[fwuerrer]

Summary

FolderWizardSelectiveSync::validatePage() only honoured the "Use virtual files instead of downloading content immediately" checkbox when the best available VFS mode was WindowsCfApi:

const bool useVirtualFiles = (mode == Vfs::WindowsCfApi) && (_virtualFilesCheckBox && _virtualFilesCheckBox->isChecked());

On Linux the best available mode is Vfs::OpenVFS, so useVirtualFiles was always false, the wizard reported useVirtualFiles=false and AccountSettings::slotFolderWizardAccepted() left FolderDefinition::virtualFilesMode at Vfs::Off. The checkbox is shown on Linux (it is a QCheckBox created whenever bestAvailableVfsMode() != Vfs::Off), so the user could tick it and it was silently ignored — the folder was created as a classic sync folder and everything was downloaded.

Fixes #11096.

Change

Accept the checkbox for every available VFS mode and let the existing Vfs::checkAvailability() call in the same function validate the selected location, instead of hard coding the Windows mode:

const bool useVirtualFiles = (mode != Vfs::Off) && (_virtualFilesCheckBox && _virtualFilesCheckBox->isChecked());

How to test

1. Linux with the OpenVFS plugin available (fuse3 + config installed).
2. Account settings → Add folder sync connection → tick Use virtual files … → finish.
3. The folder is now created with virtualFilesMode=openvfs and the files show up as placeholders instead of being downloaded.
4. Enabling virtual files afterwards in the folder settings behaves identically to before.

Without the patch the tick is discarded and the whole folder is downloaded, exactly as reported in #11096.

Notes

This very likely also addresses #11193: the "> 500 MB" and external storage exclusions are already disabled for VFS folders (DiscoveryPhase::activeFolderSizeLimit() / checkSelectiveSyncNewFolder() return early when the VFS mode is not Off), they only appeared because such folders were created without VFS at all. I would still like that one to be confirmed by the reporter before closing it.