oxframe_core/
runtime.rs

1//! Per-thread context of the scene being executed.
2//!
3//! The [`Executor`](crate::Executor) installs its runtime for the duration
4//! of each step, so free functions like [`now`] and [`wait_until`]
5//! (crate::wait_until) work inside scene code without passing handles.
6
7use std::cell::{Cell, RefCell};
8use std::rc::Rc;
9
10use oxframe_protocol::Meta;
11use rand::SeedableRng;
12use rand_chacha::ChaCha8Rng;
13
14use crate::CubicBezier;
15use crate::ease::presets;
16use crate::flow::Task;
17use crate::transition::Recorded;
18
19pub(crate) struct Runtime {
20    pub fps: f64,
21    pub frame: Cell<u32>,
22    /// Virtual time of the task being polled. It can lag behind the frame
23    /// time by a fraction of a frame: when a tween ends between frames, the
24    /// next tween starts at the exact end time, so timings do not drift.
25    pub task_time: Cell<f64>,
26    pub spawned: RefCell<Vec<Task>>,
27    pub meta: RefCell<Meta>,
28    pub meta_changed: Cell<bool>,
29    pub rng: RefCell<ChaCha8Rng>,
30    /// Set by the engine: this scene has one before it, so a transition blends.
31    pub has_previous: Cell<bool>,
32    /// The transition declared by the scene, if it starts one.
33    pub transition: RefCell<Option<Recorded>>,
34    /// Sound effects scheduled by `sound()`, in scene time.
35    pub sounds: RefCell<Vec<crate::SoundClip>>,
36    /// Spoken lines scheduled by `voice()`, in scene time.
37    pub voices: RefCell<Vec<crate::VoiceLine>>,
38}
39
40impl Runtime {
41    pub fn new(fps: f64, meta: Meta, seed: u64) -> Rc<Self> {
42        assert!(fps > 0.0 && fps.is_finite(), "fps must be positive");
43        Rc::new(Self {
44            fps,
45            frame: Cell::new(0),
46            task_time: Cell::new(0.0),
47            spawned: RefCell::new(Vec::new()),
48            meta: RefCell::new(meta),
49            meta_changed: Cell::new(false),
50            rng: RefCell::new(ChaCha8Rng::seed_from_u64(seed)),
51            has_previous: Cell::new(false),
52            transition: RefCell::new(None),
53            sounds: RefCell::new(Vec::new()),
54            voices: RefCell::new(Vec::new()),
55        })
56    }
57
58    pub fn now(&self) -> f64 {
59        f64::from(self.frame.get()) / self.fps
60    }
61}
62
63thread_local! {
64    static CURRENT: RefCell<Option<Rc<Runtime>>> = const { RefCell::new(None) };
65}
66
67/// Restores the previously installed runtime on drop.
68pub(crate) struct Installed(Option<Rc<Runtime>>);
69
70pub(crate) fn install(rt: &Rc<Runtime>) -> Installed {
71    Installed(CURRENT.with(|c| c.borrow_mut().replace(rt.clone())))
72}
73
74impl Drop for Installed {
75    fn drop(&mut self) {
76        let prev = self.0.take();
77        CURRENT.with(|c| *c.borrow_mut() = prev);
78    }
79}
80
81pub(crate) fn with<R>(f: impl FnOnce(&Runtime) -> R) -> R {
82    CURRENT.with(|c| {
83        let c = c.borrow();
84        let rt = c
85            .as_ref()
86            .expect("oxframe: this function can only be called while a scene is running");
87        f(rt)
88    })
89}
90
91/// Index of the frame being computed.
92pub fn frame() -> u32 {
93    with(|rt| rt.frame.get())
94}
95
96/// Frames per second of the running project.
97pub fn fps() -> f64 {
98    with(|rt| rt.fps)
99}
100
101/// Duration of one frame in seconds, `1 / fps`.
102pub fn dt() -> f64 {
103    with(|rt| 1.0 / rt.fps)
104}
105
106/// Time of the current frame, `frame / fps` seconds.
107pub fn now() -> f64 {
108    with(|rt| rt.now())
109}
110
111/// Whether the running scene has a scene before it.
112pub fn has_previous() -> bool {
113    with(|rt| rt.has_previous.get())
114}
115
116/// Records `spec`, letting `meta.json` override its duration the way markers
117/// do. Returns the duration to wait. Panics if the scene already started one.
