Leaflet.D3SvgOverlay

An overlay class for Leaflet, a JS library for interactive maps. Allows drawing overlay using SVG with the help of D3, a JavaScript library for manipulating documents based on data.

Features

• Easy SVG-drawing with D3
• No limitations to polylines, circles or geoJSON. Draw whatever you want with SVG
• No need to reproject your geometries on zoom, this is done using SVG scaling
• Zoom animation where Leaflet supports it

Compatible with Leaflet 0.7.x / 1.0.x

Demo

• Simple example: Swiss cities
• GeoJSON with D3

Basic usage

Include the dependency libraries:

<link href='https://cdnjs.cloudflare.com/ajax/libs/leaflet/0.7.5/leaflet.css'
           rel='stylesheet' type='text/css'/>
<script src="https://cdnjs.cloudflare.com/ajax/libs/leaflet/0.7.5/leaflet-src.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.9/d3.min.js"></script>

Include the D3SvgOverlay library:

<script src="L.D3SvgOverlay.min.js"></script>

Create a map:

var map = L.map(...);

Create an overlay:

var d3Overlay = L.d3SvgOverlay(function(selection, projection){

    var updateSelection = selection.selectAll('circle').data(dataset);
    updateSelection.enter()
        .append('circle')
        ...
        .attr("cx", function(d) { return projection.latLngToLayerPoint(d.latLng).x })
        .attr("cy", function(d) { return projection.latLngToLayerPoint(d.latLng).y });
    
});

Add it to the map:

d3Overlay.addTo(map);

Note: within the drawing callback function you can and should use the normal D3 workflow with update, .enter() and .exit() selections.

API

Factory method

L.d3SvgOverlay(<function> drawCallback, <options> options?)

• drawCallback - callback to draw/update overlay contents, it's called with arguments:
• options - overlay options object:

Drawing callback function

drawCallback(selection, projection)

• selection - D3 selection of a parent element for drawing. Put your SVG elements bound to data here
• projection - projection object. Contains methods to work with layers coordinate system and scaling

Overlay options object

available fields:

• zoomHide - (bool) hide the layer while zooming. Default is false. Useful when overlay contains a lot of elements and animation is laggy.
• zoomDraw - (bool) whether to trigger drawCallback on after zooming is done. Default is true. Useful e.g. when you want to adjust size or width of the elements depending on zoom.

Projection object

available methods/fields:

• latLngToLayerPoint(latLng, zoom?) - (function) returns L.Point projected from L.LatLng in the coordinate system of the overlay.
• layerPointToLatLng(point, zoom?) - (function) returns L.LatLng projected back from L.Point into the original CRS.
• unitsPerMeter - (float) this is a number of the overlay coordinate system units in 1 meter. Useful to get dimensions in meters.
• scale - scale of current zoom compared to the zoom level of overlay coordinate system. Useful if you want to make your elements of a size independent of zoom. Just divide the size by the scale.
• map - reference to the L.Map object, useful to get map state (zoom, viewport bounds, etc), especially when having multiple maps in the page.
• layer - reference to the L.D3SvgOverlay object, useful for extending behavior of the overlay.
• pathFromGeojson - a d3.geo.path path generator object that can generate SVG Path projected into the overlay's coordinate system from any GeoJSON

License

This code is provided under the MIT License (MIT).

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