[animations] schedule delayed animations with beginTime - #5
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An interactive page exercising the CALayer animate APIs directly, on a plain sublayer outside the render pass's management: toggle buttons for frame, opacity, and corner radius animations in immediate and delayed variants, plus scripted scenarios with fixed internal timings for the delay interactions (fresh delayed, delayed over in-flight, overlapping delayed, stacked delayed fades). Samples of the model value, presentation value, and attached animations are logged with timestamps relative to the last action, so a session on one build can be compared with a session on another, visually and by diffing the logs. This records the scheduling behavior before changing the delay mechanism.
Replace the GCD timer in `animate()` with Core Animation's own scheduling: the animation is added synchronously with `beginTime` set in the layer's time space, and the backwards fill holds the from value on screen for the delay window while the model value is already set. A zero-duration timing applies the model value immediately. A delayed animation is now a real attached animation, so behaviors the timer machinery had to reimplement come from the framework's normal paths: reset-for-reuse cleanup strips scheduled animations, releasing a layer releases them with it, and a superseding opacity retarget samples the held value through the ordinary evaluator composition. `retargetOpacity` drops the pending-timer storage, cancellation, and the pre-hide model write; the fresh-insert hold falls out of the held from delta. An interrupted in-flight animation now freezes at its sampled value for the delay window instead of continuing to play. The delayed tests become synchronous scheduled-state assertions. New pins cover the scheduling contract, the presentation hold and natural completion timing on a hosted layer, and a delayed removal completing end to end through the scheduled animation's delegate.
📝 WalkthroughWalkthroughThe change schedules delayed layer animations in layer time space, updates opacity retargeting, defines zero-duration transition behavior, expands tests, and adds a cross-platform animation playground with shared diagnostics. ChangesScheduled animation and opacity transitions
Estimated code review effort: 4 (Complex) | ~60 minutes Merge Risk: ⚪ Minimal · up to The PR changes delayed animation scheduling while preserving the production transition lifecycle. No actionable merge-blocking risk remains; only a localized Animate Lab resize follow-up and minor changelog cleanup are outstanding. Sequence Diagram(s)sequenceDiagram
participant ComposeView
participant RenderableTransition
participant CALayer
participant CABasicAnimation
ComposeView->>RenderableTransition: start or retarget transition
RenderableTransition->>CALayer: sample interrupted value
RenderableTransition->>CALayer: schedule animation with timing delay
CALayer->>CABasicAnimation: set layer-space beginTime
CALayer->>CALayer: update model value and add animation
CABasicAnimation-->>ComposeView: invoke completion after delay and duration
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 33.82% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 68 functions across 16 files. (3 skipped: 3 unsupported.)
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #5 +/- ##
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+ Coverage 93.84% 93.86% +0.01%
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Files 96 96
Lines 5526 5526
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+ Hits 5186 5187 +1
+ Misses 340 339 -1
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Inline comments:
In
`@ComposeUI/Sources/ComposeUI/ComposeNode/RenderItem/RenderableTransition`+Opacity.swift:
- Around line 149-161: The retargetOpacity animation path must complete
immediately when timing.timing.duration is zero, since updateAnimation and its
delegate are skipped. Add an explicit zero-duration completion path in
retargetOpacity while preserving the existing transition completion ordering,
and add a regression test covering zero-duration opacity removal.
In
`@ComposeUI/Tests/ComposeUITests/ComposeNode/RenderItem/RenderableTransition`+OpacityTests.swift:
- Around line 297-302: Remove the assignment that clears weakLayer before
expect(weakLayer).toEventually(beNil()), so the assertion observes the actual
layer lifetime; if needed to address the compiler warning, defer clearing
weakLayer until after the deallocation assertion.
In
`@playgrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/PlaygroundViews/Playground`+AnimateLabView.swift:
- Around line 92-94: Update the stage-size update closure to recalculate
boxLayer’s frame on every resize, including after the initial layout, while
preserving whether the box is currently left- or right-positioned. Adjust the
logic around positionBoxIfNeeded and the update callback so later
context.newFrame.size changes reposition the existing box instead of returning
early.
