CODEWITHSUNDEEP
javascriptleafletgeojson
J. Pierson
J. Pierson

Reputation: 103

Leaflet : ordering GeoJSON elements inside a layer

I'm displaying a GeoJSON layer using leaflet, with the pointToLayer function. Everything works ok so far.

But I would like to display my points in a certain order, based on a property of the GeoJSON. This is important because the radiuses of my points varies with this property, and I need to display the smaller circles on top. I hope I make myself clear.

I've tried many things, but here's what I think is my best try :

var pointLayer = L.geoJson(centroids, {
                pointToLayer: function (feature, latlng) {
                    return L.circleMarker(latlng, {
                        fillColor: "#76C551",
                        color: "#000",
                        weight: 1,
                        fillOpacity: 1
                    });
                },
                onEachFeature: function (feature, layer) {
                    var radius = calcPropRadius(feature.properties.nb);
                    layer.setRadius(radius);
                    feature.zIndexOffset = 1/feature.properties.nb*1000;
                    layer.bindPopup(feature.properties.name + " : " + String(feature.zIndexOffset));
                }
            });

You can notice that the zIndexOffset of features can be read in the popups, and they look ok. But the displaying order of the circles doesn't reflect the zIndexOffset. I've tried using the setZIndexOffset method, but as I understand it it works only with markers.

Does anyone know how to do this ? Thanks a lot for any insight !

Upvotes: 6

Views: 2198

Answers (3)

F. ALA
F. ALA

Reputation: 1031

I'd like to offer an alternative which worked for me on a similar problem.

In my case, my data had a "status" which changed over time and I needed the most critical ones to always be on top. So I ordered the data before drawing, something like:

myData.features.sort((a,b) => a.properties.status <= b.properties.status ? -1 : 1);
return (<GeoJSON data={myData}/>);

This way the critical ones were drawn last.

In your case, I believe you can order your centroids before the draw.

Upvotes: 0

J. Pierson
J. Pierson

Reputation: 103

Whereas ghybs answer works perfectly for leaflet 0.7, switching to leaflet 1.0 allows the use of panes which makes for an easier solution :

var pointLayer = L.geoJson(centroids, {
            pointToLayer: function (feature, latlng) {
                return L.circleMarker(latlng, {
                    fillColor: "#76C551",
                    color: "#000",
                    weight: 1,
                    fillOpacity: 1
                });
            },
            onEachFeature: function (feature, layer) {
                var radius = calcPropRadius(feature.properties.nb);
                layer.setRadius(radius);
                layer.setStyle({pane: 'pane'+ feature.properties.nb});
                var currentPane = map.createPane('pane' + feature.properties.nb);
                currentPane.style.zIndex = Math.round(1/feature.properties.nb*10000);
                layer.bindPopup(feature.properties.name + " : " + String(feature.zIndexOffset));
            }
        });

Hope it can be of use to someone else !

Upvotes: 4

ghybs
ghybs

Reputation: 53185

As you figured out, the zIndexOffset option is only for L.marker's.

L.circleMarker's go into the overlayPane and you can re-order them one to each other using .bringToFront() and .bringToBack() methods.

Upvotes: 2

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