xdg-desktop-portal provides a portal frontend service for Flatpak, Snap,
 and possibly other desktop containment/sandboxing frameworks. This service
 is made available to the sandboxed application, and provides mediated
 D-Bus interfaces for file access, URI opening, printing and similar
 desktop integration features.
 .
 The implementation of these interfaces is expected to require
 user confirmation before responding to the sandboxed application's
 requests. For example, when the sandboxed application ask to open a file,
 the portal implementation will open an "Open" dialog outside the sandbox,
 and will only make the selected file available to the sandboxed app if
 that dialog is confirmed.
 .
 xdg-desktop-portal is designed to be desktop-agnostic, and uses a
 desktop-environment-specific GUI backend such as xdg-desktop-portal-gtk
 to provide its functionality.