perf: avoid full pane renders for spinner animation (#1868)

4 files changed, 335 insertions, 35 deletions

diff --git a/src/protocol/wire.rs b/src/protocol/wire.rs
index d724a5ae..0d4b14bb 100644
--- a/src/protocol/wire.rs
+++ b/src/protocol/wire.rs
@@ -444,6 +444,19 @@ pub struct CellData {
     pub hyperlink: Option<u32>,
 }
 
+impl CellData {
+    pub(crate) fn from_ratatui_cell(cell: &ratatui::buffer::Cell) -> Self {
+        Self {
+            symbol: cell.symbol().to_owned(),
+            fg: color_to_u32(cell.fg),
+            bg: color_to_u32(cell.bg),
+            modifier: modifier_to_u16(cell.modifier),
+            skip: cell.skip,
+            hyperlink: None,
+        }
+    }
+}
+
 /// Cursor shape encoded as a DECSCUSR parameter.
 ///
 /// 0 = terminal default, 1 = blinking block, 2 = steady block,
@@ -527,14 +540,9 @@ impl FrameData {
                             index
                         }))
                     });
-                cells.push(CellData {
-                    symbol: cell.symbol().to_owned(),
-                    fg: color_to_u32(cell.fg),
-                    bg: color_to_u32(cell.bg),
-                    modifier: modifier_to_u16(cell.modifier),
-                    skip: cell.skip,
-                    hyperlink,
-                });
+                let mut cell = CellData::from_ratatui_cell(cell);
+                cell.hyperlink = hyperlink;
+                cells.push(cell);
             }
         }
 
diff --git a/src/server/headless.rs b/src/server/headless.rs
index 99702512..94721c38 100644
--- a/src/server/headless.rs
+++ b/src/server/headless.rs
@@ -145,6 +145,14 @@ impl RenderImpact {
     }
 }
 
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+enum ScheduledRenderImpact {
+    #[default]
+    None,
+    Animation,
+    Full,
+}
+
 fn record_render_impact(source: &'static str, impact: RenderImpact) {
     let event = match (source, impact) {
         ("api_requests", RenderImpact::Graphics) => "graphics_render_cause.api_requests",
@@ -493,6 +501,7 @@ impl HeadlessServer {
         let mut needs_render = true;
         let mut needs_full_render = true;
         let mut needs_graphics_render = false;
+        let mut needs_animation_render = false;
 
         loop {
             crate::render_prof::event("loop.tick");
@@ -589,11 +598,19 @@ impl HeadlessServer {
 
             // 6. Handle scheduled tasks.
             let now = Instant::now();
-            if self.handle_scheduled_tasks_headless(now, needs_render) {
-                needs_render = true;
-                needs_full_render = true;
-                needs_graphics_render = false;
-                crate::render_prof::event("full_render_cause.scheduled_tasks");
+            match self.handle_scheduled_tasks_headless(now, needs_render) {
+                ScheduledRenderImpact::None => {}
+                ScheduledRenderImpact::Animation => {
+                    needs_render = true;
+                    needs_animation_render = true;
+                    crate::render_prof::event("animation_render_cause.scheduled_tasks");
+                }
+                ScheduledRenderImpact::Full => {
+                    needs_render = true;
+                    needs_full_render = true;
+                    needs_graphics_render = false;
+                    crate::render_prof::event("full_render_cause.scheduled_tasks");
+                }
             }
 
             if self.handle_deferred_requests_headless() {
@@ -630,7 +647,16 @@ impl HeadlessServer {
                     crate::render_prof::event("retained_gate.not_pty_dirty");
                 }
                 let mut deferred_graphics = false;
-                let rendered_retained = if needs_graphics_render && !needs_full_render && !pty_dirty
+                let rendered_retained = if needs_animation_render
+                    && !needs_full_render
+                    && !needs_graphics_render
+                    && !pty_dirty
+                {
+                    self.render_retained_animation_update_and_stream()
+                } else if needs_graphics_render
+                    && !needs_full_render
+                    && !needs_animation_render
+                    && !pty_dirty
                 {
                     match self.render_retained_graphics_update_and_stream() {
                         RetainedGraphicsOutcome::Sent => true,
@@ -641,7 +667,10 @@ impl HeadlessServer {
                         RetainedGraphicsOutcome::Fallback => false,
                     }
                 } else {
-                    pty_dirty && !needs_full_render && self.render_retained_pty_update_and_stream()
+                    pty_dirty
+                        && !needs_full_render
+                        && !needs_animation_render
+                        && self.render_retained_pty_update_and_stream()
                 };
                 if deferred_graphics {
                     needs_render = false;
@@ -655,6 +684,7 @@ impl HeadlessServer {
                 needs_render = false;
                 needs_full_render = false;
                 needs_graphics_render = false;
+                needs_animation_render = false;
                 continue;
             }
 
