[gui] Enhance FFI library loading

[levkropp]

resolves #4175

This pull request introduces changes to improve error handling and user experience when the FFI library fails to load. The updates include a new mechanism to detect FFI availability, enhancements to the DaemonUnavailable widget, and modifications to providers for better integration.

Error Handling for FFI Library:

• src/client/gui/lib/ffi.dart: Introduced the FFILibrary class to encapsulate FFI library loading logic, handle errors gracefully, and provide utility methods (isFFIAvailable and ffiLoadError) for checking availability and accessing load errors.

User Interface Enhancements:

• src/client/gui/lib/daemon_unavailable.dart: Updated the DaemonUnavailable widget to display a fatal error message and an "Exit Application" button when the FFI library fails to load. Added a conditional check for ffiAvailableProvider to differentiate between fatal errors and regular daemon unavailability. [1] [2]

Provider Updates:

• src/client/gui/lib/providers.dart: Added a new provider, ffiAvailableProvider, to propagate the FFI availability status throughout the application. Updated grpcClientProvider and daemonAvailableProvider to incorporate FFI availability checks, ensuring dependent functionality behaves appropriately when the FFI library is unavailable. [1] [2]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.31%. Comparing base (47f57a0) to head (1352054).
⚠️ Report is 470 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4179   +/-   ##
=======================================
  Coverage   89.31%   89.31%           
=======================================
  Files         259      259           
  Lines       15684    15684           
=======================================
  Hits        14008    14008           
  Misses       1676     1676           

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[sharder996]

I'm trusting you with the finer points of engineering Dart code, I'm wondering if it's possible to make the text selectable/copyable?

[sharder996]

Do you mean to no longer have available here?

[sharder996]

You can't make the text selectable? @levkropp

[levkropp]

I added a button to copy the entire error to the clipboard. It seems more in line with how we do copying in multipass i.e with CopyableText (click to copy) and is faster for getting the error, but I have no strong feelings about it being just a SelectableText since this is a debug dialog.

[xmkg]

Tested in a local copy, the error message is being displayed when the libdart_ffi.so is absent in the library search path:

Also, the message has a nice copy button, and it works:

Exception: Failed to load libdart_ffi library: Invalid argument(s): Failed to load dynamic library 'libdart_ffi.so': libdart_ffi.so: cannot open shared object file: No such file or directory

The Exit application button also works.

The message disappears when I start the GUI with LD_LIBRARY_PATH: LD_LIBRARY_PATH=./build/lib ./build/bin/multipass.gui. Looks good to me, functionality-wise, will skim through the code with my non-existent Flutter knowledge :)

[xmkg]

LGTM, good job! Thanks for taking care of this one, @levkropp!

[sharder996]

This looks good now. Thanks for listening to my nitpicks @levkropp! 😄