enhance(sourround_replace): provide visual feedback during the operation

When the target character is pressed, the selection is temporarily updated
to display the affected positions. It restores the original selection after
the operation is cancelled or completed.

helix-term/src/commands.rs

@@ -5115,11 +5115,25 @@ fn surround_replace(cx: &mut Context) {
             }
         };
 
+        // Visual feedback
+        let selection = selection.clone();
+        let mut ranges: SmallVec<[Range; 1]> = SmallVec::new();
+        change_pos.chunks(2).for_each(|p| {
+            if p.len() == 2 {
+                let from = *p.first().unwrap();
+                let to = *p.get(1).unwrap();
+                ranges.push(Range::new(from, from + 1));
+                ranges.push(Range::new(to, to + 1));
+            }
+        });
+        let feedback = Selection::new(ranges, 0);
+        doc.set_selection(view.id, feedback);
+
         cx.on_next_key(move |cx, event| {
             let (view, doc) = current!(cx.editor);
             let to = match event.char() {
                 Some(to) => to,
-                None => return,
+                None => return doc.set_selection(view.id, selection),
             };
             let (open, close) = surround::get_pair(to);
             let transaction = Transaction::change(
@@ -5131,6 +5145,7 @@ fn surround_replace(cx: &mut Context) {
                 }),
             );
             doc.apply(&transaction, view.id);
+            doc.set_selection(view.id, selection);
             exit_select_mode(cx);
         });
     })