@@ -3396,6 +3426,69 @@ impl HeadlessServer {
         }
     }
 
+    fn render_retained_animation_update_and_stream(&mut self) -> bool {
+        crate::render_prof::event("retained_animation.attempt");
+        if !self.retained_pty_update_allowed_by_app_state()
+            || self.app.state.config_diagnostic.is_some()
+        {
+            crate::render_prof::event("retained_animation_fallback.unsafe_app_state");
+            return false;
+        }
+
+        let mut targets = Vec::new();
+        for (client_id, (cols, rows), _, _, mode) in
+            render_targets(&self.clients, self.foreground_client_id)
+        {
+            if !matches!(mode, ClientConnectionMode::App) {
+                continue;
+            }
+            let Some(client) = self.clients.get(&client_id) else {
+                return false;
+            };
+            if client.deferred_render() != DeferredRender::None
+                || client.graphics_surface_reset_pending
+            {
+                crate::render_prof::event("retained_animation_fallback.client_state");
+                return false;
+            }
+            let Some(previous) = client.render_state.last_frame().cloned() else {
+                crate::render_prof::event("retained_animation_fallback.no_last_frame");
+                return false;
+            };
+            if previous.width != cols || previous.height != rows {
+                crate::render_prof::event("retained_animation_fallback.frame_size_mismatch");
+                return false;
+            }
+            targets.push((client_id, previous));
+        }
+
+        let mut frames = Vec::with_capacity(targets.len());
+        for (client_id, previous) in targets {
+            let Some(frame) = crate::server::render_stream::render_working_animation_from_frame(
+                &mut self.app.state,
+                &self.app.terminal_runtimes,
+                previous,
+            ) else {
+                crate::render_prof::event("retained_animation_fallback.render_failed");
+                return false;
+            };
+            frames.push((client_id, frame));
+        }
+
+        let mut broken_clients = Vec::new();
+        let mut sent_all = true;
+        for (client_id, frame) in frames {
+            sent_all &= self.send_retained_frame_to_client(client_id, frame, &mut broken_clients);
+        }
+        for client_id in broken_clients {
+            self.remove_client_and_resize_if_needed(client_id);
+        }
+        if sent_all {
+            crate::render_prof::event("retained_animation.success");
+        }
+        sent_all
+    }
+
     fn render_retained_pty_update_and_stream(&mut self) -> bool {
         crate::render_prof::event("retained.attempt");
         let retained_started = crate::render_prof::timer();
@@ -3892,8 +3985,13 @@ impl HeadlessServer {
     ///
     /// Similar to `App::handle_scheduled_tasks` but without resize polling
     /// (the server doesn't have a terminal to resize).
-    fn handle_scheduled_tasks_headless(&mut self, now: Instant, geometry_dirty: bool) -> bool {
+    fn handle_scheduled_tasks_headless(
+        &mut self,
+        now: Instant,
+        geometry_dirty: bool,
+    ) -> ScheduledRenderImpact {
         let mut changed = false;
+        let mut animation_changed = false;
 
         self.app.sync_headless_animation_timer(now);
 
@@ -3960,7 +4058,7 @@ impl HeadlessServer {
                 .spinner_tick
                 .wrapping_add(app::HEADLESS_ANIMATION_TICK_STEP);
             self.app.next_animation_tick = Some(now + app::HEADLESS_ANIMATION_INTERVAL);
-            changed = true;
+            animation_changed = true;
         }
 
         if self
@@ -4020,7 +4118,13 @@ impl HeadlessServer {
                 .start_pending_agent_resumes(self.app.pending_agent_resume_due(now));
         }
         self.app.sync_headless_animation_timer(now);
-        changed
+        if changed {
+            ScheduledRenderImpact::Full
+        } else if animation_changed {
+            ScheduledRenderImpact::Animation
+        } else {
+            ScheduledRenderImpact::None
+        }
     }
 
