Implemented IGraphicsContext.SwapInterval property that supersedes IGraphicsContext.VSync. Fixes issue [#2671]: "Expose SwapInterval to GameWindow".

Source/GLControl/GLControl.cs

@@ -164,7 +164,7 @@ namespace OpenTK
             // Deferred setting of vsync mode. See VSync property for more information.
             if (initial_vsync_value.HasValue)
             {
-                Context.VSync = initial_vsync_value.Value;
+                Context.SwapInterval = initial_vsync_value.Value ? 1 : 0;
                 initial_vsync_value = null;
             }
 
@@ -331,7 +331,7 @@ namespace OpenTK
         /// <summary>
         /// Gets or sets a value indicating whether vsync is active for this GLControl.
         /// </summary>
-        [Description("Indicates whether GLControl updates are synced to the monitor's refresh.")]
+        [Description("Indicates whether GLControl updates are synced to the monitor's refresh rate.")]
         public bool VSync
         {
             get

Source/OpenTK/GameWindow.cs

@@ -518,9 +518,9 @@ namespace OpenTK
                     {
                         // Check if we have enough time for a vsync
                         if (RenderTime > 2.0 * TargetRenderPeriod)
-                            Context.VSync = false;
+                            Context.SwapInterval = 0;
                         else
-                            Context.VSync = true;
+                            Context.SwapInterval = 1;
                     }
 
                     render_period = render_args.Time = time;

Source/OpenTK/Graphics/GraphicsContext.cs

@@ -461,14 +461,36 @@ namespace OpenTK.Graphics
         }
 
         /// <summary>
-        /// Gets or sets a value indicating whether VSync is enabled.
+        /// [obsolete] Use SwapInterval property instead.
+        /// Gets or sets a value indicating whether VSync is enabled. When VSync is
+        /// enabled, <see cref="SwapBuffers()"/> calls will be synced to the refresh
+        /// rate of the <see cref="DisplayDevice"/> that contains improving visual
+        /// quality and reducing CPU usage. However, systems that cannot maintain
+        /// the requested rendering rate will suffer from large jumps in performance.
+        /// This can be counteracted by increasing the <see cref="SwapInterval"/>
+        /// value.
         /// </summary>
+        [Obsolete("Use SwapInterval property instead.")]
         public bool VSync
         {
             get { return implementation.VSync; }
             set { implementation.VSync = value;  }
         }
 
+        /// <summary>
+        /// Gets or sets a positive integer in the range [1, n), indicating the number of
+        /// <see cref="DisplayDevice"/> refreshes between consecutive
+        /// <see cref="SwapBuffers()"/> calls. The maximum value for n is
+        /// implementation-dependent. The default value is 1.
+        /// This value will only affect instances where <see cref="VSync"/> is enabled.
+        /// Invalid values will be clamped to the valid range.
+        /// </summary>
+        public int SwapInterval
+        {
+            get { return implementation.SwapInterval; }
+            set { implementation.SwapInterval = value; }
+        }
+
         /// <summary>
         /// Updates the graphics context.  This must be called when the render target
         /// is resized for proper behavior on Mac OS X.

Source/OpenTK/Graphics/GraphicsContextBase.cs

@@ -57,8 +57,20 @@ namespace OpenTK.Graphics
             get { return disposed; }
             protected set { disposed = value; }
         }
-        
+
-        public abstract bool VSync { get; set; }
+        public bool VSync
+        {
+            get { return SwapInterval > 0; }
+            set
+            {
+                if (value && SwapInterval <= 0)
+                    SwapInterval = 1;
+                else if (!value && SwapInterval > 0)
+                    SwapInterval = 0;
+            }
+        }
+
+        public abstract int SwapInterval { get; set; }
 
         public virtual void Update(IWindowInfo window) { }
 

Source/OpenTK/Graphics/IGraphicsContext.cs

@@ -42,10 +42,27 @@ namespace OpenTK.Graphics
         bool IsDisposed { get; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether VSyncing is enabled.
+        /// Gets or sets a value indicating whether VSync is enabled. When VSync is
+        /// enabled, <see cref="SwapBuffers()"/> calls will be synced to the refresh
+        /// rate of the <see cref="DisplayDevice"/> that contains improving visual
+        /// quality and reducing CPU usage. However, systems that cannot maintain
+        /// the requested rendering rate will suffer from large jumps in performance.
+        /// This can be counteracted by increasing the <see cref="SwapInterval"/>
+        /// value.
         /// </summary>
+        [Obsolete("Use SwapInterval property instead.")]
         bool VSync { get; set; }
 
