Although I am generally cautious by nature, IMHO this is too cautious - my reasons are: a) gtk has been implemented as a separate device/console b) gtk has a separate event loop c) gtk does not use lwlib. So I believe that if people are not using gtk then the impact on them will be insignifcant because the code changes are all in gtk specific files. The abstractions in 21.2 are pretty clean so if there are any changes required to the core code they are probably required anyway. Of course not having looked at the code, BillP may need to correct me on this. I do, of course, agree that switching on gtk by default is way too aggressive.