Some bug fixes

Changelog:

- Reapply some changes that got lost while rebasing from #904
- Make sure to guarantee exclusivity on the GL context (fixing multiple
possible race conditions on Windows)
- Avoid making GLRenderer disposed multiple time

Ryujinx/Ui/GLRenderer.cs

@@ -3,6 +3,7 @@ using OpenTK;
 using OpenTK.Graphics;
 using OpenTK.Graphics.OpenGL;
 using OpenTK.Input;
+using OpenTK.Platform;
 using Ryujinx.Configuration;
 using Ryujinx.Graphics.OpenGL;
 using Ryujinx.HLE;
@@ -88,7 +89,9 @@ namespace Ryujinx.Ui
 
         private void GLRenderer_Initialized(object sender, EventArgs e)
         {
+            // Release the GL exclusivity that OpenTK gave us.
             GraphicsContext.MakeCurrent(null);
+
             WaitEvent.Set();
         }
 
@@ -168,11 +171,19 @@ namespace Ryujinx.Ui
 
         public void Exit()
         {
-            _device.DisposeGpu();
+            if (IsStopped)
+            {
+                return;
+            }
 
             IsStopped = true;
             IsActive = false;
 
+            using (ScopedGLContext scopedGLContext = new ScopedGLContext(WindowInfo, GraphicsContext))
+            {
+                _device.DisposeGpu();
+            }
+
             WaitEvent.Set();
         }
 
@@ -188,8 +199,10 @@ namespace Ryujinx.Ui
 
         public void Render()
         {
-            GraphicsContext.MakeCurrent(WindowInfo);
+            using (ScopedGLContext scopedGLContext = new ScopedGLContext(WindowInfo, GraphicsContext))
+            {
                 _renderer.Initialize();
+            }
 
             while (IsActive)
             {
@@ -198,8 +211,8 @@ namespace Ryujinx.Ui
                     return;
                 }
 
-                GraphicsContext.MakeCurrent(WindowInfo);
-
+                using (ScopedGLContext scopedGLContext = new ScopedGLContext(WindowInfo, GraphicsContext))
+                {
                     GL.ClearColor(Color4.Black);
 
                     _ticks += _chrono.ElapsedTicks;
@@ -239,13 +252,13 @@ namespace Ryujinx.Ui
                     }
                 }
             }
+        }
 
         public void SwapBuffers()
         {
             OpenTK.Graphics.GraphicsContext.CurrentContext.SwapBuffers();
         }
 
-
         public void MainLoop()
         {
             while (IsActive)

Ryujinx/Ui/MainWindow.cs

@@ -433,14 +433,15 @@ namespace Ryujinx.Ui
 
             DiscordIntegrationModule.SwitchToMainMenu();
 
-            _screenExitStatus.Set();
-
             Application.Invoke(delegate
             {
                 _stopEmulation.Sensitive            = false;
                 _firmwareInstallFile.Sensitive      = true;
                 _firmwareInstallDirectory.Sensitive = true;
+
             });
+
+            _screenExitStatus.Set();
         }
 
         private static void UpdateGameMetadata(string titleId)
@@ -475,7 +476,11 @@ namespace Ryujinx.Ui
             {
                 UpdateGameMetadata(device.System.TitleIdText);
 
-                _gLWigdet?.Exit();
+                if (_gLWigdet != null)
+                {
+                    _gLWigdet.Exit();
+                    _screenExitStatus.WaitOne();
+                }
             }
 
             Dispose();
@@ -627,15 +632,11 @@ namespace Ryujinx.Ui
 
         private void Exit_Pressed(object sender, EventArgs args)
         {
-            _gLWigdet?.Exit();
-
             End(_emulationContext);
         }
 
         private void Window_Close(object sender, DeleteEventArgs args)
         {
-            _gLWigdet?.Exit();
-            
             End(_emulationContext);
         }
 

Ryujinx/Ui/ScopedGLContext.cs

@@ -0,0 +1,35 @@
+using OpenTK.Graphics;
+using OpenTK.Platform;
+using System;
+using System.Threading;
+
+namespace Ryujinx.Ui
+{
+    class ScopedGLContext : IDisposable
+    {
+        private IGraphicsContext _graphicsContext;
+
+        private static readonly object _lock = new object();
+
+        public ScopedGLContext(IWindowInfo windowInfo, IGraphicsContext graphicsContext)
+        {
+            _graphicsContext = graphicsContext;
+
+            Monitor.Enter(_lock);
+
+            MakeCurrent(windowInfo);
+        }
+
+        private void MakeCurrent(IWindowInfo windowInfo)
+        {
+            _graphicsContext.MakeCurrent(windowInfo);
+        }
+
+        public void Dispose()
+        {
+            MakeCurrent(null);
+
+            Monitor.Exit(_lock);
+        }
+    }
+}