How do I convert screen space to world space coords in Bevy using Camera2dComponents?

Question

Using Res<Events<CursorMoved>> I can get the mouse position change in screen space coordinates (zero in bottom-left corner), e.g.

#[derive(Default)]
struct State {
    cursor_moved_reader: EventReader<CursorMoved>,
}

fn set_mouse_pos(mut state: ResMut<State>, cursor_moved: Res<Events<CursorMoved>>) {
    for event in state.cursor_moved_reader.iter(&cursor_moved) {
        println!("cursor: {:?}", event.position);
    }
}

The question now is if I set SpriteComponents' transform.translation to the cursor position when using a camera from Camera2dComponents::default() a sprite with position 0, 0 is rendered in the center of the screen. What's the idiomatic way of converting between the screen space mouse coords and the camera world space coords?

Answer 1

The previous answer seems to be on the right track, however the transformation is not fully implemented and actually overengineered. Stumbled on the same problem and figured that's what the camera transform is for! This works for me:

fn window_to_world(
    position: Vec2,
    window: &Window,
    camera: &Transform,
) -> Vec3 {

    // Center in screen space
    let norm = Vec3::new(
        position.x - window.width() / 2.,
        position.y - window.height() / 2.,
        0.,
    );

    // Apply camera transform
    *camera * norm

    // Alternatively:
    //camera.mul_vec3(norm)
}