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grid.ts
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grid.ts
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/**
* Copyright 2021 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import {
AbstractViewportAlgorithm,
AlgorithmInput,
AlgorithmOutput,
ViewportAlgorithmOptions,
} from "./core";
import {
distanceBetweenPoints,
extendBoundsToPaddedViewport,
filterMarkersToPaddedViewport,
} from "./utils";
import { Cluster } from "../cluster";
import equal from "fast-deep-equal";
import { MarkerUtils, Marker } from "../marker-utils";
export interface GridOptions extends ViewportAlgorithmOptions {
gridSize?: number;
/**
* Max distance between cluster center and point in meters.
* @default 10000
*/
maxDistance?: number;
}
/**
* The default Grid algorithm historically used in Google Maps marker
* clustering.
*
* The Grid algorithm does not implement caching and markers may flash as the
* viewport changes. Instead use {@link SuperClusterAlgorithm}.
*/
export class GridAlgorithm extends AbstractViewportAlgorithm {
protected gridSize: number;
protected maxDistance: number;
protected clusters: Cluster[] = [];
protected state: { zoom: number };
constructor({ maxDistance = 40000, gridSize = 40, ...options }: GridOptions) {
super(options);
this.maxDistance = maxDistance;
this.gridSize = gridSize;
this.state = { zoom: null };
}
public calculate({
markers,
map,
mapCanvasProjection,
}: AlgorithmInput): AlgorithmOutput {
const state = { zoom: map.getZoom() };
let changed = false;
if (this.state.zoom > this.maxZoom && state.zoom > this.maxZoom) {
// still beyond maxZoom, no change
} else {
changed = !equal(this.state, state);
}
this.state = state;
if (map.getZoom() >= this.maxZoom) {
return {
clusters: this.noop({
markers,
}),
changed,
};
}
return {
clusters: this.cluster({
markers: filterMarkersToPaddedViewport(
map,
mapCanvasProjection,
markers,
this.viewportPadding
),
map,
mapCanvasProjection,
}),
};
}
protected cluster({
markers,
map,
mapCanvasProjection,
}: AlgorithmInput): Cluster[] {
this.clusters = [];
markers.forEach((marker) => {
this.addToClosestCluster(marker, map, mapCanvasProjection);
});
return this.clusters;
}
protected addToClosestCluster(
marker: Marker,
map: google.maps.Map,
projection: google.maps.MapCanvasProjection
): void {
let maxDistance = this.maxDistance; // Some large number
let cluster: Cluster = null;
for (let i = 0; i < this.clusters.length; i++) {
const candidate = this.clusters[i];
const distance = distanceBetweenPoints(
candidate.bounds.getCenter().toJSON(),
MarkerUtils.getPosition(marker).toJSON()
);
if (distance < maxDistance) {
maxDistance = distance;
cluster = candidate;
}
}
if (
cluster &&
extendBoundsToPaddedViewport(
cluster.bounds,
projection,
this.gridSize
).contains(MarkerUtils.getPosition(marker))
) {
cluster.push(marker);
} else {
const cluster = new Cluster({ markers: [marker] });
this.clusters.push(cluster);
}
}
}