Re: JSO: Why does this fail?

On Thursday, February 26, 2015 at 2:59:43 PM UTC+1, Mickaël Leduque wrote:

So the answer to

When use it ? When not use it ?

is respectively always and never ? That's easy to follow, thanks!

Hmm, no. If your JSNI calls back into Java "synchronously", then you don't need to use $entry (exceptions will still "bubble" up to your GWT.UncaughtExceptionHandler Java→JSNI→Java, and you're still in the same event-loop wrt scheduled commands). You use $entry() whenever the browser calls back into your GWT/Java code "asynchronously" (event handling, promises, etc. basically whatever comes from the browser's own event loop).

Note that $entry is re-entrant though, so calling it too many times won't break your app (but possibly affect performance).

 

2015-02-26 14:47 GMT+01:00 Thomas Broyer <t.broyer@gmail.com>:

On Thursday, February 26, 2015 at 2:25:13 PM UTC+1, Mickaël Leduque wrote:

OK thanks, thant would be

    private static <B> Thenable<B> staticThen(Thenable<B> thenable, B arg) {
      return thenable.then(arg);
    }

2015-02-26 13:41 GMT+01:00 Thomas Broyer <t.broyer@gmail.com>:

BTW, you might want to add a bunch of calls to $entry() here and there.

I wondered about that.

I have seen mention of $entry in the doc, but never saw an actual documentation on what it does, when to use it and when not to use it.

Whenever you "enter GWT code" from the outside, wrap that function with $entry().

$entry() will decorate any function and make sure that:

• exceptions are routed to the GWT.UncaughtExceptionHandler, if any.
• scheduleEntry / scheduleFinally commands are run

Basically:

function $entry(fn) {

  return function() {

    var _entry = function(fn, args) {

      try {

        runScheduledEntryCommands();

        fn.apply(this, args);

      } finally {

        funScheduledFinallyCommands();

      }

    }

    if (hasUncaughtExceptionHandler) {

      try {

        _entry(fn, arguments);

      } catch (e) {

        callUncaughtExceptionHandler(e);

      }

    } else {

      _entry(fn);

    }

  };

}

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