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ComposeUI/Sources/ComposeUI/Animations/CABasicAnimation+AnimationTiming.swiftComposeUI/Sources/ComposeUI/Animations/CALayer+Animations.swiftComposeUI/Sources/ComposeUI/ComposeNode/RenderItem/RenderableTransition+Opacity.swiftComposeUI/Tests/ComposeUITests/Animations/CALayer+AnimationsTests.swiftComposeUI/Tests/ComposeUITests/ComposeNode/RenderItem/RenderableTransition+OpacityTests.swiftComposeUI/Tests/ComposeUITests/ComposeView/ComposeView+TransitionTests.swiftplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS.xcodeproj/project.pbxprojplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/PlaygroundViews/Playground+AnimateLabView.swiftplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/ViewController.swiftplaygrounds/ComposeUIPlayground-macOS/ComposeUIPlayground-macOS.xcodeproj/project.pbxprojplaygrounds/ComposeUIPlayground-macOS/ComposeUIPlayground-macOS/ViewController.swift
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A scheduled to-only animation can't backwards-fill an unresolved from value: the fill shows the target for the whole delay window, then the animation snaps and plays. The timer-based delay never hit this because it created the animation after the wait, when Core Animation resolves the from value against the live presentation. Resolve an unresolved from value at dispatch, from the presentation value falling back to the model value. A nil optional boxes as NSNull through the generic value parameter, so both forms count as unresolved. The modifier node color animations now spell out their from value (presentation, then model, then clear), covering the never-set case where nil renders as clear, and fading instead of snapping on a first animated color change of an uncommitted layer.
A transition's completion rides on its animation's delegate, and a zero-duration timing never created an animation, so a zero-duration opacity or slide transition applied its end state without ever calling the completion, stranding the renderable in the removal bookkeeping. An instant transition (zero duration, zero delay) now applies the end state and completes synchronously. A zero-duration timing with a delay schedules the change as a snap instead: the animation is built with a sub-frame duration (Core Animation substitutes its default duration for a literal zero), holds the old value for the delay window through the fill mode, lands as an instant change after the delay, and completes through the delegate. The delay keeps one meaning everywhere: the visual change starts after the delay.
A delayed retargeting freezes the interrupted motion at its sampled value for the delay window, but the spring still launched with the velocity sampled before the freeze: the value sat still for the window and then took off with stale momentum. Carry the interrupted velocity only for an immediate retargeting, so a delayed spring launches from rest, continuing the freeze honestly.
A scheduled delayed transition is a real attached animation, so tearing it down (a superseding retargeting, a reset, or the layer leaving the layer tree) reports the animation as stopped and invokes the completion, where the cancelled timer stayed silent. The compose view cancels a transition's completion before any teardown, so the late call is inert there; the contract matters for direct transition users. Document the contract on the retargeting completion and pin the reset path: no synchronous call, exactly one call on a later run loop turn.
The released-layer test cleared its own weak reference to silence a mutation warning, so the lifetime assertion passed by construction; a `weak let` keeps the warning away and the reference honest. The hosted presentation test now waits for the presentation layer before unwrapping, and asserts the final value on the presentation instead of falling back to the model it already set. The end-to-end delayed removal now checks mid-window that the removal hasn't completed, so an immediately-completing regression can't pass it. An unhosted test comment claimed rendering behavior it can't observe; it now points at the hosted pin.
…ime space The delay elapses in the animated layer's time space, is not scaled by the animation's speed, and a scheduled animation only survives on a layer in a committed layer tree. Spell the contract out on the public delay field, the animate entry points, the animation factory, and the evaluator, and record the breaking changes in the changelog. The begin-time computation is the one line making delays correct under paused or speed-scaled layers, and every existing assertion ran on ordinary clocks where wall-clock time would also pass. Pin it on a speed-scaled layer, where the two time spaces diverge.
The animate value closures were escaping because the timer captured them; they now run synchronously, so the annotations advertised a lifetime that no longer exists. Coalesce the model fallback by value instead of by closure, collapse the retargeting fresh-start closure to a plain value, name the shared layer-time expression `currentTime` so the scheduler and the sampler visibly agree, and rename the shadowed animation key local.
