Implementing a dynamic JSX element within a marker, using react-leaflet

Question

I have a React app in which I am using Leaflet through react-leaflet, both super useful libraries.

In this app, I have a group of coordinates that need to be rendered as follows:

1. When zoomed out, cluster the coordinates into Marker Clusters like so

2. When zoomed in, each Marker needs to have

   1. A dynamic countdown timer under it
   2. A dynamic SVG countdown clock around it like so

For the clustering, I am using the react-leaflet-markercluster plugin, which works great for showing static content.

But when I need to show any dynamic content within each marker, I have no option of sending in JSX, there's only provision for static HTML as can been seen from the example available here.

// Template for getting popup html MarkerClusterGroup
// IMPORTANT: that function returns string, not JSX
function getStringPopup(name) {
  return (`
    <div>
      <b>Hello world!</b>
      <p>I am a ${name} popup.</p>
    </div>
  `);
}

// that function returns Leaflet.Popup
function getLeafletPopup(name) {
  return L.popup({ minWidth: 200, closeButton: false })
    .setContent(`
      <div>
        <b>Hello world!</b>
        <p>I am a ${name} popup.</p>
      </div>
    `);
}

Is there a way to handle this situation? How can I make a JSX marker instead of a static HTML marker?

PS: I have tried using ReactDOM.renderToStringalready, but it's an ugly hack and involves re-rendering the markers every time.

TIA!!

Here's a sample WebpackBin for you to play around with if you have a solution in mind

Answer 1

I now figured out some working code for rendering custom JSX as Marker.

It's a 95% copy of https://jahed.dev/2018/03/20/react-portals-and-leaflet/ and 5% inspiration from https://github.com/PaulLeCam/react-leaflet/blob/master/packages/react-leaflet/src/Marker.tsx

I'm sure some things can be optimized further.

import * as React from 'react';
import { createPortal } from "react-dom";
import { DivIcon, marker } from "leaflet";
import * as RL from "react-leaflet";
import { MapLayer } from "react-leaflet";
import { difference } from "lodash";

const CustomMarker = (RL as any).withLeaflet(class extends MapLayer<any> {
    leafletElement: any;
    contextValue: any;

    createLeafletElement(props: any) {
        const { map, layerContainer, position, ...rest } = props;

// when not providing className, the element's background is a white square
// when not providing iconSize, the element will be 12x12 pixels
        const icon = new DivIcon({ ...rest, className: '', iconSize: undefined });

        const el = marker(position, { icon: icon, ...rest });
        this.contextValue = { ...props.leaflet, popupContainer: el };
        return el;
    }

    updateLeafletElement(fromProps: any, toProps: any) {
        const { position: fromPosition, zIndexOffset: fromZIndexOffset, opacity: fromOpacity, draggable: fromDraggable, className: fromClassName } = fromProps;
        const { position: toPosition, zIndexOffset: toZIndexOffset, toOpacity, draggable: toDraggable, className: toClassName } = toProps;

        if(toPosition !== fromPosition) {
            this.leafletElement.setLatLng(toPosition);
        }
        if(toZIndexOffset !== fromZIndexOffset) {
            this.leafletElement.setZIndexOffset(toZIndexOffset);
        }
        if(toOpacity !== fromOpacity) {
            this.leafletElement.setOpacity(toOpacity);
        }
        if(toDraggable !== fromDraggable) {
            if(toDraggable) {
                this.leafletElement.dragging.enable();
            } else {
                this.leafletElement.dragging.disable();
            }
        }
        if(toClassName !== fromClassName) {
            const fromClasses = fromClassName.split(" ");
            const toClasses = toClassName.split(" ");
            this.leafletElement._icon.classList.remove(
                ...difference(fromClasses, toClasses)
            );
            this.leafletElement._icon.classList.add(
                ...difference(toClasses, fromClasses)
            );
        }
    }

    componentWillMount() {
        if(super.componentWillMount) {
            super.componentWillMount();
        }
        this.leafletElement = this.createLeafletElement(this.props);
        this.leafletElement.on("add", () => this.forceUpdate());
    }

    componentDidUpdate(fromProps: any) {
        this.updateLeafletElement(fromProps, this.props);
    }

    render() {
        const { children } = this.props;
        const container = this.leafletElement._icon;

        if(!container) {
            return null;
        }

        const portal = createPortal(children, container);

        const LeafletProvider = (RL as any).LeafletProvider;

        return children == null || portal == null || this.contextValue == null ? null : (
            <LeafletProvider value={this.contextValue}>{portal}</LeafletProvider>
        )
    }
});

And then just use it in you component like this:

<Map ...>
  <CustomMarker position={[50, 10]}>
    <Tooltip>
      tooltip
    </Tooltip>
    <Popup>
      popup
    </Popup>
    
    <div style={{ backgroundColor: 'red' }} onClick={() => console.log("CLICK")}>
      CUSTOM MARKER CONTENT
    </div>
    MORE CONTENT
  </CustomMarker>
</Map>

If you don't use TypeScript. Just remove the as any and : any stuff.

---

EDIT: Something automatically sets width: 12px; and height: 12px;. I'm not yet sure, how to prevent this. Everything else seems to work fine!

EDIT2: Fixed it! Using iconSize: undefined

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EDIT3: There's also this: https://github.com/OpenGov/react-leaflet-marker-layer Haven't tested it, but the example code looks good.