Thanks for all your Lisp comments. As an extra reference the tool I was thinking of for the "debug this pixel" feature was the venerable PIX: http://www.garagegames.com/community/blogs/view/14251 It was a great standalone tool, and its more modern successor is better integrated with visual studio: https://channel9.msdn.com/Events/GDC/GDC-2015/Solve-the-Toug... On the OpenGL side of things the situation has become a lot better than it was in the past with things like https://apitrace.github.io/