# spanda
*Sanskrit: स्पन्द — vibration, pulse, the throb of motion.*
A general-purpose **animation library** for Rust. Zero mandatory dependencies,
`no_std`-ready, and designed to work anywhere: terminal UIs, web (WASM),
game engines (Bevy), or native desktop apps.
## Features
- **Tweening** — animate any value from A to B with 38+ easing curves
- **Keyframe tracks** — multi-stop animations with per-segment easing
- **Timeline & Sequence** — compose animations concurrently or sequentially
- **Relative positioning** — GSAP-style `At::Start`, `At::End`, `At::Label`, `At::Offset`
- **Stagger** — offset N animations with a single call
- **Physics springs** — damped harmonic oscillator with 4 presets + `SpringN<T>` for 2D/3D/4D
- **Looping** — `Loop::Once`, `Times(n)`, `Forever`, `PingPong` on tweens and keyframes
- **Time scale** — speed up / slow down tweens and timelines at runtime
- **Callbacks** — `on_start`, `on_update`, `on_complete` on tweens (`std` feature)
- **Value modifiers** — `snap_to(grid)`, `round_to(decimals)`, custom modifiers
- **Scroll-linked animation** — `ScrollDriver` / `ScrollClock` for position-driven animations
- **Motion paths** — quadratic/cubic Bezier, CatmullRom splines, SVG path parsing, arc-length parameterization
- **Full motion path system** — `PolyPath`, `CompoundPath`, `SvgPathParser`, auto-rotate, start/end offsets
- **CSS easing** — `CubicBezier(x1,y1,x2,y2)` and `Steps(n)` on the `Easing` enum
- **Colour animation** — 9 palette types + `InLab`/`InOklch`/`InLinear` colour-space-aware wrappers (`palette` feature)
- **DrawSVG** — `draw_on` / `draw_on_reverse` stroke-dashoffset helpers
- **Shape morphing** — `MorphPath` point-by-point morph with auto-resampling
- **Inertia physics** — `Inertia` / `InertiaN<T>` friction deceleration with presets
- **Advanced easings** — `RoughEase`, `SlowMo`, `ExpoScale`, `Wiggle`, `CustomBounce`
- **Drag tracking** — `DragState` with velocity EMA, bounds, axis lock, grid snap → `InertiaN` on release
- **WASM-DOM plugins** — FLIP animations, SplitText, ScrollSmoother, Draggable, Observer (`wasm-dom` feature)
- **Animation driver** — manage multiple animations with auto-cleanup
- **Clock abstraction** — wall clock, manual clock, scroll clock, and mock clock for testing
## Getting Started
```toml
[dependencies]
spanda = "0.8"
```
### Quick Example
```rust
use spanda::{Tween, Easing};
use spanda::traits::Update;
let mut tween = Tween::new(0.0_f32, 100.0)
.duration(1.0)
.easing(Easing::EaseOutCubic)
.build();
// Simulate 10 frames:
for _ in 0..10 {
tween.update(0.1);
}
assert!(tween.is_complete());
assert!((tween.value() - 100.0).abs() < 1e-6);
```
### Looping Tween
```rust
use spanda::{Tween, Loop};
use spanda::traits::Update;
let mut tween = Tween::new(0.0_f32, 100.0)
.duration(1.0)
.looping(Loop::PingPong)
.build();
// Runs forever, bouncing between 0 and 100
for _ in 0..600 {
tween.update(1.0 / 60.0);
}
```
### Spring Animation
```rust
use spanda::spring::{Spring, SpringConfig};
use spanda::traits::Update;
let mut spring = Spring::new(SpringConfig::wobbly());
spring.set_target(100.0);
for _ in 0..300 {
spring.update(1.0 / 60.0);
}
