My Emacs used to have the ability to display the help buffer of each function everytime I was scrolling through M-x function candidates. How to enable it again? Thanks!
It is called
According to Helm documentation (C-h m from inside an Helm buffer):
helm-follow-modeis on (C-c C-f to toggle it), moving up and down Helm session or updating the list of candidates will automatically execute the persistent-action as specified for the current source.
helm-follow-mode-persistentis non-nil, the state of the mode will be restored for the following Helm sessions.
If you just want to follow candidates occasionally without enabling
helm-follow-mode, you can use C-down or C-up instead. Conversely, when
helm-follow-modeis enabled, those commands go to previous/next line without executing the persistent action.
So the easiest way is to navigate with C-down or C-up.
C-c C-f allows you to toggle this behaviour and variable
helm-follow-mode-persistent to make it persistent.