/// <summary>
/// Initializes a new instance of the <see cref="OpenTK.Graphics.GraphicsContext"/> class using
/// an external context handle that was created by a third-party library.
/// </summary>
/// <param name="handle">
/// A valid, unique handle for an external OpenGL context, or <c>ContextHandle.Zero</c> to use the current context.
/// It is an error to specify a handle that has been created through OpenTK or that has been passed to OpenTK before.
/// </param>
/// <param name="getAddress">
/// A <c>GetAddressDelegate</c> instance that accepts the name of an OpenGL function and returns
/// a valid function pointer, or <c>IntPtr.Zero</c> if that function is not supported. This delegate should be
/// implemented using the same toolkit that created the OpenGL context (i.e. if the context was created with
/// SDL_GL_CreateContext(), then this delegate should use SDL_GL_GetProcAddress() to retrieve function
/// pointers.)
/// </param>
/// <param name="getCurrent">
/// A <c>GetCurrentContextDelegate</c> instance that returns the handle of the current OpenGL context,
/// or <c>IntPtr.Zero</c> if no context is current on the calling thread. This delegate should be implemented
/// using the same toolkit that created the OpenGL context (i.e. if the context was created with
/// SDL_GL_CreateContext(), then this delegate should use SDL_GL_GetCurrentContext() to retrieve
/// the current context.)
/// </param>
public GraphicsContext(ContextHandle handle, GetAddressDelegate getAddress, GetCurrentContextDelegate getCurrent)
{
if (getAddress == null || getCurrent == null)
{
throw new ArgumentNullException();
}
lock (SyncRoot)
{
// Replace a zero-handle by the current context, if any
if (handle == ContextHandle.Zero)
{
handle = getCurrent();
}
// Make sure this handle corresponds to a valid, unique OpenGL context
if (handle == ContextHandle.Zero)
{
throw new GraphicsContextMissingException();
}
else if (available_contexts.ContainsKey(handle))
{
throw new InvalidOperationException("Context handle has already been added");
}
// We have a valid handle for an external OpenGL context, wrap it into a
// DummyGLContext instance.
implementation = new Platform.Dummy.DummyGLContext(handle, getAddress);
GetCurrentContext = getCurrent ?? GetCurrentContext;
AddContext(this);
}
implementation.LoadAll();
}
/// <summary>
/// Loads all OpenGL entry points.
/// </summary>
/// <exception cref="OpenTK.Graphics.GraphicsContextException">
/// Occurs when this instance is not current on the calling thread.
/// </exception>
public void LoadAll()
{
if (GraphicsContext.CurrentContext != this)
{
throw new GraphicsContextException();
}
implementation.LoadAll();
}
