Migrating to 2.0

Lagrangian 2.0 makes the world deterministic. The API of springs, dragging, the scroller and the adapters is unchanged, so most projects only update the version.

pnpm update @sweberdev/lagrangian @sweberdev/lagrangian-react @sweberdev/lagrangian-svelte

What changed

• Sleeping and sensors are decided in every simulation step, not once per animation frame. A body still falls asleep after a second at rest, but the exact moment no longer depends on the frame rate, and onEnter and onLeave fire in the step in which a body crosses the edge. In a few scenes a body now falls asleep or triggers a sensor one or two frames earlier or later than before.
• world.step(dt) also settles and senses. In 1.x a manual step moved the bodies only. Now it does everything a frame does except drawing, so a manually stepped world matches a running one.
• Node 22 or newer is required to build and test (Node 20 reached its end of life). The packages run in every browser they ran in before.

Keep the old behaviour

const world = new World({ bounds, legacyStepping: true });

legacyStepping restores the 1.x timing of sleeping and sensors. It is meant as a bridge: it is removed in 2.1, and a world with it is not reproducible across frame rates.

New in 2.0

• seed and world.random() for random numbers that repeat.
• world.advance(seconds), world.time, world.snapshot(), world.restore() and world.hash(). See Reproducible runs.
• Lagrangian Pro 1.0.1 and newer works with 2.x. Pro 1.0.0 declares a peer range below 2: update it first (pnpm update @weber-development/lagrangian-pro) or your package manager warns.

Lagrangian Pro 2.0

Pro 2.0 is the same API plus new parts, so most projects only update the version. Two behaviours change:

• Parts start dragging after the finger moved a few pixels, not on touch-down, so that a part around another one can find out who gets the finger. A tap no longer stops a running animation of a sheet, drawer or carousel until the finger moves. See Gestures.
• Nested parts hand over: a carousel on its last slide passes a swipe outwards to the drawer or page around it, where 1.x moved both.

New in Pro 2.0: stack navigation (stackNav, useStackNav), the gesture referee contend, and the packages @weber-development/lagrangian-pro-vue and @weber-development/lagrangian-pro-svelte. Pro 1.0.1 and newer allow Lagrangian 2 in their peer range.

Removed

Nothing from the 1.x API was marked deprecated, so no export is removed.

Not yet available

@sweberdev/lagrangian-vue could not be published to npm so far (the registry rejects the first publish of the new package). It will follow at the same version as soon as that works.