In the graphics code, logic was present for in the vertex buffer classes to...

In the graphics code, logic was present for in the vertex buffer classes to track the OpenGL context in the event that multiple windows used a different OpenGL context (a different context may not share vertex buffers, textures, etc.).  We share the OpenGL context among multiple wb_view windows.  Both the deprecated QGLWidget which we currently use (and the newer QOpenGLWIdget) make it very easy for context sharing.  Since the logic for non-context sharing was cumbersome, and is not needed, it has been removed.