fix: restore saved machine screens after reconnect (#4126)

refs #3842

5 files changed, 108 insertions, 8 deletions

diff --git a/src/client/shell/endpoints.rs b/src/client/shell/endpoints.rs
index d3823d54..c27358e5 100644
--- a/src/client/shell/endpoints.rs
+++ b/src/client/shell/endpoints.rs
@@ -208,6 +208,7 @@ impl ClientShellState {
         let Some(snapshot) = endpoint.snapshot.clone() else {
             return false;
         };
+        let generation = endpoint.snapshot_generation;
         let switching_endpoint = endpoint_id != &self.active_endpoint_id;
         let agent_scroll = self.agent_scroll;
         if switching_endpoint {
@@ -215,7 +216,7 @@ impl ClientShellState {
             self.pane_surface = None;
             self.pending_pane_surface = None;
         }
-        self.apply_active_snapshot(snapshot);
+        self.apply_active_snapshot(snapshot, generation);
         if switching_endpoint {
             // The aggregate agent list belongs to the client, not one endpoint.
             self.agent_scroll = agent_scroll;
@@ -653,16 +654,21 @@ impl ClientShellState {
     }
 
     fn apply_cached_endpoint_snapshot(&mut self, endpoint_id: &ClientEndpointId) {
-        let Some(snapshot) = self
+        let Some((snapshot, generation)) = self
             .endpoints
             .iter()
             .find(|endpoint| &endpoint.endpoint_id == endpoint_id)
-            .and_then(|endpoint| endpoint.snapshot.clone())
+            .and_then(|endpoint| {
+                endpoint
+                    .snapshot
+                    .clone()
+                    .map(|snapshot| (snapshot, endpoint.snapshot_generation))
+            })
         else {
             return;
         };
         if endpoint_id == &self.active_endpoint_id {
-            self.apply_active_snapshot(snapshot);
+            self.apply_active_snapshot(snapshot, generation);
         }
     }
 }
diff --git a/src/client/shell/state.rs b/src/client/shell/state.rs
index 8f2aec43..04e87169 100644
--- a/src/client/shell/state.rs
+++ b/src/client/shell/state.rs
@@ -895,6 +895,8 @@ pub(super) struct ClientCopyModeState {
 pub(crate) struct ClientShellState {
     pub(super) config: ClientShellConfig,
     pub(super) snapshot: Option<Box<ClientShellSnapshot>>,
+    pub(super) active_snapshot_generation: Option<u64>,
+    pub(super) pane_surface_generation: Option<u64>,
     pub(super) pane_surface: Option<PaneSurfaceFrame>,
     /// A future projection surface waits here until its matching snapshot arrives. The visible
     /// pane surface always remains an exact snapshot pair.
@@ -1054,6 +1056,8 @@ impl ClientShellState {
         Self {
             config,
             snapshot: None,
+            active_snapshot_generation: None,
+            pane_surface_generation: None,
             pane_surface: None,
             pending_pane_surface: None,
             graphics: crate::kitty_graphics::surface::ClientState::default(),
@@ -1309,7 +1313,11 @@ impl ClientShellState {
         self.dismissed_product_announcement = None;
     }
 
-    pub(super) fn apply_active_snapshot(&mut self, mut snapshot: Box<ClientShellSnapshot>) {
+    pub(super) fn apply_active_snapshot(
+        &mut self,
+        mut snapshot: Box<ClientShellSnapshot>,
+        generation: Option<u64>,
+    ) {
         snapshot
             .commands
             .retain(|command| command.action != crate::protocol::ClientShellCommandAction::Unknown);
@@ -1320,13 +1328,21 @@ impl ClientShellState {
         };
         let endpoint_boot_changed =
             self.snapshot.is_some() && self.graphics.scope() != graphics_scope;
+        let generation_changed = self.active_snapshot_generation != generation;
         if !endpoint_boot_changed
+            && !generation_changed
             && self.snapshot.as_ref().is_some_and(|current| {
                 current.boot_id == snapshot.boot_id && snapshot.revision < current.revision
             })
         {
             return;
         }
+        // Screen revisions restart per connection. Keep the displayed surface for selection
+        // content comparisons, but retire speculative frames from the old connection.
+        if generation_changed {
+            self.pending_pane_surface = None;
+        }
+        self.active_snapshot_generation = generation;
         self.graphics.set_scope(&graphics_scope);
         let command_bindings_changed = self.snapshot.as_ref().is_none_or(|current| {
             current.commands.len() != snapshot.commands.len()
@@ -1618,7 +1634,8 @@ impl ClientShellState {
             return;
         }
         if self.pane_surface.as_ref().is_some_and(|current| {
-            current.boot_id == surface.boot_id
+            self.pane_surface_generation == self.active_snapshot_generation
+                && current.boot_id == surface.boot_id
                 && (surface.projection_revision < current.projection_revision
                     || (surface.projection_revision == current.projection_revision
                         && surface.surface_revision < current.surface_revision))
@@ -1646,7 +1663,8 @@ impl ClientShellState {
             || surface.projection_revision < snapshot.revision
             || (!retain_future && surface.projection_revision != snapshot.revision)
             || self.pane_surface.as_ref().is_some_and(|current| {
-                current.boot_id == surface.boot_id
+                self.pane_surface_generation == self.active_snapshot_generation
+                    && current.boot_id == surface.boot_id
                     && (surface.projection_revision < current.projection_revision
                         || (surface.projection_revision == current.projection_revision
                             && surface.surface_revision < current.surface_revision))
@@ -1817,6 +1835,7 @@ impl ClientShellState {
         self.graphics
             .set_scene(std::mem::take(&mut surface.graphics));
         self.pane_surface = Some(surface);
+        self.pane_surface_generation = self.active_snapshot_generation;
         self.invalidate_link_hover();
         self.resume_mobile_switcher_if_ready();
         self.reconcile_input_source();
diff --git a/src/client/shell/surface_patch.rs b/src/client/shell/surface_patch.rs
index 87f947fa..6c829acf 100644
--- a/src/client/shell/surface_patch.rs
+++ b/src/client/shell/surface_patch.rs
@@ -113,7 +113,8 @@ impl ClientShellState {
         let Some(current) = self.pane_surface.as_ref() else {
             return ClientPaneSurfacePatchOutcome::Rejected;
         };
-        if patch.boot_id != current.boot_id
+        if self.pane_surface_generation != self.active_snapshot_generation
+            || patch.boot_id != current.boot_id
             || patch.projection_revision != current.projection_revision
             || patch.base_surface_revision != current.surface_revision
             || patch.surface_revision != current.surface_revision.saturating_add(1)
diff --git a/src/client/shell/tests/endpoints.rs b/src/client/shell/tests/endpoints.rs
index 1edba8e6..4ac8183c 100644
--- a/src/client/shell/tests/endpoints.rs
+++ b/src/client/shell/tests/endpoints.rs
@@ -1527,6 +1527,53 @@ fn new_connection_generation_accepts_a_lower_same_boot_projection_revision() {
 }
 
