Diagrams frequently asked questions.
1 Can I render a diagram to the screen and then know which part of the diagram a user has clicked on?
Yes. See the user manual section on using queries.
It seems this can be caused on OS X by a mixture of 32- and 64-bit libraries. For example see this bug report. Ensure that your GHC and your gtk libraries are either both 32-bit or both 64-bit.