration/VSyncMode.cs

@@ -4,7 +4,8 @@ namespace Ryujinx.Common.Configuration
     {
         Switch,
         Unbounded,
-        Custom
+        Custom,
+        Vrr
     }
 
     public static class VSyncModeExtensions
@@ -13,8 +14,9 @@ namespace Ryujinx.Common.Configuration
             vsync switch
             {
                 VSyncMode.Switch => customEnabled ? VSyncMode.Custom : VSyncMode.Unbounded,
-                VSyncMode.Unbounded => VSyncMode.Switch,
                 VSyncMode.Custom => VSyncMode.Unbounded,
+                VSyncMode.Unbounded => VSyncMode.Vrr,
+                VSyncMode.Vrr => VSyncMode.Switch,
                 _ => VSyncMode.Switch
             };
     }

src/Ryujinx.Graphics.Vulkan/Window.cs

@@ -282,7 +282,14 @@ namespace Ryujinx.Graphics.Vulkan
 
         private static PresentModeKHR ChooseSwapPresentMode(PresentModeKHR[] availablePresentModes, VSyncMode vSyncMode)
         {
-            if (vSyncMode == VSyncMode.Unbounded && availablePresentModes.Contains(PresentModeKHR.ImmediateKhr))
+            // VRR: FifoRelaxed lets the display's variable refresh rate (G-Sync/FreeSync) drive the refresh
+            // in fullscreen, smoothing a fluctuating frame rate without tearing. Immediate (full VSync off)
+            // was tried first but could hang the GPU under load, so FifoRelaxed is used instead.
+            if (vSyncMode == VSyncMode.Vrr && availablePresentModes.Contains(PresentModeKHR.FifoRelaxedKhr))
+            {
+                return PresentModeKHR.FifoRelaxedKhr;
+            }
+            else if (vSyncMode == VSyncMode.Unbounded && availablePresentModes.Contains(PresentModeKHR.ImmediateKhr))
             {
                 return PresentModeKHR.ImmediateKhr;
             }

src/Ryujinx/Assets/Styles/Themes.xaml

@@ -18,6 +18,7 @@
             <Color x:Key="Switch">#FF2EEAC9</Color>
             <Color x:Key="Unbounded">#FFFF4554</Color>
             <Color x:Key="Custom">#6483F5</Color>
+            <Color x:Key="Vrr">#FF4CD964</Color>
             <Color x:Key="Warning">#800080</Color>
             <Color x:Key="CustomConfig">#00B5B8</Color>
         </ResourceDictionary>
@@ -38,6 +39,7 @@
             <Color x:Key="Switch">#13c3a4</Color>
             <Color x:Key="Unbounded">#FFFF4554</Color>
             <Color x:Key="Custom">#6483F5</Color>
+            <Color x:Key="Vrr">#FF4CD964</Color>
             <Color x:Key="Warning">#800080</Color>
             <Color x:Key="CustomConfig">#00B5B8</Color>
         </ResourceDictionary>
@@ -58,6 +60,7 @@
             <Color x:Key="Switch">#FF2EEAC9</Color>
             <Color x:Key="Unbounded">#FFFF4554</Color>
             <Color x:Key="Custom">#6483F5</Color>
+            <Color x:Key="Vrr">#FF4CD964</Color>
             <Color x:Key="Warning">#FFA500</Color>
             <Color x:Key="CustomConfig">#00B5B8</Color>
         </ResourceDictionary>

src/Ryujinx/UI/ViewModels/MainWindowViewModel.cs

@@ -1369,7 +1369,12 @@ namespace Ryujinx.Ava.UI.ViewModels
                         VSyncModeColor = new SolidColorBrush(clr);
                     }
 
-                    VSyncModeText = args.VSyncMode == "Custom" ? "Custom" : "VSync";
+                    VSyncModeText = args.VSyncMode switch
+                    {
+                        "Custom" => "Custom",
+                        "Vrr" => "VRR",
+                        _ => "VSync"
+                    };
                     DockedStatusText = args.DockedMode;
                     AspectRatioStatusText = args.AspectRatio;
                     GameStatusText = args.GameStatus;