Rendering VTK in external OpenGL context with single buffering reports OpenGL error
I already asked a question in the forum, where I state that I'm pretty sure that this behavior is a bug.
When using a vtkExternalOpenGLWindow with an FBO and single buffering, VTK (actually the initialization of the vtkOpenGLState) is reporting an error (GL_INVALID_ENUM, GL_INVALID_OPERATION) because the object wants to get the GL_DRAW_BUFFER/GL_READ_BUFFER's GL_FRONT, which is actually not present when using single buffering.
Please let me know if you need any further information! I'm also happy to submit a minimal working example.