assert!(spring.is_settled());
```
### Multi-Dimensional Spring (SpringN)
```rust
use spanda::spring::{SpringN, SpringConfig};
use spanda::traits::Update;
let mut spring = SpringN::new(SpringConfig::wobbly(), [0.0_f32, 0.0]);
spring.set_target([100.0, 200.0]);
for _ in 0..1000 {
spring.update(1.0 / 60.0);
}
let pos = spring.position(); // [f32; 2]
assert!(spring.is_settled());
```
### Timeline with Relative Positioning
```rust
use spanda::timeline::{Timeline, At};
use spanda::tween::Tween;
use spanda::easing::Easing;
let mut tl = Timeline::new()
.add("fade", Tween::new(0.0_f32, 1.0).duration(0.5).build(), 0.0);
// Place "slide" right after "fade" ends
tl.add_at("slide", Tween::new(0.0_f32, 100.0).duration(0.8).build(), 0.8, At::End);
// Place "glow" at the same time as "fade"
tl.add_at("glow", Tween::new(0.0_f32, 1.0).duration(0.3).build(), 0.3, At::Label("fade"));
tl.play();
```
### Staggered Animations
```rust
use spanda::timeline::stagger;
use spanda::tween::Tween;
use spanda::traits::Update;
let tweens: Vec<_> = (0..5).map(|i| {
let end = (i + 1) as f32 * 20.0;
(Tween::new(0.0_f32, end).duration(0.5).build(), 0.5)
}).collect();
let mut timeline = stagger(tweens, 0.1);
timeline.play();
// Animations start at t=0.0, 0.1, 0.2, 0.3, 0.4
```
### Scroll-Linked Animation
```rust
use spanda::scroll::ScrollDriver;
use spanda::tween::Tween;
let mut driver = ScrollDriver::new(0.0, 1000.0);
driver.add(Tween::new(0.0_f32, 100.0).duration(1.0).build());
// Drive animation from scroll position instead of time
driver.set_position(500.0); // 50% scroll
```
### Motion Path Animation
```rust
use spanda::path::{MotionPath, MotionPathTween, PathEvaluate};
use spanda::easing::Easing;
use spanda::traits::Update;
let path = MotionPath::new()
.cubic([0.0_f32, 0.0], [50.0, 100.0], [100.0, 100.0], [150.0, 0.0])
.line([150.0, 0.0], [200.0, 0.0]);
let mut tween = MotionPathTween::new(path)
.duration(2.0)
.easing(Easing::EaseInOutCubic);
tween.update(1.0);
let pos = tween.value(); // position along the curve
```
### Smooth Path Through Points (PolyPath)
```rust
use spanda::motion_path::PolyPath;
let path = PolyPath::from_points(vec![
[0.0, 0.0],
[100.0, 50.0],
[200.0, 0.0],
[300.0, 50.0],
]);
let pos = path.position(0.5); // arc-length parameterized
let angle = path.rotation_deg(0.5); // auto-rotate angle
```
### SVG Path Parsing
```rust
use spanda::svg_path::SvgPathParser;
use spanda::motion_path::CompoundPath;
let commands = SvgPathParser::parse("M 0 0 C 50 100 100 100 150 0 L 200 0");
let path = CompoundPath::new(commands)
.start_offset(0.1)
.end_offset(0.9);
let pos = path.position(0.5);
```
### CSS Cubic-Bezier Easing
```rust
use spanda::{Tween, Easing};
use spanda::traits::Update;
let mut tween = Tween::new(0.0_f32, 100.0)
.duration(1.0)
.easing(Easing::CubicBezier(0.25, 0.1, 0.25, 1.0)) // CSS ease
.build();
tween.update(0.5);
```
### Colour Animation (palette feature)
```rust,ignore
use palette::Srgba;
use spanda::{Tween, Easing};
use spanda::colour::InLab;
use spanda::traits::Update;
// Interpolate in CIE L*a*b* for perceptually smooth gradients
let mut tween = Tween::new(
InLab(Srgba::new(1.0, 0.0, 0.0, 1.0)), // red
