On 06.05.2020 14:57, Henry Skoglund wrote:
Hi, when running apps on Windows without a window, you'll be missing out
on a lot of inter-process stuff like WM_QUIT (that's why it's common for
windowless apps to create a hidden, non-interactive window just to be
able to receive all those WM_XXX). So no aboutToQuit() will be emitted
for you when you skip creating that widget window.
How would one create a hidden, non-interactive window with Qt?
But there's an API for windowless apps where you can receive a control
signal, e.g. Ctrl-C was pressed or someone (like the Task Manager) is
shutting down the app, more here:
https://docs.microsoft.com/en-us/windows/console/setconsolectrlhandler
and the callback:
https://docs.microsoft.com/en-us/windows/console/handlerroutine
There's no support for that API in Qt but it's pretty easy to use.
Here's an example, I created a vanilla Qt console app, and changed
main.cpp to this:
-----------------------------------------
#include <QCoreApplication>
#include <windows.h>
BOOL WINAPI CtrlHandler(DWORD fdwCtrlType)
{
switch (fdwCtrlType)
{
case CTRL_CLOSE_EVENT:
::OutputDebugStringA("Ctrl-Close event"); // catch taskkill or
Task Manager End task
return TRUE;
default:
return FALSE;
}
}
int main(int argc, char *argv[])
{
QCoreApplication app(argc, argv);
SetConsoleCtrlHandler(CtrlHandler, TRUE);
return app.exec();
}
-----------------------------------------
Note: I'm using OutputDebugString and DbgView.exe to view the output,
qDebug() output has a tendency to disappear when you test with "End
task" from TaskManager.
Note 2: this API is very flakey if you try it from a GUI-built .exe, for
Qt apps I mean built with "QT += core gui etc" in the .pro file, and use
of QApplication in main.cpp. Instead you need to build your app like a
Qt console app, "QT -= gui" and CONFIG += console, and use
QCoreApplication in main.cpp, like in my example above.
That's the solution we're using in plain console QCoreApplications.
However, in this case, we have a QApplication which is showing or not
showing a GUI depending on some commandline args. So that will probably
not work robustly in this situation.
Thanks!
_______________________________________________
Interest mailing list
Interest@qt-project.org
https://lists.qt-project.org/listinfo/interest
