Command Palette

Searchable command launcher accessible via Alt+Space (configurable). Addresses #59 as an alternative to traditional text menus — all application actions are discoverable through fuzzy search.

Architecture

File	Purpose
src/ui/command_palette.rs	UI widget: overlay, fuzzy search, keyboard/mouse navigation, rendering
src/app/commands.rs	Command registry: maps ShortcutCommand to palette metadata (icon, category)
src/app/platform.rs	Platform hooks: Windows WH_KEYBOARD hook to suppress Alt+Space system menu
src/app/input_handling.rs	Pre-render key consumption for non-conflicting shortcuts (Ctrl+Shift+P)
src/app/central_panel.rs	Palette rendering (during render) + dispatch_palette_command()
src/app/mod.rs	Deferred dispatch: stores pending command, executes after render

Key Design Decisions

Deferred Command Dispatch

Commands selected from the palette are not dispatched during render_central_panel(). Instead, the selected ShortcutCommand is stored in pending_palette_command and dispatched after render in update(), alongside keyboard shortcuts. This prevents mid-render state mutations (e.g., handle_toggle_view_mode() changing tab.view_mode) that caused STATUS_STACK_BUFFER_OVERRUN crashes in release builds.

Windows Alt+Space Suppression

Windows opens a system menu (Restore/Move/Size/Close) on Alt+Space for all windows, including borderless ones. This happens via WM_SYSCOMMAND/SC_KEYMENU before egui sees the key event. A WH_KEYBOARD thread hook installed via SetWindowsHookExW intercepts Alt+Space at the keyboard message level, blocks it (returns 1), and sets an AtomicBool flag. The app checks this flag each frame and toggles the palette.

This approach was chosen over WndProc subclassing (which failed due to winit window class restrictions) and consume_key (which only affects egui's input, not the OS).

Mouse vs Keyboard Navigation

The palette tracks last_mouse_pos and only updates the selected row from mouse hover when the mouse has actually moved. This prevents a stationary mouse from overriding arrow key navigation — a common UX issue in custom list widgets.

Palette-Only Commands

Commands like OpenWorkspace and CloseWorkspace have no default keyboard shortcut (they use a dummy F12 binding). The palette hides the shortcut badge for these using KeyBinding::has_modifiers().

Data Flow

Alt+Space pressed
  ├─ [Windows] WH_KEYBOARD hook → blocks key, sets PALETTE_TOGGLED flag
  │   └─ update() checks flag → command_palette.toggle()
  └─ [macOS/Linux] consume_command_palette_key() → consume_key() from egui input
      └─ command_palette.toggle()

User selects command
  └─ central_panel: palette.show() → output.selected_command = Some(cmd)
      └─ stored in pending_palette_command (NOT dispatched mid-render)

After render (in update())
  └─ if pending_palette_command.take() → dispatch_palette_command(ctx, cmd)
      └─ routes to existing handler (handle_save_file, handle_toggle_view_mode, etc.)

Fuzzy Search

Uses fuzzy-matcher crate (SkimMatcherV2). Search text is "{category} {display_name}" per command. Recent commands get a +100 score boost. Results capped at 15.

Recent Commands

Stored in VecDeque<ShortcutCommand> (max 20). Persisted via Settings::command_palette_recent and restored on app startup. Front = most recent (duplicate entries are moved to front).

Adding New Commands

1. Add variant to ShortcutCommand in src/config/settings.rs
2. Add to all(), display_name(), category(), default_binding()
3. Add icon in src/app/commands.rs → icon_for_command()
4. Add dispatch in src/app/central_panel.rs → dispatch_palette_command()
5. Add name in src/ui/settings.rs → shortcut_command_name()