v0.4.0 Wave 19: animation enhancements (triggers, delays, motion paths, reduce-motion, Animation Pane)

[900Labs]

Summary

Wave 19 extends the animation system with triggers (OnClick/WithPrevious/AfterPrevious), delays, motion paths, a per-slide reduce-motion override, and a dedicated Animation Pane.

What changed

Model (slides-core)

• Trigger enum (OnClick/WithPrevious/AfterPrevious). BuildStep gains trigger, delay_ms, motion_path: Option<Vec<Rect>>. BuildEffect::MotionPath variant. Slide.reduce_motion: Option<bool>.
• 4 reversible commands: SetBuildStepTrigger, SetBuildStepDelay, SetBuildStepMotionPath, SetSlideReduceMotion.
• All additive (#[serde(default)]) — old decks behave identically.

Animation crate (slides-animation)

• build_timeline is now trigger-aware: WithPrevious fires simultaneously, AfterPrevious chains after the prior step's end. Click groups computed.
• Motion path interpolation: linear between waypoints, duration split evenly.
• build_timeline_reduced: instant frames for reduce-motion mode.
• CSS keyframes for motion paths.

Desktop (apps/desktop/)

• AnimationPane.svelte (+363 lines): ordered step list with trigger dropdown, duration/delay sliders, drag-to-reorder, reduce-motion toggle.
• MotionPathEditor.svelte (+202 lines): canvas-based waypoint editor with click-to-add, save/cancel.
• 4 Tauri commands, all transactional. Zero @html.

Review process

Control-tower pipeline on all 3 components. Model: fully CLEAN. Animation crate: CLEAN (1 NIT — Eq dropped from BuildFrame due to f64, harmless). Desktop: fully CLEAN. One svelte-check warning fixed before merge.

Test results

• 373 workspace tests pass (slides-core +10, slides-animation +9).
• npm run check (svelte-check): 0 errors, 0 warnings.
• scripts/verify-local.sh: green. scripts/verify-public-release.sh: green.

Remaining v0.4.0 item

Wave 20: custom layouts per template + rehearse timings (final v0.4.0 wave).