feat: improve map zoom controls

app.js

@@ -72,6 +72,7 @@ const map = new ol.Map({
   controls: ol.control
     .defaults.defaults({ rotate: false })
     .extend([
+      createVisibleLayersExtentControl(),
       new ol.control.Rotate({
         autoHide: true,
         label: createNorthPointerIcon(),
@@ -118,6 +119,21 @@ function createNorthPointerIcon() {
   return icon;
 }
 
+function createVisibleLayersExtentControl() {
+  const element = document.createElement("div");
+  element.className = "ol-visible-layers-extent ol-unselectable ol-control";
+
+  const button = document.createElement("button");
+  button.type = "button";
+  button.title = "Zoom to visible layers";
+  button.setAttribute("aria-label", "Zoom to visible layers");
+  button.textContent = "⤢";
+  button.addEventListener("click", () => fitToVisibleLayers());
+
+  element.append(button);
+  return new ol.control.Control({ element });
+}
+
 async function searchParcela(event) {
   event.preventDefault();
 
@@ -296,6 +312,34 @@ function fitToLayerExtent(layer) {
   });
 }
 
+function fitToVisibleLayers() {
+  const visibleLayers = availableLayers.filter((layer) => selectedLayers.includes(layer.name));
+  const projectedExtents = visibleLayers
+    .filter((layer) => layer.extent && layer.extent.every(Number.isFinite))
+    .map((layer) => ol.proj.transformExtent(layer.extent, "EPSG:4326", "EPSG:3857"));
+
+  if (!projectedExtents.length) {
+    updateStatus("Select a layer with a published extent to zoom to it.", "error");
+    return;
+  }
+
+  const combinedExtent = projectedExtents.reduce(
+    (combined, extent) => [
+      Math.min(combined[0], extent[0]),
+      Math.min(combined[1], extent[1]),
+      Math.max(combined[2], extent[2]),
+      Math.max(combined[3], extent[3]),
+    ],
+    [Infinity, Infinity, -Infinity, -Infinity],
+  );
+
+  map.getView().fit(combinedExtent, {
+    padding: [64, 64, 64, 64],
+    duration: 500,
+    maxZoom: 18,
+  });
+}
+
 function childElementsByName(node, localName) {
   return [...(node?.children || [])].filter((child) => child.localName === localName);
 }