Transitions

Transition components are utilities that let you add motion to components.

Introduction

Base UI offers higher-level components and low-level hooks that can be used to add animations to components as they enter and exit the screen.

Components

Base UI offers two components to cover the majority of use cases using CSS transitions and animations.

CSS Transition

With a CSS transition, you can smoothly change CSS property values. The CSS Transition component works by adding specified class names when an element should be visible and hidden; it's up to you to define any transitions for these classes.

The following example defines the open and close classes, and sets the CSS Transition component to apply them accordingly: Since the close class has multiple transitions with different durations (transform transitions for 400ms, and opacity and filter transitions for 200ms), you must let the transition component know which property takes the longest to finish. The lastTransitionedPropertyOnExit serves exactly this purpose.

<style>{styles}</style>
<PopupWithTrigger>
  <CssTransition
    enterClassName="open"
    exitClassName="close"
    lastTransitionedPropertyOnExit="transform"
  >
    <PopupBody>This is an animated popup</PopupBody>
  </CssTransition>
</PopupWithTrigger>

<style>{styles}</style>
<PopupWithTrigger>
  <CssTransition
    enterClassName="open"
    exitClassName="close"
    lastTransitionedPropertyOnExit="transform"
  >
    <PopupBody>This is an animated popup</PopupBody>
  </CssTransition>
</PopupWithTrigger>

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Normally, if an element appears in the DOM and already has a CSS class with a transition, this transition is not fired (because there's no state to transition from). The CSS Transition component works around this issue by mounting the component with the exitClassName and, after a brief moment, changing the class name to enterClassName. This ensures the enter transition is applied even if the transitioned element is removed from the DOM when exited.

CSS Animation

CSS animations offer more flexibility than transitions. You can define multiple keyframes for better control over animation playback.

The CSS Animation component triggers an animation by applying a CSS class (either from the enterClassName or exitClassName prop).

<style>{styles}</style>
<PopupWithTrigger>
  <CssAnimation
    enterClassName="anim-open"
    exitClassName="anim-close"
    enterAnimationName="open-animation"
    exitAnimationName="close-animation"
  >
    <PopupBody>This is an animated popup</PopupBody>
  </CssAnimation>
</PopupWithTrigger>

<style>{styles}</style>
<PopupWithTrigger>
  <CssAnimation
    enterClassName="anim-open"
    exitClassName="anim-close"
    enterAnimationName="open-animation"
    exitAnimationName="close-animation"
  >
    <PopupBody>This is an animated popup</PopupBody>
  </CssAnimation>
</PopupWithTrigger>

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Hooks

If the built-in components don't cover your needs, or if you want to trigger transitions from your components, you can use the useTransitionTrigger and useTransitionStateManager hooks. Use the useTransitionTrigger hook in the component that controls the transitions—for example, the Popup uses it internally to request the appearance of its contents.

Use the useTransitionStateManager with the components that need to be transitioned. The CSS Animation and CSS Transition components call this hook when being rendered.

Calling useTransitionTrigger returns a context (along with other properties) that's read by useTransitionStateManager.

<Trivia label="Did you know?">
  <SlideDown>
    The Eiffel Tower can grow more than six inches during the summer thanks to
    heat expanding the iron.
  </SlideDown>
</Trivia>

<Trivia label="Did you know?">
  <SlideDown>
    The Eiffel Tower can grow more than six inches during the summer thanks to
    heat expanding the iron.
  </SlideDown>
</Trivia>

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Using third-party libraries

You can create a custom adapter to work with third-party animation libraries. Such an adapter should use the useTransitionStateManager hook and convert its result into a format the library understands.

See the examples below.

Material UI (React Transition Group)

You can use any of the transitions from Material UI, or custom transitions built with React Transition Group, using an adapter shown in the following demo.

<PopupWithTrigger>
  <MaterialUITransitionAdapter>
    <Fade timeout={250}>
      <PopupBody>This is an animated popup</PopupBody>
    </Fade>
  </MaterialUITransitionAdapter>
</PopupWithTrigger>

<PopupWithTrigger>
  <MaterialUITransitionAdapter>
    <Fade timeout={250}>
      <PopupBody>This is an animated popup</PopupBody>
    </Fade>
  </MaterialUITransitionAdapter>
</PopupWithTrigger>

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React Spring

React Spring, another popular animation library, also can be used with the Base UI transitions API.

<PopupWithTrigger>
  <ReactSpringTransition>
    <PopupBody>This is an animated popup</PopupBody>
  </ReactSpringTransition>
</PopupWithTrigger>

<PopupWithTrigger>
  <ReactSpringTransition>
    <PopupBody>This is an animated popup</PopupBody>
  </ReactSpringTransition>
</PopupWithTrigger>

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