I've been busy setting up Perforce source control on a Cache 2017.2.2.865.0 instance. Everything is mostly done and working through studio hooks. Checking out, modifying and checking back in works correctly but I would like to know what the hook, override, setting is to force studio to check if the class needs to be checked out or is already checked out by another user before you are allowed to edit it.
Scenario is a user opens a class, perforce serves the latest version. The user then starts to edit but before anything is done on the code there should be a check if the class has been checked out. If not prompt the user to checkout and if it has already been checked out display an error message.