CTGUI was written to build the TGUI.Net binding, CTGUI wasn't really intended to be used directly. This is why the library lacks documentation and doesn't has a separate forum section.
You can use the library, you just shouldn't expect it to be as user-friendly as TGUI or TGUI.Net.
The problem seems to be that MenuItemClicked isn't of type SignalItem in c++ (and you thus can't use tguiWidget_connectItemSelected), but it has type SignalItemHierarchy.
The SignalItemHierarchy supports functions with 3 sets of parameters:
- No parameters at all (use tguiWidget_connect in CTGUI for this)
- A string parameter with the menu item that was clicked (use tguiWidget_connectString in CTGUI for this)
- A vector of strings with the hierarchy of the clicked menu item (if you don't have submenus then it contains 2 items: the menu and the menu item). This is apparently not available in CTGUI and TGUI.Net.
Although not related to your issue, is there a reason why you are using an older CTGUI version? The last tagged version seems to be 0.8.6, but the CTGUI master branch itself should actually be up-to-date with 0.8.7