Daniel Friesen wrote:
setHook (old style tag hooks), and setFunctionTagHook (new style function tag hooks).
setHook and setFunctionTagHook both set <tag> style hooks. Originally we just had setHook, it had one short argument list. Later on that argument list was changed to add $frame to it. the newer setFunctionTagHook uses a different argument order, which appears to be the same set of arguments, just the first two and last two seam to be flipped.
I'm not exactly sure of the difference, but setFunctionTagHook definitely exists because of preprocessor improvements and because applying the new parsing behaviors to setHook would result in different behavior for tags or code bugs... perhaps attr="{{{1}}}"'s are expanded in setFunctionTagHook's because they are parsed by the preprocessor.
setFunctionTagHook was added so that you could expand variables inside tags. Then setHook() got added $frame and the need for such hook type disappeared. I'd like to kill it, although it has been there for some time (if any list reader uses it, please stand up).
or what the setFunctionHook style $flags are for
It's unused.
The primary difference is that setHook <tag> hooks are parsed in an old style, iirc pre-1.12 style. setFunctionTagHook are parsed by the preprocessor that parses parser functions, the contents aren't preprocessed but it's still parsed by the preprocessor.
The preprocessor doesn't mind about it. The preprocessor makes one block with everything between <tags> whereas it enters into braces blocks. No matter which kind of function tag is done, the extension itself need to recursiveTagParse it.