tangramjs

README

go-http-tangramjs

go-http-tangramjs is an HTTP middleware package for including Tangram.js (v0.21.1) assets in web applications.

Documentation

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

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

Example

package main

import (
	"embed"
	"github.com/aaronland/go-http-tangramjs"
	"html/template"
	"log"
	"net/http"
)

//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) {
		err := t.Execute(rsp, nil)
		return
	}

	return http.HandlerFunc(fn), nil
}

func main() {

	api_key := "****"
	style_url := "/tangram/refill-style.zip"

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

	mux := http.NewServeMux()

	tangramjs.AppendAssetHandlers(mux)
	
	map_handler, _:= ExampleHandler(t)

	tangramjs_opts := tangramjs.DefaultTangramJSOptions()
	tangramjs_opts.NextzenOptions.APIKey = api_key
	tangramjs_opts.NextzenOptions.StyleURL = style_url

	map_handler = tangramjs.AppendResourcesHandler(map_handler, tangramjs_opts)

	mux.Handle("/", map_handler)

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

	http.ListenAndServe(endpoint, mux)
}

Error handling omitted for the sake of 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 APIKEY=XXXXXX
go run -mod vendor cmd/example/main.go -api-key XXXXXX
2021/05/05 15:31:06 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://github.com/tangrams/tangram
• https://github.com/aaronland/go-http-leaflet

Documentation

Overview

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

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

Example

import (
	"embed"
	"github.com/aaronland/go-http-tangramjs"
	"html/template"
	"log"
	"net/http"
)

//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) {
		err := t.Execute(rsp, nil)
		return
	}

	return http.HandlerFunc(fn), nil
}

func main() {

	api_key := "****"
	style_url := "/tangram/refill-style.zip"

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

	mux := http.NewServeMux()

	tangramjs.AppendAssetHandlers(mux)

	map_handler, _:= ExampleHandler(t)

	tangramjs_opts := tangramjs.DefaultTangramJSOptions()
	tangramjs_opts.NextzenOptions.APIKey = api_key
	tangramjs_opts.NextzenOptions.StyleURL = style_url

	map_handler = tangramjs.AppendResourcesHandler(map_handler, tangramjs_opts)

	mux.Handle("/", map_handler)

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

	http.ListenAndServe(endpoint, mux)
}

Index

• Constants
• Variables
• func AppendAssetHandlers(mux *http.ServeMux) error
• func AppendAssetHandlersWithPrefix(mux *http.ServeMux, prefix string) error
• func AppendResourcesHandler(next http.Handler, opts *TangramJSOptions) http.Handler
• func AppendResourcesHandlerWithPrefix(next http.Handler, opts *TangramJSOptions, prefix string) http.Handler
• func AssetsHandler() (http.Handler, error)
• func AssetsHandlerWithPrefix(prefix string) (http.Handler, error)
• type NextzenOptions
  • func DefaultNextzenOptions() *NextzenOptions
• type TangramJSOptions
  • func DefaultTangramJSOptions() *TangramJSOptions

Constants

const NEXTZEN_MVT_ENDPOINT string = "https://tile.nextzen.org/tilezen/vector/v1/512/all/{z}/{x}/{y}.mvt"

NEXTZEN_MVT_ENDPOINT is the default endpoint for Nextzen vector tiles

Variables

var APPEND_LEAFLET_ASSETS = true

By default the go-http-tangramjs package will also include and reference Leaflet.js assets using the aaronland/go-http-leaflet package. If you want or need to disable this behaviour set this variable to false.

var APPEND_LEAFLET_RESOURCES = true

By default the go-http-tangramjs package will also include and reference Leaflet.js resources using the aaronland/go-http-leaflet package. If you want or need to disable this behaviour set this variable to false.

Functions

func AppendAssetHandlers

func AppendAssetHandlers(mux *http.ServeMux) error

Append all the files in the net/http FS instance containing the embedded Tangram.js assets to an *http.ServeMux instance.

func AppendAssetHandlersWithPrefix

func AppendAssetHandlersWithPrefix(mux *http.ServeMux, prefix string) error

Append all the files in the net/http FS instance containing the embedded Tangram.js assets to an *http.ServeMux instance ensuring that all URLs are prepended with prefix.

func AppendResourcesHandler

func AppendResourcesHandler(next http.Handler, opts *TangramJSOptions) http.Handler

AppendResourcesHandler will rewrite any HTML produced by previous handler to include the necessary markup to load Tangram.js files and related assets.

func AppendResourcesHandlerWithPrefix

func AppendResourcesHandlerWithPrefix(next http.Handler, opts *TangramJSOptions, prefix string) http.Handler

AppendResourcesHandlerWithPrefix will rewrite any HTML produced by previous handler to include the necessary markup to load Tangram.js files and related assets ensuring that all URIs are prepended with a prefix.

func AssetsHandler

func AssetsHandler() (http.Handler, error)

AssetsHandler returns a net/http FS instance containing the embedded Tangram.js assets that are included with this package.

func AssetsHandlerWithPrefix

func AssetsHandlerWithPrefix(prefix string) (http.Handler, error)

AssetsHandler returns a net/http FS instance containing the embedded Tangram.js assets that are included with this package ensuring that all URLs are stripped of prefix.

Types

type NextzenOptions

type NextzenOptions struct {
	// A valid Nextzen developer API key
	APIKey string
	// The URL for a valid Tangram.js style.
	StyleURL string
	// The URL template to use for fetching Nextzen map tiles.
	TileURL string
}

NextzenOptions provides configuration variables for Nextzen map tiles.

func DefaultNextzenOptions

func DefaultNextzenOptions() *NextzenOptions

Return a *NextzenOptions struct with default values.

type TangramJSOptions

type TangramJSOptions struct {
	// A list of Tangram.js Javascript files to append to HTML resources.
	JS []string
	// A list of Tangram.js CSS files to append to HTML resources.
	CSS []string
	// A NextzenOptions instance.
	NextzenOptions *NextzenOptions
	// A leaflet.LeafletOptions instance.
	LeafletOptions *leaflet.LeafletOptions
}

TangramJSOptions provides a list of JavaScript and CSS link to include with HTML output as well as options for Nextzen tiles and Leaflet.js.

func DefaultTangramJSOptions

func DefaultTangramJSOptions() *TangramJSOptions

Return a *TangramJSOptions struct with default values.