118pub fn begin_transition(mut spec: Recorded) -> f64 {
119    with(|rt| {
120        if rt.transition.borrow().is_some() {
121            panic!("oxframe: a scene can declare only one transition; call it once, at the start");
122        }
123        let stored = rt.meta.borrow().transition.as_ref().map(|t| t.seconds);
124        if let Some(seconds) = stored {
125            spec.seconds = if seconds.is_finite() {
126                seconds.max(0.0)
127            } else {
128                0.0
129            };
130        } else if spec.seconds.is_finite() && spec.seconds > 0.0 {
131            let seconds = spec.seconds;
132            rt.meta.borrow_mut().transition = Some(oxframe_protocol::TransitionMeta { seconds });
133            rt.meta_changed.set(true);
134        } else {
135            spec.seconds = 0.0;
136        }
137        let seconds = spec.seconds;
138        if seconds > 0.0 {
139            *rt.transition.borrow_mut() = Some(spec);
140        }
141        seconds
142    })
143}
144
145/// Virtual time of the current task — where the next animation starts.
146pub fn time() -> f64 {
147    with(|rt| rt.task_time.get())
148}
149
150/// Value of tunable `name` from `meta.json`; `default` is recorded there on
151/// first use. Use through the `tune!` macro.
152pub fn tunable(name: &str, default: f64) -> f64 {
153    with(|rt| {
154        let mut meta = rt.meta.borrow_mut();
155        if let Some(v) = meta.tunables.get(name) {
156            return *v;
157        }
158        meta.tunables.insert(name.to_owned(), default);
159        rt.meta_changed.set(true);
160        default
161    })
162}
163
164/// Named easing from `meta.json`; `default` is recorded there on first use.
165/// Use through the `ease!` macro.
166pub fn ease_named(name: &str, default: Option<CubicBezier>) -> CubicBezier {
167    with(|rt| {
168        let mut meta = rt.meta.borrow_mut();
169        if let Some(v) = meta.eases.get(name) {
170            return CubicBezier::from_array(*v);
171        }
172        let default = default.unwrap_or(presets::DEFAULT);
173        meta.eases.insert(name.to_owned(), default.to_array());
174        rt.meta_changed.set(true);
175        default
176    })
177}
178
179/// Marker time from `meta.json`; the current task time is recorded on first
180/// encounter.
181pub(crate) fn marker(name: &str) -> f64 {
182    with(|rt| {
183        let mut meta = rt.meta.borrow_mut();
184        if let Some(v) = meta.markers.get(name) {
185            return *v;
186        }
187        let t = rt.task_time.get();
188        meta.markers.insert(name.to_owned(), t);
189        rt.meta_changed.set(true);
190        t
191    })
192}
193
194/// Copy of the running scene's markers, eases and tunables.
195pub fn meta_snapshot() -> Meta {
196    with(|rt| rt.meta.borrow().clone())
197}
198
199/// Runs `f` with the scene's random generator. It is seeded from the
200/// project seed and the scene name, so results are reproducible; never use
201/// `rand::rng()` or other entropy sources in scenes.
202pub fn with_rng<R>(f: impl FnOnce(&mut ChaCha8Rng) -> R) -> R {
203    with(|rt| f(&mut rt.rng.borrow_mut()))
204}
205
206/// Uniform random number in `[0, 1)` from the scene's seeded generator.
207pub fn random() -> f64 {
208    use rand::RngExt;
209    with_rng(|r| r.random::<f64>())
210}
211
212/// Uniform random number in `[min, max)` from the scene's seeded generator.
213pub fn random_range(min: f64, max: f64) -> f64 {
214    min + (max - min) * random()
215}
216
217/// A generator seeded by the caller. Drawing with this does not advance the
218/// scene's [`random`] generator, and the same seed always yields the same
219/// sequence, including after a seek.
220#[derive(Clone)]
221pub struct SeededRng(ChaCha8Rng);
222
223impl SeededRng {
224    /// Generator for `seed`. The same seed is the same sequence.
225    pub fn new(seed: u64) -> Self {
226        Self(ChaCha8Rng::seed_from_u64(seed))
227    }
228
229    /// Uniform number in `[0, 1)`.
230    pub fn next_f64(&mut self) -> f64 {
231        use rand::RngExt;
232        self.0.random::<f64>()
233    }
234
235    /// Uniform number in `span` (`end` is excluded).
236    pub fn range(&mut self, span: std::ops::Range<f64>) -> f64 {
237        let w = span.end - span.start;
238        span.start + w * self.next_f64()
239    }
240}
oxframe_core/runtime.rs

oxframe_core/
runtime.rs
