fix(eog): add completion for AVIF and WEBP files

[Rogach]

I'm not sure what to write here - it is what it says on the tin, I've just added two more file extensions.

[akinomyoga]

I tried to find a page that lists the supported file formats, but it seems to be hard to list the supported file formats. The page [1] doesn't seem to list many file formats including the suggested .avif and .webp. Meanwhile, the Wikipedia article [2] seems to list those file formats, but it doesn't seem to be based on official information.

• [1] Supported image formats
• [2] Eye of GNOME - Wikipedia

The source repository [3] doesn't seem to contain the file formats either (based on the code search). Instead, it seems to call an external function gdk_pixbuf_get_formats to get the list of formats [4].

• [3] GNOME / Eye of GNOME · GitLab
• [4] src/eog-pixbuf-util.c · master · GNOME / Eye of GNOME · GitLab

The function gdk_pixbuf_get_formats seems to be from the GdkPixbuf library. The GdkPixbuf library seems to recommend creating an external loader module for each file format, so it is hard to pre-determine which formats are supported by the system. At least, the file formats avif and webp seem to be supported by external modules.

• [5] [feature request] add support for webp (#103) · Issues · GNOME / gdk-pixbuf · GitLab
• [6] Add an AVIF loader (!76) · Merge requests · GNOME / gdk-pixbuf · GitLab
• [7] Add a gdk-pixbuf module by linkmauve · Pull Request #182 · AOMediaCodec/libavif
• [8] aruiz/webp-pixbuf-loader: WebP Image format GdkPixbuf loader

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Edit: There seem to be several ways to dynamically get the file formats supported in the present system [9,10].

• [9] c - What image formats are supported by Gdk-Pixbuf (Gtk-Image?) by Default? - Stack Overflow
• [10] gdk-pixbuf-query-loaders(1) - Linux man page

[scop]

I'm not sure what to write here - it is what it says on the tin, I've just added two more file extensions.

FWIW, I usually just leave it empty or say "SSIA.".

There seem to be several ways to dynamically get the file formats supported in the present system

That would be interesting. However at least on Ubuntu 20, gdk-pixbuf-query-loaders is not installed in $PATH (it's buried in /usr/lib/x86_64-linux-gnu/gdk-pixbuf-2.0), and doesn't seem that the output format is documented (not that that would prevent us from happily scraping stuff everywhere though ;)). The Python recipe looks cleaner, but requires modules that are not necessarily present (e.g. gi), and I'm not sure if even Python can be assumed present. But I guess we could make something work from these, if someone's interested.

[scop]

Resolved conflicts, sorted the regex elements, fixed up commit message, merged, thanks 👍