The animate lab copied the transition revival page's logging toolkit: the animation describer, the value formatters, and the button factory were byte-identical twins, one font size apart. Move them into a shared Playground.Debug namespace and a shared button factory, and keep only the page-specific log prefixes and state describers in the pages.
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Inline comments:
In `@CHANGELOG.md`:
- Line 22: Update the ScrollViewType changelog entry by replacing the comma
between its independent clauses with a semicolon or “and,” while preserving the
existing wording.
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📒 Files selected for processing (17)
CHANGELOG.mdComposeUI/Sources/ComposeUI/Animations/AnimationTiming.swiftComposeUI/Sources/ComposeUI/Animations/CABasicAnimation+AnimationTiming.swiftComposeUI/Sources/ComposeUI/Animations/CABasicAnimation+Evaluate.swiftComposeUI/Sources/ComposeUI/Animations/CALayer+Animations.swiftComposeUI/Sources/ComposeUI/ComposeNode/RenderItem/RenderableTransition+Opacity.swiftComposeUI/Sources/ComposeUI/ComposeNode/RenderItem/RenderableTransition+Slide.swiftComposeUI/Sources/ComposeUI/ComposeNodes/ModifierNode.swiftComposeUI/Tests/ComposeUITests/Animations/CALayer+AnimationsTests.swiftComposeUI/Tests/ComposeUITests/ComposeNode/RenderItem/RenderableTransition+OpacityTests.swiftComposeUI/Tests/ComposeUITests/ComposeNode/RenderItem/RenderableTransition+SlideTests.swiftComposeUI/Tests/ComposeUITests/ComposeView/ComposeView+TransitionTests.swiftplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS.xcodeproj/project.pbxprojplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/PlaygroundViews/Playground+AnimateLabView.swiftplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/PlaygroundViews/Playground+Debug.swiftplaygrounds/ComposeUIPlayground-iOS/ComposeUIPlayground-iOS/PlaygroundViews/Playground+TransitionRevivalView.swiftplaygrounds/ComposeUIPlayground-macOS/ComposeUIPlayground-macOS.xcodeproj/project.pbxproj
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Adding the unreleased section inadvertently carried a stray edit into the released 0.0.5 entry, turning its semicolon into a comma splice. Recast the entry as a single clause.
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Summary
Replaces the GCD timer delay in
CALayer.animate()with Core Animation's native scheduling, simplifies the opacity retargeting on top of it, and hardens the semantics through three independent strict reviews plus bot-review triage (one commit per issue).animate()(CALayer+Animations.swift)beginTime = layer.currentTime + delayin the layer's time space. The delay elapses in the layer's time space: a paused or speed-scaled layer scales pending delays with it..bothfill mode (backwards fill) holds thefromvalue on screen for the delay window while the model value is already set, so the rendered output matches the old timer behavior.from/toare evaluated before the model write, preserving additive from-delta correctness. An unresolved (nil) from value on a scheduled non-additive animation is resolved at dispatch (presentation value, falling back to the model value), because the fill can't hold an unresolved value — theModifierNodecolor animations also spell out their from values explicitly (presentation → model → clear).retargetOpacity(RenderableTransition+Opacity.swift)A delayed retargeting is now a real attached animation, so the behaviors the timer machinery had to reimplement come from the framework's normal paths:
isInFlightprobe, and pre-hide model write are deleted; the fresh-insert hold falls out of the held from delta.delay()utilityKept as a general-purpose utility (no longer used by the animate path).
Tests
fromValue, futurebeginTime), making them deterministic.weak let), the hosted test guardspresentation()before unwrapping, and unhosted test comments no longer claim rendering behavior they can't observe.Review provenance
Three independent strict reviews (structural + correctness) triaged into 8 fix commits; CodeRabbit and Codex PR comments triaged, replied, and resolved (two were duplicates of the review findings and were already fixed; two were declined with rationale on the threads).
Verification