Greetings, Tobja -

Let me be clear: I'm NOT a PBNI expert. Ha! Far from it. But I have created a DLL/PBX in C++ using PBNI and I've waded through some, not all, of the documentation.

Every PB application is, of course, heavily dependent on the PowerBuilder Virtual Machine (PBVM). PBNI provides a means for 1) creating PB extension in C++ that can be called from a PowerBuilder application (what I've done in the past), and 2) using some PB functionality from a C++ application. I don't believe it was designed to run an entire PB application, which is what I think you are attempting to accomplish.

When a PB app starts, the Application Object is the starting point. It asks the PBVM to create the application's global variables and global objects, such as SQLCA and, yes, the Message object, among others, before the Open event fires and the application "takes off".

When a C++ application is in charge, I may be wrong, but I doubt if anything close to that occurs just because the application establishes hooks into the PBVM in order to access PB objects such as windows, NVO's, structures or global functions. So it doesn't really surprise me that there is no Message object in the scenario you have described.

If your goal is to have the C++ application ask the PBVM to run a PB application, you may have to emulate the functionality of the application object or see if you can make the PBVM instantiate and utilize the application object contained in the PB application.

HTH

Regards, John

Thanks for your quick reply John! Very much appreciated.

Yes, as Arnd Schmidt pointed out in a comment, there is also the RunApplication method, which is, in my understanding, the second of two possibilities we are offered for starting the PB-Application. The first one being the one that I used in the attached example, which is, after having created an instance of the IPB_Session Interface, using the IPB_Session's method NewObject to create an instance of the Application object, and then triggering the open event of that instantiated object.

The reason I thought this approach is going to work, is that the documentation states so:

"[...]the application runs from C++ as it does in PowerBuilder"

And the documentation uses that very approach. So I guess either I did something wrong or then it is actually not the case that "the application runs from C++ as it does in PowerBuilder"...

Concerning the RunApplication method, I did try this approach as well, but ran into other kinds of problems, namely that this function does not return until the application being run is closed; So having my message loop in the same thread that also calls RunApplication resulted in no message being processed at all, i.e. the application starting without any windows showing up.

I actually came quite far when I used a std::thread object to call the RunApplication method in a second thread - The PB-App started, windows showed up, even the ones that read from the Message object. But then this meant that I had to use the same instance of an IPB_Session object in two different threads, which I guess explains all of the access violation exceptions that I ran into sooner or later in every trial. (Note that I have no idea of what I'm doing or talking about when it comes to threads, let alone sharing variables between them!)

One of my PBNI projects has the C++ code instantiating a PB NVO and calling functions within it. Some of the functions open windows.

If you are starting a complex PB app from C++, why not just run the EXE?

Here is an example of an EXE that instantiates an object and calls a function:

https://www.topwizprogramming.com/downloads/pbni_console.zip

Things to note:

Visual Studio 2017

The PB code is 10.5 but can easily be migrated. In the C code change the LoadLibrary function to use the correct vm.

The function being called has an array argument so you get to see how that is done.

The exe is a console app so start a command prompt window and run the exe from there.