[TYPO3-core] Hooks vs Signals in TYPO3 CMS core

[Roland]

hi everybody,

[1] when should we use a Hook and when should be use a Signal in TYPO3 CMS
core?
[2] is there a significant performance difference between Hooks and
Signals...
[2a] ...in terms of pure existence in the TYPO3 CMS core?
[2b] ...in terms of making usage of that Hook/Signal?

After a quick look into the signal slot dispatcher's code i would assume
that there should not be much difference performancewise. It implements
SingletonInterface and there is not much voodoo going on in the dispatch()
and connect() methods.

Therefore i would conclude to use only Signals instead of Hooks from now on
if one of those is needed.

Do you agree?

Two current patches at review.typo3.org:

* https://review.typo3.org/#/c/32871/
* https://review.typo3.org/#/c/32862/

I am looking forward to your opinion.

Kind regards

Roland