@Chris-Kawa
wow, so simple :)
and so fast answer!! woooow
Thank you very much!
Its works!

void MainWindow::onStatusChanged(PVOID p) { qDebug() << "void *p address" << p; SERVICE_NOTIFY_2A* temp_pNotifyBuffer = static_cast<SERVICE_NOTIFY_2A*>(p); //MainWindow* ptr_mainWindow = static_cast<MainWindow*>(p); //qDebug() << ptr_mainWindow->m_test_string; qDebug() << temp_pNotifyBuffer->pContext; qDebug() << static_cast<MainWindow*>(temp_pNotifyBuffer->pContext)->m_test_string; }

Service man opened
pcontext address 0x8ff6a0
void *p address 0x8ff6bc
0x8ff6a0
"look it"

I was misled that in Visual studio the example with "direct" transformation worked. And I went the wrong way ..