feat: animate loading spinners in pane titles

src/thumbnail.rs

@@ -87,6 +87,15 @@ impl Thumbnail {
         }
     }
 
+    pub fn is_loading(&self) -> bool {
+        self.selected.is_some()
+            && self.error.is_none()
+            && !self
+                .image
+                .as_ref()
+                .is_some_and(|image| image.complete && image.protocol.protocol_type().is_some())
+    }
+
     pub fn draw(&mut self, frame: &mut Frame, area: Rect) {
         self.poll();
         if area.width == 0 || area.height == 0 || self.selected.is_none() {
@@ -301,6 +310,7 @@ mod tests {
         let mut terminal = Terminal::new(TestBackend::new(100, 40)).unwrap();
         for area in [Rect::new(3, 2, 80, 18), Rect::new(7, 4, 30, 8)] {
             terminal.draw(|frame| thumbnail.draw(frame, area)).unwrap();
+            assert!(thumbnail.is_loading());
             let response = requests_rx
                 .recv_timeout(Duration::from_secs(2))
                 .unwrap()
@@ -308,6 +318,7 @@ mod tests {
                 .unwrap();
             replies_tx.send(Ok(response)).unwrap();
             terminal.draw(|frame| thumbnail.draw(frame, area)).unwrap();
+            assert!(!thumbnail.is_loading());
             let buffer = terminal.backend().buffer();
             let pixels: Vec<_> = (0..40)
                 .flat_map(|y| (0..100).map(move |x| (x, y)))