refactor(ui): optimize record sharing and centralize layout management

Refactor `App` and `DrillState` to use `Rc` for efficient sharing of frozen
records and integrate a persistent `layout` field.

- Update `DrillState` to use `Rc<Vec<(CellKey, CellValue)>>` for records.
- Add `layout` field to `App` .
- Implement `rebuild_layout()` in `App` to refresh the grid layout.
- Ensure `layout` is rebuilt after applying effects and handling key
  events.
- Update `App::new` and `App::cmd_context` to use the new layout
  management.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-26B-A4B-it-GGUF:UD-Q5_K_XL)

src/ui/app.rs

@@ -5,23 +5,25 @@ use std::path::PathBuf;
 use std::sync::Arc;
 use std::time::{Duration, Instant};
 
+use std::rc::Rc;
+
 use crate::command::cmd::CmdContext;
 use crate::command::keymap::{Keymap, KeymapSet};
 use crate::import::wizard::ImportWizard;
 use crate::model::cell::CellValue;
 use crate::model::Model;
 use crate::persistence;
+use crate::ui::grid::{
+    compute_col_widths, compute_row_header_width, compute_visible_cols, parse_number_format,
+};
 use crate::view::GridLayout;
 
 /// Drill-down state: frozen record snapshot + pending edits that have not
 /// yet been applied to the model.
 #[derive(Debug, Clone, Default)]
 pub struct DrillState {
-    /// Frozen snapshot of records shown in the drill view.
+    /// Frozen snapshot of records shown in the drill view (Rc for cheap cloning).
-    pub records: Vec<(
+    pub records: Rc<Vec<(crate::model::cell::CellKey, crate::model::cell::CellValue)>>,
-        crate::model::cell::CellKey,
-        crate::model::cell::CellValue,
-    )>,
     /// Pending edits keyed by (record_idx, column_name) → new string value.
     /// column_name is either "Value" or a category name.
     pub pending_edits: std::collections::HashMap<(usize, String), String>,
@@ -100,11 +102,18 @@ pub struct App {
     pub buffers: HashMap<String, String>,
     /// Transient keymap for Emacs-style prefix key sequences (g→gg, y→yy, etc.)
     pub transient_keymap: Option<Arc<Keymap>>,
+    /// Current grid layout, derived from model + view + drill_state.
+    /// Rebuilt via `rebuild_layout()` after state changes.
+    pub layout: GridLayout,
     keymap_set: KeymapSet,
 }
 
 impl App {
     pub fn new(model: Model, file_path: Option<PathBuf>) -> Self {
+        let layout = {
+            let view = model.active_view();
+            GridLayout::with_frozen_records(&model, view, None)
+        };
         Self {
             model,
             file_path,
@@ -131,17 +140,26 @@ impl App {
             expanded_cats: std::collections::HashSet::new(),
             buffers: HashMap::new(),
             transient_keymap: None,
+            layout,
             keymap_set: KeymapSet::default_keymaps(),
         }
     }
 
