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Cleaned up temporary context construction
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The temporary context is now retained until the actual context has been
constructed. If we don't do this, then WGL_ARB_create_context may fail
to work correctly on specific GPUs (e.g. Intel). This may affect issue
#19.
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@thefiddler
thefiddler committed Dec 18, 2013
1 parent a57b4c4 commit d8a4ca1
Showing 1 changed file with 123 additions and 88 deletions.
211 changes: 123 additions & 88 deletions Source/OpenTK/Platform/Windows/WinGLContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,88 +28,111 @@ namespace OpenTK.Platform.Windows
internal sealed class WinGLContext : DesktopGraphicsContext
{
static readonly object LoadLock = new object();
static readonly object SyncRoot = new object();

bool vsync_supported;

readonly WinGraphicsMode ModeSelector;

#region --- Contructors ---

static WinGLContext()
// We need to create a temp context in order to load
// wgl extensions (e.g. for multisampling or GL3).
// We cannot rely on any WGL extensions before
// we load them with the temporary context.
class TemporaryContext : IDisposable
{
lock (LoadLock)
public ContextHandle Context;

public TemporaryContext(INativeWindow native)
{
// We need to create a temp context in order to load
// wgl extensions (e.g. for multisampling or GL3).
// We cannot rely on OpenTK.Platform.Wgl until we
// create the context and call Wgl.LoadAll().
Debug.Print("Creating temporary context for wgl extensions.");
using (INativeWindow native = new NativeWindow())
Debug.WriteLine("[WGL] Creating temporary context to load extensions");

if (native == null)
throw new ArgumentNullException();

// Create temporary context and load WGL entry points
// First, set a compatible pixel format to the device context
// of the temp window
WinWindowInfo window = native.WindowInfo as WinWindowInfo;
WinGraphicsMode selector = new WinGraphicsMode(window.DeviceContext);
WinGLContext.SetGraphicsModePFD(selector, GraphicsMode.Default, window);

bool success = false;

// Then, construct a temporary context and load all wgl extensions
Context = new ContextHandle(Wgl.CreateContext(window.DeviceContext));
if (Context != ContextHandle.Zero)
{
// Create temporary context and load WGL entry points
// First, set a compatible pixel format to the device context
// of the temp window
WinWindowInfo window = native.WindowInfo as WinWindowInfo;
WinGraphicsMode selector = new WinGraphicsMode(window.DeviceContext);
SetGraphicsModePFD(selector, GraphicsMode.Default, window);

// Then, construct a temporary context and load all wgl extensions
ContextHandle temp_context = new ContextHandle(Wgl.CreateContext(window.DeviceContext));
if (temp_context != ContextHandle.Zero)
{
// Make the context current.
// Note: on some video cards and on some virtual machines, wglMakeCurrent
// may fail with an errorcode of 6 (INVALID_HANDLE). The suggested workaround
// is to call wglMakeCurrent in a loop until it succeeds.
// See https://www.opengl.org/discussion_boards/showthread.php/171058-nVidia-wglMakeCurrent()-multiple-threads
// Sigh...
for (int retry = 0; retry < 5; retry++)
{
bool success = Wgl.MakeCurrent(window.DeviceContext, temp_context.Handle);
if (!success)
{
Debug.Print("wglMakeCurrent failed with error: {0}. Retrying", Marshal.GetLastWin32Error());
System.Threading.Thread.Sleep(10);
}
else
{
// wglMakeCurrent succeeded, we are done here!
break;
}
}

// Load wgl extensions and destroy temporary context
Wgl.LoadAll();
Wgl.MakeCurrent(IntPtr.Zero, IntPtr.Zero);
Wgl.DeleteContext(temp_context.Handle);
}
else
// Make the context current.
// Note: on some video cards and on some virtual machines, wglMakeCurrent
// may fail with an errorcode of 6 (INVALID_HANDLE). The suggested workaround
// is to call wglMakeCurrent in a loop until it succeeds.
// See https://www.opengl.org/discussion_boards/showthread.php/171058-nVidia-wglMakeCurrent()-multiple-threads
// Sigh...
for (int retry = 0; retry < 5 && !success; retry++)
{
Debug.Print("wglCreateContext failed with error: {0}", Marshal.GetLastWin32Error());
success = Wgl.MakeCurrent(window.DeviceContext, Context.Handle);
if (!success)
{
Debug.Print("wglMakeCurrent failed with error: {0}. Retrying", Marshal.GetLastWin32Error());
System.Threading.Thread.Sleep(10);
}
}
}
else
{
Debug.Print("[WGL] CreateContext failed with error: {0}", Marshal.GetLastWin32Error());
}

if (!success)
{
Debug.WriteLine("[WGL] Failed to create temporary context");
}
}

public void Dispose()
{
if (Context != ContextHandle.Zero)
{
Wgl.MakeCurrent(IntPtr.Zero, IntPtr.Zero);
Wgl.DeleteContext(Context.Handle);
}
}
}

#region --- Contructors ---

public WinGLContext(GraphicsMode format, WinWindowInfo window, IGraphicsContext sharedContext,
int major, int minor, GraphicsContextFlags flags)
{
// There are many ways this code can break when accessed by multiple threads. The biggest offender is
// the sharedContext stuff, which will only become valid *after* this constructor returns.
// The easiest solution is to serialize all context construction - hence the big lock, below.
lock (SyncRoot)
lock (LoadLock)
{
if (window == null)
throw new ArgumentNullException("window", "Must point to a valid window.");
if (window.Handle == IntPtr.Zero)
throw new ArgumentException("window", "Must be a valid window.");

