class App

Application entry point and process-level runtime services.

App owns the runtime bootstrap sequence for the engine. It initializes Kha, input devices, audio, default resources, shader compilation, and the main frame loop.

In normal projects App is configured declaratively through compile-time @:app.* metadata handled by the @:autoBuild macro on this class. The macro collects those metadata entries, builds a kha.SystemOptions object, and rewrites main() into a call to start.

Typical usage:

@:app.title("Game")
@:app.window(width = 750, height = 500)
@:app.framebuffer(samplesPerPixel = 2, verticalSync = false)
class Main extends s.App {
}

The example above becomes roughly:

s.App.start({
	title: "Game",
	window: {
		width: 750,
		height: 500
	},
	framebuffer: {
		samplesPerPixel: 2,
		verticalSync: false
	}
}, window -> {
	// original main body
});

@:app.* metadata are therefore just shortcuts for kha.SystemOptions. The supported top-level metadata names are:

• @:app.title(value:String) Sets SystemOptions.title. This is the process title and the default window title. If window.title is omitted, Kha copies this value into it.
• @:app.width(value:Int) Sets SystemOptions.width. Kha treats this as a shortcut for window.width and overwrites the nested window width when the value is greater than 0.
• @:app.height(value:Int) Sets SystemOptions.height. Kha treats this as a shortcut for window.height and overwrites the nested window height when the value is greater than 0.
• @:app.window(...) Sets SystemOptions.window using named fields from kha.WindowOptions.
• @:app.framebuffer(...) Sets SystemOptions.framebuffer using named fields from kha.FramebufferOptions.
• @:app.audio(...) Sets SystemOptions.audio using named fields from Kha's internal audio options object.

Supported @:app.window(...) fields:

• title:String Window title. Overrides @:app.title(...) for the actual OS window caption.
• x:Int Horizontal window position in screen coordinates. -1 lets the backend choose automatically.
• y:Int Vertical window position in screen coordinates. -1 lets the backend choose automatically.
• width:Int Initial client width in pixels.
• height:Int Initial client height in pixels.
• display:Int Display index for multi-monitor setups. -1 lets the backend choose.
• visible:Bool Whether the window starts visible.
• windowFeatures:kha.WindowFeatures Bitmask of optional window capabilities. Combine flags with |.
• mode:kha.WindowMode Window presentation mode.

Available kha.WindowFeatures flags for windowFeatures:

• kha.WindowFeatures.None No optional features.
• kha.WindowFeatures.FeatureResizable Allows the user to resize the window.
• kha.WindowFeatures.FeatureMinimizable Allows minimizing the window.
• kha.WindowFeatures.FeatureMaximizable Allows maximizing the window.
• kha.WindowFeatures.FeatureBorderless Requests a borderless window.
• kha.WindowFeatures.FeatureOnTop Requests an always-on-top window.

The default Kha feature mask is:

kha.WindowFeatures.FeatureResizable
| kha.WindowFeatures.FeatureMaximizable
| kha.WindowFeatures.FeatureMinimizable

Available kha.WindowMode values for mode:

• kha.WindowMode.Windowed Uses a regular OS window.
• kha.WindowMode.Fullscreen Uses regular fullscreen mode.
• kha.WindowMode.ExclusiveFullscreen Uses exclusive fullscreen mode. In Kha this is primarily meaningful on Windows and may switch the monitor resolution.

Supported @:app.framebuffer(...) fields:

• frequency:Int Preferred refresh frequency in Hz. The backend may ignore unsupported values.
• verticalSync:Bool Enables or disables vertical sync.
• colorBufferBits:Int Requested color buffer precision in bits.
• depthBufferBits:Int Requested depth buffer precision in bits.
• stencilBufferBits:Int Requested stencil buffer precision in bits.
• samplesPerPixel:Int Requested MSAA sample count. Use 1 to disable multisampling.

Supported @:app.audio(...) fields:

• allowMobileWebAudio:Bool HTML5-only Kha option that enables audio2.Audio initialization on mobile browsers. Use this when the application must opt into mobile Web Audio behavior.

Example with less common options:

@:app.title("Game")
@:app.window(
	width = 1280,
	height = 720,
	mode = kha.WindowMode.Windowed,
	windowFeatures = kha.WindowFeatures.FeatureResizable
		| kha.WindowFeatures.FeatureMaximizable
)
@:app.framebuffer(
	verticalSync = true,
	samplesPerPixel = 4,
	depthBufferBits = 24,
	stencilBufferBits = 8
)
@:app.audio(allowMobileWebAudio = true)
class Main extends s.App {}

In normal projects you usually interact with App through: - @:app.* metadata to configure startup - state to react to lifecycle changes - input to access shared mouse and keyboard devices

start still exists as the low-level runtime entry point, but direct calls are mostly useful for custom bootstraps or tooling code.

App is process-wide. It should be treated as a singleton-style service layer, not as something instantiated manually.

See also:

• kha.SystemOptions

• kha.WindowOptions

• kha.FramebufferOptions

• kha.WindowMode

• kha.WindowFeatures