decoder: Use GFile instead of PathBuf

This allows to show images from locations that don't
have a representation with path.

This also works around not being able to read files in trash:///

Closes #56

Part-of: <https://gitlab.gnome.org/Incubator/loupe/-/merge_requests/174>

src/util/mod.rs

@@ -154,6 +154,25 @@ pub async fn untrash(path: &Path) -> anyhow::Result<()> {
     error
 }
 
+pub trait BufReadSeek: std::io::BufRead + std::io::Seek {}
+
+impl BufReadSeek for std::io::BufReader<gio::InputStreamRead<gio::FileInputStream>> {}
+
+pub trait ToBufRead {
+    fn to_buf_read(&self) -> anyhow::Result<Box<dyn BufReadSeek>>;
+}
+
+impl ToBufRead for gio::File {
+    fn to_buf_read(&self) -> anyhow::Result<Box<dyn BufReadSeek>> {
+        let read = self
+            .read(gio::Cancellable::NONE)
+            .context(gettext("Failed to open image"))?
+            .into_read();
+
+        Ok(Box::new(std::io::BufReader::new(read)))
+    }
+}
+
 #[derive(Debug, Clone, Copy)]
 pub enum Position {
     First,