zng_var/vars.rs
1//!: Vars service.
2
3use std::{mem, sync::Arc, thread::ThreadId, time::Duration};
4
5use parking_lot::Mutex;
6use smallbox::SmallBox;
7use zng_app_context::{app_local, context_local};
8use zng_time::{DInstant, Deadline, INSTANT, INSTANT_APP};
9use zng_unit::{Factor, FactorUnits as _, TimeUnits as _};
10
11use smallbox::smallbox;
12
13use crate::{
14 AnyVar, Var,
15 animation::{Animation, AnimationController, AnimationHandle, AnimationTimer, ModifyInfo},
16 var,
17};
18
19/// Represents the last time a variable was mutated or the current update cycle.
20#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, bytemuck::NoUninit)]
21#[repr(transparent)]
22pub struct VarUpdateId(pub(crate) u32);
23impl VarUpdateId {
24 /// ID that is never new.
25 pub const fn never() -> Self {
26 VarUpdateId(0)
27 }
28
29 fn next(&mut self) {
30 if self.0 == u32::MAX {
31 self.0 = 1;
32 } else {
33 self.0 += 1;
34 }
35 }
36}
37impl Default for VarUpdateId {
38 fn default() -> Self {
39 Self::never()
40 }
41}
42
43pub(super) type VarUpdateFn = SmallBox<dyn FnMut() + Send + 'static, smallbox::space::S8>;
44
45app_local! {
46 pub(crate) static VARS_SV: VarsService = VarsService::new();
47}
48context_local! {
49 pub(crate) static VARS_MODIFY_CTX: Option<ModifyInfo> = None;
50 pub(crate) static VARS_ANIMATION_CTRL_CTX: Box<dyn AnimationController> = {
51 let r: Box<dyn AnimationController> = Box::new(());
52 r
53 };
54}
55
56type AnimationFn = SmallBox<dyn FnMut(AnimationUpdateInfo) -> Option<Deadline> + Send, smallbox::space::S8>;
57
58pub(crate) struct VarsService {
59 // animation config
60 animations_enabled: Var<bool>,
61 sys_animations_enabled: Var<bool>,
62 frame_duration: Var<Duration>,
63 animation_time_scale: Var<Factor>,
64
65 // VARS_APP stuff
66 app_waker: Option<SmallBox<dyn Fn() + Send + Sync + 'static, smallbox::space::S2>>,
67 modify_trace: Option<SmallBox<dyn Fn(&'static str) + Send + Sync + 'static, smallbox::space::S2>>,
68
69 // AnyVar::perm storage
70 perm: Mutex<Vec<AnyVar>>,
71
72 // update state
73 update_id: VarUpdateId,
74 updates: Mutex<Vec<(ModifyInfo, VarUpdateFn)>>,
75 updating_thread: Option<ThreadId>,
76 updates_after: Mutex<Vec<(ModifyInfo, VarUpdateFn)>>,
77
78 // animations state
79 ans_animations: Mutex<Vec<AnimationFn>>,
80 ans_animation_imp: usize,
81 ans_current_modify: ModifyInfo,
82 ans_animation_start_time: Option<DInstant>,
83 ans_next_frame: Option<Deadline>,
84}
85impl VarsService {
86 pub(crate) fn new() -> Self {
87 let sys_animations_enabled = var(true);
88 Self {
89 animations_enabled: sys_animations_enabled.cow(),
90 sys_animations_enabled,
91 frame_duration: var((1.0 / 60.0).secs()),
92 animation_time_scale: var(1.fct()),
93
94 app_waker: None,
95 modify_trace: None,
96
97 perm: Mutex::new(vec![]),
98
99 update_id: VarUpdateId::never(),
100 updates: Mutex::new(vec![]),
101 updating_thread: None,
102 updates_after: Mutex::new(vec![]),
103
104 ans_animations: Mutex::new(vec![]),
105 ans_animation_imp: 0,
106 ans_current_modify: ModifyInfo::never(),
107 ans_animation_start_time: None,
108 ans_next_frame: None,
109 }
110 }
111
112 fn wake_app(&self) {
113 if let Some(w) = &self.app_waker {
114 w();
115 }
116 }
117}
118
119/// Variable updates and animation service.
120pub struct VARS;
121impl VARS {
122 /// Id of the current vars update in the app scope.
