Object guide

Use this page when you know what you want to build but not which Kael object to reach for.

Application objects

Object	Purpose	Use it for
`Application`	Starts and owns the runtime	Process startup and the main event loop
`App`	Accesses application services	Windows, tasks, files, clipboard, and global state
`Window`	Handles one rendered surface	Focus, input, drawing, and window operations
`WindowOptions`	Describes a new window	Size, title, appearance, and placement
`CapabilityReport`	Reports platform support	Choosing a native path or a portable fallback

State and rendering

Object	Purpose	Use it for
`Entity<T>`	Owns reactive application state	Models that outlive one render call
`Context<T>`	Reads and updates an entity	Listeners, notifications, tasks, and child entities
`Render`	Turns state into elements	Views with retained state
`RenderOnce`	Turns a value into elements once	Small value components and builders
`IntoElement`	Converts a value into a UI element	Return types from render methods
`Subscription`	Keeps an event listener alive	Observing entities, windows, and application events
`FocusHandle`	Identifies a focus target	Keyboard input and focus movement

The normal update path is:

input → entity.update(...) → cx.notify() → Render → retained scene → platform renderer

Layout and components

Object or function	Purpose	Use it for
`div()`	Creates the base layout element	Flex, grid, spacing, color, borders, and children
`Styled`	Adds style methods	Size, alignment, typography, and visual state
`kael_ui::init`	Registers the component system	Any app that uses `kael_ui` controls
`Theme`	Holds component design tokens	Product colors, type, radius, and density
`Button`, `Input`, `Select`	Ready made controls	Common interactive UI
`AppShell`	Creates an application frame	Sidebars, toolbars, and main content

Large data and graphics

Object or function	Purpose	Use it for
`uniform_list`	Virtualizes equal height rows	Logs, feeds, and simple tables
`list`	Builds a measured list	Rows with variable height
`VirtualList`	Adds higher level virtual list behavior	Product lists using `kael_ui`
`VirtualSheetGrid`	Virtualizes rows and columns	Spreadsheet surfaces
`canvas`	Runs custom retained drawing	Charts, whiteboards, and editors
`Scene`	Stores platform render primitives	Low level retained output
`PortableScene2d`	Describes portable 2D scene data	Game and simulation foundations

Async, files, and web content

Object	Purpose	Use it for
`Task<T>`	Represents scheduled async work	Fetching, parsing, saving, and delayed updates
`BackgroundExecutor`	Runs work away from UI rendering	CPU work that should not block a frame
`ExternalFile`	Carries a file name, type, and bytes	Portable open and drop workflows
`PrintJob`	Describes printable content	Native print dialogs and browser printing
`WebView`	Hosts a web owned surface	Compatibility islands and existing web products

Start with Application, one root Entity, and a Render view. Add services only when the feature needs them. See Core concepts for the working code and One codebase for platform boundaries.