Debug.Print("OpenGL will be bound to window:{0} on thread:{1}", window.Handle,
System.Threading.Thread.CurrentThread.ManagedThreadId);

lock (LoadLock)
IntPtr current_context = Wgl.GetCurrentContext();
INativeWindow temp_window = null;
TemporaryContext temp_context = null;
try
{
if (current_context == IntPtr.Zero)
{
// Create temporary context to load WGL extensions
temp_window = new NativeWindow();
temp_context = new TemporaryContext(temp_window);
current_context = Wgl.GetCurrentContext();
if (current_context != IntPtr.Zero && current_context == temp_context.Context.Handle)
{
Wgl.LoadAll();
}
}

Debug.Print("OpenGL will be bound to window:{0} on thread:{1}", window.Handle,
System.Threading.Thread.CurrentThread.ManagedThreadId);

ModeSelector = new WinGraphicsMode(window.DeviceContext);
Mode = SetGraphicsModePFD(ModeSelector, format, (WinWindowInfo)window);

Expand Down Expand Up @@ -146,44 +169,57 @@ public WinGLContext(GraphicsMode format, WinWindowInfo window, IGraphicsContext
if (Handle == ContextHandle.Zero)
Debug.Print("failed. (Error: {0})", Marshal.GetLastWin32Error());
}
catch (EntryPointNotFoundException e) { Debug.Print(e.ToString()); }
catch (NullReferenceException e) { Debug.Print(e.ToString()); }
catch (Exception e) { Debug.Print(e.ToString()); }
}
}

if (Handle == ContextHandle.Zero)
{
// Failed to create GL3-level context, fall back to GL2.
Debug.Write("Falling back to GL2... ");
Handle = new ContextHandle(Wgl.CreateContext(window.DeviceContext));
if (Handle == ContextHandle.Zero)
{
// Failed to create GL3-level context, fall back to GL2.
Debug.Write("Falling back to GL2... ");
Handle = new ContextHandle(Wgl.CreateContext(window.DeviceContext));
if (Handle == ContextHandle.Zero)
throw new GraphicsContextException(
String.Format("Context creation failed. Wgl.CreateContext() error: {0}.",
Marshal.GetLastWin32Error()));
}

Debug.WriteLine(String.Format("success! (id: {0})", Handle));

// Todo: is this comment still true?
// On intel drivers, wgl entry points appear to change
// when creating multiple contexts. As a workaround,
// we reload Wgl entry points every time we create a
// new context - this solves the issue without any apparent
// side-effects (i.e. the old contexts can still be handled
// using the new entry points.)
// Sigh...
Wgl.LoadAll();
if (Handle == ContextHandle.Zero)
Handle = new ContextHandle(Wgl.CreateContext(window.DeviceContext));
if (Handle == ContextHandle.Zero)
throw new GraphicsContextException(
String.Format("Context creation failed. Wgl.CreateContext() error: {0}.",
Marshal.GetLastWin32Error()));
}

if (sharedContext != null)
Debug.WriteLine(String.Format("success! (id: {0})", Handle));
}
finally
{
Marshal.GetLastWin32Error();
Debug.Write(String.Format("Sharing state with context {0}: ", sharedContext));
bool result = Wgl.ShareLists((sharedContext as IGraphicsContextInternal).Context.Handle, Handle.Handle);
Debug.WriteLine(result ? "success!" : "failed with win32 error " + Marshal.GetLastWin32Error());
if (temp_context != null)
{
temp_context.Dispose();
temp_context = null;
}
if (temp_window != null)
{
temp_window.Dispose();
temp_window = null;
}
}
}

// Todo: is this comment still true?
// On intel drivers, wgl entry points appear to change
// when creating multiple contexts. As a workaround,
// we reload Wgl entry points every time we create a
// new context - this solves the issue without any apparent
// side-effects (i.e. the old contexts can still be handled
// using the new entry points.)
// Sigh...
Wgl.MakeCurrent(window.DeviceContext, Handle.Handle);
Wgl.LoadAll();

if (sharedContext != null)
{
Marshal.GetLastWin32Error();
Debug.Write(String.Format("Sharing state with context {0}: ", sharedContext));
bool result = Wgl.ShareLists((sharedContext as IGraphicsContextInternal).Context.Handle, Handle.Handle);
Debug.WriteLine(result ? "success!" : "failed with win32 error " + Marshal.GetLastWin32Error());
}
}

static ArbCreateContext GetARBContextFlags(GraphicsContextFlags flags)
Expand Down Expand Up @@ -231,7 +267,6 @@ public override void SwapBuffers()

public override void MakeCurrent(IWindowInfo window)
{
lock (SyncRoot)
lock (LoadLock)
{
bool success;
Expand Down Expand Up @@ -347,7 +382,7 @@ static bool IsValid(IntPtr address)
{
// See https://www.opengl.org/wiki/Load_OpenGL_Functions
long a = address.ToInt64();
bool is_valid = (a < -1 )|| (a > 3);
bool is_valid = (a < -1) || (a > 3);
return is_valid;
}

Expand Down Expand Up @@ -379,7 +414,7 @@ internal static GraphicsMode SetGraphicsModePFD(WinGraphicsMode mode_selector,
Functions.DescribePixelFormat(
window.DeviceContext, (int)mode.Index.Value,
API.PixelFormatDescriptorSize, ref pfd);

Debug.WriteLine(mode.Index.ToString());

if (!Functions.SetPixelFormat(window.DeviceContext, (int)mode.Index.Value, ref pfd))
Expand Down

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