Support function objects in Leaflet options.
hansthen opened this issue · comments
Is your feature request related to a problem? Please describe.
This is not so much a problem as rather a cleanup. All leaflet objects can be configured using an options
dictionary. Many of these objects allow javascript functions inside options
. So far in Folium, these javascript functions were typically implemented in the folium templates and could not be supplied by users. (With a few exceptions).
Describe the solution you'd like
We can use JsCode
to allow users to create javascript functions as part of the configuration. Several Layer
s could benefit from this addition. For instance: folium.GeoJson could be extended with methods for on_each_feature
and point_to_layer
. By adding javascript method handlers, we increase the flexibility of the user. It would allow the user more interactivity. E.g. showing something else in a popup than just the properties of a geojson layer, or adding new shapes.
Describe alternatives you've considered
The main alternative is that we do nothing. This has the advantage of keeping Folium simple. However, the extra power and flexibility outweigh the additional complexity. (At least in my view). It would probably be best to document these as advanced features.
Additional context
I noted that in several locations, the folium objects generate their own implementations of javascript options. E.g. folium.GeoJson generates an on_each_feature
object if a popup or tooltip is configured. We would need to decide how to handle this. The easiest solution would be to disallow certain combinations. Staying with the GeoJson example, if you pass on_each_feature
you cannot also pass a popup
or tooltip
argument.
Implementation
folium is maintained by volunteers. Can you help make a PR if we want to implement this feature?
I'm not sure if I completely follow, could you maybe give a short code snippet as an example?
Is this about allowing any Folium options
to have JsCode
values? I would like that, but not sure how (without touching every template).
Update: is this maybe what you mean? #1856
It's something different from #1856. To a certain extent it is about allowing any Folium class' options
have JsCode
arguments. And you are right, it would involve touching a lot of templates, but the work can be subdivided into smaller steps.
As an example: if one looks at the L.GeoJson
documentation, the user can provide functions for pointToLayer
and onEachFeature
. This is currently not possible in Folium.
I would like the user to be able to create a folium.GeoJson
object with point_to_layer
and on_each_feature
function objects.
E.g.
geojson = GeoJson(
point_to_layer = JsCode("""
function(feature, latlng) {
if(feature.properties.type === "X")
return new CircleMarker(latlng, {radius: 10});
else
return new Circle(latlng, {radius: feature.properties.radius));
}
""")
)
My plan of approach would be
Step 1
Go through all Folium children of branca.Element
and make sure that when the class accepts a **kwargs
argument that is passed to the Leaflet class, it will check if any of the arguments is a JsCode
object and convert it accordingly. Some Folium classes generate their own version of these javascript function objects. Like GeoJson. In that case ensure that the one from **kwargs
cannot blindly override the one generated in the Folium template.
Step 2
Go through all of the Folium children of branca.Element
that have a corresponding Leaflet class. If the Leaflet class documents function objects, add these as explicit arguments to the Folium class __init__
method and document them.