cockpit-client: cannot download files in cockpit-files

[jelly]

Trying to use cockpit-client to browse my nas and download files fails without an error. Resulting in no files being downloaded.

This makes sense as the flatpak has no filesystem access by default so it doesn't work out of the box, trying to give it access to xdg-download or the whole $HOME dir with flatseal downloading does nothing.

The web browser console doesn't report any errors nor is it clear if the download button triggered any JavaScript.

[jelly]

The issue here can be that we implement downloading with window.open which works in a normal desktop, but as this is a flatpak it can't spawn a new window likely.

Even better would be if we could implement a portal for saving files, we don't support downloading multiple files. anyway.

Furthermore cockpit-client would not be able to show the progress of the downloaded file even if it worked, so that needs some more thought as well.

[jelly]

The issue is easily reproducible without a flatpak:

./bots/vm-run -s cockpit.socket fedora-40
./src/client/cockpit-client --external-ws http://127.0.0.2:9091

Then try to download anything. I recall we explicitly use window.open because of browser handling of failed downloads which Firefox or Chrome doesn't handle well.