Transitioncomponent

Wrap children in a React View Transition, applying the configured transition classes.

• Allows known view transition types in TransitionClasses (default/forward/back) to be overridden.
  
  • These must correspond to a ::view-transition(.className) that is set in CSS.
• Supports variant classes, e.g. <Transition overlay> applies ::view-transition(.overlay) from Transition.css.

The base View Transition wrapper. It wraps its children in React 19's <ViewTransition> and applies named CSS transition classes, so swapping content between renders produces a smooth animation. Use it directly to specify any transition class names, or reach for a preset variant — <FadeTransition>, <CollapseTransition>, <VerticalTransition>, <HorizontalTransition>.

Things to know:

• Set default for the base transition; forward and back default to it and let you pick a direction-aware variant. The class names must correspond to ::view-transition-old(.className) / ::view-transition-new(.className) rules in your CSS.
• Pass overlay to raise the transition group above surrounding content during the animation (z-index: 100, from Transition.css).
• Direction is driven by the active view-transition type. Call setTransitionType("forward") (or "back") inside a startTransition() callback before navigating; the variants read that type to choose the correct slide.

Usage

Custom transition

import { Transition } from "shelving/ui";

<Transition default="zoom" forward="zoomIn" back="zoomOut">
  {children}
</Transition>

Overlay

import { Transition } from "shelving/ui";

<Transition default="fade" overlay>
  <Notification/>
</Transition>

Setting the direction with setTransitionType()

import { HorizontalTransition, setTransitionType, requireNavigation } from "shelving/ui";
import { startTransition } from "react";

function go(direction: "forward" | "back", url: string) {
  const nav = requireNavigation();
  startTransition(() => {
    setTransitionType(direction);
    nav.forward(url);
  });
}

// In the layout — slides right on forward, left on back:
<HorizontalTransition>
  <Router routes={ROUTES}/>
</HorizontalTransition>

Styling

Transitions are driven by CSS ::view-transition-* pseudo-element rules keyed on the transition class names, not by per-component --variable hooks. <Transition> itself only ships the overlay rule:

The overlay variant sets z-index: 100 on ::view-transition-group(.overlay). The preset variants document their own timing/distance hooks (--fade-transition-duration, --vertical-transition-size / -duration, --horizontal-transition-size / -duration) on their pages.

Global tokens it reads — none directly; the preset variants fall back to --duration-fast / --duration-normal.