+        /// <summary>
+        /// Gets or sets a positive integer in the range [1, n), indicating the number of
+        /// <see cref="DisplayDevice"/> refreshes between consecutive
+        /// <see cref="SwapBuffers()"/> calls. The maximum value for n is
+        /// implementation-dependent. The default value is 1.
+        /// This value will only affect instances where <see cref="VSync"/> is enabled.
+        /// Invalid values will be clamped to the valid range.
+        /// </summary>
+        int SwapInterval { get; set; }
+
         /// <summary>
         /// Updates the graphics context.  This must be called when the region the graphics context
         /// is drawn to is resized.

Source/OpenTK/Platform/Dummy/DummyGLContext.cs

@@ -24,6 +24,7 @@ namespace OpenTK.Platform.Dummy
     {
         // This mode is not real. To receive a real mode we'd have to create a temporary context, which is not desirable!
         bool vsync;
+        int swap_interval;
         static int handle_count;
         Thread current_thread;
 
@@ -82,7 +83,17 @@ namespace OpenTK.Platform.Dummy
 
         public override IntPtr GetAddress(string function) { return IntPtr.Zero; }
 
-        public override bool VSync { get { return vsync; } set { vsync = value; } }
+        public override int SwapInterval
+        {
+            get
+            {
+                return swap_interval;
+            }
+            set
+            {
+                swap_interval = value;
+            }
+        }
 
         public override void Update(IWindowInfo window)
         { }

Source/OpenTK/Platform/Egl/EglContext.cs

@@ -39,7 +39,7 @@ namespace OpenTK.Platform.Egl
 
         EglWindowInfo WindowInfo;
         IntPtr HandleAsEGLContext { get { return Handle.Handle; } set { Handle = new ContextHandle(value); } }
-        bool vsync = true;   // Default vsync value is defined as 1 (true) in EGL.
+        int swap_interval = 1; // Default interval is defined as 1 in EGL.
 
         #endregion
 
@@ -117,18 +117,18 @@ namespace OpenTK.Platform.Egl
             get { return Egl.GetCurrentContext() == HandleAsEGLContext; }
         }
 
-        public override bool VSync
+        public override int SwapInterval
         {
             get
             {
                 // Egl.GetSwapInterval does not exist, so store and return the current interval.
                 // The default interval is defined as 1 (true).
-                return vsync;
+                return swap_interval;
             }
             set
             {
-                if (Egl.SwapInterval(WindowInfo.Display, value ? 1 : 0))
+                if (Egl.SwapInterval(WindowInfo.Display, value))
-                    vsync = value;
+                    swap_interval = value;
                 else
                     Debug.Print("[Warning] Egl.SwapInterval({0}, {1}) failed.", WindowInfo.Display, value);
             }

Source/OpenTK/Platform/MacOS/AglContext.cs

@@ -44,7 +44,6 @@ namespace OpenTK.Platform.MacOS
 
     class AglContext : DesktopGraphicsContext
     {
-        bool mVSync = false;
         // Todo: keep track of which display adapter was specified when the context was created.
         // IntPtr displayID;
 
@@ -427,16 +426,24 @@ namespace OpenTK.Platform.MacOS
             get { return (Handle.Handle == Agl.aglGetCurrentContext()); }
         }
 
-        public override bool VSync
+        public override int SwapInterval
         {
-            get { return mVSync; }
+            get {
+                int swap_interval = 0;
+                if (Agl.aglGetInteger(Handle.Handle, Agl.ParameterNames.AGL_SWAP_INTERVAL, out swap_interval))
+                {
+                    return swap_interval;
+                }
+                else
+                {
+                    MyAGLReportError("aglGetInteger");
+                    return 0;
+                }
+            }
             set
             {
-                int intVal = value ? 1 : 0;
+                if (!Agl.aglSetInteger(Handle.Handle, Agl.ParameterNames.AGL_SWAP_INTERVAL, ref value))
-                
+                    MyAGLReportError("aglSetInteger");
-                Agl.aglSetInteger(Handle.Handle, Agl.ParameterNames.AGL_SWAP_INTERVAL, ref intVal);
-                
-                mVSync = value;
             }
         }
 

