fix: preserve focused viewer geometry during activation (#3746)

* fix: preserve focused viewer geometry during activation

refs #3744

* fix: preserve geometry through activation sync

refs #3744

---------

Co-authored-by: akbash-bot <300245827+akbash-bot@users.noreply.github.com>

2 files changed, 155 insertions, 1 deletions

diff --git a/src/server/headless/surface_interest.rs b/src/server/headless/surface_interest.rs
index 7270be0d..9772fc03 100644
--- a/src/server/headless/surface_interest.rs
+++ b/src/server/headless/surface_interest.rs
@@ -69,7 +69,20 @@ impl HeadlessServer {
             // explicitly requests the bounded replay after its coherent frame is visible.
             self.sent_window_title = None;
             self.resize_shared_runtime_to_effective_size_with_pending_agent_resumes(true);
-            self.claim_shell_tab_geometry(client_id, true);
+            let focused_viewer_already_owns_tab = self
+                .shell_tab_id_for_client(client_id)
+                .is_some_and(|tab_id| {
+                    self.clients.iter().any(|(&other_id, client)| {
+                        other_id != client_id
+                            && client.is_active_shell_client()
+                            && client.outer_terminal_focus == Some(true)
+                            && self.shell_tab_id_for_client(other_id).as_deref()
+                                == Some(tab_id.as_str())
+                    })
+                });
+            if !focused_viewer_already_owns_tab {
+                self.claim_shell_tab_geometry(client_id, true);
+            }
         } else {
             self.tab_geometry_controllers
                 .retain(|_, controller_id| *controller_id != client_id);
diff --git a/src/server/headless/tests/surface_interest.rs b/src/server/headless/tests/surface_interest.rs
index 591f6a8f..df06dc03 100644
--- a/src/server/headless/tests/surface_interest.rs
+++ b/src/server/headless/tests/surface_interest.rs
@@ -36,6 +36,22 @@ fn lifecycle_resize() -> crate::protocol::ClientMessage {
     }
 }
 
+fn request_active_surface(server: &mut HeadlessServer, client_id: u64, request_id: &str) {
+    let boot_id = server.client_shell_boot_id.clone();
+    assert!(
+        server.handle_server_event(ServerEvent::ClientShellEndpointRequest {
+            client_id,
+            boot_id,
+            request: Box::new(api::schema::Request {
+                id: request_id.into(),
+                method: api::schema::Method::ClientShellSurfaceSet(
+                    api::schema::ClientShellSurfaceSetParams { active: true },
+                ),
+            }),
+        })
+    );
+}
+
 #[tokio::test]
 async fn metadata_only_shell_is_isolated_until_surface_activation() {
     let mut server = test_headless_server();
@@ -244,6 +260,131 @@ async fn metadata_only_shell_is_isolated_until_surface_activation() {
 }
 