123 ///
124 /// Variable with [`AnyVar::last_update`] equal to this are *new*.
125 pub fn update_id(&self) -> VarUpdateId {
126 VARS_SV.read().update_id
127 }
128
129 /// Read-write that defines if animations are enabled on the app.
130 ///
131 /// The value is the same as [`sys_animations_enabled`], if set the variable disconnects from system config.
132 ///
133 /// [`sys_animations_enabled`]: Self::sys_animations_enabled
134 pub fn animations_enabled(&self) -> Var<bool> {
135 VARS_SV.read().animations_enabled.clone()
136 }
137
138 /// Read-only that tracks if animations are enabled in the operating system.
139 ///
140 /// This is `true` by default, it updates when the operating system config changes.
141 pub fn sys_animations_enabled(&self) -> Var<bool> {
142 VARS_SV.read().sys_animations_enabled.read_only()
143 }
144
145 /// Variable that defines the global frame duration, the default is 60fps `(1.0 / 60.0).secs()`.
146 pub fn frame_duration(&self) -> Var<Duration> {
147 VARS_SV.read().frame_duration.clone()
148 }
149
150 /// Variable that defines a global scale for the elapsed time of animations.
151 pub fn animation_time_scale(&self) -> Var<Factor> {
152 VARS_SV.read().animation_time_scale.clone()
153 }
154
155 /// Info about the current context when requesting variable modification.
156 ///
157 /// If is currently inside a [`VARS.animate`] closure, or inside a [`Var::modify`] closure requested by an animation, or inside
158 /// an [`AnimationController`], returns the info that was collected at the moment the animation was requested. Outside of animations
159 /// gets an info with [`importance`] guaranteed to override the [`modify_importance`].
160 ///
161 /// [`importance`]: ModifyInfo::importance
162 /// [`modify_importance`]: AnyVar::modify_importance
163 /// [`AnimationController`]: crate::animation::AnimationController
164 /// [`VARS.animate`]: VARS::animate
165 pub fn current_modify(&self) -> ModifyInfo {
166 match VARS_MODIFY_CTX.get_clone() {
167 Some(current) => current, // override set by modify and animation closures.
168 None => VARS_SV.read().ans_current_modify.clone(),
169 }
170 }
171
172 /// Adds an `animation` closure that is called every frame to update captured variables, starting after next frame.
173 ///
174 /// This is used to implement all [`Var<T>`] animations, it enables any kind of variable animation,
175 /// including multiple variables.
176 ///
177 /// Returns an [`AnimationHandle`] that can be used to monitor the animation status and to [`stop`] or to
178 /// make the animation [`perm`].
179 ///
180 /// # Variable Control
181 ///
182 /// Animations assume *control* of a variable on the first time they cause its value to be new, after this
183 /// moment the [`AnyVar::is_animating`] value is `true` and [`AnyVar::modify_importance`] is the animation's importance,
184 /// until the animation stops. Only one animation can control a variable at a time, if an animation loses control of a
185 /// variable all attempts to modify it from inside the animation are ignored.
186 ///
187 /// Later started animations steal control from previous animations, update, modify or set calls also remove the variable
188 /// from being affected by a running animation, even if just set to an equal value, that is, not actually updated.
189 ///
190 /// # Nested Animations
191 ///
192 /// Other animations can be started from inside the animation closure, these *nested* animations have the same importance
193 /// as the *parent* animation, the animation handle is different and [`AnyVar::is_animating`] is `false` if the nested animation
194 /// is dropped before the *parent* animation. But because the animations share the same importance the parent animation can
195 /// set the variable again.
196 ///
197 /// You can also use the [`EasingTime::seg`] method to get a normalized time factor for a given segment or slice of the overall time,
198 /// complex animations targeting multiple variables can be coordinated with precision using this method.
199 ///
200 /// # Examples
201 ///
202 /// The example animates a `text` variable from `"Animation at 0%"` to `"Animation at 100%"`, when the animation
203 /// stops the `completed` variable is set to `true`.
