Then it's trivial. Look at the main function of B, it will probably instantiate a main widget, you can use that as a child widget of your application

@JonB This is a quote from the example given on the link listed. It's from QT, in an explanation of how this works. It's not a string that I came up with, or that I'm using.

@kshegunov Right... Thanks, something didnt trigger in the brain. Now its fine: connect(uap, &CUaProxy::uaItemChanged, this, [this, i]( const CUaProxy::MsgType msgt, const int riskIndex, const QVariant& value) { this->onUaMsgReceived(msgt, i, riskIndex, value); }, Qt::QueuedConnection); Also needed Qt::QueuedConnection eventually.

@romsharkov Hi there, Do I understand correctly that you have managed to run a QQmlProcess in a separate process? I am asking it because I have came across pretty much the same problem: https://github.com/sailfish-sdk/sdk-harbour-rpmvalidator/pull/79#issuecomment-307348648 If you could tell me some words of you implementation details that would be awesome! Thanks in advance!

@Chris-Kawa thanks for the hint. Works now :)

@Chris-Kawa yes that is an option, but what if erros appear while the processes running? If i put the MessageBox after the for-loop i need a mechanism to check if there was an error or not. therefore i wanted to use Signal and Slot for the process. EDIT i solved it. I wrote a function in which i check if there where errors with readAllStandardError and if the size of it is zero, no error appeared and the show the message box.

I understand your advice. 1 app access the file and the other app communicate directly to the first app. However, I aimed to use a memory-mapped-file just because I read some articles where it said this is one of the best practice to communicate two process without lossing information. Is this correct? I am really interested in your advices, so I present my case: GUI <-> MainAPP <-> SPortAPP GUI can be anything made for anybody with the only requirement of implementing a protocol/API to communicate to MainAPP. (e.g. sockets) MainAPP is my application who implement mathematics, logic, etc and defines the behaviour of my system. It cannot lose any information so I thought I might save it on a file. SPortAPP is a propietary protocol implementation whereby external systems read/write information to the database of MainAPP . This app shouldn't interact directly to MainAPP So, Such information must be available to read and write by both MainAPP and SPortAPP. what is your opinion about it? Do you reccomend any other type of implementation?