visgl / deck.gl / 8255023837

import Transition, {TransitionSettings as BaseTransitionSettings} from '../transitions/transition';

import TransitionInterpolator from '../transitions/transition-interpolator';

import type {IViewState} from './view-state';

import type {Timeline} from '@luma.gl/engine';

import type {InteractionState} from './controller';

const noop = () => {};

// Enums cannot be directly exported as they are not transpiled correctly into ES5, see https://github.com/visgl/deck.gl/issues/7130

export const TRANSITION_EVENTS = {

  BREAK: 1,

  SNAP_TO_END: 2,

  IGNORE: 3

} as const;

type TransitionEvent = 1 | 2 | 3;

export type TransitionProps = {

  /** Transition duration in milliseconds, default value 0, implies no transition. When using `FlyToInterpolator`, it can also be set to `'auto'`. */

  transitionDuration?: number | 'auto';

  /** An interpolator object that defines the transition behavior between two viewports. */

  transitionInterpolator?: TransitionInterpolator;

  /** Easing function that can be used to achieve effects like "Ease-In-Cubic", "Ease-Out-Cubic", etc. Default value performs Linear easing. */

  transitionEasing?: (t: number) => number;

  /** Controls how to process a new view state change that occurs during an existing transition. */

  transitionInterruption?: TransitionEvent;

  /** Callback fired when requested transition starts. */

  onTransitionStart?: (transition: Transition) => void;

  /** Callback fired when requested transition is interrupted. */

  onTransitionInterrupt?: (transition: Transition) => void;

  /** Callback fired when requested transition ends. */

  onTransitionEnd?: (transition: Transition) => void;

};

const DEFAULT_EASING = t => t;

const DEFAULT_INTERRUPTION = TRANSITION_EVENTS.BREAK;

type TransitionSettings = BaseTransitionSettings & {

  interpolator: TransitionInterpolator;

  easing: (t: number) => number;

  interruption: TransitionEvent;

  startProps: Record<string, any>;

  endProps: Record<string, any>;

};

export default class TransitionManager<ControllerState extends IViewState<ControllerState>> {

  getControllerState: (props: any) => ControllerState;

  props?: TransitionProps;

  propsInTransition: Record<string, any> | null;

  transition: Transition;

  onViewStateChange: (params: {

    viewState: Record<string, any>;

    oldViewState: Record<string, any>;

  }) => void;

  onStateChange: (state: InteractionState) => void;

  constructor(opts: {

    timeline: Timeline;

    getControllerState: (props: any) => ControllerState;

    onViewStateChange?: (params: {

      viewState: Record<string, any>;

      oldViewState: Record<string, any>;

    }) => void;

    onStateChange?: (state: InteractionState) => void;

  }) {

    this.getControllerState = opts.getControllerState;

    this.propsInTransition = null;

    this.transition = new Transition(opts.timeline);

  }

  finalize(): void {

    this.transition.cancel();

  }

  // Returns current transitioned viewport.

  getViewportInTransition(): Record<string, any> | null {

  // Process the vewiport change, either ignore or trigger a new transition.

  // Return true if a new transition is triggered, false otherwise.

  processViewStateChange(nextProps: TransitionProps) {

    let transitionTriggered = false;

    const currentProps = this.props;

    // Set this.props here as '_triggerTransition' calls '_updateViewport' that uses this.props.

    this.props = nextProps;

    // NOTE: Be cautious re-ordering statements in this function.

    if (!currentProps || this._shouldIgnoreViewportChange(currentProps, nextProps)) {

      return false;

    }

    if (this._isTransitionEnabled(nextProps)) {

      let startProps = currentProps;

      this._triggerTransition(startProps, nextProps);

      transitionTriggered = true;

    return transitionTriggered;

  }

  updateTransition() {

    this.transition.update();

  }

  // Helper methods

  _isTransitionEnabled(props: TransitionProps): boolean {

    const {transitionDuration, transitionInterpolator} = props;

    return (

      ((transitionDuration as number) > 0 || transitionDuration === 'auto') &&

      Boolean(transitionInterpolator)

    );

  }

  _isUpdateDueToCurrentTransition(props: TransitionProps): boolean {

    if (this.transition.inProgress && this.propsInTransition) {

      // @ts-expect-error

      return (this.transition.settings as TransitionSettings).interpolator.arePropsEqual(

        props,

        this.propsInTransition

      );

  }

  _shouldIgnoreViewportChange(currentProps: TransitionProps, nextProps: TransitionProps): boolean {

    if (this.transition.inProgress) {

      // @ts-expect-error

      const transitionSettings = this.transition.settings as TransitionSettings;

      // Ignore update if it is requested to be ignored

      return (

        transitionSettings.interruption === TRANSITION_EVENTS.IGNORE ||

        // Ignore update if it is due to current active transition.

        this._isUpdateDueToCurrentTransition(nextProps)

      );

    }

    if (this._isTransitionEnabled(nextProps)) {

      // Ignore if none of the viewport props changed.

      return (nextProps.transitionInterpolator as TransitionInterpolator).arePropsEqual(

        currentProps,

        nextProps

      );

    }

    return true;

  }

  _triggerTransition(startProps: TransitionProps, endProps: TransitionProps): void {

    const startViewstate = this.getControllerState(startProps);

    const endViewStateProps = this.getControllerState(endProps).shortestPathFrom(startViewstate);

    // update transitionDuration for 'auto' mode

    const transitionInterpolator = endProps.transitionInterpolator as TransitionInterpolator;

    const duration = transitionInterpolator.getDuration

    const initialProps = transitionInterpolator.initializeProps(startProps, endViewStateProps);

    this.propsInTransition = {};

    const transitionSettings: TransitionSettings = {

      duration,

      easing: endProps.transitionEasing || DEFAULT_EASING,

      interpolator: transitionInterpolator,

      interruption: endProps.transitionInterruption || DEFAULT_INTERRUPTION,

      startProps: initialProps.start,

      endProps: initialProps.end,

      onStart: endProps.onTransitionStart,

      onUpdate: this._onTransitionUpdate,

      onInterrupt: this._onTransitionEnd(endProps.onTransitionInterrupt),

      onEnd: this._onTransitionEnd(endProps.onTransitionEnd)

    };

    this.transition.start(transitionSettings);

    this.onStateChange({inTransition: true});

    this.updateTransition();

  }

  _onTransitionEnd(callback?: (transition: Transition) => void) {

    return transition => {

      this.propsInTransition = null;

      this.onStateChange({

        inTransition: false,

        isZooming: false,

        isPanning: false,

        isRotating: false

      });

    };

  }

  _onTransitionUpdate = transition => {

    // NOTE: Be cautious re-ordering statements in this function.

    const {

      time,

      settings: {interpolator, startProps, endProps, duration, easing}

    } = transition;

    const t = easing(time / duration);

    const viewport = interpolator.interpolateProps(startProps, endProps, t);

    // This gurantees all props (e.g. bearing, longitude) are normalized

    // So when viewports are compared they are in same range.

    this.propsInTransition = this.getControllerState({

      ...this.props,

      ...viewport

    }).getViewportProps();

    this.onViewStateChange({

      viewState: this.propsInTransition,

      oldViewState: this.props as TransitionProps

    });

  };

}