     /// Initiates graceful shutdown.
@@ -4825,6 +4929,22 @@ mod tests {
         (server, client_rx, pane_id)
     }
 
+    fn set_first_test_pane_working(server: &mut HeadlessServer) {
+        server.app.state.ensure_test_terminals();
+        let pane_id = server.app.state.workspaces[0].tabs[0].root_pane;
+        let terminal_id = server.app.state.workspaces[0].tabs[0].panes[&pane_id]
+            .attached_terminal_id
+            .clone();
+        let terminal = server
+            .app
+            .state
+            .terminals
+            .get_mut(&terminal_id)
+            .expect("test terminal");
+        terminal.detected_agent = Some(crate::detect::Agent::Pi);
+        terminal.state = crate::detect::AgentState::Working;
+    }
+
     fn assert_frame_data_eq(actual: &FrameData, expected: &FrameData) {
         assert_eq!(
             (actual.width, actual.height),
@@ -4851,6 +4971,88 @@ mod tests {
         }
     }
 
+    #[tokio::test]
+    async fn retained_animation_matches_full_render_for_mixed_client_sizes() {
+        fn test_server_with_mobile_client() -> (
+            HeadlessServer,
+            std::sync::mpsc::Receiver<Vec<u8>>,
+            std::sync::mpsc::Receiver<Vec<u8>>,
+        ) {
+            let (mut server, desktop_rx, _) = retained_test_server(
+                b"\x1b]8;;https://example.com\x1b\\\x1b[4:3mlinked\x1b[0m\x1b]8;;\x1b\\",
+            );
+            set_first_test_pane_working(&mut server);
+            let (mobile_tx, _mobile_control_rx, mobile_rx) = test_client_writer();
+            server.clients.insert(
+                2,
+                ClientConnection::new(
+                    (44, 20),
+                    crate::kitty_graphics::HostCellSize::default(),
+                    crate::terminal_theme::TerminalTheme::default(),
+                    None,
+                    2,
+                    RenderEncoding::SemanticFrame,
+                    Some(mobile_tx),
+                ),
+            );
+            (server, desktop_rx, mobile_rx)
+        }
+
+        let (mut retained_server, retained_desktop_rx, retained_mobile_rx) =
+            test_server_with_mobile_client();
+        let (mut full_server, full_desktop_rx, full_mobile_rx) = test_server_with_mobile_client();
+
+        retained_server.render_and_stream();
+        let _ = retained_desktop_rx
+            .recv_timeout(Duration::from_millis(100))
+            .expect("retained desktop baseline");
+        let _ = retained_mobile_rx
+            .recv_timeout(Duration::from_millis(100))
+            .expect("retained mobile baseline");
+        full_server.render_and_stream();
+        let _ = full_desktop_rx
+            .recv_timeout(Duration::from_millis(100))
+            .expect("full desktop baseline");
+        let _ = full_mobile_rx
+            .recv_timeout(Duration::from_millis(100))
+            .expect("full mobile baseline");
+
+        retained_server.app.state.spinner_tick = app::HEADLESS_ANIMATION_TICK_STEP;
+        full_server.app.state.spinner_tick = app::HEADLESS_ANIMATION_TICK_STEP;
+
+        assert!(retained_server.render_retained_animation_update_and_stream());
+        full_server.render_and_stream();
+
+        let retained_desktop = read_server_frame(
+            retained_desktop_rx
+                .recv_timeout(Duration::from_millis(100))
+                .expect("retained desktop animation"),
+        );
+        let retained_mobile = read_server_frame(
+            retained_mobile_rx
+                .recv_timeout(Duration::from_millis(100))
+                .expect("retained mobile animation"),
+        );
+        let full_desktop = read_server_frame(
+            full_desktop_rx
+                .recv_timeout(Duration::from_millis(100))
+                .expect("full desktop animation"),
+        );
+        let full_mobile = read_server_frame(
+            full_mobile_rx
+                .recv_timeout(Duration::from_millis(100))
+                .expect("full mobile animation"),
+        );
+
+        assert_frame_data_eq(&retained_desktop, &full_desktop);
+        assert_frame_data_eq(&retained_mobile, &full_mobile);
+        assert_eq!(
+            retained_server.app.state.view.layout,
+            crate::app::state::ViewLayout::Desktop
+        );
+        assert!(!retained_desktop.hyperlinks.is_empty());
+    }
+
     #[test]
     fn foreground_client_applies_client_keybindings() {
         let mut server = test_headless_server();
@@ -5938,7 +6140,10 @@ next_tab = ""
             Some("short lived")
         );
 
