go-http-leaflet

go-http-leaflet is an HTTP middleware package for including Leaflet.js (v1.9.3) assets in web applications.

Documentation

go-http-leaflet is an HTTP middleware package for including Leaflet.js assets in web applications. It exports two principal methods:

• leaflet.AppendAssetHandlers(*http.ServeMux) which is used to append HTTP handlers to a http.ServeMux instance for serving Leaflet JavaScript files, and related assets.
• leaflet.AppendResourcesHandler(http.Handler, *LeafletOptions) which is used to rewrite any HTML produced by previous handler to include the necessary markup to load Leaflet

This package doesn't specify any code or methods for how Leaflet.js is used. It only provides method for making Leaflet.js available to existing applications.

By default this package only appends assets and resources for Leaflet.js but it also includes the necessary assets to enable the use of the leaflet-hash, Leaflet.fullscreen and leaflet-geoman plugins. These are enabled by invoking the corresponding EnableHash, EnableFullscreen and EnableDraw methods on the leaflet.LeafletOptions instance.

Example

package main

import (
        "embed"
	"flag"
	"log"
	"net/http"

	"github.com/aaronland/go-http-leaflet"
)

//go:embed *.html
var FS embed.FS

func ExampleHandler(templates *template.Template) (http.Handler, error) {

	t := templates.Lookup("example")

	fn := func(rsp http.ResponseWriter, req *http.Request) {
		t.Execute(rsp)
		return
	}

	return http.HandlerFunc(fn), nil
}

func main() {

	t, _ := template.ParseFS(FS, "*.html")

	http.NewServeMux()

	leaflet_opts := leaflet.DefaultLeafletOptions()
	leaflet_opts.EnableHash()
	leaflet_opts.EnableFullscreen()
	leaflet_opts.EnableDraw()

	leaflet.AppendAssetHandlers(mux, leaflet_opts)
	
	example_handler, _ := ExampleHandler(t)
	example_handler = leaflet.AppendResourcesHandler(example_handler, leaflet_opts)

	mux.Handle("/", example_handler)

	endpoint := "localhost:8080"
	log.Printf("Listening for requests on %s\n", endpoint)

	http.ListenAndServe(endpoint, mux)
}

Error handling omitted for brevity.

You can see an example of this application by running the cmd/example application. You can do so by invoking the example Makefile target. For example:

$> make example
go run -mod vendor cmd/example/main.go -enable-hash -enable-fullscreen -enable-draw -tile-url 'https://tile.openstreetmap.org/{z}/{x}/{y}.png'
2021/05/05 10:53:53 Listening for requests on localhost:8080

The when you open the URL http://localhost:8080 in a web browser you should see the following:

See also

• https://leafletjs.com
• https://github.com/mlevans/leaflet-hash
• https://github.com/Leaflet/Leaflet.fullscreen
• https://github.com/geoman-io/leaflet-geoman