204 ///
205 /// ```
206 /// # use zng_var::{*, animation::easing};
207 /// # use zng_txt::*;
208 /// # use zng_unit::*;
209 /// # use zng_clone_move::*;
210 /// #
211 /// fn animate_text(text: &Var<Txt>, completed: &Var<bool>) {
212 /// let transition = animation::Transition::new(0u8, 100);
213 /// let mut prev_value = 101;
214 /// VARS.animate(clmv!(text, completed, |animation| {
215 /// let step = easing::expo(animation.elapsed_stop(1.secs()));
216 /// let value = transition.sample(step);
217 /// if value != prev_value {
218 /// if value == 100 {
219 /// animation.stop();
220 /// let _ = completed.set(true);
221 /// }
222 /// let _ = text.set(formatx!("Animation at {value}%"));
223 /// prev_value = value;
224 /// }
225 /// }))
226 /// .perm()
227 /// }
228 /// ```
229 ///
230 /// Note that the animation can be stopped from the inside, the closure parameter is an [`Animation`]. In
231 /// the example this is the only way to stop the animation, because [`perm`] was called. Animations hold a clone
232 /// of the variables they affect and exist for the duration of the app if not stopped, causing the app to wake and call the
233 /// animation closure for every frame.
234 ///
235 /// This method is the most basic animation interface, used to build all other animations, its rare that you
236 /// will need to use it directly, most of the time animation effects can be composted using the [`Var`] easing and mapping
237 /// methods.
238 ///
239 /// ```
240 /// # use zng_var::{*, animation::easing};
241 /// # use zng_txt::*;
242 /// # use zng_unit::*;
243 /// # fn demo() {
244 /// let value = var(0u8);
245 /// let text = value.map(|v| formatx!("Animation at {v}%"));
246 /// value.ease(100, 1.secs(), easing::expo);
247 /// # }
248 /// ```
249 ///
250 /// # Optimization Tips
251 ///
252 /// When no animation is running the app *sleeps* awaiting for an external event, update request or timer elapse, when at least one
253 /// animation is running the app awakes every [`VARS.frame_duration`]. You can use [`Animation::sleep`] to *pause* the animation
254 /// for a duration, if all animations are sleeping the app is also sleeping.
255 ///
256 /// Animations lose control over a variable permanently when a newer animation modifies the var or
257 /// the var is modified directly, but even if the animation can't control any variables **it keeps running**.
258 /// This happens because the system has no insight of all side effects caused by the `animation` closure. You
259 /// can use the [`VARS.current_modify`] and [`AnyVar::modify_importance`] to detect when the animation no longer affects
260 /// any variables and stop the animation to avoid awaking the app for no reason.
261 ///
262 /// These optimizations are already implemented by the animations provided as methods of [`Var<T>`].
263 ///
264 /// # External Controller
265 ///
266 /// The animation can be controlled from the inside using the [`Animation`] reference, it can be stopped using the returned
267 /// [`AnimationHandle`], and it can also be controlled by a registered [`AnimationController`] that can manage multiple
268 /// animations at the same time, see [`with_animation_controller`] for more details.
269 ///
270 /// [`Animation::sleep`]: Animation::sleep
271 /// [`stop`]: AnimationHandle::stop
272 /// [`perm`]: AnimationHandle::perm
273 /// [`with_animation_controller`]: VARS::with_animation_controller
274 /// [`VARS.frame_duration`]: VARS::frame_duration
275 /// [`VARS.current_modify`]: VARS::current_modify
276 /// [`EasingTime::seg`]: crate::animation::easing::EasingTime::seg
277 pub fn animate<A>(&self, animation: A) -> AnimationHandle
278 where
279 A: FnMut(&Animation) + Send + 'static,
280 {
281 VARS.animate_impl(smallbox!(animation))
282 }
283
284 /// Calls `animate` while `controller` is registered as the animation controller.
285 ///
286 /// The `controller` is notified of animation events for each animation spawned by `animate` and can affect then with the same
287 /// level of access as [`VARS.animate`]. Only one controller can affect animations at a time.
288 ///
289 /// This can be used to manage multiple animations at the same time, or to get [`VARS.animate`] level of access to an animation
290 /// that is not implemented to allow such access. Note that animation implementers are not required to support the full
291 /// [`Animation`] API, for example, there is no guarantee that a restart requested by the controller will repeat the same animation.
292 ///
293 /// The controller can start new animations, these animations will have the same controller if not overridden, you can
294 /// use this method and the `()` controller to avoid this behavior.