-        assert!(server.handle_scheduled_tasks_headless(deadline + Duration::from_millis(1), false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(deadline + Duration::from_millis(1), false),
+            ScheduledRenderImpact::Full
+        );
 
         assert_eq!(server.app.agent_metadata_deadline, None);
         assert_eq!(
@@ -5969,12 +6174,38 @@ next_tab = ""
     }
 
     #[test]
+    fn headless_scheduled_animation_is_distinct_but_other_changes_win() {
+        let mut server = test_headless_server();
+        server.app.state.workspaces = vec![crate::workspace::Workspace::test_new("working")];
+        set_first_test_pane_working(&mut server);
+        let now = Instant::now();
+        server.app.next_animation_tick = Some(now);
+
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(now, false),
+            ScheduledRenderImpact::Animation
+        );
+
+        server.app.next_animation_tick = Some(now);
+        server.app.state.config_diagnostic = Some("expired".into());
+        server.app.config_diagnostic_deadline = Some(now);
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(now, false),
+            ScheduledRenderImpact::Full
+        );
+        assert!(server.app.state.config_diagnostic.is_none());
+    }
+
+    #[test]
     fn headless_scheduled_tasks_clears_disabled_agent_manifest_update_deadline() {
         let mut server = test_headless_server();
         let now = Instant::now();
         server.app.next_agent_manifest_update_check = Some(now - Duration::from_millis(1));
 
-        assert!(!server.handle_scheduled_tasks_headless(now, false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(now, false),
+            ScheduledRenderImpact::None
+        );
         assert_eq!(server.app.next_agent_manifest_update_check, None);
     }
 
@@ -6030,7 +6261,10 @@ next_tab = ""
         });
         server.app.pending_agent_resume_deadline = Some(Instant::now() - Duration::from_millis(1));
 
-        assert!(!server.handle_scheduled_tasks_headless(Instant::now(), true));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(Instant::now(), true),
+            ScheduledRenderImpact::None
+        );
         assert!(server.app.terminal_runtimes.get(&terminal_id).is_none());
         assert!(server
             .app
@@ -6084,7 +6318,10 @@ next_tab = ""
         });
         server.app.pending_agent_resume_deadline = Some(Instant::now() - Duration::from_millis(1));
 
-        assert!(!server.handle_scheduled_tasks_headless(Instant::now(), false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(Instant::now(), false),
+            ScheduledRenderImpact::None
+        );
         assert!(server.app.terminal_runtimes.get(&terminal_id).is_none());
         assert!(server
             .app
@@ -9311,7 +9548,10 @@ next_tab = ""
             }
         );
         let deadline = server.app.toast_deadline.expect("api toast deadline");
-        assert!(server.handle_scheduled_tasks_headless(deadline, false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(deadline, false),
+            ScheduledRenderImpact::Full
+        );
         assert!(server.app.state.toast.is_none());
         assert!(server.app.toast_deadline.is_none());
     }
@@ -9438,7 +9678,10 @@ next_tab = ""
             .state
             .next_pending_agent_notification_deadline()
             .expect("pending notification deadline");
-        assert!(server.handle_scheduled_tasks_headless(deadline, false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(deadline, false),
+            ScheduledRenderImpact::Full
+        );
 
         let first = read_server_message(
             client_control_rx
@@ -9526,7 +9769,10 @@ next_tab = ""
             .state
             .next_pending_agent_notification_deadline()
             .expect("pending notification deadline");
-        assert!(server.handle_scheduled_tasks_headless(deadline, false));
+        assert_eq!(
+            server.handle_scheduled_tasks_headless(deadline, false),
+            ScheduledRenderImpact::Full
+        );
 
         let first = read_server_message(
             client_control_rx
diff --git a/src/server/render_stream.rs b/src/server/render_stream.rs
index f1f6c428..41a5781d 100644
--- a/src/server/render_stream.rs
+++ b/src/server/render_stream.rs
@@ -345,6 +345,45 @@ pub(crate) fn render_virtual_with_runtime_registry(
     (buffer, cursor)
 }
 
