Context sharing in an extensible MDI app

In my experience, context sharing is very hard to implement reliably on arbitrary hardware. Out-of-the-box, you lose support for Intel/windows where context sharing isn't supported at all (I don't know whether this has changed with their recent 3.1 drivers).

Another thing to keep in mind is that context sharing may fail when creating contexts with different pixel formats (e.g. with and without antialiasing) or different versions (GL 2.x and 3.x). Finally, some GL objects cannot be shared (e.g. GL3.x vertex array objects).

Consider following a different approach: create a single OpenGL context and use MakeCurrent() to attach it to different windows. The current implementation has a limitation in that MakeCurrent() only works on windows with pixel formats set (e.g. GLControls, see #2474: WinGLContext.MakeCurrent only works for windows used to create an opengl context). Even so, this is significantly more reliable than multiple contexts with sharing.

GTK# with GLWidget? In this case, you will be able to call GraphicsContext.MakeCurrent(IWindowInfo) on any GLWidget (since all GLWidgets have a pixel format set).

In short: create as many GLWidgets as you need; ignore all GraphicsContexts other than the first one; call MakeCurrent to draw using the first context on any GLWidget. The only limitation is that you won't be able to call MakeCurrent on arbitrary windows until muhkuh's code is merged.