295 ///
296 /// [`Animation`]: crate::animation::Animation
297 /// [`VARS.animate`]: VARS::animate
298 pub fn with_animation_controller<R>(&self, controller: impl AnimationController, animate: impl FnOnce() -> R) -> R {
299 let controller: Box<dyn AnimationController> = Box::new(controller);
300 let mut opt = Some(Arc::new(controller));
301 VARS_ANIMATION_CTRL_CTX.with_context(&mut opt, animate)
302 }
303
304 /// Schedule a custom closure to run as a variable modify callback.
305 ///
306 /// The closure `m` will run after the current update, any variable it modifies will be new in the next update, like a binding.
307 pub fn modify(&self, debug_name: &'static str, m: impl FnOnce() + Send + 'static) {
308 self.schedule_update(debug_name, m);
309 }
310
311 pub(crate) fn schedule_update(&self, value_type_name: &'static str, apply_update: impl FnOnce() + Send + 'static) {
312 let mut once = Some(apply_update);
313 self.schedule_update_impl(
314 value_type_name,
315 smallbox!(move || {
316 let once = once.take().unwrap();
317 once();
318 }),
319 );
320 }
321
322 pub(crate) fn perm(&self, var: AnyVar) {
323 VARS_SV.read().perm.lock().push(var);
324 }
325}
326
327/// VARS APP integration.
328#[expect(non_camel_case_types)]
329pub struct VARS_APP;
330impl VARS_APP {
331 /// Register a closure called when [`apply_updates`] should be called because there are changes pending.
332 ///
333 /// # Panics
334 ///
335 /// Panics if already called for the current app. This must be called by app framework implementers only.
336 ///
337 /// [`apply_updates`]: Self::apply_updates
338 pub fn init_app_waker(&self, waker: impl Fn() + Send + Sync + 'static) {
339 let mut vars = VARS_SV.write();
340 assert!(vars.app_waker.is_none());
341 vars.app_waker = Some(smallbox!(waker));
342 }
343
344 /// Register a closure called when a variable modify is about to be scheduled. The
345 /// closure parameter is the type name of the variable type.
346 ///
347 /// # Panics
348 ///
349 /// Panics if already called for the current app. This must be called by app framework implementers only.
350 pub fn init_modify_trace(&self, trace: impl Fn(&'static str) + Send + Sync + 'static) {
351 let mut vars = VARS_SV.write();
352 assert!(vars.modify_trace.is_none());
353 vars.modify_trace = Some(smallbox!(trace));
354 }
355
356 /// If [`apply_updates`] will do anything.
357 ///
358 /// [`apply_updates`]: Self::apply_updates
359 pub fn has_pending_updates(&self) -> bool {
360 !VARS_SV.write().updates.get_mut().is_empty()
361 }
362
363 /// Sets the `sys_animations_enabled` read-only variable.
364 pub fn set_sys_animations_enabled(&self, enabled: bool) {
365 VARS_SV.read().sys_animations_enabled.set(enabled);
366 }
367
368 /// Apply all pending updates, call hooks and update bindings.
369 ///
370 /// This must be called by app framework implementers only.
371 pub fn apply_updates(&self) {
372 let _s = tracing::trace_span!("VARS").entered();
373 let _t = INSTANT_APP.pause_for_update();
374 VARS.apply_updates_and_after(0)
375 }
376
377 /// Does one animation frame if the frame duration has elapsed.
378 ///
379 /// This must be called by app framework implementers only.
380 pub fn update_animations(&self, timer: &mut impl AnimationTimer) {
381 VARS.update_animations_impl(timer);
382 }
383
384 /// Register the next animation frame, if there are any active animations.
385 ///
386 /// This must be called by app framework implementers only.
387 pub fn next_deadline(&self, timer: &mut impl AnimationTimer) {
388 VARS.next_deadline_impl(timer)
389 }
390}
391
392impl VARS {
393 fn schedule_update_impl(&self, value_type_name: &'static str, update: VarUpdateFn) {
394 let vars = VARS_SV.read();
395 if let Some(trace) = &vars.modify_trace {
396 trace(value_type_name);
397 }
398 let cur_modify = match VARS_MODIFY_CTX.get_clone() {
399 Some(current) => current, // override set by modify and animation closures.
400 None => vars.ans_current_modify.clone(),
401 };
402
403 if let Some(id) = vars.updating_thread {
404 if std::thread::current().id() == id {
405 // is binding request, enqueue for immediate exec.