 #[test]
+fn reconnect_same_endpoint_accepts_new_generation_surface_revision() {
+    for previous_revision in [9, 1] {
+        let (mut state, endpoint_id) = state_with_remote();
+        let mut previous = snapshot();
+        previous.boot_id = "shared-server-boot".into();
+        previous.revision = previous_revision;
+        state.cache_endpoint_snapshot_inactive_for_generation(&endpoint_id, 4, Box::new(previous));
+        assert!(state.activate_endpoint_projection(&endpoint_id));
+        let mut previous_surface = surface();
+        previous_surface.boot_id = "shared-server-boot".into();
+        previous_surface.projection_revision = previous_revision;
+        previous_surface.surface_revision = 9;
+        state.set_pane_surface(previous_surface.clone());
+        previous_surface.projection_revision += 1;
+        state.set_pane_surface(previous_surface);
+        assert!(state.pending_pane_surface.is_some());
+        state.agent_scroll = 7;
+
+        state.mark_endpoint_disconnected(&endpoint_id);
+        let mut reconnected = snapshot();
+        reconnected.boot_id = "shared-server-boot".into();
+        reconnected.revision = 1;
+        state.cache_endpoint_snapshot_inactive_for_generation(
+            &endpoint_id,
+            5,
+            Box::new(reconnected),
+        );
+        assert_eq!(state.snapshot.as_ref().unwrap().revision, previous_revision);
+        assert_eq!(state.pane_surface.as_ref().unwrap().surface_revision, 9);
+
+        state.set_endpoint_status(&endpoint_id, ClientEndpointStatus::Online);
+        assert!(state.activate_endpoint_projection(&endpoint_id));
+        let mut reconnected_surface = surface();
+        reconnected_surface.boot_id = "shared-server-boot".into();
+        reconnected_surface.projection_revision = 1;
+        reconnected_surface.surface_revision = 1;
+        state.set_pane_surface(reconnected_surface);
+
+        assert_eq!(state.snapshot.as_ref().unwrap().revision, 1);
+        assert_eq!(state.pane_surface.as_ref().unwrap().projection_revision, 1);
+        assert_eq!(state.pane_surface.as_ref().unwrap().surface_revision, 1);
+        assert!(state.pending_pane_surface.is_none());
+        assert_eq!(state.agent_scroll, 7);
+    }
+}
+
+#[test]
 fn reconnect_snapshot_waits_for_coherent_activation_before_replacing_projection() {
     let (mut state, endpoint_id) = state_with_remote();
     assert!(state.activate_endpoint_projection(&endpoint_id));
diff --git a/src/client/shell/tests/mouse_selection.rs b/src/client/shell/tests/mouse_selection.rs
index 0a54203e..ccb9b86d 100644
--- a/src/client/shell/tests/mouse_selection.rs
+++ b/src/client/shell/tests/mouse_selection.rs
@@ -579,6 +579,33 @@ fn double_click_drag_invalidates_cached_boundaries_outside_selected_cells() {
 }
 
 #[test]
+fn reconnect_word_selection_tracks_content_changes() {
+    for content_changed in [false, true] {
+        let mut state = word_drag_state(true);
+        let initial = start_word_drag(&mut state);
+        word_row_reply(&mut state, &initial, "alpha bravo charlie");
+        let mut next_surface = state.pane_surface.as_ref().unwrap().clone();
+        if content_changed {
+            next_surface.panes[0].content_revision += 2;
+            next_surface.frame.cells[14].symbol = " ".into();
+        }
+        let endpoint_id = state.active_endpoint_id.clone();
+        let snapshot = state.snapshot.as_ref().unwrap().clone();
+        state.mark_endpoint_disconnected(&endpoint_id);
+        state.cache_endpoint_snapshot_inactive_for_generation(&endpoint_id, 1, snapshot);
+        state.set_endpoint_status(
+            &endpoint_id,
+            crate::client::endpoint::ClientEndpointStatus::Online,
+        );
+        assert!(state.activate_endpoint_projection(&endpoint_id));
+        state.set_pane_surface(next_surface);
+
+        assert_eq!(state.selection.is_some(), !content_changed);
+        assert_eq!(state.word_selection_gesture.is_some(), !content_changed);
+    }
+}
+
+#[test]
 fn double_click_release_ignores_reply_after_focus_or_content_changes() {
     for focus_changed in [false, true] {
         let mut state = word_drag_state(true);