When do you use PhaseAnimator, Canvas and TimelineView?

PhaseAnimator cycles a view through a list of phases (any Sequence of values), applying a content closure per phase and an animation closure for each transition between them. It suits looping or triggered effects (a pulse, a “shake then settle”) without a state machine; pass a trigger to run it once per change instead of continuously. For richer timing across several properties, keyframeAnimator lets you define tracks of keyframes (linear, spring, cubic) for a value struct. Both run in SwiftUI’s animation system, so they honour Reduce Motion only if you handle it.

Canvas is an immediate-mode drawing surface: a closure receives a GraphicsContext and size and draws paths, images, text and resolved symbols directly, with no per-item view or identity. That makes it far cheaper than thousands of views for particles, charts, grids and games, at the cost of no accessibility and no built-in interaction (you add gestures, and accessibility labels on the container, yourself). TimelineView re-evaluates its content on a schedule (every frame with .animation, periodic, or at specific dates) and passes the current date, which is the way to draw things that change with time: clocks, countdowns, or a Canvas animated by the date. Combined as TimelineView(.animation) { ctx in Canvas { … } }, they form SwiftUI’s particle and custom-animation engine. Pick views for most UI, Canvas when the count of items makes views too heavy, and TimelineView when time itself is the input.