Ribbon key tips: Alt shows codes on tabs, buttons and menu items

A lone Alt shows a code on every ribbon tab and quick-access button.
Typing a tab code opens the tab and shows the codes of its buttons,
dropdowns, slide-outs and collapsed panels; a button code runs it, a
dropdown or slide-out code opens it and shows its item codes, Esc goes
back one level. Codes follow the reference ribbon; buttons without a
reference counterpart get none and unnamed menu items are numbered.

Codes are drawn as accent pills over the widgets that reported their
bounds in the current frame, with a hint bar under the ribbon. While
the tips are open keys go to them only. The automation gets a keytips
action and read operation.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/view/mod.rs

@@ -2252,12 +2252,23 @@ bg={bg_ms:.1}ms n={view_count}"
             iced::widget::Space::new().width(0).height(0).into()
         };
 
+        // Key tips: the hint bar under the dropdowns, the codes above all.
+        let (keytip_bar, keytip_layer): (Element<'_, Message>, Element<'_, Message>) =
+            self.ribbon.keytip_layers().unwrap_or_else(|| {
+                (
+                    iced::widget::Space::new().width(0).height(0).into(),
+                    iced::widget::Space::new().width(0).height(0).into(),
+                )
+            });
+
         let composed = stack![
             main_ui,
+            keytip_bar,
             dropdown_layer,
             qselect_layer,
             snap_override_layer,
             open_progress_layer,
+            keytip_layer,
         ];
 
         // If the Plot Style editor was launched from PLOT, keep the Plot dialog
@@ -2547,9 +2558,18 @@ impl OpenCADStudio {
             event::listen_with(|ev, status, win_id| {
                 use iced::event::Status;
                 match ev {
+                    iced::Event::Mouse(iced::mouse::Event::ButtonPressed(_))
+                        if crate::ui::ribbon::keytips_active() =>
+                    {
+                        crate::ui::ribbon::keytip_pointer_pressed();
+                        Some(Message::KeyTip(crate::ui::ribbon::KeyTipInput::Hide))
+                    }
                     iced::Event::Mouse(iced::mouse::Event::ButtonPressed(
                         iced::mouse::Button::Left,
-                    )) => Some(Message::PropPointerPressed),
+                    )) => {
+                        crate::ui::ribbon::keytip_pointer_pressed();
+                        Some(Message::PropPointerPressed)
+                    }
                     iced::Event::Window(window::Event::CloseRequested) => {
                         Some(Message::WindowCloseRequested(win_id))
                     }
@@ -2562,6 +2582,9 @@ impl OpenCADStudio {
                     iced::Event::Window(window::Event::FileDropped(path)) => {
                         Some(Message::FileDropped(path))
                     }
+                    iced::Event::Keyboard(keyboard::Event::KeyReleased { key, .. }) => {
+                        crate::ui::ribbon::keytip_key_released(&key)
+                    }
                     iced::Event::Keyboard(keyboard::Event::ModifiersChanged(m)) => {
                         // `command()` is Cmd on macOS, Ctrl elsewhere — the
                         // platform multi-select modifier for the layer list.
@@ -2575,8 +2598,14 @@ impl OpenCADStudio {
                         physical_key,
                         modifiers,
                         text,
+                        repeat,
                         ..
                     }) => {
+                        if let Some(keytip) =
+                            crate::ui::ribbon::keytip_key_pressed(&key, modifiers, repeat)
+                        {
+                            return keytip;
+                        }
                         #[cfg(target_arch = "wasm32")]
                         let accel = modifiers.command();
                         // AltGr reaches Windows apps as Ctrl+Alt, and a macOS