Using Jonathan Woithe's September 2015 recipe, I reproduced this bug 
report's problems on Fedora 23 with gtk3 in the emacs-25 branch, and 
installed the attached patches, which fixed the bugs for me.

I do like the idea of moving the IDLWAVE stuff to an ELPA package, 
though I don't have time to do that myself.

I'm boldly marking the bug as fixed.

http://bugs.gnu.org/18997