+    /// Rebuild the grid layout from current model, view, and drill state.
+    /// Note: `with_frozen_records` already handles pruning internally.
+    pub fn rebuild_layout(&mut self) {
+        let view = self.model.active_view();
+        let frozen = self.drill_state.as_ref().map(|s| Rc::clone(&s.records));
+        self.layout = GridLayout::with_frozen_records(&self.model, view, frozen);
+    }
+
     pub fn cmd_context(&self, key: KeyCode, _mods: KeyModifiers) -> CmdContext<'_> {
         let view = self.model.active_view();
-        let frozen_records = self.drill_state.as_ref().map(|s| s.records.clone());
+        let layout = &self.layout;
-        let layout = GridLayout::with_frozen_records(&self.model, view, frozen_records);
         let (sel_row, sel_col) = view.selected;
         CmdContext {
             model: &self.model,
+            layout,
             mode: &self.mode,
             selected: view.selected,
             row_offset: view.row_offset,
@@ -158,34 +176,39 @@ impl App {
             cat_panel_cursor: self.cat_panel_cursor,
             view_panel_cursor: self.view_panel_cursor,
             tile_cat_idx: self.tile_cat_idx,
-            cell_key: layout.cell_key(sel_row, sel_col),
+            view_back_stack: &self.view_back_stack,
-            row_count: layout.row_count(),
+            view_forward_stack: &self.view_forward_stack,
-            col_count: layout.col_count(),
+            display_value: {
-            none_cats: layout.none_cats.clone(),
+                let key = layout.cell_key(sel_row, sel_col);
-            view_back_stack: self.view_back_stack.clone(),
+                if let Some(k) = &key {
-            view_forward_stack: self.view_forward_stack.clone(),
+                    if let Some((idx, dim)) = crate::view::synthetic_record_info(k) {
-            records_col: if layout.is_records_mode() {
+                        self.drill_state
-                Some(layout.col_label(sel_col))
+                            .as_ref()
-            } else {
+                            .and_then(|s| s.pending_edits.get(&(idx, dim)).cloned())
-                None
+                            .or_else(|| layout.resolve_display(k))
+                            .unwrap_or_default()
+                    } else {
+                        self.model
+                            .get_cell(k)
+                            .map(|v| v.to_string())
+                            .unwrap_or_default()
+                    }
+                } else {
+                    String::new()
+                }
             },
-            records_value: if layout.is_records_mode() {
-                // Check pending edits first, then fall back to original
-                let col_name = layout.col_label(sel_col);
-                let pending = self.drill_state.as_ref().and_then(|s| {
-                    s.pending_edits.get(&(sel_row, col_name.clone())).cloned()
-                });
-                pending.or_else(|| layout.records_display(sel_row, sel_col))
-            } else {
-                None
-            },
-            // Approximate visible rows/cols from terminal size.
-            // Chrome: title(1) + border(2) + col_headers(n_col_levels) + separator(1)
-            //         + tile_bar(1) + status_bar(1) = ~8 rows of chrome.
             visible_rows: (self.term_height as usize).saturating_sub(8),
-            // Visible cols depends on column widths — use a rough estimate.
+            visible_cols: {
-            // The grid renderer does the precise calculation.
+                let (fmt_comma, fmt_decimals) = parse_number_format(&view.number_format);
-            visible_cols: ((self.term_width as usize).saturating_sub(30) / 12).max(1),
+                let col_widths = compute_col_widths(&self.model, layout, fmt_comma, fmt_decimals);
+                let row_header_width = compute_row_header_width(layout);
+                compute_visible_cols(
+                    &col_widths,
+                    row_header_width,
+                    self.term_width,
+                    view.col_offset,
+                )
+            },
             expanded_cats: &self.expanded_cats,
             key_code: key,
         }
@@ -195,6 +218,7 @@ impl App {
         for effect in effects {
             effect.apply(self);
         }
+        self.rebuild_layout();
     }
 
     /// True when the model has no categories yet (show welcome screen)
@@ -203,6 +227,8 @@ impl App {
     }
 
     pub fn handle_key(&mut self, key: KeyEvent) -> Result<()> {
+        self.rebuild_layout();
+
         // Transient keymap (prefix key sequence) takes priority
         if let Some(transient) = self.transient_keymap.take() {
             let effects = {
@@ -247,7 +273,7 @@ impl App {
     pub fn hint_text(&self) -> &'static str {
         match &self.mode {
             AppMode::Normal => "hjkl:nav  i:edit  R:records  P:prune  F/C/V:panels  T:tiles  [:]:page  >:drill  ::cmd",
-            AppMode::Editing { .. } => "Enter:commit  Esc:cancel",
+            AppMode::Editing { .. } => "Enter:commit  Tab:commit+right  Esc:cancel",
             AppMode::FormulaPanel => "n:new  d:delete  jk:nav  Esc:back",
             AppMode::FormulaEdit { .. } => "Enter:save  Esc:cancel  — type: Name = expression",
             AppMode::CategoryPanel => "jk:nav  Space:cycle-axis  n:new-cat  a:add-items  d:delete  Esc:back",
@@ -371,6 +397,187 @@ mod tests {
         assert_eq!(app.buffers.get("command").map(|s| s.as_str()), Some("q"));
     }
 
