UI: Formulas › Function Library as labelled buttons with category menus

The Function Library group was a big Insert Function button followed by
AutoSum and seven big category buttons that all drew the same icon, the
widest group on the Formulas tab. It is now laid out as Excel lays it
out when the window is not wide enough for a big button per category:
big Insert Function and AutoSum buttons, then the categories as
labelled small buttons in columns of three:

  Recently Used    Text                 Math & Trig
  Financial        Date & Time          More Functions
  Logical          Lookup & Reference

- The category buttons draw a new code-drawn icon, Icon::FnBook, a book
  whose spine and glyph (star, coins, question mark, letter, clock,
  magnifier, theta, dots) take the category's colour from the theme's
  category palette. icons::paint_accent draws an icon with an accent
  colour, and widgets::small_button_accent is a small button that uses
  it; small_button is unchanged for its callers.
- AutoSum stays the big split button: the icon inserts SUM, the label
  and arrow open the AutoSum menu, which now reads Sum, Average, Count
  Numbers, Max, Min and More Functions… and is shared with Home ›
  Editing. Its tooltip names the control only, so the shortcut comes
  from the platform lookup (Alt+= on Windows and Linux).
- Each category menu lists its functions with their descriptions on
  hover and ends with Insert Function…, which opens the dialog with
  that category. More Functions cascades into Statistical, Engineering,
  Cube, Information, Compatibility and Web. Recently Used lists what
  the engine's formulas.recentlyUsed returns.
- The function categories, the function list (built once) and the menus
  live in a new function_library module; the dialog's category labels
  come from it.
- keytips.json gains MR for Recently Used, Excel's sequence. Labelled
  small and big buttons report their label to accessibility.
- The one-line labels (Date & Time, Lookup & Reference, Math & Trig,
  More Functions) replace the two-line keys in every interface
  language, with the same words. Recently Used is translated in Czech,
  German, Spanish, French, Japanese, Korean, Portuguese, Russian and
  Chinese; the other languages show it in English, their fallback.

Tests: tests/it/function_library.rs covers the layout (columns of three
level with the tab's other columns), each category menu and its Insert
Function… row, the More Functions cascade, the AutoSum split button and
its menu, and the MR key tip. A ribbon unit test keeps Command-key
glyphs out of the ribbon's text. chart_resize picks the chart menu's
Delete now that Home › Cells' Delete has an accessible name.

docs/architecture.md

@@ -1,6 +1,6 @@
 # Architecture
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-25 · **Change:** trivial (the hidden names that hold macros; earlier: macro engine on the engine building blocks) · **Target:** Microsoft Excel (Microsoft 365)
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-31 · **Change:** minor (Function Library module; accent icons; earlier: the hidden names that hold macros) · **Target:** Microsoft Excel (Microsoft 365)
 
 How GridCraft is built today. Rules for contributors are in [`AGENTS.md`](../AGENTS.md).
 
@@ -59,13 +59,19 @@ drawing its own:
   `icons::paint_on_sheet`) keep their light values. `theme::contrast_tests` holds every
   foreground/background pair to WCAG 2 (4.5:1 for text, 3:1 for glyphs) in both themes; a new
   token pair is added there. Icons (`icons.rs`, drawn in code) take their paper and category
-  colours (`theme::Cat`) from the tokens.
+  colours (`theme::Cat`) from the tokens; `icons::paint_accent` gives an icon an accent colour,
+  drawn on its coloured part when it has one (the spine and glyph of `Icon::FnBook`).
 - **Ribbon widgets**: `widgets.rs` has the buttons every tab is built from (`big_button`,
-  `small_button`, `split_button`, `big_split_button`, `toggle_button`), translated through
-  `i18n` in one place. Split buttons return the main and arrow responses separately, with
-  accessible names (`AutoSum`, `AutoSum options`). The ribbon card scrolls a tab wider than the
-  window, with arrows at its edges; `ribbon::RibbonOverflow` records the groups' size each frame,
+  `small_button`, `small_button_accent`, `split_button`, `big_split_button`, `toggle_button`),
+  translated through `i18n` in one place. Split buttons return the main and arrow responses
+  separately, with accessible names (`AutoSum`, `AutoSum options`); big and small buttons
+  report their label (an icon-only one its tooltip) as their accessible name. The ribbon card
+  scrolls a tab wider than the window, with arrows at its edges; `ribbon::RibbonOverflow` records the groups' size each frame,
   and a test keeps every tab within the card's three rows.
+- **Function Library**: `function_library.rs` holds the function categories (engine id and
+  label, in the Insert Function dialog's order), the function list built once from
+  `cmd::formulas::function_list`, and the menus of Formulas › Function Library, including the
+  AutoSum menu that Home › Editing shares.
 - **Code editor**: `widgets::code_editor(ui, id, &mut text, Lang, max_lines)` (`code_editor.rs`)
   edits code in the monospace font with `Tokens::syntax` colours: Python (keywords, strings
   including triple-quoted ones, numbers, comments, builtins) and LaTeX (commands, scripts,
@@ -159,6 +165,7 @@ rpm, tarball), FreeBSD, and web (WASM; WebGPU or WebGL2). Release workflows in
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-31 | minor | Function Library module (`function_library.rs`); accent icons (`icons::paint_accent`, `widgets::small_button_accent`) |
 | 2026-10-25 | trivial | The hidden names that hold macros are `_gc_macro_<n>_<k>` |
 | 2026-10-24 | minor | Macro engine on the building blocks (`macros/`, `cmd/macros.rs`) |
 | 2026-10-24 | minor | Engine building blocks for multi-command actions: undo groups, recording buffer, document trust, chunked hidden-name storage |

