plugin.rs

use bevy::{asset::Asset, ecs::component::Component, prelude::*};

use crate::{Animator, AnimatorState, AssetAnimator};

/// Plugin to add systems related to tweening of common components and assets.
///
/// This plugin adds systems for a predefined set of components and assets, to allow their
/// respective animators to be updated each frame:
/// - [`Transform`]
/// - [`Text`]
/// - [`Style`]
/// - [`Sprite`]
/// - [`ColorMaterial`]
///
/// This ensures that all predefined lenses work as intended, as well as any custom lens
/// animating the same component or asset type.
///
/// For other components and assets, including custom ones, the relevant system needs to be
/// added manually by the application:
/// - For components, add [`component_animator_system::<T>`] where `T: Component`
/// - For assets, add [`asset_animator_system::<T>`] where `T: Asset`
/// 
/// This plugin is entirely optional. If you want more control, you can instead add manually
/// the relevant systems for the exact set of components and assets actually animated.
///
/// [`Transform`]: https://docs.rs/bevy/0.6.0/bevy/transform/components/struct.Transform.html
/// [`Text`]: https://docs.rs/bevy/0.6.0/bevy/text/struct.Text.html
/// [`Style`]: https://docs.rs/bevy/0.6.0/bevy/ui/struct.Style.html
/// [`Sprite`]: https://docs.rs/bevy/0.6.0/bevy/sprite/struct.Sprite.html
/// [`ColorMaterial`]: https://docs.rs/bevy/0.6.0/bevy/sprite/struct.ColorMaterial.html
#[derive(Debug, Clone, Copy)]
pub struct TweeningPlugin;

impl Plugin for TweeningPlugin {
    fn build(&self, app: &mut App) {
        app.add_system(component_animator_system::<Transform>)
            .add_system(component_animator_system::<Text>)
            .add_system(component_animator_system::<Style>)
            .add_system(component_animator_system::<Sprite>)
            .add_system(asset_animator_system::<ColorMaterial>);
    }
}

/// Animator system for components.
///
/// This system extracts all components of type `T` with an `Animator<T>` attached to the same entity,
/// and tick the animator to animate the component.
pub fn component_animator_system<T: Component>(
    time: Res<Time>,
    mut query: Query<(&mut T, &mut Animator<T>)>,
) {
    for (ref mut target, ref mut animator) in query.iter_mut() {
        if animator.state == AnimatorState::Paused {
            continue;
        }
        // Play all tracks in parallel
        for seq in &mut animator.tracks_mut().tracks {
            seq.tick(time.delta(), target);
        }
    }
}

/// Animator system for assets.
///
/// This system ticks all `AssetAnimator<T>` components to animate their associated asset.
pub fn asset_animator_system<T: Asset>(
    time: Res<Time>,
    mut assets: ResMut<Assets<T>>,
    mut query: Query<&mut AssetAnimator<T>>,
) {
    for ref mut animator in query.iter_mut() {
        if animator.state == AnimatorState::Paused {
            continue;
        }
        if let Some(target) = assets.get_mut(animator.handle()) {
            // Play all tracks in parallel
            for seq in &mut animator.tracks_mut().tracks {
                seq.tick(time.delta(), target);
            }
        }
    }
}