HTML5 deployment: progress comes into sight

[Mark Wieder]

On 05/31/2017 02:35 PM, hh via use-livecode wrote:
> "Synchronous" means here that the callback is done in the order it appears in
> the list of js instructions, i.e. "synchronous to the instruction order".
> 
> If you say in your js function
> 
>     instruction1;
>     callback1;
>     instruction2;
>     callback2;
> 
> then you can't control what's done first. This is the price we have
> to pay for speed (multi-threading).
> It is even possible that callback2 arrives at LC _before_ one of
>         instruction1; callback1; instruction2;
> is finished.

I had a similar need in PowerDebug in order to handle asynchronous 
events over socket connections for remote debugging. And dealt with it 
thusly:

Requests are sent asynchronously and trigger a callback message when 
they're done. The callback message payload contains a reference to the 
message that called it. That way a callback handler can associate the 
returned message with the calling handler, and if needed a wait loop can 
implement a procedural pseudo-synchronous call.

It's kind of the way session cookies work in a browser. It probably 
won't work for every use case, but when I need to define a statement 
order from asynchronous events it does the trick.

-- 
  Mark Wieder
  ahsoftware at gmail.com