406 vars.updates.lock().push((cur_modify, update));
407 } else {
408 // is request from app task thread when we are already updating, enqueue for exec after current update.
409 vars.updates_after.lock().push((cur_modify, update));
410 }
411 } else {
412 // request from any app thread,
413 vars.updates.lock().push((cur_modify, update));
414 vars.wake_app();
415 }
416 }
417
418 fn apply_updates_and_after(&self, depth: u8) {
419 let mut vars = VARS_SV.write();
420
421 match depth {
422 0 => {
423 vars.update_id.next();
424 vars.ans_animation_start_time = None;
425 }
426 10 => {
427 // high-pressure from worker threads, skip
428 return;
429 }
430 _ => {}
431 }
432
433 // updates requested by other threads while was applying updates
434 let mut updates = mem::take(vars.updates_after.get_mut());
435 // normal updates
436 if updates.is_empty() {
437 updates = mem::take(vars.updates.get_mut());
438 } else {
439 updates.append(vars.updates.get_mut());
440 }
441 // apply pending updates
442 if !updates.is_empty() {
443 debug_assert!(vars.updating_thread.is_none());
444 vars.updating_thread = Some(std::thread::current().id());
445
446 drop(vars);
447 update_each_and_bindings(updates, 0);
448
449 vars = VARS_SV.write();
450 vars.updating_thread = None;
451
452 if !vars.updates_after.get_mut().is_empty() {
453 drop(vars);
454 VARS.apply_updates_and_after(depth + 1)
455 }
456 }
457
458 fn update_each_and_bindings(updates: Vec<(ModifyInfo, VarUpdateFn)>, depth: u16) {
459 if depth == 1000 {
460 tracing::error!(
461 "updated variable bindings 1000 times, probably stuck in an infinite loop\n\
462 will skip next updates"
463 );
464 return;
465 }
466
467 for (info, mut update) in updates {
468 #[allow(clippy::redundant_closure)] // false positive
469 VARS_MODIFY_CTX.with_context(&mut Some(Arc::new(Some(info))), || (update)());
470
471 let mut vars = VARS_SV.write();
472 let updates = mem::take(vars.updates.get_mut());
473 if !updates.is_empty() {
474 drop(vars);
475 update_each_and_bindings(updates, depth + 1);
476 }
477 }
478 }
479 }
480
481 fn animate_impl(&self, mut animation: SmallBox<dyn FnMut(&Animation) + Send + 'static, smallbox::space::S4>) -> AnimationHandle {
482 let mut vars = VARS_SV.write();
483
484 // # Modify Importance
485 //
486 // Variables only accept modifications from an importance (IMP) >= the previous IM that modified it.
487 //
488 // Direct modifications always overwrite previous animations, so we advance the IMP for each call to
489 // this method **and then** advance the IMP again for all subsequent direct modifications.
490 //
491 // Example sequence of events:
492 //
493 // |IM| Modification | Accepted
494 // |--|---------------|----------
495 // | 1| Var::set | YES
496 // | 2| Var::ease | YES
497 // | 2| ease update | YES
498 // | 3| Var::set | YES
499 // | 3| Var::set | YES
500 // | 2| ease update | NO
501 // | 4| Var::ease | YES
502 // | 2| ease update | NO
503 // | 4| ease update | YES
504 // | 5| Var::set | YES
505 // | 2| ease update | NO
506 // | 4| ease update | NO
507
508 // ensure that all animations started in this update have the same exact time, we update then with the same `now`
509 // timestamp also, this ensures that synchronized animations match perfectly.
510 let start_time = if let Some(t) = vars.ans_animation_start_time {
511 t
512 } else {
513 let t = INSTANT.now();
514 vars.ans_animation_start_time = Some(t);
515 t
516 };
517
518 let mut anim_imp = None;
519 if let Some(c) = VARS_MODIFY_CTX.get_clone()
520 && c.is_animating()
521 {
522 // nested animation uses parent importance.
