Provide an icon with tooltip in the TextEntry URL widget to let users know of validation errors when testing a CalDAV / Webcal / HTTPS link to subscribe to
Currently, when an error is encountered in the backend, the text field simply becomes red but doesn't tell the user any details.
Short of implementing a more general UI for errors in #17, an easy straightforward way to solve the problem for this particular dialog window is to use GtkEntry's ability to set icons and tooltips on those icons: https://blog.gtk.org/2019/03/15/entries-in-gtk-4/
Simply set the standard named warning icon, and a tooltip that reveals the error reported by validate_url_cb
. When the status changes again to a valid status, or the entry is cleared in validate_url_cb
, unset the tooltip and icon.
This would at least make it work for the desktop usecase. It'll be much better than nothing.