+    #[test]
+    fn col_offset_scrolls_when_cursor_moves_past_visible_columns() {
+        use crate::model::cell::{CellKey, CellValue};
+        // Create a model with 8 wide columns. Column item names are 30 chars
+        // each → column widths ~31 chars. With term_width=80, row header ~4,
+        // data area ~76 → only ~2 columns actually fit. But the rough estimate
+        // (80−30)/12 = 4 over-counts, so viewport_effects never scrolls.
+        let mut m = Model::new("T");
+        m.add_category("Row").unwrap();
+        m.add_category("Col").unwrap();
+        m.category_mut("Row").unwrap().add_item("R1");
+        for i in 0..8 {
+            let name = format!("VeryLongColumnItemName_{i:03}");
+            m.category_mut("Col").unwrap().add_item(&name);
+        }
+        // Populate a value so the model isn't empty
+        let key = CellKey::new(vec![
+            ("Row".to_string(), "R1".to_string()),
+            ("Col".to_string(), "VeryLongColumnItemName_000".to_string()),
+        ]);
+        m.set_cell(key, CellValue::Number(1.0));
+
+        let mut app = App::new(m, None);
+        app.term_width = 80;
+
+        // Press 'l' (right) 3 times to move cursor to column 3.
+        // Only ~2 columns fit in 76 chars of data area (each col ~26 chars wide),
+        // so column 3 is well off-screen. The buggy estimate (80−30)/12 = 4
+        // thinks 4 columns fit, so it won't scroll until col 4.
+        for _ in 0..3 {
+            app.handle_key(KeyEvent::new(KeyCode::Char('l'), KeyModifiers::NONE))
+                .unwrap();
+        }
+
+        assert_eq!(
+            app.model.active_view().selected.1,
+            3,
+            "cursor should be at column 3"
+        );
+        assert!(
+            app.model.active_view().col_offset > 0,
+            "col_offset should scroll when cursor moves past visible area (only ~2 cols fit \
+             in 80-char terminal with 26-char-wide columns), but col_offset is {}",
+            app.model.active_view().col_offset
+        );
+    }
+
+    #[test]
+    fn home_jumps_to_first_col() {
+        let mut app = two_col_model();
+        app.model.active_view_mut().selected = (1, 1);
+        app.handle_key(KeyEvent::new(KeyCode::Home, KeyModifiers::NONE))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected, (1, 0));
+    }
+
+    #[test]
+    fn end_jumps_to_last_col() {
+        let mut app = two_col_model();
+        app.model.active_view_mut().selected = (1, 0);
+        app.handle_key(KeyEvent::new(KeyCode::End, KeyModifiers::NONE))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected, (1, 1));
+    }
+
+    #[test]
+    fn page_down_scrolls_by_three_quarters_visible() {
+        let mut app = two_col_model();
+        // Add enough rows
+        for i in 0..30 {
+            app.model
+                .category_mut("Row")
+                .unwrap()
+                .add_item(&format!("R{i}"));
+        }
+        app.term_height = 28; // ~20 visible rows → delta = 15
+        app.model.active_view_mut().selected = (0, 0);
+        app.handle_key(KeyEvent::new(KeyCode::PageDown, KeyModifiers::NONE))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected.1, 0, "column preserved");
+        assert!(
+            app.model.active_view().selected.0 > 0,
+            "row should advance on PageDown"
+        );
+        // 3/4 of ~20 = 15
+        assert_eq!(app.model.active_view().selected.0, 15);
+    }
+
+    #[test]
+    fn page_up_scrolls_backward() {
+        let mut app = two_col_model();
+        for i in 0..30 {
+            app.model
