feat: expose pane scroll state

2 files changed, 52 insertions, 0 deletions

diff --git a/src/app/api/panes.rs b/src/app/api/panes.rs
index c4e6321d..60b2e93b 100644
--- a/src/app/api/panes.rs
+++ b/src/app/api/panes.rs
@@ -1877,6 +1877,22 @@ mod tests {
         (app, public_pane_id, rx)
     }
 
+    fn app_with_scrollback_runtime() -> (App, String, PaneId) {
+        let (mut app, public_pane_id) = app_with_test_workspace();
+        let pane_id = app.state.workspaces[0].tabs[0].root_pane;
+        let lines = (0..20)
+            .map(|line| format!("line {line:02}\n"))
+            .collect::<String>();
+        let runtime = crate::terminal::TerminalRuntime::test_with_scrollback_bytes(
+            20,
+            5,
+            1000,
+            lines.as_bytes(),
+        );
+        app.state.insert_test_runtime(pane_id, runtime);
+        (app, public_pane_id, pane_id)
+    }
+
     fn metadata_params(pane_id: String) -> PaneReportMetadataParams {
         PaneReportMetadataParams {
             pane_id,
@@ -1929,6 +1945,32 @@ mod tests {
     }
 
     #[tokio::test]
+    async fn api_pane_get_exposes_scroll_metrics() {
+        let (mut app, public_pane_id, pane_id) = app_with_scrollback_runtime();
+        let runtime = app
+            .state
+            .runtime_for_pane_in_workspace(&app.terminal_runtimes, 0, pane_id)
+            .expect("runtime");
+        runtime.scroll_up(3);
+
+        let response = app.handle_pane_get(
+            "req".into(),
+            PaneTarget {
+                pane_id: public_pane_id,
+            },
+        );
+
+        let success: SuccessResponse = serde_json::from_str(&response).unwrap();
+        let ResponseResult::PaneInfo { pane } = success.result else {
+            panic!("expected pane info response");
+        };
+        let scroll = pane.scroll.expect("scroll metrics");
+        assert_eq!(scroll.offset_from_bottom, 3);
+        assert!(scroll.max_offset_from_bottom >= scroll.offset_from_bottom);
+        assert_eq!(scroll.viewport_rows, 5);
+    }
+
+    #[tokio::test]
     async fn api_pane_send_keys_preserves_legacy_control_c_aliases() {
         let (mut app, pane_id, mut rx) = app_with_send_key_runtime(3);
 
diff --git a/src/app/creation.rs b/src/app/creation.rs
index bfc4cd03..13fc0a8e 100644
--- a/src/app/creation.rs
+++ b/src/app/creation.rs
@@ -375,6 +375,15 @@ impl App {
         let pane = ws.pane_state(pane_id)?;
         let terminal = self.state.terminals.get(&pane.attached_terminal_id)?;
         let tab_idx = ws.find_tab_index_for_pane(pane_id)?;
+        let scroll = self
+            .state
+            .runtime_for_pane_in_workspace(&self.terminal_runtimes, ws_idx, pane_id)
+            .and_then(|runtime| runtime.scroll_metrics())
+            .map(|metrics| crate::api::schema::PaneScrollInfo {
+                offset_from_bottom: metrics.offset_from_bottom as u64,
+                max_offset_from_bottom: metrics.max_offset_from_bottom as u64,
+                viewport_rows: metrics.viewport_rows as u64,
+            });
         let focused = self.state.active == Some(ws_idx)
             && ws.active_tab == tab_idx
             && ws
@@ -401,6 +410,7 @@ impl App {
             custom_status: presentation.custom_status,
             state_labels: presentation.state_labels,
             agent_session: terminal_agent_session_info(terminal),
+            scroll,
             revision: terminal.revision,
         })
     }