Extract reusable menu and keyboard scanner core

docs/scanner-architecture.md

@@ -0,0 +1,65 @@
+# Scanner architecture
+
+The scanner has four boundaries: content, traversal, presentation and execution.
+All desktop scanning shares the Rust `Session<Technique>` lifecycle and
+`scanning_runtime::Adapter` platform boundary. Local and Remote switches feed
+that same session. No item scanner captures keys, runs native input, persists
+settings or owns a timer thread.
+
+## Adding an item scanner
+
+Use `scan_items::ItemScanner<Action>` with a small typed action enum. Supply
+`scan_tree::Node::Group` nodes with stable group IDs and `Leaf` action identities.
+Group IDs must be unique among siblings; leaf identities must be unique within
+their group. They must identify the operation, not its current label or bounds.
+The `rows` convenience constructor is for fixed row layouts: its positional row
+IDs are not suitable when groups can reorder. Supply explicit groups in that case.
+Empty groups are removed. Explicitly identified groups retain their identity even
+with one child. Anonymous branches and fixed single-item rows collapse as before.
+
+Call `handle` with normalized switch actions and `advance` with elapsed time only
+when the containing session permits movement. The core owns the interval,
+direction, completed passes, suspension and nested Back navigation. Read its
+navigator to build a presentation. Do not add a second interval in the provider.
+`Policy` preserves the existing menu/keyboard differences during migration:
+menus resume their selection; keyboards resume at the root. Keyboard manual
+steps reset completed passes; existing menu manual steps do not.
+
+Use `replace` when action availability or layout structure changes. Identified
+groups and leaves retain their selection through reordering; a removed target
+returns to the nearest surviving ancestor's first item with a full interval.
+Any changed content invalidates pending activation. Identical content preserves
+both timing and pending activation. Update labels and bounds separately when the
+available actions have not changed. Do not put captured text into action IDs.
+
+Before asynchronous execution, call `begin_activation` and retain the returned
+revision. While pending, the core does not advance or select. Complete with that
+same revision; stale or repeated completions return false. Restart and content
+replacement cancel pending activation. The runtime's existing input generation
+checks remain authoritative across whole-session replacement, disconnect and
+capture cancellation; an item revision is local to one scanner instance.
+
+The tests in `scan_items` provide a platform-free example using editing actions,
+including reordered content, cancellation, exactly-once completion and timing.
+
+## Existing providers
+
+- `scan_menu` supplies typed menu actions and tile geometry. It delegates traversal
+  to the item scanner and retains its existing three-column layout and parent stack.
+- `scan_keyboard` supplies keys, modifiers, pages, prediction availability and
+  geometry. It delegates traversal and pending activation to the item scanner.
+  Prediction tokens still guard insertion, and queued prediction replacement
+  remains a keyboard policy. Unchanged suggestions never restart the interval.
+- `point_scan` retains its continuous movement strategy and uses the shared
+  navigator for grid scanning. `point_workflow` composes point, menus, countdown,
+  keyboard and execution-error stages within one session.
+- Native hosts render `Frame` without activating Switchify. Domain actions are
+  executed through the existing typed workflow requests and platform adapters.
+
+## Following stages
+
+Issue #801 adds validated shared settings and per-area overrides to this core.
+Issue #802 adds a main-window React content adapter and foreground/modal ownership.
+Those stages do not require individual screens to implement traversal or timers.
+They must preserve the current input generation checks, cleanup, native focus,
+point countdown cancellation and Remote behaviour.

src-tauri/src/lib.rs

@@ -25,6 +25,7 @@ mod protocol;
 mod remote_scan;
 mod scan_executor;
 mod scan_host;
+mod scan_items;
 mod scan_keyboard;
 mod scan_menu;
 mod scan_tile;

src-tauri/src/point_workflow.rs

@@ -188,7 +188,7 @@ impl Workflow {
             }
             Item::Setting(setting) => return Some(Request::Setting(setting)),
             Item::Display(next) => return Some(Request::Display(next)),
-            Item::Pause => self.menu.suspended = true,
+            Item::Pause => self.menu.suspend(),
             Item::Reverse => {
                 self.menu.handle(Action::Reverse);
             }
@@ -260,7 +260,7 @@ impl Technique for Workflow {
         self.stage = Stage::Menu;
         self.menu = Menu::new(Kind::Actions, self.point.config.block_interval_ms);
         self.parent_menu.clear();
-        self.menu.suspended = true;
+        self.menu.suspend();
         self.error = Some(message);
     }
     fn execution_succeeded(&mut self) {
@@ -407,7 +407,7 @@ impl Technique for Workflow {
     fn phase(&self) -> Phase {
         match self.stage {
             Stage::KeyboardOpening => Phase::Workflow(WorkflowPhase::KeyboardOpening),
-            Stage::Keyboard => Phase::Workflow(if self.keyboard.suspended {
+            Stage::Keyboard => Phase::Workflow(if self.keyboard.suspended() {
                 WorkflowPhase::KeyboardSuspended
             } else {
                 WorkflowPhase::Keyboard
@@ -417,7 +417,7 @@ impl Technique for Workflow {
             Stage::Point => Phase::Point(self.point.phase()),
             Stage::Destination => Phase::Workflow(WorkflowPhase::DragDestination),
             Stage::Executing => Phase::Workflow(WorkflowPhase::Executing),
-            Stage::Menu => Phase::Workflow(if self.menu.suspended {
+            Stage::Menu => Phase::Workflow(if self.menu.suspended() {
                 WorkflowPhase::MenuSuspended
             } else if self.menu.kind == Kind::ConfirmDrag {
                 WorkflowPhase::DragConfirmation
@@ -826,7 +826,7 @@ mod tests {
         w.advance(5000);
         assert_eq!(w.frame(), frame);
         assert!(w.handle(Action::Select).is_none());
-        assert!(!w.menu.suspended);
+        assert!(!w.menu.suspended());
         assert_eq!(w.source, (120, 80));
     }
     #[test]

src-tauri/src/scan_host.rs

@@ -799,7 +799,9 @@ mod title_tests {
             for units in [1.0, 2.0] {
                 let mut menu = Menu::new(Kind::Actions, 500);
                 for paused in [false, true] {
-                    menu.suspended = paused;
+                    if paused {
+                        menu.suspend();
+                    }
                     let frame = menu.frame((0, 0), screen, units);
                     let label = frame.label.as_ref().unwrap();
                     let MenuTitle { rect, scale } =