+                .category_mut("Row")
+                .unwrap()
+                .add_item(&format!("R{i}"));
+        }
+        app.term_height = 28;
+        app.model.active_view_mut().selected = (20, 0);
+        app.handle_key(KeyEvent::new(KeyCode::PageUp, KeyModifiers::NONE))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected.0, 5);
+    }
+
+    #[test]
+    fn jump_last_row_scrolls_with_small_terminal() {
+        let mut app = two_col_model();
+        // Total rows: A, B, C + R0..R9 = 13 rows. Last row = 12.
+        for i in 0..10 {
+            app.model.category_mut("Row").unwrap().add_item(&format!("R{i}"));
+        }
+        app.term_height = 13; // ~5 visible rows
+        app.model.active_view_mut().selected = (0, 0);
+        // G jumps to last row (row 12)
+        app.handle_key(KeyEvent::new(KeyCode::Char('G'), KeyModifiers::NONE))
+            .unwrap();
+        let last = app.model.active_view().selected.0;
+        assert_eq!(last, 12, "should be at last row");
+        // With only ~5 visible rows and 13 rows, offset should scroll.
+        // Bug: hardcoded 20 means `12 >= 0 + 20` is false → no scroll.
+        let offset = app.model.active_view().row_offset;
+        assert!(
+            offset > 0,
+            "row_offset should scroll when last row is beyond visible area, but is {offset}"
+        );
+    }
+
+    #[test]
+    fn ctrl_d_scrolls_viewport_with_small_terminal() {
+        let mut app = two_col_model();
+        for i in 0..30 {
+            app.model
+                .category_mut("Row")
+                .unwrap()
+                .add_item(&format!("R{i}"));
+        }
+        app.term_height = 13; // ~5 visible rows
+        app.model.active_view_mut().selected = (0, 0);
+        // Ctrl+d scrolls by 5 rows
+        app.handle_key(KeyEvent::new(KeyCode::Char('d'), KeyModifiers::CONTROL))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected.0, 5);
+        // Press Ctrl+d again — now at row 10 with only 5 visible rows,
+        // row_offset should have scrolled (not stay at 0 due to hardcoded 20)
+        app.handle_key(KeyEvent::new(KeyCode::Char('d'), KeyModifiers::CONTROL))
+            .unwrap();
+        assert_eq!(app.model.active_view().selected.0, 10);
+        assert!(
+            app.model.active_view().row_offset > 0,
+            "row_offset should scroll with small terminal, but is {}",
+            app.model.active_view().row_offset
+        );
+    }
+
+    #[test]
+    fn tab_in_edit_mode_commits_and_moves_right() {
+        let mut app = two_col_model();
+        app.model.active_view_mut().selected = (0, 0);
+        // Enter edit mode
+        app.handle_key(KeyEvent::new(KeyCode::Char('i'), KeyModifiers::NONE))
+            .unwrap();
+        assert!(matches!(app.mode, AppMode::Editing { .. }));
+        // Type a digit
+        app.handle_key(KeyEvent::new(KeyCode::Char('5'), KeyModifiers::NONE))
+            .unwrap();
+        // Press Tab — should commit, move right, re-enter edit mode
+        app.handle_key(KeyEvent::new(KeyCode::Tab, KeyModifiers::NONE))
+            .unwrap();
+        // Should be in edit mode on column 1
+        assert!(
+            matches!(app.mode, AppMode::Editing { .. }),
+            "should be in edit mode after Tab, but mode is {:?}",
+            app.mode
+        );
+        assert_eq!(
+            app.model.active_view().selected.1,
+            1,
+            "should have moved to column 1"
+        );
+    }
+
     #[test]
     fn command_mode_buffer_cleared_on_reentry() {
         use crossterm::event::KeyEvent;