Add the ability to centre and zoom the map with URL params. #50

webassets/js/map.js

@@ -210,6 +210,7 @@ function loadOptions() {
         // to be called after these are set up, but if the URL params ask for "embedded mode", this will suppress
         // loading settings, so this needs to be called before that.
         loadURLParams();
+        loadMapURLParams();
 
         // Load settings from settings storage now all the controls are available
         loadSettings();
@@ -344,6 +345,30 @@ function enableWABWAIGrid(show) {
     }
 }
 
+// Load map-specific URL parameters for center position and zoom level.
+// These set Leaflet state directly rather than form controls, so they live here rather than in loadURLParams().
+// If any parameter is applied, firstLoad is set to false so updateMap() does not override the position.
+function loadMapURLParams() {
+    let params = new URLSearchParams(document.location.search);
+    let lat = parseFloat(params.get("map-center-lat"));
+    let lon = parseFloat(params.get("map-center-lon"));
+    let zoom = parseFloat(params.get("map-zoom"));
+
+    let hasLatLon = !isNaN(lat) && !isNaN(lon);
+    let hasZoom = !isNaN(zoom);
+
+    if (hasLatLon || hasZoom) {
+        if (hasLatLon && hasZoom) {
+            map.setView([lat, lon], zoom);
+        } else if (hasLatLon) {
+            map.setView([lat, lon], map.getZoom());
+        } else {
+            map.setZoom(zoom);
+        }
+        firstLoad = false;
+    }
+}
+
 // Set up the map
 function setUpMap() {
     // Create map
@@ -415,7 +440,8 @@ function setUpMap() {
         backgroundTileLayer.bringToBack();
     }
 
-    // Display a default view.
+    // Display a default view. This will only last until the spots are first loaded, at which point the map will zoom
+    // to the extent of ths spots.
     map.setView([30, 0], 3);
 }