Re: Ada-Oriented GUI

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2018-03-21 18:04, Dan'l Miller wrote:
> On Wednesday, March 21, 2018 at 11:27:56 AM UTC-5, Dmitry A. Kazakov wrote:
>> On 21/03/2018 15:30, Dan'l Miller wrote:
>>
>>> Rx is directly aiming at solving that entire problem space.  Quite well, btw, especially regarding concurrent scheduler-based handling events arriving haphazard from drastically-different concerns:  human GUI events, application lifetime events, network traffic arrival events, asynchronous OS events (e.g., filesystem I/O), and so forth.
>>
>> Scheduling implies that order of events is not preserved, right? How
>> consistency is achieved?
> 
> The order of each sequence of events from a single-threaded sender is strictly preserved in Rx (including under the numerous filtering mechanisms).

So it is inconsistent unless packed into single thread. No difference, 
exiting GUI do just same.

> Conversely, there is no order to preserve between different single-threaded senders.

Surely there is. The order is application level semantics. Threads are 
possibly implementation artifacts, e.g. worker tasks.

(This is a general problem of event-driven architectures. They are 
non-scalable, non-composable, unstructured and unmaintainable when 
become large).

> E.g., async filesystem I/O events can interleave GUI human-activity events can interleave application-lifecycle events can interleave network packet-arrival events arbitrarily and differently each execution.

I don't see how this is related to GUI design issues, except that when 
file system I/O indirectly cause GUI events. Then ordering of the events 
(output-pending, output-complete) must evidently be preserved when used 
in a progress indicator.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de