App is the handle that allows you to create windows and menus

Image holds a handle to a platform-specific image structure (e.g. NSImage on macOS).

KeyCombination represents a key together with zero or more modifiers. It is used to set up keyboard shortcuts.

A Menu has a title and a list of entries. It is a non-leaf node in the menu tree.

MenuEntry is the interface for menus and menu items.

A MenuItem has a title and can be clicked on. It is a leaf node in the menu tree.

Modifier represents zero or more modifier keys (control, shift, option, etc)

Notification represents a desktop notification

Rect represents a rectangular region on the screen

A screen represents a rectangular display, normally corresponding to a physical display. "Device coordinates" means a position on a screen measured fr

Window represents a window registered with the native UI toolkit (e.g. NSWindow on macOS)

WindowOptions contains options for creating windows

appManager is the singleton for managing app instances

cerr holds a C-allocated error, which must be freed explicitly.

menuManager translates Menus and MenuItems to their native equivalent (e.g. NSMenuItem on macOS)