[flutter_local_notifications_linux] migrate to xdg-desktop-portal for notifications

[Merrit]

The xdg-desktop-portal is the new standard for desktop notifications
and is supported by GNOME, KDE, and other desktop environments. It
also works with Flatpak and Snap applications.

Resolves #1757

[Merrit]

Created as a draft for a couple reasons:

• I added support for the notification callback to the supporting package, which needs to be merged first.

• The current API exposed by the xdg-desktop-portal is more limited than the current implementation that uses the DBus service, and losing that functionality is unwanted.

  Specifically I think the missing features are:

  • body images
  • sound control
  • action icons
  • position on screen

  There is an open proposal for a v2 of the notifications portal currently being discussed that would add these sorts of features (and more).

That said, everything regarding sending notifications, body markup, actions, callbacks, etc seems to be working well - and crucially also working from within Flatpak, which was the big problem for my use case.

For anyone else needing Flatpak support, you can use a git override until this change can be merged:

dependency_overrides:
# Override flutter_local_notifications to use the fork with the fix for
# Flatpak until the fix is merged.
# See: https://github.com/MaikuB/flutter_local_notifications/issues/1757
flutter_local_notifications:
  git:
    url: https://github.com/Merrit/flutter_local_notifications.git
    ref: d5d529cb2278deba2ca8244025256348483a1cdd
    path: flutter_local_notifications

[MaikuB]

Thanks for the PR. I'll take a look when I can block out some time to sit through this properly. Not though that I don't use Linux and I'm not particularly familiar with the ecosystem so I would suggest trying to see if there are others in the community that could help out with this

P.S. you may see me trying to update the plugin with a more urgent quick fix ahead of this PR given Flutter 3.10 just landed on stable and included Dart 3 so believe I need to to bump the max Dart SDK constraints

[Merrit]

No worries, I don't expect everyone to be familiar with Linux. I wanted to make the PR smaller, but everything was pretty entwined. If there is anything I can do to help, just let me know! 😃

P.S. you may see me trying to update the plugin with a more urgent quick fix ahead of this PR given Flutter 3.10 just landed on stable and included Dart 3 so believe I need to to bump the max Dart SDK constraints

Sounds like a good idea 💙

[MaikuB]

If there is anything I can do to help, just let me know!

If there are others in the community that you know that you could contact to help review and/or provide feedback on this then that would be great. On that note, since the issue was originally raised by you, do you think you'd be able to check this out @emersion?

[MaikuB]

I left some general comments on the PR though didn't actually get to test it out. As a whole the changes make sense to me but don't want to lose functionality so would like to wait until the missing functionality is officially supported

[MaikuB]

what the reason behind this change? i wasn't expecting example app to require this kind of the change given the intent behind the PR

[Merrit]

Ah yeah, forgot to document that. I believe it didn't work, and troubleshooting indicated it was when it had an underscore.

[MaikuB]

I saw you shared some details on how there are some proposals given the missing functionality etc. You probably figured but I would say until that is addressed then the changes in the PR wouldn't be part of a stable release of the plugin

[Merrit]

As a whole the changes make sense to me but don't want to lose functionality so would like to wait until the missing functionality is officially supported

Sounds reasonable :)

FYI, I did ask some people if anyone could help review but so far no takers.

[Merrit]

Update

My PR for the supporting package hasn't had any movement. Canonical appears to have abandoned the package - hasn't seen any activity in a long time, and when I reached out to them directly to ask about the status of the project it was ignored.

In addition it appears that #1757 was incorrect about org.freedesktop.Notifications not being available in Flatpak - it seems to be undocumented because they prefer you use the new implementation, but you can use it by adding --talk-name=org.freedesktop.Notifications to the finish-args of the flatpak manifest, at which point flutter_local_notifications works just fine as-is.

Given these developments I suggest we close this PR to keep the repo clean, and update #1757 with the information to use --talk-name=org.freedesktop.Notifications. Migrating to org.freedesktop.portal.Notification can be revisited if and when the new new spec proposal gets implemented, and actually has the desired features.

[emersion]

Note that --talk-name=org.freedesktop.Notifications basically punches a hole through the sandbox. It makes the sandbox insecure to some extent, e.g. because it allows the sandboxed app to manipulate notifications of other apps (by guessing their IDs, which is a simple counter). So it's more of a workaround than a proper solution.

[Merrit]

Yeah, I understand they want people to use the new implementation for good reasons. Given the lack of support for needed features though, IMHO workaround seems proper until v2 of the new portal is available.