523 anim_imp = Some(c.importance);
524 }
525 let anim_imp = match anim_imp {
526 Some(i) => i,
527 None => {
528 // not nested, advance base imp
529 let mut imp = vars.ans_animation_imp.wrapping_add(1);
530 if imp == 0 {
531 imp = 1;
532 }
533
534 let mut next_imp = imp.wrapping_add(1);
535 if next_imp == 0 {
536 next_imp = 1;
537 }
538
539 vars.ans_animation_imp = next_imp;
540 vars.ans_current_modify.importance = next_imp;
541
542 imp
543 }
544 };
545
546 let (handle_owner, handle) = AnimationHandle::new();
547 let weak_handle = handle.downgrade();
548
549 let controller = VARS_ANIMATION_CTRL_CTX.get();
550
551 let anim = Animation::new(vars.animations_enabled.get(), start_time, vars.animation_time_scale.get());
552
553 drop(vars);
554
555 controller.on_start(&anim);
556 let mut controller = Some(controller);
557 let mut anim_modify_info = Some(Arc::new(Some(ModifyInfo {
558 handle: Some(weak_handle.clone()),
559 importance: anim_imp,
560 })));
561
562 let mut vars = VARS_SV.write();
563
564 vars.ans_animations.get_mut().push(smallbox!(move |info: AnimationUpdateInfo| {
565 let _handle_owner = &handle_owner; // capture and own the handle owner.
566
567 if weak_handle.upgrade().is_some() {
568 if anim.stop_requested() {
569 // drop
570 controller.as_ref().unwrap().on_stop(&anim);
571 return None;
572 }
573
574 if let Some(sleep) = anim.sleep_deadline() {
575 if sleep > info.next_frame {
576 // retain sleep
577 return Some(sleep);
578 } else if sleep.0 > info.now {
579 // sync-up to frame rate after sleep
580 anim.reset_sleep();
581 return Some(info.next_frame);
582 }
583 }
584
585 anim.reset_state(info.animations_enabled, info.now, info.time_scale);
586
587 VARS_ANIMATION_CTRL_CTX.with_context(&mut controller, || {
588 VARS_MODIFY_CTX.with_context(&mut anim_modify_info, || animation(&anim))
589 });
590
591 // retain until next frame
592 //
593 // stop or sleep may be requested after this (during modify apply),
594 // these updates are applied on the next frame.
595 Some(info.next_frame)
596 } else {
597 // drop
598 controller.as_ref().unwrap().on_stop(&anim);
599 None
600 }
601 }));
602
603 vars.ans_next_frame = Some(Deadline(INSTANT.now()));
604
605 vars.wake_app();
606
607 handle
608 }
609
610 fn update_animations_impl(&self, timer: &mut dyn AnimationTimer) {
611 let mut vars = VARS_SV.write();
612 if let Some(next_frame) = vars.ans_next_frame
613 && timer.elapsed(next_frame)
614 {
615 let mut animations = mem::take(vars.ans_animations.get_mut());
616 debug_assert!(!animations.is_empty());
617
618 let info = AnimationUpdateInfo {
619 animations_enabled: vars.animations_enabled.get(),
620 time_scale: vars.animation_time_scale.get(),
621 now: timer.now(),
622 next_frame: next_frame + vars.frame_duration.get(),
623 };
624
625 let mut min_sleep = Deadline(info.now + Duration::from_secs(60 * 60));
626
627 drop(vars);
628
629 animations.retain_mut(|animate| {
630 if let Some(sleep) = animate(info) {
631 min_sleep = min_sleep.min(sleep);
632 true
633 } else {
634 false
635 }
636 });
637
638 let mut vars = VARS_SV.write();
639
640 let self_animations = vars.ans_animations.get_mut();
641 if !self_animations.is_empty() {
642 min_sleep = Deadline(info.now);
643 }
644 animations.append(self_animations);
645 *self_animations = animations;
646
647 if !self_animations.is_empty() {
648 vars.ans_next_frame = Some(min_sleep);
649 timer.register(min_sleep);
650 } else {
651 vars.ans_next_frame = None;
652 }
653 }
654 }
655
656 fn next_deadline_impl(&self, timer: &mut dyn AnimationTimer) {
657 if let Some(next_frame) = VARS_SV.read().ans_next_frame {
658 timer.register(next_frame);
659 }
660 }
661}
662
663#[derive(Clone, Copy)]
664struct AnimationUpdateInfo {
665 animations_enabled: bool,
666 now: DInstant,
667 time_scale: Factor,
668 next_frame: Deadline,
669}