 #[tokio::test]
+async fn background_surface_activation_preserves_focused_viewer_geometry() {
+    let mut server = test_headless_server();
+    let pane_id = install_shared_view_test_runtime(&mut server);
+    let (focused_control, _) = connect_test_shell(&mut server, 7, 68, 17);
+    let _ = focused_control.recv().expect("focused client snapshot");
+    assert!(server.handle_server_event(ServerEvent::ClientShellFocus {
+        client_id: 7,
+        focused: true,
+    }));
+    let focused_size = server.app.state.workspaces[0].test_runtimes[&pane_id].current_size();
+    assert_eq!(focused_size, (17, 67));
+    let shared_tab_id = server.shell_tab_id_for_client(7).expect("focused tab");
+    assert_eq!(
+        server.tab_geometry_controllers.get(&shared_tab_id),
+        Some(&7)
+    );
+
+    let (writer, background_control, _) = test_client_writer();
+    assert!(
+        server.handle_server_event(ServerEvent::ClientShellConnected {
+            client_id: 8,
+            surface_cols: 100,
+            surface_rows: 35,
+            cell_width_px: 0,
+            cell_height_px: 0,
+            pixel_mouse: false,
+            direct_graphics: false,
+            endpoint_keybindings: false,
+            mouse_capture: false,
+            surface_active: false,
+            writer,
+        })
+    );
+    let _ = background_control
+        .recv()
+        .expect("background client snapshot");
+
+    request_active_surface(&mut server, 8, "activate-background-surface");
+    let _ = background_control
+        .recv()
+        .expect("background surface activation response");
+    assert_eq!(
+        server.shell_tab_id_for_client(8).as_deref(),
+        Some(shared_tab_id.as_str())
+    );
+    assert_eq!(server.clients[&7].outer_terminal_focus, Some(true));
+    assert_eq!(server.clients[&8].outer_terminal_focus, None);
+    assert_eq!(
+        server.app.state.workspaces[0].test_runtimes[&pane_id].current_size(),
+        focused_size,
+        "surface activation must not transiently resize a focused viewer's tab"
+    );
+    assert_eq!(
+        server.tab_geometry_controllers.get(&shared_tab_id),
+        Some(&7)
+    );
+
+    assert!(server.handle_server_event(ServerEvent::ClientShellFocus {
+        client_id: 8,
+        focused: false,
+    }));
+    assert_eq!(server.clients[&7].outer_terminal_focus, Some(true));
+    assert_eq!(server.clients[&8].outer_terminal_focus, Some(false));
+    assert_eq!(
+        server.app.state.workspaces[0].test_runtimes[&pane_id].current_size(),
+        focused_size
+    );
+    assert_eq!(
+        server.tab_geometry_controllers.get(&shared_tab_id),
+        Some(&7)
+    );
+
+    request_active_surface(&mut server, 8, "synchronize-background-surface");
+    let _ = background_control
+        .recv()
+        .expect("background presentation synchronization response");
+    assert_eq!(
+        server.app.state.workspaces[0].test_runtimes[&pane_id].current_size(),
+        focused_size
+    );
+    assert_eq!(
+        server.tab_geometry_controllers.get(&shared_tab_id),
+        Some(&7)
+    );
+    shutdown_test_runtimes(&mut server);
+}
+
+#[tokio::test]
+async fn focused_surface_reassertion_reclaims_tab_geometry() {
+    let mut server = test_headless_server();
+    let pane_id = install_shared_view_test_runtime(&mut server);
+    let (focused_control, _) = connect_test_shell(&mut server, 8, 100, 35);
+    let _ = focused_control.recv().expect("focused client snapshot");
+    assert!(server.handle_server_event(ServerEvent::ClientShellFocus {
+        client_id: 8,
+        focused: true,
+    }));
+    let shared_tab_id = server.shell_tab_id_for_client(8).expect("focused tab");
+
+    let (other_control, _) = connect_test_shell(&mut server, 7, 68, 17);
+    let _ = other_control.recv().expect("other client snapshot");
+    assert!(server.claim_shell_tab_geometry(7, false));
+    assert_eq!(
+        server.app.state.workspaces[0].test_runtimes[&pane_id].current_size(),
+        (17, 67)
+    );
+
+    request_active_surface(&mut server, 8, "reassert-focused-surface");
+    let _ = focused_control
+        .recv()
+        .expect("focused surface reassertion response");
+
+    assert_eq!(server.clients[&8].outer_terminal_focus, Some(true));
+    assert_eq!(
+        server.app.state.workspaces[0].test_runtimes[&pane_id].current_size(),
+        (35, 99)
+    );
+    assert_eq!(
+        server.tab_geometry_controllers.get(&shared_tab_id),
+        Some(&8)
+    );
+    shutdown_test_runtimes(&mut server);
+}
+
+#[tokio::test]
 async fn presentation_sync_epoch_replays_modes_and_title() {
     let mut server = test_headless_server();
     let (writer, control_rx, _render_rx) = test_client_writer();