Add docs for how to use ocall. about cljs-oops

[LeifAndersen]

(In the case of this specific bug, it seems to be expanding to a dynamic call to cljs.core.js_fn_QMARK_, which is undefined. (Which I guess makes sense as js-fn?is a macro and not a function.)

[nicolaus1990]

Hello @LeifAndersen,

I had the same problem with the js-fn? macro. But this is unrelated to your oops library issue. The problem is that [[https://cljs.github.io/api/cljs.core/js-fnQMARK][js-fn?]] (used in some namespace in oops) requires Clojurescript 1.10.844 and above. And you are most probably using an older clourescript version.

Concerning the usage for ocall, for me the following worked:
#+begin_src clojure
(ocall!+ (get-js-obj) "ellipse" x y w h)
;; Where "ellipse" is the function name of a js object, and arguments x, y, w,
;; and h are integers, in this particular case. Note, however, for some arguments,
;; like sequences, I had to use function clj->js to make it work.
#+end_src

If that doesn't help: The above example came from a proof of concept I wrote using the p5.js library (former processing.js graphics library). I managed to make it work with figwheel-main (for hot-reloading) and even make advance
compilation work for a small example (thanks to oops library). You could check that out [[https://gitlab.com/nicolaus1990/cljs-examples/-/tree/master/p5_examples/p5-example-2][here]], if you think that might help.

[LeifAndersen]

... requires Clojurescript 1.10.844 and above. And you are most probably using an older clourescript version.

At the time of opening this issue, I was running: 1.10.872 (I have since upgraded to 1.10.932).

Concerning the usage for ocall, for me the following worked:

I'll try it out, thanks for the suggestion.