DnD to unmounted volumes
Drag and drop should be made possible even for unmounted volumes in the sidebar to provide a more intuitive and consistent experience.
Current behaviour
- file gets dragged from a mounted, open directory to a volume in the sidebar
- as the volume is unmounted, the "drop location" is greyed out and does nothing.
Suggested change
- file gets dragged from a mounted, open directory to a volume in the sidebar
- as the volume is unmounted, the "drop location" is showing a message (such as "Mount volume") on hover and when the file is dropped the volume is mounted (with authentication etc. if required) and the file is queued for copy.
- The user could also be asked for confirmation to mount the volume (such as a "This volume needs to be mounted to copy the file" dialog with Continue/Cancel buttons), and later warned if the file could not be copied to the destination for some reason.
- For MTP and similar things, most devices allow DnD to "subdirectories" (such as Internal Storage, SD Card...) but not to the "main" element in the sidebar itself. The user may be prompted to choose a "child" to copy to (with a drop-down popover from the sidebar item perhaps, or with a dialog window)