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From: DrPi <314@drpi.fr>
Subject: Re: PubSub
Date: Sun, 1 Nov 2020 11:36:37 +0100
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Le 31/10/2020 à 19:38, Dmitry A. Kazakov a écrit :
> On 31/10/2020 18:58, DrPi wrote:
> 
>> Another question indirectly concerning GUI programming : Does a Ada 
>> "PubSub" package exist ?
> 
> Yes. We have a commercial middleware 100% in Ada. We use that thing in 
> automation and control systems. Naturally, it provides 
> publisher/subscriber services, distributed or not with controlled QoS. 
> That is so to say horizontal communication between applications or 
> tasks. It also has a vertical communication aspect abstracting 
> hardware/protocols from application. E.g. you can publish/subscribe to a 
> MQTT topic, or to an EtherCAT object, or to a CANOpen dictionary object 
> etc without even knowing if that really the thing, something else or 
> another application.
>   Having said that, for horizontal communication inside single process 
> you do not need that in Ada. Many things done for other languages are 
> not needed in Ada.
> 
> Ada protected objects and tasks provide much more efficient, safer 
> (typed) and easier to use way to communicate between tasks.
> 
What I'm looking for is not inter-task communication. It is some sort of 
message dispatcher (which is not thread safe). It is like a GUI event 
manager but for custom events.
A simple description here : https://wiki.wxpython.org/WxLibPubSub

This is very useful when using a GUI since it allows to directly send 
messages to windows/dialogs/controls.