engine/examples/simple_window/src/main.rs

use anyhow::Result;

use ecs::*;
use engine::prelude::*;

fn main() -> Result<()> {
    let mut world_builder = World::builder();

    Engine::new::<GameState>(EngineCreateInfo::default(), &mut world_builder)?;

    world_builder.add_system(GameState::update);
    world_builder.resources.insert(GameState::default());

    let scene: &mut Scene = world_builder.resources.get_mut()?;
    let view = scene.view_mut();
    let camera_control = FreeCameraControl::new(view)?;
    world_builder.resources.insert(camera_control);

    world_builder.build().run()
}

#[derive(Default, Resource)]
enum GameState {
    #[default]
    Startup,

    Game(Game),
}

impl GameState {
    fn update(world: &mut World) -> Result<bool> {
        let me = world.resources.get_mut_unchecked::<Self>();

        match me {
            GameState::Startup => *me = GameState::Game(Game),
            GameState::Game(game) => game.update(world)?,
        }

        Ok(true)
    }
}

impl EventConsumer for GameState {
    fn event(&mut self, world: &mut World, event: EngineEvent<'_>) -> Result<()> {
        match self {
            GameState::Startup => (),
            GameState::Game(game) => game.event(world, event)?,
        }

        Ok(())
    }
}

struct Game;

impl Game {
    fn update(&mut self, _world: &mut World) -> Result<()> {
        Ok(())
    }

    fn event(&mut self, world: &mut World, event: EngineEvent<'_>) -> Result<()> {
        match event {
            EngineEvent::MouseButtonDown(MouseButton::Left) => {
                let camera_control: &mut FreeCameraControl = world.resources.get_mut()?;
                camera_control.mouse_down();
            }
            EngineEvent::MouseButtonUp(MouseButton::Left) => {
                let camera_control: &mut FreeCameraControl = world.resources.get_mut()?;
                camera_control.mouse_release();
            }
            EngineEvent::MouseMotion(x, y) => {
                let (scene, camera_control): (&mut Scene, &mut FreeCameraControl) =
                    world.resources.get_mut()?;

                camera_control.mouse_move(x, y, scene.view_mut())?;
            }

            _ => (),
        }

        Ok(())
    }
}