Instead of rewriting img src to file:// URIs, rewrite to a custom
feedthemonkey-img:/// scheme. A WebKit URI scheme handler is registered
on the WebView's WebContext that:
- Serves the image directly from the cache directory if present.
- On a cache miss (e.g. after the user deletes ~/.cache), spawns a
reqwest download in the tokio runtime, then resumes on the GLib main
loop via glib::spawn_future_local and serves the freshly downloaded
bytes — all transparent to the WebView.
This means deleting the cache directory never results in permanently
broken images; they are silently re-fetched on first access.
Both cache.json (article list) and the images directory are
regeneratable from the server, so they belong in XDG_CACHE_HOME
(~/.cache/net.jeena.FeedTheMonkey/) rather than XDG_DATA_HOME.
After fetching articles, all remote images referenced in article content
are downloaded to ~/.local/share/net.jeena.FeedTheMonkey/images/ and
their src attributes rewritten to file:// URIs. Subsequent loads of the
same article (including from the cache on the next startup) display
images without a network connection.
Metered-connection awareness: image caching is skipped automatically
when GIO reports the network connection as metered, regardless of the
preference setting.
A "Cache Images" toggle in Preferences lets the user disable caching
entirely (stored in the cache-images GSettings key).
After each refresh, images no longer referenced by any article in the
current unread list are deleted from the cache directory to prevent
unbounded disk growth.
