negation

hello

would it exist a mean to create some « negation » better adapted to the size of the text


here you can see that the native « negation » of TeXmacs only bars the x^2 instead of barring the whole f(x+x^2+1)

of course it could be done manyally for example with « ink here » 
but i am looking for a more efficient and proper way to do it

what could be changed in TeXmacs to get that

can i write this into a « suggestion » on TeXmacs’ page ?

or does it still existe ?

the aim of course as usual for me is to get an easy shortcut (like n n)

Vincent