Source/OpenTK/Platform/MacOS/CarbonBindings/Agl.cs

@@ -425,15 +425,20 @@ namespace OpenTK.Platform.MacOS
         /*
          ** Per context options
          */
-        [DllImport(agl)] internal static extern byte aglEnable(AGLContext ctx, ParameterNames pname);
-        [DllImport(agl)] internal static extern byte aglDisable(AGLContext ctx, ParameterNames pname);
-        [DllImport(agl)] static extern byte aglIsEnabled(AGLContext ctx, GLenum pname);
         [DllImport(agl)]
-        internal static extern byte aglSetInteger(AGLContext ctx, ParameterNames pname, ref int @params);
+        internal static extern bool aglEnable(AGLContext ctx, ParameterNames pname);
         [DllImport(agl)]
-        internal static extern byte aglSetInteger(AGLContext ctx, ParameterNames pname, int []@params);
+        internal static extern bool aglDisable(AGLContext ctx, ParameterNames pname);
         [DllImport(agl)]
-        static extern byte aglGetInteger(AGLContext ctx, GLenum pname, int* @params);
+        static extern bool aglIsEnabled(AGLContext ctx, GLenum pname);
+        [DllImport(agl)]
+        internal static extern bool aglSetInteger(AGLContext ctx, ParameterNames pname, ref int param);
+        [DllImport(agl)]
+        internal static extern bool aglSetInteger(AGLContext ctx, ParameterNames pname, int[] @params);
+        //[DllImport(agl)]
+        //static extern bool aglGetInteger(AGLContext ctx, ParameterNames pname, int* @params);
+        [DllImport(agl)]
+        internal static extern bool aglGetInteger(AGLContext ctx, ParameterNames pname, out int param);
 
         /*
          ** Font function

Source/OpenTK/Platform/Windows/WinGLContext.cs

@@ -203,18 +203,18 @@ namespace OpenTK.Platform.Windows
 
         #endregion
 
-        #region public bool VSync
+        #region SwapInterval
 
-        /// <summary>
+        public override int SwapInterval
-        /// Gets or sets a System.Boolean indicating whether SwapBuffer calls are synced to the screen refresh rate.
-        /// </summary>
-        public override bool VSync
         {
             get
             {
                 lock (LoadLock)
                 {
-                    return vsync_supported && Wgl.Ext.GetSwapInterval() != 0;
+                    if (vsync_supported)
+                        return Wgl.Ext.GetSwapInterval();
+                    else
+                        return 0;
                 }
             }
             set
@@ -222,7 +222,7 @@ namespace OpenTK.Platform.Windows
                 lock (LoadLock)
                 {
                     if (vsync_supported)
-                        Wgl.Ext.SwapInterval(value ? 1 : 0);
+                        Wgl.Ext.SwapInterval(value);
                 }
             }
         }

Source/OpenTK/Platform/X11/X11GLContext.cs

@@ -30,7 +30,7 @@ namespace OpenTK.Platform.X11
         IntPtr display;
         X11WindowInfo currentWindow;
         bool vsync_supported;
-        int vsync_interval;
+        int swap_interval = 1; // As defined in GLX_SGI_swap_control
         bool glx_loaded;
 
         #endregion
@@ -348,13 +348,16 @@ namespace OpenTK.Platform.X11
 
         #endregion
 
-        #region VSync
+        #region SwapInterval
 
-        public override bool VSync
+        public override int SwapInterval
         {
             get
             {
-                return vsync_supported && vsync_interval != 0;
+                if (vsync_supported)
+                    return swap_interval;
+                else
+                    return 0;
             }
             set
             {
@@ -362,12 +365,12 @@ namespace OpenTK.Platform.X11
                 {
                     ErrorCode error_code = 0;
                     using (new XLock(Display))
-                    {
+                        error_code = Glx.Sgi.SwapInterval(value);
-                        error_code = Glx.Sgi.SwapInterval(value ? 1 : 0);
+
-                    }
+                    if (error_code == X11.ErrorCode.NO_ERROR)
-                    if (error_code != X11.ErrorCode.NO_ERROR)
+                        swap_interval = value;
+                    else
                         Debug.Print("VSync = {0} failed, error code: {1}.", value, error_code);
-                    vsync_interval = value ? 1 : 0;
                 }
             }
         }