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-30 · **Change:** minor (checkbox cells print as boxes; earlier: Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; earlier: editing a hyperlink loads its existing fields; earlier: AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
+> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-31 · **Change:** minor (Formulas › Function Library as labelled buttons with category menus; earlier: checkbox cells print as boxes; Ctrl+arrow and Ctrl+Shift+arrow while pointing a formula reference; editing a hyperlink loads its existing fields; AutoSum over a selected row puts its total to the right; ribbon catalog count 276 / 292) · **Target:** Microsoft Excel (Microsoft 365), Excel for Mac 16.113.4
 
 Interaction, controls and feel, against Excel. Part of [target-app-parity.md](target-app-parity.md).
 **UI/UX fidelity: ~55% ready, 50–80 h** (estimated). Ribbon command coverage is measured
@@ -18,6 +18,7 @@ Sources: `crates/ui-egui/src` (ribbon, grid, editor, formula bar, dialogs, panes
 | Title bar, Quick Access Toolbar, AutoSave toggle | yes | yes | done; macOS window controls misaligned (#170), Dock icon size (#169) |
 | Ribbon: tabs, groups, split buttons, galleries, contextual tabs | yes | yes (Table Design, Chart Design, Format, PivotTable, Header & Footer tabs); Fill Color, Font Color and the Format Cells colour pickers end with Recent Colors and More Colors… (#928); large split buttons (Formulas › AutoSum); arrows at the card's edges scroll a tab wider than the window | done; missing contextual tabs for pictures, shapes, sparklines, slicers; groups do not collapse when narrow |
 | Ribbon collapse, simplified ribbon, customize ribbon/QAT | yes | partial | customization missing (File ▸ Options is the one missing File command) |
+| Formulas › Function Library | Insert Function, AutoSum, Recently Used and a menu per function category | yes (10-24): a big Insert Function button and three columns of labelled small buttons, the layout Excel uses when the window is not wide enough for a big button per category; each category's book icon has its own colour; a category menu shows each function's description on hover and ends with Insert Function…, which opens the dialog on that category; More Functions cascades into Statistical, Engineering, Cube, Information, Compatibility and Web; AutoSum is a split button whose menu (Sum, Average, Count Numbers, Max, Min, More Functions…) Home › Editing shares; Recently Used has the MR key tip | the wide layout with a big button per category is not offered; Recently Used lists what `formulas.recentlyUsed` returns |
 | Ribbon: tabs, groups, split buttons, galleries, contextual tabs | yes | yes (Table Design, Chart Design, Format, PivotTable tabs) | done; missing contextual tabs for pictures, shapes, sparklines, header/footer, slicers |
 | Ribbon collapse, simplified ribbon, customize ribbon/QAT | yes | partial | customization missing |
 | Key tips (Alt / F10 then letters) | yes, every ribbon control | **initial** (#43, 10-10): Alt or F10 shows key tips on Home for alignment, Paste Special and AutoFit plus legacy Alt sequences; other tabs and controls not yet (#33, #49) | 3–5 h |
@@ -194,6 +195,7 @@ scrollbar bugs 2–4 · pixel/feel pass against observed Excel 7–12.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-31 | minor | Formulas › Function Library: Insert Function, the AutoSum split button and three columns of labelled small buttons with category colours; category menus end with Insert Function…; More Functions cascades; Home › Editing shares the AutoSum menu; MR key tip for Recently Used |
 | 2026-10-30 | minor | Checkbox cells print and export to PDF as boxes, as on screen: unchecked white with a grey outline, checked green with a white tick (#2972). They printed their value as TRUE or FALSE; other values in a checkbox cell still print as text |
 | 2026-10-29 | minor | Formula pointing from the keyboard: Ctrl+arrow (⌘arrow) moves the pointed cell to the edge of its data and Ctrl+Shift+arrow (⌘⇧arrow) extends the pointed range there, as the same keys move and extend the selection, so typing `=COUNTIF(`, clicking the top of a column and pressing ⌘⇧↓ points at the whole column of data; the keys used to move or extend by one cell. A range reaching the sheet edge is written as whole columns or rows (`A:B`). The editor reads the modifiers of the arrow's own key event, so a keystroke pressed and released within one frame (a control client's `ui.key`, an automation tool) keeps its Shift and Ctrl |
 | 2026-10-29 | minor | Insert Hyperlink opens with an existing link's address, display text and ScreenTip (#2876). An address-only edit preserves the cell's content and formula; Cancel leaves the link unchanged, and Undo restores the edit |