QFileDialog has memory

[Perdrix]

I've got an mf that operates on a QFileDialog member variable.

If I call it the first time the filename field at the bottom is empty:

If I then select (say) three files, select Open to open the files and then reinvoke the mf, the filename field now contains the first of the files I selected on the previous invocation:

How do I prevent that memory effect? I already tried fileDialog.selectFile(QString());

My code:

void CStackingDlg::OnAddpictures()
{
	ZFUNCTRACE_RUNTIME();
	QSettings			settings;
	QString				directory;
	QString				extension;
	uint				filterIndex = 0;
	QString				strTitle;

	directory = settings.value("Folders/AddPictureFolder").toString();

	extension = settings.value("Folders/AddPictureExtension").toString();

	filterIndex = settings.value("Folders/AddPictureIndex", 0U).toUInt();
	
	if (extension.isEmpty())
		extension = "bmp";			// Note that Qt doesn't want/ignores leading . in file extensions

	fileDialog.setWindowTitle(QCoreApplication::translate("StackingDlg", "Open Light Frames...", "IDS_TITLE_OPENLIGHTFRAMES"));
	fileDialog.setDefaultSuffix(extension);
	fileDialog.setFileMode(QFileDialog::ExistingFiles);

	const QStringList filters({
		QCoreApplication::translate("StackingDlg", "Picture Files (*.bmp *.jpg *.jpeg *.tif *.tiff *.png *.fit *.fits *.fts *.cr2 *.cr3 *.crw *.nef *.mrw *.orf *.raf *.pef *.x3f *.dcr *.kdc *.srf *.arw *.raw *.dng *.ia *.rw2)"),
		QCoreApplication::translate("StackingDlg", "Windows Bitmaps (*.bmp)"),
		QCoreApplication::translate("StackingDlg", "JPEG or PNG Files (*.jpg *.jpeg *.png)"),
		QCoreApplication::translate("StackingDlg", "TIFF Files (*.tif *.tiff)"),
		QCoreApplication::translate("StackingDlg", "RAW Files (*.cr2 *.cr3 *.crw *.nef *.mrw *.orf *.raf *.pef *.x3f *.dcr *.kdc *.srf *.arw *.raw *.dng *.ia *.rw2)"),
		QCoreApplication::translate("StackingDlg", "FITS Files (*.fits *.fit *.fts)"),
		QCoreApplication::translate("StackingDlg", "All Files (*)")
		});

	fileDialog.setNameFilters(filters);
	fileDialog.selectFile(QString());		// No file(s) selected
	if (!directory.isEmpty())
		fileDialog.setDirectory(directory);

	//
	// A value of zero for filterIndex means that the user hasn't previously chosen a name filter.
	// 
	// If the user *has* previously chosen a name filter, then that index is 1 based, not zero based.
	// This means that the index must be decremented to index into the list of name filters.
	//
	// Should a name filter not have been chosen the system will initially select the first one.
	//
	if (filterIndex > 0)
	{
		fileDialog.selectNameFilter(filters.at(filterIndex-1));
	}

	ZTRACE_RUNTIME("About to show file open dlg");
	if (QDialog::Accepted == fileDialog.exec())
	{
		QGuiApplication::setOverrideCursor(QCursor(Qt::WaitCursor));
		QStringList files = fileDialog.selectedFiles();
		for (int i = 0; i < files.size(); i++)
		{
			fs::path file(files.at(i).toStdU16String());		// as UTF-16

			m_Pictures.AddFile((LPCTSTR)file.generic_wstring().c_str(), m_Pictures.GetCurrentGroupID(), m_Pictures.GetCurrentJobID());
			directory = QString::fromStdU16String(file.remove_filename().generic_u16string());
			extension = QString::fromStdU16String(file.extension().generic_u16string());
		};
		QGuiApplication::restoreOverrideCursor();
		m_Pictures.RefreshList();

		//
		// What filter has the user actually selected, or has been auto-selected?
		// Note that the index value we store is 1 based, not zero based, so add one to the selected index.
		// 
		filterIndex = filters.indexOf(fileDialog.selectedNameFilter());
		filterIndex++;		
		settings.setValue("Folders/AddPictureFolder", directory);
		settings.setValue("Folders/AddPictureExtension", extension);
		settings.setValue("Folders/AddPictureIndex", filterIndex);

		UpdateGroupTabs();
	};
	UpdateListInfo();
}

[jsulm]

@Perdrix One easy solution would be to create one dialog instance each time you need one, instead of reusing the same instance. Or use static https://doc.qt.io/qt-5/qfiledialog.html#getOpenFileNames

[JonB]

@jsulm
Correct, but this is a reasonable request from @Perdrix. It does seem there isn't a way to clear what has been typed into the File name: box (e.g. https://forum.qt.io/topic/60821/clear-file-selection-in-a-qfiledialog). If the OP tries fileDialog.selectFile("") instead of fileDialog.selectFile(QString()), just in case, and that still does not clear, is there really no way to re-use a dialog instance which has previously had a name typed into it? Seems like a strange omission....

[jsulm]

@Perdrix @JonB I could not find anything. A change request in Qt bug-tracker would make sense.