Merge pull request #127 from NogginBops/context-fixes

Fix OpenGL context issues when using multiple GLWpfControls.

src/Example/TabbedMainWindowTest.xaml.cs

@@ -21,15 +21,20 @@ public TabbedMainWindowTest()
         {
             InitializeComponent();
             GLWpfControlSettings mainSettings = new GLWpfControlSettings {MajorVersion = 4, MinorVersion = 1, Profile = ContextProfile.Compatability, ContextFlags = ContextFlags.Debug};
+            // Start() makes the controls context current.
             Control1.Start(mainSettings);
+            // We call Context.MakeCurrent() to make this explicitly clear.
+            Control1.Context.MakeCurrent();
             scene1.Initialize();
 
             GLWpfControlSettings insetSettings = new GLWpfControlSettings {MajorVersion = 4, MinorVersion = 1, Profile = ContextProfile.Compatability, ContextFlags = ContextFlags.Debug, Samples = 8};
             Control2.Start(insetSettings);
+            Control2.Context.MakeCurrent();
             scene2.Initialize();
 
             GLWpfControlSettings transparentSettings = new GLWpfControlSettings { MajorVersion = 4, MinorVersion = 1, Profile = ContextProfile.Compatability, ContextFlags = ContextFlags.Debug, TransparentBackground = true};
             Control3.Start(transparentSettings);
+            Control3.Context.MakeCurrent();
             scene3.Initialize();
 
             Control1.KeyDown += Control1_KeyDown;

src/GLWpfControl/GLWpfControl.cs

@@ -29,6 +29,7 @@ static GLWpfControl()
 
         /// <summary>
         /// Called whenever rendering should occur.
+        /// GLWpfControl makes sure that it's OpenGL context is current when this event happens.
         /// </summary>
         public event Action<TimeSpan>? Render;
 
@@ -37,7 +38,10 @@ static GLWpfControl()
         /// This is only for extremely advanced use, where a non-display out task needs to run.
         /// Examples of these are an async Pixel Buffer Object transfer or Transform Feedback.
         /// If you do not know what these are, do not use this function.
+        /// 
+        /// GLWpfControl makes sure that it's OpenGL context is current when this event happens.
         /// </summary>
+        [Obsolete("There is no difference between Render and AsyncRender. Use Render.")]
         public event Action? AsyncRender;
 
         /// <summary>
@@ -101,6 +105,8 @@ public bool RenderContinuously {
 
         /// <summary>
         /// The currently used OpenGL context, or null if no OpenGL context is created.
+        /// It is not safe to call <see cref="IGraphicsContext.MakeCurrent"/> on this context on any other thread
+        /// than the one the <see cref="GLWpfControl"/> is running on.
         /// </summary>
         [CLSCompliant(false)]
         public IGraphicsContext? Context => _renderer?.GLContext;

src/GLWpfControl/GLWpfControlRenderer.cs

@@ -22,6 +22,7 @@ internal sealed class GLWpfControlRenderer : IDisposable
         private readonly DxGlContext _context;
 
         public event Action<TimeSpan>? GLRender;
+        [Obsolete("There is no difference between GLRender and GLAsyncRender. Use GLRender.")]
         public event Action? GLAsyncRender;
 
         /// <summary>The width of this buffer in pixels.</summary>
@@ -76,6 +77,8 @@ public void ReallocateFramebufferIfNeeded(double width, double height, double dp
 
             if (D3dImage == null || FramebufferWidth != newWidth || FramebufferHeight != newHeight || MultisampleType != msaaType)
             {
+                _context.GraphicsContext.MakeCurrent();
+
                 if (D3dImage != null)
                 {
                     GL.DeleteFramebuffer(GLFramebufferHandle);
@@ -195,6 +198,8 @@ public void Render(DrawingContext drawingContext)
                 return;
             }
 
+            _context.GraphicsContext.MakeCurrent();
+
             TimeSpan curFrameStamp = _stopwatch.Elapsed;
             TimeSpan deltaT = curFrameStamp - _lastFrameStamp;
             _lastFrameStamp = curFrameStamp;

src/GLWpfControl/GLWpfControlSettings.cs

@@ -28,6 +28,8 @@ public sealed class GLWpfControlSettings
         /// <summary>
         /// May be null. If defined, an external context will be used, of which the caller is responsible
         /// for managing the lifetime and disposal of.
+        /// The management of the context sent to the <see cref="GLWpfControl"/> becomes the responsibility of the <see cref="GLWpfControl"/>.
+        /// Trying to call <see cref="IGraphicsContext.MakeCurrent"/> on this context on some other thread might lead to uninteded consequences.
         /// </summary>
         [CLSCompliant(false)]
         public IGraphicsContext? ContextToUse { get; set; }