So if anyone finds the same issue, the workaround can be found here: https://github.com/probonopd/linuxdeployqt/issues/554

I just put the line:
qputenv("QTWEBENGINE_CHROMIUM_FLAGS", "--disable-gpu --no-sandbox");

And everything started to work.

This is because of virtualbox 3d acceleration support opengl version 2.0
it looks like qt multimedia(6.2) need opengl at least 3.0 version

Below was how to know it.
mesa log enable and log like below

Mesa: glGenTextures 1
Mesa: glBindTexture GL_TEXTURE_2D 2
Mesa: FLUSH_VERTICES in bind_texture_object
Mesa: FLUSH_VERTICES in teximage
Mesa: glTexImage2D GL_TEXTURE_2D 0 GL_R8 960 360 1 0 GL_RED GL_UNSIGNED_BYTE (nil)
Mesa debug output: GL_INVALID_VALUE in glTexImage2D(internalFormat=GL_R8)

GL_R8 variable is available upper than opengl 3.0

That's why we have to see green screen in virtualbox 3d acceleration

Sorry for resurrecting this, but in case anyone stumbles over the same issue I would like to help out. The issue was in fact not related to my application finding the plugin DLL (open62541_backend.dll), but finding another DLL which the plugin relies on. On my development machine I fixed the problem by adding Qt/bin and QtCreator/bin paths to my PATH environment variable (a bad idea in my opintion but it did the job).

However, while deploying I stumbled over this issue again, with the root cause being a bit harder to find this time. After some digging it turned out that the plugin relies on msvcr100.dll which is part of Microsoft Visual C++ 2010 Service Pack 1. So installing this (very old package) or shipping the dll as part of the application will fix the issue. The dll can be found in the system32 folder, not within the compiler directories.

For anyone else coming across a similar problem, tools like dependency walker and procmon will your best friend. Procmon showed me that once open62541_backend.dll was loaded, the application tried to find msvcr100.dll in many different locations without success.

Hi and welcome to devnet,

How are you moving the code from one machine to the other ?

Check the time stamp of these files on your other machine.

Could be due to missing OpenSSL. Try debugging the app to see if you get ssl related errors. More about Android and OpenSSL here: https://doc.qt.io/qt-5/android-openssl-support.html

Alright,
with much time and an extensive amout of google search I managed to cobble a working QOpenGLWidget program together.

I used this official Qt-Example as a basline:
http://doc.qt.io/qt-5/qtopengl-cube-example.html

here is the combination with my Tesseract code
https://github.com/DeiVadder/Tesseract-Challenge-OpenGL

It's working, yeah me!!, but I have the feeling that it's far from ideal. I'm just glad I managed to draw something in 3d.

Anyway, closed and solved.

Hi and welcome to devnet,

That's a question you should bring to the interest mailing list. You'll find there Qt's developers/maintainers. This forum is more user oriented.

Hi and welcome to devnet,

Don't copy these DLLs, unless it has changed over time, Qt Creator is build with MSVC and you have a MinGW Qt build. You should rather get the official OpenSSL package and install that one to use with your application.

I know this question is old, but it seems noone is answering BLE related questions here. (I've just posted such a question myself, and fear noone will anwer it either).

I developed an app based on the same example, and it worked fine under both android 4.3.2, 5.1.2, and 6.0. However, the customer came with an android 5.01, and sure enough, the app did not work as expected. It seemed to "hang" and tried to connect to two devices at the same time, etc. We did not investigate it further. This was with Qt 5.6, so the issue is not resolved, and may never be, since with newer versions of Android it is working fine.

Hi and welcome to devnet,

To get a grasp about just follow the tutorials linked in the QtWidgets module introduction.

You can then take a look at QProcess for calling external programs.

Hope it helps

PS: It's Qt, QT stands for Apple QuickTime that you might also be using.

Yep It's not supported on Windows. Easiest is to use Ubuntu. You should be able to install it in for example VirtualBox and share the USB device there.

@Pheelbert Yes missed the mentioning of data() here.
You're Welcome :-) Happy Coding.