how to get operator area?

[AlexKapustin]

Currently API allows to get position of operator, but it's not allowed to know size of operator.
Sometimes it's useful to build some extra layers (for example additional menu for active/selected operator).
For example, if I want to build additional menu on top of selected operator, it's not possible for me to adjust menu width, because I do not know operator width.

[AlexKapustin]

#124 I created MR, to resolve the problem.
(Get client rect information)

[sdrdis]

Thanks for your contribution!