InLab(Srgba::new(0.0, 0.0, 1.0, 1.0)), // blue
)
.duration(1.0)
.easing(Easing::EaseInOutCubic)
.build();
tween.update(0.5);
let colour = tween.value().0; // Srgba
```
### Sequence Composition
```rust
use spanda::timeline::Sequence;
use spanda::tween::Tween;
use spanda::traits::Update;
let mut timeline = Sequence::new()
.then(Tween::new(0.0_f32, 100.0).duration(0.5).build(), 0.5)
.gap(0.1)
.then(Tween::new(100.0_f32, 0.0).duration(0.3).build(), 0.3)
.build();
timeline.play();
timeline.update(0.9);
```
## Feature Flags
| `std` | *(default)* wall-clock driver, thread-safe internals |
| `serde` | `Serialize`/`Deserialize` on all public types |
| `bevy` | `SpandaPlugin` for Bevy 0.13 |
| `wasm` | `requestAnimationFrame` driver |
| `wasm-dom` | DOM plugins: FLIP, SplitText, ScrollSmoother, Draggable, Observer |
| `palette` | Colour interpolation via the `palette` crate |
| `tokio` | `async` / `.await` on timeline completion |
## Bevy Integration
```rust,ignore
use bevy::prelude::*;
use spanda::integrations::bevy::{SpandaPlugin, TweenCompleted, SpringSettled};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_plugins(SpandaPlugin)
.run();
}
```
## WASM Integration
```rust,ignore
use spanda::integrations::wasm::RafDriver;
let mut driver = RafDriver::new();
driver.pause(); // pause animations
driver.resume(); // resume
driver.set_time_scale(2.0); // 2x speed
// Call driver.tick(timestamp_ms) from your rAF callback.
```
## Benchmarks
```bash
cargo bench
```
## Tests
```bash
cargo test # unit + integration + doc tests
cargo test --tests # integration tests only
```
## Project Structure
```
src/
├── lib.rs — crate root, re-exports
├── traits.rs — Interpolate, Animatable, Update
├── easing.rs — 38 easing functions + CubicBezier + Steps + 5 advanced
├── tween.rs — Tween<T>, TweenBuilder, TweenState
├── keyframe.rs — KeyframeTrack, Keyframe, Loop
├── timeline.rs — Timeline, Sequence, At, stagger
├── spring.rs — Spring, SpringConfig, SpringN, SpringAnimatable
├── clock.rs — Clock, WallClock, ManualClock, MockClock
├── driver.rs — AnimationDriver, AnimationId
├── scroll.rs — ScrollClock, ScrollDriver
├── path.rs — BezierPath, MotionPath, MotionPathTween
├── bezier.rs — CatmullRomSpline, PathEvaluate2D
├── motion_path.rs — PolyPath, CompoundPath, PathCommand
├── svg_path.rs — SvgPathParser (SVG d-attribute parser)
├── colour.rs — colour interpolation (feature = "palette")
├── svg_draw.rs — DrawSVG stroke-dashoffset helpers
├── morph.rs — MorphPath shape morphing + resample
├── inertia.rs — Inertia, InertiaN friction deceleration
├── drag.rs — DragState, DragConstraints, PointerData
└── integrations/
├── mod.rs
├── bevy.rs — SpandaPlugin (feature = "bevy")
├── wasm.rs — RafDriver (feature = "wasm")
├── split_text.rs — SplitText character/word splitting
├── flip.rs — FlipState, FlipAnimation (feature = "wasm-dom")
├── scroll_smoother.rs — ScrollSmoother (feature = "wasm-dom")
├── draggable.rs — Draggable DOM binding (feature = "wasm-dom")
└── observer.rs — Observer unified input (feature = "wasm-dom")
```
## License
Licensed under either of
- [Apache License, Version 2.0](LICENSE-APACHE)
- [MIT License](LICENSE-MIT)
at your option.