To fix warnings:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/shared_ptr_base.h:588:8: warning: delete called on non-final 'NifOsg::ControllerFunction' that has virtual functions but non-virtual destructor
[-Wdelete-non-virtual-dtor]
delete __p;
^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/shared_ptr_base.h:595:4: note: in instantiation of function template specialization
'std::__shared_count<__gnu_cxx::_S_atomic>::__shared_count<NifOsg::ControllerFunction *>' requested here
: __shared_count(__p)
^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/shared_ptr_base.h:1079:17: note: in instantiation of function template specialization
'std::__shared_count<__gnu_cxx::_S_atomic>::__shared_count<NifOsg::ControllerFunction *>' requested here
: _M_ptr(__p), _M_refcount(__p, typename is_array<_Tp>::type())
^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/shared_ptr.h:129:25: note: in instantiation of function template specialization 'std::__shared_ptr<NifOsg::ControllerFunction,
__gnu_cxx::_S_atomic>::__shared_ptr<NifOsg::ControllerFunction, void>' requested here
shared_ptr(_Yp* __p) : __shared_ptr<_Tp>(__p) { }
^
/home/elsid/dev/openmw/components/nifosg/nifloader.cpp:242:39: note: in instantiation of function template specialization 'std::shared_ptr<NifOsg::ControllerFunction>::shared_ptr<NifOsg::ControllerFunction, void>' requested here
callback->setFunction(std::shared_ptr<NifOsg::ControllerFunction>(new NifOsg::ControllerFunction(key)));
^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/unique_ptr.h:78:2: warning: delete called on non-final 'MWGui::ResponseCallback' that has virtual functions but non-virtual destructor
[-Wdelete-non-virtual-dtor]
delete __ptr;
^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/7.3.1/../../../../include/c++/7.3.1/bits/unique_ptr.h:268:4: note: in instantiation of member function 'std::default_delete<MWGui::ResponseCallback>::operator()' requested here
get_deleter()(__ptr);
^
/home/elsid/dev/openmw/apps/openmw/mwgui/dialogue.cpp:58:23: note: in instantiation of member function 'std::unique_ptr<MWGui::ResponseCallback, std::default_delete<MWGui::ResponseCallback> >::~unique_ptr' requested here
PersuasionDialog::PersuasionDialog(ResponseCallback* callback)
^
(Shift)Tab cycles, arrow keys move to the next button in that direction, Enter/Space accepts.
Note: Unless MyGUI is hacked to bits, clicking on an empty space will annoyingly reset the key focus. Not sure how to deal with that yet.
The visual highlight for selected buttons requires MyGUI commit 632d007429d0bf0c7d7f6c5db4a08353a63dd839 or later to appear (to be released in 3.2.3).