Advanced configuration

This chapter describes somewhat more advanced techniques to configure a clld app.

Custom map icons

clld uses leaflet to display maps. Thus, techniques to use custom map markers are based on corresponding mechanisms for leaflet.

Using custom leaflet markers with clld requires the following steps:

  1. Define a javascript function in your app’s project.js which can be used as marker factory; the signature of this function must be as follows:
MYAPP.icon_factory(feature, size)
  • feature – GeoJSON feature object.
  • size – Size in pixels of the marker.

L.Icon instance.

  1. Make this function available to clld by assigning it to a name in CLLD.MapIcons:
CLLD.MapIcons['myname'] = MYAPP.icon_factory;
  1. Configure a map to use the custom icons:
class MyMap(clld.web.maps.Map):
    def get_options(self):
        return {
            'icons': 'myname',

The name passed as map options will be used to look up the function. This function will be called for each feature object encountered in the GeoJSON object defining a map’s content, i.e. if you want to use special properties of a language or a parameter value in your algorithm to compute the appropriate marker, you will probably have to define a custom GeoJSON adapter for the map as well (see GeoJSON adapters).

A full example to create custom icons which display a number on top of a standard icon could look as follows:

  1. In myapp/static/project.js add
MYAPP.NumberedDivIcon = L.Icon.extend({
    options: {
        number: '',
        className: 'my-div-icon'
    createIcon: function () {
        var div = document.createElement('div');
        var img = this._createImg(this.options['iconUrl']);
        var numdiv = document.createElement('div');
        numdiv.setAttribute ( "class", "number" );
            top: -this.options['iconSize'][0].toString() + 'px',
            left: 0 + 'px',
            'font-size': '12px'
        numdiv.innerHTML = this.options['number'] || '';
        div.appendChild (img);
        div.appendChild (numdiv);
        this._setIconStyles(div, 'icon');
        return div;

CLLD.MapIcons['numbered'] = function(feature, size) {
    return new MYAPP.NumberedDivIcon({
        iconUrl: url ==,
        iconSize: [size, size],
        iconAnchor: [Math.floor(size/2), Math.floor(size/2)],
        popupAnchor: [0, 0],
  1. In myapp/static/project.css add
.my-div-icon {
    background: transparent;
    border: none;

.leaflet-marker-icon .number{
    position: relative;
    font-weight: bold;
    text-align: center;
    vertical-align: middle;