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animated_ui.rs
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animated_ui.rs
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//! Shows how to use animation clips to animate UI properties.
use bevy::{
animation::{
animated_field, AnimationEntityMut, AnimationEvaluationError, AnimationTarget,
AnimationTargetId,
},
prelude::*,
};
use std::any::TypeId;
// Holds information about the animation we programmatically create.
struct AnimationInfo {
// The name of the animation target (in this case, the text).
target_name: Name,
// The ID of the animation target, derived from the name.
target_id: AnimationTargetId,
// The animation graph asset.
graph: Handle<AnimationGraph>,
// The index of the node within that graph.
node_index: AnimationNodeIndex,
}
// The entry point.
fn main() {
App::new()
.add_plugins(DefaultPlugins)
// Note that we don't need any systems other than the setup system,
// because Bevy automatically updates animations every frame.
.add_systems(Startup, setup)
.run();
}
impl AnimationInfo {
// Programmatically creates the UI animation.
fn create(
animation_graphs: &mut Assets<AnimationGraph>,
animation_clips: &mut Assets<AnimationClip>,
) -> AnimationInfo {
// Create an ID that identifies the text node we're going to animate.
let animation_target_name = Name::new("Text");
let animation_target_id = AnimationTargetId::from_name(&animation_target_name);
// Allocate an animation clip.
let mut animation_clip = AnimationClip::default();
// Create a curve that animates font size.
animation_clip.add_curve_to_target(
animation_target_id,
AnimatableCurve::new(
animated_field!(TextFont::font_size),
AnimatableKeyframeCurve::new(
[0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0]
.into_iter()
.zip([24.0, 80.0, 24.0, 80.0, 24.0, 80.0, 24.0]),
)
.expect(
"should be able to build translation curve because we pass in valid samples",
),
),
);
// Create a curve that animates font color. Note that this should have
// the same time duration as the previous curve.
//
// This time we use a "custom property", which in this case animates TextColor under the assumption
// that it is in the "srgba" format.
animation_clip.add_curve_to_target(
animation_target_id,
AnimatableCurve::new(
TextColorProperty,
AnimatableKeyframeCurve::new([0.0, 1.0, 2.0, 3.0].into_iter().zip([
Srgba::RED,
Srgba::GREEN,
Srgba::BLUE,
Srgba::RED,
]))
.expect(
"should be able to build translation curve because we pass in valid samples",
),
),
);
// Save our animation clip as an asset.
let animation_clip_handle = animation_clips.add(animation_clip);
// Create an animation graph with that clip.
let (animation_graph, animation_node_index) =
AnimationGraph::from_clip(animation_clip_handle);
let animation_graph_handle = animation_graphs.add(animation_graph);
AnimationInfo {
target_name: animation_target_name,
target_id: animation_target_id,
graph: animation_graph_handle,
node_index: animation_node_index,
}
}
}
// Creates all the entities in the scene.
fn setup(
mut commands: Commands,
asset_server: Res<AssetServer>,
mut animation_graphs: ResMut<Assets<AnimationGraph>>,
mut animation_clips: ResMut<Assets<AnimationClip>>,
) {
// Create the animation.
let AnimationInfo {
target_name: animation_target_name,
target_id: animation_target_id,
graph: animation_graph,
node_index: animation_node_index,
} = AnimationInfo::create(&mut animation_graphs, &mut animation_clips);
// Build an animation player that automatically plays the UI animation.
let mut animation_player = AnimationPlayer::default();
animation_player.play(animation_node_index).repeat();
// Add a camera.
commands.spawn(Camera2d);
// Build the UI. We have a parent node that covers the whole screen and
// contains the `AnimationPlayer`, as well as a child node that contains the
// text to be animated.
commands
.spawn((
// Cover the whole screen, and center contents.
Node {
position_type: PositionType::Absolute,
top: Val::Px(0.0),
left: Val::Px(0.0),
right: Val::Px(0.0),
bottom: Val::Px(0.0),
justify_content: JustifyContent::Center,
align_items: AlignItems::Center,
..default()
},
animation_player,
AnimationGraphHandle(animation_graph),
))
.with_children(|builder| {
// Build the text node.
let player = builder.parent_entity();
builder
.spawn((
Text::new("Bevy"),
TextFont {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 24.0,
..default()
},
TextColor(Color::Srgba(Srgba::RED)),
TextLayout::new_with_justify(JustifyText::Center),
))
// Mark as an animation target.
.insert(AnimationTarget {
id: animation_target_id,
player,
})
.insert(animation_target_name);
});
}
// A type that represents the color of the first text section.
//
// We implement `AnimatableProperty` on this to define custom property accessor logic
#[derive(Clone)]
struct TextColorProperty;
impl AnimatableProperty for TextColorProperty {
type Property = Srgba;
fn evaluator_id(&self) -> EvaluatorId {
EvaluatorId::Type(TypeId::of::<Self>())
}
fn get_mut<'a>(
&self,
entity: &'a mut AnimationEntityMut,
) -> Result<&'a mut Self::Property, AnimationEvaluationError> {
let text_color = entity
.get_mut::<TextColor>()
.ok_or(AnimationEvaluationError::ComponentNotPresent(TypeId::of::<
TextColor,
>(
)))?
.into_inner();
match text_color.0 {
Color::Srgba(ref mut color) => Ok(color),
_ => Err(AnimationEvaluationError::PropertyNotPresent(TypeId::of::<
Srgba,
>(
))),
}
}
}