@deck.gl/core/dist/transitions/linear-interpolator.js

deck.gl core library

// deck.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
import TransitionInterpolator from "./transition-interpolator.js";
import { lerp } from '@math.gl/core';
const DEFAULT_PROPS = ['longitude', 'latitude', 'zoom', 'bearing', 'pitch'];
const DEFAULT_REQUIRED_PROPS = ['longitude', 'latitude', 'zoom'];
/**
 * Performs linear interpolation of two view states.
 */
export default class LinearInterpolator extends TransitionInterpolator {
    /**
     * @param {Object} opts
     * @param {Array} opts.transitionProps - list of props to apply linear transition to.
     * @param {Array} opts.around - a screen point to zoom/rotate around.
     * @param {Function} opts.makeViewport - construct a viewport instance with given props.
     */
    constructor(opts = {}) {
        // Backward compatibility
        const transitionProps = Array.isArray(opts) ? opts : opts.transitionProps;
        const normalizedOpts = Array.isArray(opts) ? {} : opts;
        normalizedOpts.transitionProps = Array.isArray(transitionProps)
            ? {
                compare: transitionProps,
                required: transitionProps
            }
            : transitionProps || {
                compare: DEFAULT_PROPS,
                required: DEFAULT_REQUIRED_PROPS
            };
        super(normalizedOpts.transitionProps);
        this.opts = normalizedOpts;
    }
    initializeProps(startProps, endProps) {
        const result = super.initializeProps(startProps, endProps);
        const { makeViewport, around } = this.opts;
        if (makeViewport && around) {
            const startViewport = makeViewport(startProps);
            const endViewport = makeViewport(endProps);
            const aroundPosition = startViewport.unproject(around);
            result.start.around = around;
            Object.assign(result.end, {
                around: endViewport.project(aroundPosition),
                aroundPosition,
                width: endProps.width,
                height: endProps.height
            });
        }
        return result;
    }
    interpolateProps(startProps, endProps, t) {
        const propsInTransition = {};
        for (const key of this._propsToExtract) {
            propsInTransition[key] = lerp(startProps[key] || 0, endProps[key] || 0, t);
        }
        if (endProps.aroundPosition && this.opts.makeViewport) {
            // Linear transition should be performed in common space
            const viewport = this.opts.makeViewport({ ...endProps, ...propsInTransition });
            Object.assign(propsInTransition, viewport.panByPosition(endProps.aroundPosition, 
            // anchor point in current screen coordinates
            lerp(startProps.around, endProps.around, t)));
        }
        return propsInTransition;
    }
}
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