+pub(crate) fn render_working_animation_from_frame(
+    app_state: &mut AppState,
+    terminal_runtimes: &TerminalRuntimeRegistry,
+    mut frame: FrameData,
+) -> Option<FrameData> {
+    let area = Rect::new(0, 0, frame.width, frame.height);
+    crate::ui::compute_view_without_resizing_panes(app_state, terminal_runtimes, area);
+
+    let backend = CursorTrackingBackend::new(area.width, area.height);
+    let mut terminal = ratatui::Terminal::new(backend).ok()?;
+    terminal
+        .draw(|frame| {
+            crate::ui::render_working_animation(app_state, terminal_runtimes, frame);
+        })
+        .ok()?;
+
+    let updated_area = if app_state.view.layout == crate::app::state::ViewLayout::Mobile {
+        app_state.view.mobile_header_rect
+    } else {
+        app_state.view.sidebar_rect
+    };
+    if updated_area.x.saturating_add(updated_area.width) > frame.width
+        || updated_area.y.saturating_add(updated_area.height) > frame.height
+    {
+        return None;
+    }
+
+    let rendered = terminal.backend().buffer();
+    frame.graphics.clear();
+    for y in updated_area.y..updated_area.y.saturating_add(updated_area.height) {
+        for x in updated_area.x..updated_area.x.saturating_add(updated_area.width) {
+            let index = usize::from(y) * usize::from(frame.width) + usize::from(x);
+            let cell = rendered.cell((x, y))?;
+            frame.cells[index] = crate::protocol::CellData::from_ratatui_cell(cell);
+        }
+    }
+    Some(frame)
+}
+
 fn popup_terminal_cursor(
     app_state: &AppState,
     terminal_runtimes: &TerminalRuntimeRegistry,
diff --git a/src/ui.rs b/src/ui.rs
index 6d5c02f1..ed1f6a7d 100644
--- a/src/ui.rs
+++ b/src/ui.rs
@@ -394,19 +394,10 @@ pub fn render_with_runtime_registry(
     terminal_runtimes: &TerminalRuntimeRegistry,
     frame: &mut Frame,
 ) {
-    let sidebar_area = app.view.sidebar_rect;
     let tab_bar_area = app.view.tab_bar_rect;
     let terminal_area = app.view.terminal_area;
 
-    if app.view.layout == ViewLayout::Mobile {
-        render_mobile_header(app, terminal_runtimes, frame, app.view.mobile_header_rect);
-    } else if sidebar_area.width > 0 {
-        if app.sidebar_collapsed {
-            render_sidebar_collapsed(app, frame, sidebar_area);
-        } else {
-            render_sidebar(app, terminal_runtimes, frame, sidebar_area);
-        }
-    }
+    render_working_animation(app, terminal_runtimes, frame);
     if app.view.layout != ViewLayout::Mobile {
         render_tab_bar(app, frame, tab_bar_area);
     }
@@ -457,6 +448,22 @@ pub fn render_with_runtime_registry(
     }
 }
 
+pub(crate) fn render_working_animation(
+    app: &AppState,
+    terminal_runtimes: &TerminalRuntimeRegistry,
+    frame: &mut Frame,
+) {
+    if app.view.layout == ViewLayout::Mobile {
+        render_mobile_header(app, terminal_runtimes, frame, app.view.mobile_header_rect);
+    } else if app.view.sidebar_rect.width > 0 {
+        if app.sidebar_collapsed {
+            render_sidebar_collapsed(app, frame, app.view.sidebar_rect);
+        } else {
+            render_sidebar(app, terminal_runtimes, frame, app.view.sidebar_rect);
+        }
+    }
+}
+
 fn render_notifications(app: &AppState, frame: &mut Frame, terminal_area: Rect) {
     let has_config_diagnostic = app.config_diagnostic.is_some();
     if let Some(message) = &app.config_diagnostic {