feat(Composer): Add initial autocomplete support

[bleakgrey]

This PR enables account handle autocomplete for the Compose dialog.

The implementation depends on gtksourceview-5, the library that makes interactive text suggestions possible in other GNOME apps like Text Editor or Builder. I felt reluctant to introduce new dependencies, but I figured this one was probably already available on the host system since we target GNOME.

In its current state, it's more of a proof-of-concept (although being a useful thing to have already). If viable, we could iterate on it further:

• Consider using different styling of the popup window
• Autocomplete instance emojis via a separate provider
• Replace Gtk.Label with Tuba.LabelWithWidgets once it's ready
• Implement spell checking?
• Utilize SourceView's syntax highlighting. Pleroma supports Markdown/HTML posts, so maybe we could support multiple content types too?

Tested against GNOME 44 SDK with gtksourceview-5 5.8.0.

[GeopJr]

Looks great so far!

I adapted it to libsoup3 & added Tag.search for hashtags - not sure if adding hashtag support in the same provider is the best idea so I left it at that

[bleakgrey]

Lgtm.

Each provider is supposed to autocomplete just one type of data, so they are better off being separate classes. I'll add tag and instance emoji providers as separate PRs.

I got carried away while refactoring and ended up making a HashtagProvider as well. Here's how it looks like now:

[Megaf]

Lgtm.

Each provider is supposed to autocomplete just one type of data, so they are better off being separate classes. I'll add tag and instance emoji providers as separate PRs.

I got carried away while refactoring and ended up making a HashtagProvider as well. Here's how it looks like now:

This is looking great! Would it be possible to change the colour of the FediverseID/Hastag once it is "selected/validaded"? So, we know we are actually sending a message to that FediverseID.

[GeopJr]

Added emojiprovider (might be too strict, I made it check if it starts with but we can switch to contains)

I think it can make it on 0.2.0!

• Does it need a custom stylescheme for dark mode? On my machine at least, it's white on dark mode
• Does it use anything from 5.8 or will <= 5.6 also work? Since almost everyone ships 5.6 at most right now (Debian Sid, Fedora, Alpine, Snap core22, Freebsd (5.4))

Screencast.from.2023-03-31.21-16-02.webm

[bleakgrey]

I completely forgot that style schemes exist, but now it should respect the app color theme.

As for the library version... well, I did manage to compile this PR with 5.6.0... but I had to remove something that definitely shouldn't be a breaking change. For some reason the library version fields make valac spit out gibberish, at least on my Ubuntu.

[GeopJr]

ah https://gitlab.gnome.org/GNOME/gtksourceview/-/issues/308 fixed in 5.7.1, guess we will add it to troubleshooting when we move to that version 🤷

edit:

added a meson arg so we add them when the version is >= 5.7.1

[GeopJr]

Made completion provider use its own image_cache with 1min maintenance since the images have already been freed by the time the user scrolls back in all providers:

before

Screencast.from.2023-04-02.11-52-33.webm

after

Screencast.from.2023-04-02.11-51-39.webm

[GeopJr]

Merging! I split some of the raised issues into their own ones: #153, #154

Thanks!