How to simulate user input to a native QFileDialog in Windows?

[dave2]

In Windows, I need to simulate user input to a QFileDialog for opening a file. More specifically, I need to:

1. enter the name of the file to open
2. accept the dialog

The QFileDialog was opened in native mode (which is the default on Windows), something which I can't change.

findChildren<QWidget*>() returns an empty list on such a native dialog, so I can't programmatically send QKeyEvent's to a QLineEdit (in order to simulate entry of the file name), or send a QMouseEvent to the "Open" button (in order to simulate acceptance of the dialog).

I tried the following:

fileDialog->selectFile("C:/foo/bar.txt"); // (1)
static_cast<QDialog*>(fileDialog)->accept(); // (2)

Note about (2): This weird cast is necessary, because QDialog::accept() is public, but QFileDialog::accept() is protected. Since accept() is virtual, (2) calls QFileDialog::accept(), as intended.

After (1), I can see C:/foo/bar.txt entered in the edit field of the dialog.

(2), however, does not work: the dialog remains open. When debugging into QFileDialog::accept(), I can see the reason of accept()'s failure: the call to QFileDialog::selectedUrls() (qfiledialog.cpp, line 2700) returns an empty list. This, in turn, is due to the fact that QFileDialogPrivate::userSelectedFiles() (qfiledialog.cpp, line 1216) also returns an empty list.

So, is there a way to do that with the Qt API, or should I dive into the (ugly!) Windows API?

My environment: Windows 10, Visual Studio 2017, Qt 6.1

[Axel Spoerl]

@dave2
Synthesizing Qt key and mouse events with a native file dialog will not work, I am afraid. The native dialog doesn't know about Qt.

You can either send Qt events to a non-native dialog, as proposed by @mpergand. Or you dive into the Windows API to simulate what needs to be simulated.

[mpergand]

@dave2
Seems to work with non native dialog:

QApplication app(argc, argv);

QFileDialog fileDialog;
fileDialog.setOption(QFileDialog::DontUseNativeDialog);
fileDialog.selectFile( your file );
fileDialog.show();

QTimer::singleShot(2000, [&fileDialog]()
{
	QKeyEvent press(QEvent::KeyPress, Qt::Key_Return,0);
	qApp->sendEvent(&fileDialog,&press);

	QKeyEvent release(QEvent::KeyRelease, Qt::Key_Return,0);  // seems optional
	qApp->sendEvent(&fileDialog,&release);

	qDebug()<<fileDialog.selectedFiles();
});

[SGaist]

Hi,

Can you explain your use case ? Are you implementing tests ?

[Axel Spoerl]

@dave2
Synthesizing Qt key and mouse events with a native file dialog will not work, I am afraid. The native dialog doesn't know about Qt.

You can either send Qt events to a non-native dialog, as proposed by @mpergand. Or you dive into the Windows API to simulate what needs to be simulated.

[dave2]

@mpergand I trust that the code you propose works for a non native dialog. But since I am dealing with a native dialog, it doesn't really help.

[dave2]

@SGaist I am implementing a demo, which goes through a typical usage scenario of our application.

[dave2]

@Axel-Spoerl That's what I was fearing, but thanks for confirming.