Trait EngineApp 

pub trait EngineApp:
    AgentProvider
    + PhaseProvider
    + Send
    + Sync {
    // Required methods
    fn window_config() -> WindowConfig
       where Self: Sized;
    fn new() -> Self
       where Self: Sized;
    fn setup(&mut self, world: &mut GameWorld, runtime: &Runtime);
    fn update(&mut self, world: &mut GameWorld, inputs: &[InputEvent]);

    // Provided methods
    fn on_shutdown(&mut self) { ... }
    fn intercept_window_event(
        &mut self,
        _event: &dyn Any,
        _window: &dyn KhoraWindow,
    ) -> bool { ... }
    fn before_frame(
        &mut self,
        _world: &mut GameWorld,
        _runtime: &Runtime,
        _window: &dyn KhoraWindow,
    ) { ... }
    fn before_agents(&mut self, _world: &mut GameWorld, _runtime: &Runtime) { ... }
    fn after_agents(&mut self, _world: &mut GameWorld, _runtime: &Runtime) { ... }
}

The single generic bound for the engine’s application type.

An application must implement AgentProvider and PhaseProvider. AgentProvider::register_agents is where the app registers its custom agents with the DCC — game logic belongs in custom agents using ExecutionTiming and ExecutionPhase, not in a free-form update() method.

The engine also requires these inherent methods on the app type:

• window_config() -> WindowConfig
• new() -> Self
• setup(&mut self, world: &mut GameWorld)
• update(&mut self, world: &mut GameWorld, inputs: &[InputEvent])
• on_shutdown(&mut self)

Examples

A minimal application. setup populates the world once; update runs every frame. The optional hooks (on_shutdown, before_frame, …) keep their no-op defaults.

use khora_sdk::prelude::*;
use khora_sdk::{
    AgentProvider, DccService, EngineApp, GameWorld, PhaseProvider, Runtime,
    WindowConfig,
};

struct MyGame {
    frame: u64,
}

impl EngineApp for MyGame {
    fn window_config() -> WindowConfig {
        WindowConfig::default()
    }
    fn new() -> Self {
        MyGame { frame: 0 }
    }
    fn setup(&mut self, world: &mut GameWorld, _runtime: &Runtime) {
        world.spawn_camera(ecs::Camera::new_perspective(
            std::f32::consts::FRAC_PI_4,
            16.0 / 9.0,
            0.1,
            1000.0,
        ));
    }
    fn update(&mut self, _world: &mut GameWorld, _inputs: &[InputEvent]) {
        self.frame += 1;
    }
}

impl AgentProvider for MyGame {
    fn register_agents(&self, _dcc: &DccService, _runtime: &mut Runtime) {}
}
impl PhaseProvider for MyGame {}

Required Methods

fn window_config() -> WindowConfig

where Self: Sized,

Returns the window configuration for the application.

fn new() -> Self

where Self: Sized,

Creates a new instance of the application.

fn setup(&mut self, world: &mut GameWorld, runtime: &Runtime)

Called once during engine initialization to set up the game world.

fn update(&mut self, world: &mut GameWorld, inputs: &[InputEvent])

Called every frame to update game logic.

Provided Methods

fn on_shutdown(&mut self)

Called during shutdown to clean up application resources.

fn intercept_window_event( &mut self, _event: &dyn Any, _window: &dyn KhoraWindow, ) -> bool

Optional: intercept a raw window event before the engine translates it into an InputEvent. Return true if the event was consumed (e.g., by an egui overlay) and should NOT be forwarded to game logic.

Default: do not intercept.

fn before_frame( &mut self, _world: &mut GameWorld, _runtime: &Runtime, _window: &dyn KhoraWindow, )

Optional: called once per frame BEFORE update. Use to begin a UI overlay frame (e.g., egui::Context::begin_frame) and render shell chrome (menus, docks, panels) that produces UI commands.

fn before_agents(&mut self, _world: &mut GameWorld, _runtime: &Runtime)

Optional: called after the renderer’s begin_frame and before the scheduler dispatches agents. Use to switch the renderer to an offscreen viewport target (e.g., set_render_to_viewport(true)).

fn after_agents(&mut self, _world: &mut GameWorld, _runtime: &Runtime)

Optional: called after agent execution and submit_frame_graph, but BEFORE the renderer’s end_frame. Use to render gizmos to the offscreen viewport, switch back to the swapchain (set_render_to_viewport(false)), and present a UI overlay (render_overlay).

Implementors