From 4b9e06c4a8a7eebc429c5a6cc6babf7081c7f055 Mon Sep 17 00:00:00 2001
From: Jeremy D Monin <jdmonin@nand.net>
Date: Mon, 16 May 2022 23:03:27 -0400
Subject: [PATCH] leaflet-demo: add location permalink to url hash, from
 github.com/MarcChasse/leaflet.Permalink

---
 leaflet-demo.html | 61 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/leaflet-demo.html b/leaflet-demo.html
index d354dc0..7bec06a 100644
--- a/leaflet-demo.html
+++ b/leaflet-demo.html
@@ -23,13 +23,72 @@
         <div id="map"></div>
 
         <script>
-            var map = L.map('map').setView([0, 0], 3);
+            // permalink support: https://github.com/MarcChasse/leaflet.Permalink
+            L.Permalink = {
+                //gets the map center, zoom-level and rotation from the URL if present, else uses default values
+                getMapLocation: function (zoom, center) {
+                    'use strict';
+                    zoom = (zoom || zoom === 0) ? zoom : 18;
+                    center = (center) ? center : [52.26869, -113.81034];
 
+                    if (window.location.hash !== '') {
+                        var hash = window.location.hash.replace('#', '');
+                        var parts = hash.split(',');
+                        if (parts.length === 3) {
+                            center = {
+                                lat: parseFloat(parts[0]),
+                                lng: parseFloat(parts[1])
+                            };
+                            zoom = parseInt(parts[2].slice(0, -1), 10);
+                        }
+                    }
+                    return {zoom: zoom, center: center};
+                },
+
+                setup: function (map) {
+                    'use strict';
+                    var shouldUpdate = true;
+                    var updatePermalink = function () {
+                        if (!shouldUpdate) {
+                            // do not update the URL when the view was changed in the 'popstate' handler (browser history navigation)
+                            shouldUpdate = true;
+                            return;
+                        }
+
+                        var center = map.getCenter();
+                        var hash = '#' +
+                                Math.round(center.lat * 100000) / 100000 + ',' +
+                                Math.round(center.lng * 100000) / 100000 + ',' +
+                                map.getZoom() + 'z';
+                        var state = {
+                            zoom: map.getZoom(),
+                            center: center
+                        };
+                        window.history.pushState(state, 'map', hash);
+                    };
+
+                    map.on('moveend', updatePermalink);
+
+                    // restore the view state when navigating through the history, see
+                    // https://developer.mozilla.org/en-US/docs/Web/API/WindowEventHandlers/onpopstate
+                    window.addEventListener('popstate', function (event) {
+                        if (event.state === null) {
+                            return;
+                        }
+                        map.setView(event.state.center, event.state.zoom);
+                        shouldUpdate = false;
+                    });
+                }
+            };
+
+            var mapPos = L.Permalink.getMapLocation(3, [0, 0]);
+            var map = L.map('map', { center: mapPos.center, zoom: mapPos.zoom });
             L.tileLayer('/tile/{z}/{x}/{y}.png', {
                 maxZoom: 18,
                 attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors, <a href="https://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>',
                 id: 'base'
             }).addTo(map);
+            L.Permalink.setup(map);
         </script>
     </body>
 </html>