Hello, I implemented C++ helper class to use ImGUI in Panda3D C++.
The codes draw ImGUI rendering data and connect Panda3D mouse & keyboard input with ImGUI.
I hope this helps!
ps. Note that there is flickering bug by wrong scissoring. Sometimes, some rendered GUIs are gone. (https://github.com/bluekyu/rpcpp_plugins/issues/18)